- freely available
Genes 2014, 5(3), 518-535; doi:10.3390/genes5030518
Abstract: In the decade that has passed since the initial release of the Human Genome, numerous advancements in science and technology within and beyond genetics and genomics have been encouraged and enhanced by the availability of this vast and remarkable data resource. Progress in understanding three common, complex diseases: age-related macular degeneration (AMD), Alzheimer’s disease (AD), and multiple sclerosis (MS), are three exemplars of the incredible impact on the elucidation of the genetic architecture of disease. The approaches used in these diseases have been successfully applied to numerous other complex diseases. For example, the heritability of AMD was confirmed upon the release of the first genome-wide association study (GWAS) along with confirmatory reports that supported the findings of that state-of-the art method, thus setting the foundation for future GWAS in other heritable diseases. Following this seminal discovery and applying it to other diseases including AD and MS, the genetic knowledge of AD expanded far beyond the well-known APOE locus and now includes more than 20 loci. MS genetics saw a similar increase beyond the HLA loci and now has more than 100 known risk loci. Ongoing and future efforts will seek to define the remaining heritability of these diseases; the next decade could very well hold the key to attaining this goal.
In celebration of the 10th anniversary of the completion of the Human Genome Project, it is pertinent to take a step back and reflect on the progress that has been made in genetic and genomic research over the past decade by exploring the knowledge gleaned from the extensive wealth of information provided by the Human Genome Project (HGP). Herein we provide a concise historical overview of three signature human diseases that have strong but complex genetic etiologies: age-related macular degeneration (AMD), multiple sclerosis (MS), and Alzheimer’s disease (AD). The significant progress in defining the genetic architecture of these diseases, beginning with the pre-genome-wide association study (GWAS)-era and concluding with the current state of each, and what lies ahead for these complex diseases reflects the great progress that has been made in general in the study of multifactorial diseases, and provides a brief glimpse at what we can hope the next decade of genomic research will provide.
2. Age-Related Macular Degeneration (AMD) and the First Genome-Wide Association Study
Age-related macular degeneration an ocular neurodegenerative disease that results primarily in loss of central vision, is a major cause of visual impairment and blindness in elderly populations worldwide. Although there was at one time substantial controversy over the strength of the genetic effects in AMD, genetic and epidemiological research, established that there is a significant genetic component to AMD, estimated to be 45%–70% . This was supported by twin studies that reported higher incidence of disease in monozygotic versus dizygotic twins [1,2,3,4,5] and family studies in which risk for developing AMD between first degree relatives ranges from 2–3 [3,6,7]. This knowledge encouraged the application of increasingly sophisticated genomic techniques to elucidate the genetic etiology of AMD susceptibility and pathogenesis. Prior to major genetic breakthroughs such as the completion of the HGP, it was well established that inflammatory and immunologic mediators contribute to AMD (e.g., [8,9,10,11,12,13]). However, this knowledge did not lead to identification of any confirmed genetic loci for AMD. Following the trends at that time in applying the available statistical genetic techniques, numerous genetic linkage studies using multiplex families and (primarily) affected sibships were attempted [14,15,16,17,18,19,20,21,22]. Notably, The ABCA4 (ABCR) locus on chromosome 1p21, identified for its involvement in autosomal recessive Stargardt disease retinopathy [23,24,25,26,27], was one of the first loci identified as involved in AMD, though not all reports have been consistent [23,24,25,26,27,28,29,30,31]. While linkage studies continued to provide suggestive evidence of a role of genetics, they did not find any definitive locus for AMD. In a large meta-analysis of most of these genetic linkage studies, several chromosomal regions were identified as highly likely to harbor AMD genes, most convincingly including chromosome 1q23.3–q32 and 10q26 .
With the continuing evolution of HGP resources, in particular the identification of very large numbers of single nucleotide polymorphisms (SNPs) [33,34] multiple new experimental designs for identifying AMD loci were employed. SNPs provided several advantages over the then prevalent microsatellite markers; the two most important were the high density of SNPs across the genome, and their much higher fidelity in genotyping. The culmination of the efforts of four independent studies using four complementary study designs was a convergence on the discovery of the association between AMD and the gene encoding the complement factor H protein (CFH), located on chromosome 1q32. In one of the first reported genome-wide association studies (GWAS), Klein et al.  screened 96 AMD cases and 50 non-AMD controls to evaluate variants associated with AMD. The GWAS method implements a hypothesis-free approach in which a large number of SNPs are genotyped across the genome and evaluated for association with disease. This particular study evaluated 116,204 successfully genotyped SNPs and detected association between AMD and an intronic SNP in CFH (p < 10−7). Linkage disequilibrium analysis and localization using resequencing in this region led to the discovery of a nonsynonymous SNP in exon 9 of CFH; this SNP, rs1061170, causes the substitution of a histidine for a tyrosine at amino acid 402 (Y402H).
Independently and concurrently with the Klein et al. study , Haines et al.  also identified the association with the Y402H variant, but by implementing a purely locational genomic approach. By focusing on and extending slightly beyond the 24 Mb region implicated by linkage studies of AMD [14,15,22] they identified a five-SNP haplotype spanning a 261 kb region surrounding the Regulators of Complement Activation (RCA) gene cluster by genotyping only 61 SNPs in two independent datasets. Both affected and unaffected individuals homozygous for the risk haplotype were sequenced for the genes residing in this haplotype. Their hypothesis was that having controlled for the locus specific genetic background (e.g., the haplotype), frequency differences for variants between cases and controls would identify the causal variation. Scanning the coding region of CFH in those individuals, Y402H was by far the most significantly different of the 11 detected variants. Follow-up genotyping in the original datasets confirmed that the Y402H variant was significantly associated with risk for AMD and that a surprisingly high proportion of the genetic variation in AMD could be attributed to the Y402H variant.
Implementing yet another independent, concurrent, and complimentary approach to localize AMD-causing variants, Edwards et al. also identified the Y402H variant using a fine-mapping approach focused on this same general region on chromosome 1 . This study centered efforts on 86 SNPs located in coding sequences encompassing the RCA locus in a case-control sample. The most significant of the 29 associated variants located in the RCA was again rs1061170 (Y402H) in CFH. Replication analysis evaluating this and 13 additional SNPs typed in a second case-control sample confirmed the association of Y402H with AMD. Further analysis established that that C (risk)-allele carrying individuals accounted for approximately half of cases.
Hageman and colleagues also confirmed the Y402H variant, applying yet a fourth genetic analysis method . They applied prior biological knowledge of the involvement of CFH (also called HF1) in membranoproliferative glomerulonephritis type II (MPGNII), a disease in which patients develop ocular drusen nearly identical to those found in AMD patients. The genetic lesion for MPGNII resides in the same chromosome 1q31–32 region that was also implicated in linkage studies of AMD [14,15,22]. Evaluating two samples of unrelated individuals for AMD-associated variation in CFH, this group also detected evidence for association between AMD and the Y402H variant.
These four studies simultaneously reported the role of variation in a chromosome 1 region that had previously been highlighted in AMD linkage studies [14,15,22]; identifying this major genetic determinant of AMD, something that even a year earlier was thought not to exist, was a major landmark in genetics of complex disease. These results, while obviously important for AMD research, provided the first validation of the GWAS approach. Up to that point, hundreds of papers had been written about the potential of the GWAS study design, but very little had been published on actual implementation. Dr. Elias Zherhouni, then Director of NIH, highlighted these studies as a major breakthrough in health research . This very strong validation imparted the necessary confidence in GWAS to invigorate its application to numerous other diseases. Over the past nine years more than 2000 GWAS studies that have been published .
Since the initial discovery of the Y402H CFH variant, substantial progress has been made in understanding the genetics of AMD. This includes the localization of the strongest single genetic effect in AMD on chromosome 10q26 (through positional localization approach) to the region containing ARMS2 and HTRA1 (e.g., [41,42,43,44,45,46,47]), though there is still controversy whether either one or both of these genes contains the causal variant (e.g. [46,47,48,49]).
In the CFH region, in addition to the high-effect Y402H variant, a deletion of CFHR1 and CFHR3 was detected and determine to be protective for AMD  (e.g., [51,52,53]). Various additional studies focused on the potential role of additional complement mediators in AMD. Gold et al. explored additional alternative complement pathway activators beyond CFH and determined that variants in complement factor b (BF/CFB) and C2 are highly protective against AMD . A coding variant in C3 was also determined to be associated with AMD [55,56,57]. A variant upstream of the CFI gene was also determined to influence AMD risk . A variant in the CFD gene was associated with AMD but replicated almost solely in females . More recently discovered AMD-associated loci have been detect in/near genes ADAMTS9, B3GALTL, CETP, COL8A1-FILIP1L, IER3-DDR1, LIPC, RAD51B, SLC16A8, TGFBR1 and TIMP3 [60,61,62].
GWAS studies in AMD now include over 1 million markers [61,63,64,65]. Though the traditional GWAS approach has been incredibly informative for many diseases, a great deal of the genetic proportion of many of these diseases remains to be fully elucidated even after applying straightforward and complex GWAS methods . Approaches to enhance the detection of genetic variation associated with disease have necessarily expanded beyond the traditional GWAS to broaden the range of discovery and increase the power of detection; one technique that aids in this process is imputing variants—using known genetic information from a reference sample. Obviously increasing the sample size of genetic studies of complex diseases is crucial to accelerate the identification of disease-specific variants. Expanding the number of testable variants is now a more attainable goal using imputation, a technique that can significantly increase the number of tested variants beyond those interrogated by a GWAS through informing genotypes of untyped SNPs [67,68]. Combining known genotypes at GWAS-interrogated SNPs with available sequence data from a reference panel and inferring untyped SNPs in the dataset based on haplotype frequencies allows for the inference of numerous SNPs with varying degrees of confidence and accuracy. This method increases the power of GWAS by increasing the number of SNPs that can be tested, it can also lead to more efficient identification of causal variants and/or SNPs in high linkage disequilibrium with a causal variant [67,68]. Imputation has been implemented in several studies of AMD to enhance the ability to detect associated variants [61,63,69]. For example, the most recent publication from the AMD Gene Consortium reports seven novel variants that were detected using imputed data in addition to confirming 12 previously identified variants .
An additional method to utilize genome-wide data beyond the traditional association analysis is to perform pathway enrichment analyses. The goal of such analyses is identify biological relationships between associated genetic signals and pathways of interest in a particular disease. Pathway analysis can be performed by a comprehensive review of GWAS results to assess overrepresentation of SNPs meeting a specific threshold that occur within biological pathways . These enhance GWAS by evaluating potentially biologically relevant signals that might otherwise be overlooked because of the numerous false-positive results that occur in large GWAS studies . These have the potential to highlight otherwise undetected small and/or interactive effects that are important to evaluate in addition to and in the context of the overall genome-wide results. Using the INRICH (Interval-based Enrichment Analysis Tool for Genome Wide Association Studies) pathway analysis tool  to evaluate overall results, the AMD Gene Consortium not only confirmed previously implicated AMD pathways, but also determined additional pathways of interest in the most recent publication which detected enrichment of complement and atherosclerotic pathway-encoding genes as well as genes involved in pathways of collagen and extracellular region, complement and coagulation cascades, lipoprotein metabolism, and regulation of apoptosis .
The impressive impact that genetic information can have on our understanding of disease pathophysiology is highlighted in the recent publication by Yang et al. in which they report that ARMS2/HTRA1 risk alleles contribute to AMD pathogenesis by decreasing the defense capabilities of superoxide dismutase 2 (SOD2) and thereby cause the retinal pigment epithelium to be more susceptibility to oxidative damage . Having an explanation for the role the variants have in the disease is crucial to further elucidating disease mechanisms both genetically and physiologically. Additionally, genetic studies implicate VEGF as having a role in AMD and current AMD treatment and clinical trials utilize this information for treatment of neovascular AMD (reviewed in ), thus highlighting the utility of genetic data for clinical impact.
3. Alzheimer’s Disease
Alzheimer’s disease (AD) is a genetically heterogeneous neurologic disorder that is the leading cause of dementia among the elderly. It is characterized by the progressive loss of cognitive ability beyond what is normally associated with aging. AD is a complex disease that is influenced by both environmental and genetic mediators, the most significant of which is age [74,75]. The heritability of AD is estimated between 60%–80%. Before 1985, there was very significant debate about whether or not genetics played any role in AD (e.g., [76,77,78,79,80]). However, in 1987, using some of the earliest technologies employing genomic markers, a locus for the rare early onset AD (EOAD) was identified , and in 1991 the responsible variation in the APP gene was located .
Expansions of genomic marker sets, developed through early HGP efforts, were used to further identify two additional early onset genes in the early 1990’s [82,83,84,85,86]. Simultaneously and independently, the emerging technologies of genomic markers and genetic linkage analysis were applied to the far more common late onset Alzheimer’s disease (LOAD), which accounts for 99% of AD cases . Using these techniques, Pericak-Vance et al. identified a locus on chromosome 19 near the gene encoding apolipoprotein E (APOE) [88,89], which was at that time thought to only be involved in cardiovascular disease. This locus has three distinct alleles: ∈2, ∈3, and ∈4. Corder et al. characterized a dose-dependent association between the APOE-∈4 allele and an increased risk of LOAD . Mutations in the EOAD genes are causal, with very high penetrance, and opened avenues for exploring the pathophysiology of AD. However, in aggregate they explain less than 1% of AD. In contrast, APOE explains at least 25% of AD. A year after determining the role of the ∈4 variant in LOAD susceptibility, it became apparent that the ∈2 allele provided an independently protective effect on LOAD .
The APOE finding was pivotal for two reasons. Within the AD research community, it provided a new avenue and a completely different view of the genetic etiology of AD. More generally, however, this was one of the very first examples of how the emerging technologies of the HGP could be successfully applied to diseases lacking a simple Mendelian inheritance pattern, i.e., what are commonly called complex diseases. The finding of the APOE-∈2 allele protective effect was also one of the first examples of different alleles carrying different effects on a complex disease, a pivotal moment in AD research and broadly in the field of genetics.
Innumerable attempts to identify additional genomic variations modulating the risk of LOAD followed these groundbreaking APOE discoveries, using the increasingly dense set of known variations and emerging sequencing techniques (cataloged in Alzgene.org). These efforts were primarily applied to specific genes of interest; that is, employing a focused candidate gene approach. Although there were numerous reports of significant associations, no consensus arose that any of these were true effects. It was not until GWAS became a viable approach [92,93,94], and multiple datasets were combined, that additional LOAD loci become visible and confirmed [95,96,97]. The most recent efforts by the Alzheimer Disease Genetics Consortium (ADGC) and the International Genomics of Alzheimer’s Project (IGAP) have greatly increased the number of known loci associated with LOAD. In the 2011 Naj et al. report, a three-stage design (discovery stage 1, replication stages 2–3) was utilized; this analysis evaluated >18,000 cases and >29,000 controls using both joint- and meta-analysis approaches and novel genome-wide significant hits were detected at SNPs in MS4A4A, CD2AP, EPHA1 and CD33 . In Lambert et al. 2013, the IGAP reported an additional eleven novel LOAD susceptibility loci after analyzing genotyped and imputed data in a two-stage meta-analysis of >25,000 cases and >48,000 controls . There are now over 20 loci identified that influence LOAD . Importantly, using the pathway approach, the amyloid precursor protein and tau pathways are confirmed by this most recent large GWAS in addition to the newly implicated hippocampal synaptic function, cytoskeletal function and axonal transport, regulation of gene expression and post-translational modification of proteins, and microglial and myeloid cell function pathways .
4. Multiple Sclerosis
Multiple sclerosis (MS) is a common cause of neurological disability involving inflammatory demyelination of the central nervous system [98,99,100,101]. There is ample evidence that MS has a strong genetic component, but like so many other complex diseases, non-genetic influences are also important (e.g., [99,102,103,104]). MS is also a complex, heterogeneous disease in which significant efforts to unravel the role of genetics have been made. Unlike both AMD and LOAD, the first and strongest genetic effect in MS was identified well before the HGP was undertaken. Because MS is an autoimmune disease, it was strongly suspected that the major histocompatibility locus (MHC) would be involved. More specifically, there was a focus on the human leukocyte antigen loci on chromosome 6. In the early 1970’s the HLA loci could be genotyped using blood antigen reactions, allowing assignment of genotypes without directly examining the DNA. Through a number of efforts (e.g., [99,103,104,105,106,107,108,109]) a strong risk association with the HLA-DR locus, and specifically the 15*01 allele was identified.
Despite this auspicious beginning, identifying additional MS loci languished. As with the other complex diseases, genetic linkage analysis was applied to multiplex MS families, with varying results. Some early genetic linkage studies confirmed the role of HLA , while others did not . Additional studies, using the increasingly dense DNA marker sets and larger datasets, ultimately demonstrated and confirmed that the HLA locus was the single largest genetic effect, and that any other MS loci would have at most modest individual effects [109,110,112,113,114,115,116]. These studies did highlight several other possible loci, but did not have the resolution to identify specific associated genetic variations [115,116].
Finally, in 2007, nearly 30 years after the initial association finding, a second locus for MS was identified [117,118]. Gregory et al. employed a genomic convergence approach that integrated data from genetic linkage studies, genetic association studies, model system gene expression data, and in vitro functional data to narrow in on a specific locus and a functional polymorphism in the interleukin-7 receptor α chain (IL7R) . Independently, the International Multiple Sclerosis Genetics Consortium (IMSGC) published results from one of the first large-scale GWAS studies, using 334,923 GWAS SNPs. The IMSGC used a hybrid study design that included a family-based study of 931 family trios and an independent dataset set of cases and controls . These analyses confirmed the role of genetic variation in IL7RA and also highlighted variations in IL2RA.
These results also had broad implications for the field of MS resarch. The IMSGC GWAS was still one of the first such studies done with a well-powered dataset and demonstrated that family-based and case-control GWAS approaches were both useful methods for exploring genetic information. In addition, like AMD, the convergence of independent approaches (GWAS and gene-targeted methods) further validated that GWAS could identify relevant associated loci. Subsequent studies with much larger datasets [96,119,120] have now identified over 100 total loci associated with MS.
Efforts in MS have shown substantial increases in the number of independent loci associated with this disease. The most recent IMSGC study evaluated in two stages more than 80,000 individuals of European ancestry . This analysis expanded the known MS loci by 48, raising the total number of discrete MS-associated loci to 103. In addition, the IMSGC interrogated specific genomic regions and hypotheses using a custom array, the Immunochip. The group efficiently utilized extensive amounts of data by assembling multiple studies and utilizing imputation methods and then applying conditional and joint analysis methods . Such methods are becoming more common in the efforts to expand the power to detect common variation in many multifactorial diseases. The strongest of the novel hits from this analysis implicates a SNP in the region between BCL10 and DDAH1 ; BCL10 is an activator of nuclear factor (NF)-κB signaling which is involved in gene expression control of inflammation, immunity, cell proliferation and apoptosis and has been explored as a clinical target for MS [73,119,121].
Pathway analysis in MS has also proven useful. The IMSGC study additionally sought to evaluate the Gene Ontology (GO) processes of the associated variants using the MetaCore (); their results indicated, as expected, that most variants fall in or near genes with immune function . Another recent endeavor to evaluate pathways involved in MS utilized results from eight MS GWAS datasets and prioritized genes in the cell adhesion molecule (CAM) biological pathway with the Cytoscape software [120,123]. Their findings highlighted five networks that were associated with susceptibility to MS—again supporting the utility of expanding beyond traditional case-control association analyses of GWAS data and encouraging the use of multiple datasets to determine enrichment of signals that might otherwise not have been detected using a traditional GWAS approach .
5. Conclusions and Future Directions
Since the completion of the HGP and shortly after the first GWAS, thousands more GWAS have been reported ; these have brought forth great progress in numerous diseases that previously were only hypothesized to have a genetic component. Large-scale collaborative efforts have raised the number of known AMD, AD, and MS loci to 19 , 20 , and 103 , respectively. Efforts to increase sample size have been successful, as evidenced by the largest and most recently reported analyses of AMD , AD  and MS , which each evaluated >74,000 individuals; however, other techniques are necessary to evaluate and explore as data becomes increasingly large and complex. Whole exome and whole genome sequencing are more recent approaches to generating genetic data that allow investigation far beyond the capabilities of the GWAS, and their utility is just starting to take shape in studies of many complex common diseases, including those mentioned herein. These will enable the study of rare and low frequency variants, which have been implicated as a potential source of missing heritability in many genetic diseases . Analysis of data from exome arrays, designed to jointly interrogate data relevant to association studies of common variants and sequencing studies of rare variants, will improve genetic analysis of disease by providing greater coverage of known susceptibility loci and enhancing the likelihood for discovery of novel disease loci.
For each of these diseases, the fact that there is a genetic component is irrefutable; this knowledge has, over the past decade, most certainly been confirmed and expounded upon with the completion of the human genome sequence. As genetic knowledge continues to grow, and as clinical phenotyping techniques improve, further genetic variation influencing AMD, AD, and MS will likely be detectable and, hopefully, their roles in these diseases will be more clearly defined . We can anticipate that as our understanding of genetic etiology of these diseases grows, future studies will further explore rare variations contributing to disease, the role of copy number variants, and the genetics of these diseases in non-European populations. Additionally, the role of currently undetermined environmental factors and their interactions with genetic variants must continue to be elucidated. The global objective of prior and ongoing studies is certainly to improve the current comprehension of new and existing disease loci in order that the biology of these diseases can be fully explicated in the hope of attaining improved strategies for disease treatment and prevention in the future.
The last decade has doubtlessly ushered in dramatic advances in the amount of shared data available to genetic researchers. Resources such as the NHLBI Grand Opportunity Exome Sequencing Project , the 1000Genomes , ENCODE , and the International HapMap Project [128,129] provide seemingly limitless amounts of data—all geared toward further understanding the intricacies of the human genome and how alterations of it influence human variation. We have provided a brief genetic history of three diseases that are exemplars of developing approaches to apply the incredible resources of the HGP. Such progress will most certainly continue to improve and exponentially increase in the next decade to facilitate a greater understanding of these and other complex diseases, as well as usher in the realization of personalized medicine.
This work was supported by NIH T32 EY007157 (Jessica N. Cooke Bailey), Alzheimer’s Disease Genetics Consortium, funded by NIA grant U01AG032984 (Margaret A. Pericak-Vance, Jonathan L. Haines), BrightFocus Foundation grant A2011048 (Margaret A. Pericak-Vance), DOD grant W81XWH-12-1-0013 (Margaret A. Pericak-Vance, Jonathan L. Haines), NEI grants 7R01EY012118 (Margaret A. Pericak-Vance, Jonathan L. Haines), 1R01EY022310 (Jonathan L. Haines, Margaret A. Pericak-Vance), 1R01EY023164 (Margaret A. Pericak-Vance), and 1R01EY020928 (Margaret A. Pericak-Vance), NIA grants 1R01AG027944 (Margaret A. Pericak-Vance, Jonathan L. Haines) and R01AG19085 (Margaret A. Pericak-Vance, Jonathan L. Haines) and NINDS grant R01NS032830 (Margaret A. Pericak-Vance, Jonathan L. Haines).
Jessica N. Cooke Bailey wrote and edited the manuscript. Margaret A. Pericak-Vance conceived the idea for the manuscript and reviewed and edited the manuscript. Jonathan L. Haines conceived the idea for the manuscript, wrote, reviewed and edited the manuscript.
Conflicts of Interest
The authors declare no conflict of interest.
- Seddon, J.M.; Cote, J.; Page, W.F.; Aggen, S.H.; Neale, M.C. The US twin study of age-related macular degeneration: Relative roles of genetic and environmental influences. Arch. Ophthalmol. 2005, 123, 321–327. [Google Scholar] [CrossRef]
- Hammond, C.J.; Webster, A.R.; Snieder, H.; Bird, A.C.; Gilbert, C.E.; Spector, T.D. Genetic influence on early age-related maculopathy: A twin study. Ophthalmology 2002, 109, 730–736. [Google Scholar] [CrossRef]
- Klaver, C.C.; Wolfs, R.C.; Assink, J.J.; van Duijn, C.M.; Hofman, A.; de Jong, P.T. Genetic risk of age-related maculopathy. Population-based familial aggregation study. Arch. Ophthalmol. 1998, 116, 1646–1651. [Google Scholar] [CrossRef]
- Klein, M.L.; Mauldin, W.M.; Stoumbos, V.D. Heredity and age-related macular degeneration. Observations in monozygotic twins. Arch. Ophthalmol. 1994, 112, 932–937. [Google Scholar] [CrossRef]
- Meyers, S.M. A twin study on age-related macular degeneration. Trans. Am. Ophthalmol. Soc. 1994, 92, 775–843. [Google Scholar]
- Heiba, I.M.; Elston, R.C.; Klein, B.E.; Klein, R. Sibling correlations and segregation analysis of age-related maculopathy: The beaver dam eye study. Genet. Epidemiol. 1994, 11, 51–67. [Google Scholar] [CrossRef]
- Seddon, J.M.; Cote, J.; Davis, N.; Rosner, B. Progression of age-related macular degeneration: Association with body mass index, waist circumference, and waist-hip ratio. Arch. Ophthalmol. 2003, 121, 785–792. [Google Scholar] [CrossRef]
- Anderson, D.H.; Mullins, R.F.; Hageman, G.S.; Johnson, L.V. A role for local inflammation in the formation of drusen in the aging eye. Am. J. Ophthalmol. 2002, 134, 411–431. [Google Scholar] [CrossRef]
- Anderson, D.H.; Radeke, M.J.; Gallo, N.B.; Chapin, E.A.; Johnson, P.T.; Curletti, C.R.; Hancox, L.S.; Hu, J.; Ebright, J.N.; Malek, G.; et al. The pivotal role of the complement system in aging and age-related macular degeneration: Hypothesis re-visited. Prog. Retin. Eye Res. 2010, 29, 95–112. [Google Scholar] [CrossRef]
- Ding, X.; Patel, M.; Chan, C.C. Molecular pathology of age-related macular degeneration. Prog. Retin. Eye Res. 2009, 28, 1–18. [Google Scholar] [CrossRef]
- Patel, M.; Chan, C.C. Immunopathological aspects of age-related macular degeneration. Semin. Immunopathol. 2008, 30, 97–110. [Google Scholar] [CrossRef]
- Penfold, P.L.; Killingsworth, M.C.; Sarks, S.H. Senile macular degeneration: The involvement of immunocompetent cells. Graefes Arch. Clin. Exp. Ophthalmol. 1985, 223, 69–76. [Google Scholar] [CrossRef]
- Tuo, J.; Grob, S.; Zhang, K.; Chan, C.C. Genetics of immunological and inflammatory components in age-related macular degeneration. Ocul. Immunol. Inflamm. 2012, 20, 27–36. [Google Scholar] [CrossRef]
- Abecasis, G.R.; Yashar, B.M.; Zhao, Y.; Ghiasvand, N.M.; Zareparsi, S.; Branham, K.E.; Reddick, A.C.; Trager, E.H.; Yoshida, S.; Bahling, J.; et al. Age-related macular degeneration: A high-resolution genome scan for susceptibility loci in a population enriched for late-stage disease. Am. J. Hum. Genet. 2004, 74, 482–494. [Google Scholar] [CrossRef]
- Iyengar, S.K.; Song, D.; Klein, B.E.; Klein, R.; Schick, J.H.; Humphrey, J.; Millard, C.; Liptak, R.; Russo, K.; Jun, G.; et al. Dissection of genomewide-scan data in extended families reveals a major locus and oligogenic susceptibility for age-related macular degeneration. Am. J. Hum. Genet. 2004, 74, 20–39. [Google Scholar] [CrossRef]
- Klein, M.L.; Schultz, D.W.; Edwards, A.; Matise, T.C.; Rust, K.; Berselli, C.B.; Trzupek, K.; Weleber, R.G.; Ott, J.; Wirtz, M.K. Age-related macular degeneration. Clinical features in a large family and linkage to chromosome 1q. Arch. Ophthalmol. 1998, 116, 1082–1088. [Google Scholar] [CrossRef]
- Majewski, J.; Schultz, D.W.; Weleber, R.G.; Schain, M.B.; Edwards, A.O.; Matise, T.C.; Acott, T.S.; Ott, J.; Klein, M.L. Age-related macular degeneration—A genome scan in extended families. Am. J. Hum. Genet. 2003, 73, 540–550. [Google Scholar] [CrossRef]
- Seddon, J.M.; Santangelo, S.L.; Book, K.; Chong, S.; Cote, J. A genomewide scan for age-related macular degeneration provides evidence for linkage to several chromosomal regions. Am. J. Hum. Genet. 2003, 73, 780–790. [Google Scholar] [CrossRef]
- Tuo, J.; Bojanowski, C.M.; Chan, C.C. Genetic factors of age-related macular degeneration. Prog. Retin. Eye Res. 2004, 23, 229–249. [Google Scholar] [CrossRef]
- Weeks, D.E.; Conley, Y.P.; Mah, T.S.; Paul, T.O.; Morse, L.; Ngo-Chang, J.; Dailey, J.P.; Ferrell, R.E.; Gorin, M.B. A full genome scan for age-related maculopathy. Hum. Mol. Genet. 2000, 9, 1329–1349. [Google Scholar] [CrossRef]
- Weeks, D.E.; Conley, Y.P.; Tsai, H.J.; Mah, T.S.; Rosenfeld, P.J.; Paul, T.O.; Eller, A.W.; Morse, L.S.; Dailey, J.P.; Ferrell, R.E.; et al. Age-related maculopathy: An expanded genome-wide scan with evidence of susceptibility loci within the 1q31 and 17q25 regions. Am. J. Ophthalmol. 2001, 132, 682–692. [Google Scholar] [CrossRef]
- Weeks, D.E.; Conley, Y.P.; Tsai, H.J.; Mah, T.S.; Schmidt, S.; Postel, E.A.; Agarwal, A.; Haines, J.L.; Pericak-Vance, M.A.; Rosenfeld, P.J.; et al. Age-related maculopathy: A genomewide scan with continued evidence of susceptibility loci within the 1q31, 10q26, and 17q25 regions. Am. J. Hum. Genet. 2004, 75, 174–189. [Google Scholar] [CrossRef]
- Allikmets, R. A photoreceptor cell-specific ATP-binding transporter gene (ABCR) is mutated in recessive Stargardt macular dystrophy. Nat. Genet. 1997, 17, 122. [Google Scholar]
- Allikmets, R. Further evidence for an association of ABCR alleles with age-related macular degeneration. The International ABCR Screening Consortium. Am. J. Hum. Genet. 2000, 67, 487–491. [Google Scholar] [CrossRef]
- Allikmets, R.; Shroyer, N.F.; Singh, N.; Seddon, J.M.; Lewis, R.A.; Bernstein, P.S.; Peiffer, A.; Zabriskie, N.A.; Li, Y.; Hutchinson, A.; et al. Mutation of the Stargardt disease gene (ABCR) in age-related macular degeneration. Science 1997, 277, 1805–1807. [Google Scholar] [CrossRef]
- Meyers, S.M.; Greene, T.; Gutman, F.A. A twin study of age-related macular degeneration. Am. J. Ophthalmol. 1995, 120, 757–766. [Google Scholar]
- Shroyer, N.F.; Lewis, R.A.; Yatsenko, A.N.; Wensel, T.G.; Lupski, J.R. Cosegregation and functional analysis of mutant ABCR (ABCA4) alleles in families that manifest both Stargardt disease and age-related macular degeneration. Hum. Mol. Genet. 2001, 10, 2671–2678. [Google Scholar] [CrossRef]
- Fritsche, L.G.; Fleckenstein, M.; Fiebig, B.S.; Schmitz-Valckenberg, S.; Bindewald-Wittich, A.; Keilhauer, C.N.; Renner, A.B.; Mackensen, F.; Mossner, A.; Pauleikhoff, D.; et al. A subgroup of age-related macular degeneration is associated with mono-allelic sequence variants in the ABCA4 gene. Invest. Ophthalmol. Vis. Sci. 2012, 53, 2112–2118. [Google Scholar] [CrossRef]
- Guymer, R.H.; Heon, E.; Lotery, A.J.; Munier, F.L.; Schorderet, D.F.; Baird, P.N.; McNeil, R.J.; Haines, H.; Sheffield, V.C.; Stone, E.M. Variation of codons 1961 and 2177 of the Stargardt disease gene is not associated with age-related macular degeneration. Arch. Ophthalmol. 2001, 119, 745–751. [Google Scholar] [CrossRef]
- Rivera, A.; White, K.; Stohr, H.; Steiner, K.; Hemmrich, N.; Grimm, T.; Jurklies, B.; Lorenz, B.; Scholl, H.P.; Apfelstedt-Sylla, E.; et al. A comprehensive survey of sequence variation in the ABCA4 (ABCR) gene in Stargardt disease and age-related macular degeneration. Am. J. Hum. Genet. 2000, 67, 800–813. [Google Scholar] [CrossRef]
- Webster, A.R.; Heon, E.; Lotery, A.J.; Vandenburgh, K.; Casavant, T.L.; Oh, K.T.; Beck, G.; Fishman, G.A.; Lam, B.L.; Levin, A.; et al. An analysis of allelic variation in the ABCA4 gene. Invest. Ophthalmol. Vis. Sci. 2001, 42, 1179–1189. [Google Scholar]
- Fisher, S.A.; Abecasis, G.R.; Yashar, B.M.; Zareparsi, S.; Swaroop, A.; Iyengar, S.K.; Klein, B.E.; Klein, R.; Lee, K.E.; Majewski, J. Meta-analysis of genome scans of age-related macular degeneration. Hum. Mol. Genet. 2005, 14, 2257–2264. [Google Scholar] [CrossRef]
- dbSNP. Available online: http://www.ncbi.nlm.nih.gov/SNP/ (accessed on 7 March 2014).
- Thorisson, G.A.; Stein, L.D. The SNP Consortium website: Past, present and future. Nucleic Acids Res. 2003, 31, 124–127. [Google Scholar] [CrossRef]
- Klein, R.J.; Zeiss, C.; Chew, E.Y.; Tsai, J.Y.; Sackler, R.S.; Haynes, C.; Henning, A.K.; SanGiovanni, J.P.; Mane, S.M.; Mayne, S.T.; et al. Complement factor H polymorphism in age-related macular degeneration. Science 2005, 308, 385–389. [Google Scholar] [CrossRef]
- Haines, J.L.; Hauser, M.A.; Schmidt, S.; Scott, W.K.; Olson, L.M.; Gallins, P.; Spencer, K.L.; Kwan, S.Y.; Noureddine, M.; Gilbert, J.R.; et al. Complement factor H variant increases the risk of age-related macular degeneration. Science 2005, 308, 419–421. [Google Scholar] [CrossRef]
- Edwards, A.O.; Ritter, R., III; Abel, K.J.; Manning, A.; Panhuysen, C.; Farrer, L.A. Complement factor H polymorphism and age-related macular degeneration. Science 2005, 308, 421–424. [Google Scholar] [CrossRef]
- Hageman, G.S.; Anderson, D.H.; Johnson, L.V.; Hancox, L.S.; Taiber, A.J.; Hardisty, L.I.; Hageman, J.L.; Stockman, H.A.; Borchardt, J.D.; Gehrs, K.M.; et al. A common haplotype in the complement regulatory gene factor H (HF1/CFH) predisposes individuals to age-related macular degeneration. Proc. Natl. Acad. Sci. USA 2005, 102, 7227–7232. [Google Scholar] [CrossRef]
- Zerhouni, E. House subcommittee of labor-HHS-Education appropriations. Available online: http://legislative.csancer.gov/files/appropriations-2006-04-06.pdf (accessed on 1 March 2014).
- Welter, D.; Macarthur, J.; Morales, J.; Burdett, T.; Hall, P.; Junkins, H.; Klemm, A.; Flicek, P.; Manolio, T.; Hindorff, L.; et al. The NHGRI GWAS Catalog, a curated resource of SNP-trait associations. Nucleic Acids Res. 2014, 42, D1001–D1006. [Google Scholar] [CrossRef]
- Goate, A.; Chartier-Harlin, M.C.; Mullan, M.; Brown, J.; Crawford, F.; Fidani, L.; Giuffra, L.; Haynes, A.; Irving, N.; James, L.; et al. Segregation of a missense mutation in the amyloid precursor protein gene with familial Alzheimer’s disease. Nature 1991, 349, 704–706. [Google Scholar] [CrossRef]
- Jakobsdottir, J.; Conley, Y.P.; Weeks, D.E.; Mah, T.S.; Ferrell, R.E.; Gorin, M.B. Susceptibility genes for age-related maculopathy on chromosome 10q26 29. Am. J. Hum. Genet. 2005, 77, 389–407. [Google Scholar] [CrossRef]
- Schmidt, S.; Hauser, M.A.; Scott, W.K.; Postel, E.A.; Agarwal, A.; Gallins, P.; Wong, F.; Chen, Y.S.; Spencer, K.; Schnetz-Boutaud, N.; et al. Cigarette smoking strongly modifies the association of LOC387715 and age-related macular degeneration. Am. J. Hum. Genet. 2006, 78, 852–864. [Google Scholar] [CrossRef]
- Schwartz, S.G.; Agarwal, A.; Kovach, J.L.; Gallins, P.J.; Cade, W.; Postel, E.A.; Wang, G.; Ayala-Haedo, J.; Spencer, K.M.; Haines, J.L.; et al. The ARMS2 A69S variant and bilateral advanced age-related macular degeneration. Retina 2012, 32, 1486–1491. [Google Scholar] [CrossRef]
- Shuler, R.K., Jr.; Hauser, M.A.; Caldwell, J.; Gallins, P.; Schmidt, S.; Scott, W.K.; Agarwal, A.; Haines, J.L.; Pericak-Vance, M.A.; Postel, E.A. Neovascular age-related macular degeneration and its association with LOC387715 and complement factor H polymorphism. Arch. Ophthalmol. 2007, 125, 63–67. [Google Scholar] [CrossRef]
- Wang, G. Chromosome 10q26 locus and age-related macular degeneration: A progress update. Exp. Eye Res. 2014, 119, 1–7. [Google Scholar] [CrossRef]
- Wang, G.; Dubovy, S.R.; Kovach, J.L.; Schwartz, S.G.; Agarwal, A.; Scott, W.K.; Haines, J.L.; Pericak-Vance, M.A. Variants at chromosome 10q26 locus and the expression of HTRA1 in the retina. Exp.Eye Res. 2013, 112, 102–105. [Google Scholar] [CrossRef]
- Dewan, A.; Liu, M.; Hartman, S.; Zhang, S.S.; Liu, D.T.; Zhao, C.; Tam, P.O.; Chan, W.M.; Lam, D.S.; Snyder, M.; et al. HTRA1 promoter polymorphism in wet age-related macular degeneration. Science 2006, 314, 989–992. [Google Scholar]
- Yang, Z.; Camp, N.J.; Sun, H.; Tong, Z.; Gibbs, D.; Cameron, D.J.; Chen, H.; Zhao, Y.; Pearson, E.; Li, X.; et al. A variant of the HTRA1 gene increases susceptibility to age-related macular degeneration. Science 2006, 314, 992–993. [Google Scholar] [CrossRef]
- Hughes, A.E.; Orr, N.; Esfandiary, H.; Diaz-Torres, M.; Goodship, T.; Chakravarthy, U. A common CFH haplotype, with deletion of CFHR1 and CFHR3, is associated with lower risk of age-related macular degeneration. Nat. Genet. 2006, 38, 1173–1177. [Google Scholar] [CrossRef]
- Fritsche, L.G.; Lauer, N.; Hartmann, A.; Stippa, S.; Keilhauer, C.N.; Oppermann, M.; Pandey, M.K.; Kohl, J.; Zipfel, P.F.; Weber, B.H.; et al. An imbalance of human complement regulatory proteins CFHR1, CFHR3 and factor H influences risk for age-related macular degeneration (AMD). Hum. Mol. Genet. 2010, 19, 4694–4704. [Google Scholar] [CrossRef]
- Sawitzke, J.; Im, K.M.; Kostiha, B.; Dean, M.; Gold, B. Association assessment of copy number polymorphism and risk of age-related macular degeneration. Ophthalmology 2011, 118, 2442–2446. [Google Scholar] [CrossRef]
- Spencer, K.L.; Hauser, M.A.; Olson, L.M.; Schmidt, S.; Scott, W.K.; Gallins, P.; Agarwal, A.; Postel, E.A.; Pericak-Vance, M.A.; Haines, J.L. Protective effect of complement factor B and complement component 2 variants in age-related macular degeneration. Hum. Mol. Genet. 2007, 16, 1986–1992. [Google Scholar] [CrossRef]
- Gold, B.; Merriam, J.E.; Zernant, J.; Hancox, L.S.; Taiber, A.J.; Gehrs, K.; Cramer, K.; Neel, J.; Bergeron, J.; Barile, G.R.; et al. Variation in factor B (BF) and complement component 2 (C2) genes is associated with age-related macular degeneration. Nat. Genet. 2006, 38, 458–462. [Google Scholar] [CrossRef]
- Maller, J.B.; Fagerness, J.A.; Reynolds, R.C.; Neale, B.M.; Daly, M.J.; Seddon, J.M. Variation in complement factor 3 is associated with risk of age-related macular degeneration. Nat. Genet. 2007, 39, 1200–1201. [Google Scholar] [CrossRef]
- Spencer, K.L.; Olson, L.M.; Anderson, B.M.; Schnetz-Boutaud, N.; Scott, W.K.; Gallins, P.; Agarwal, A.; Postel, E.A.; Pericak-Vance, M.A.; Haines, J.L. C3 R102G polymorphism increases risk of age-related macular degeneration. Hum. Mol. Genet. 2008, 17, 1821–1824. [Google Scholar] [CrossRef]
- Yates, J.R.; Sepp, T.; Matharu, B.K.; Khan, J.C.; Thurlby, D.A.; Shahid, H.; Clayton, D.G.; Hayward, C.; Morgan, J.; Wright, A.F.; et al. Complement C3 variant and the risk of age-related macular degeneration. N. Engl. J. Med. 2007, 357, 553–561. [Google Scholar] [CrossRef]
- Fagerness, J.A.; Maller, J.B.; Neale, B.M.; Reynolds, R.C.; Daly, M.J.; Seddon, J.M. Variation near complement factor I is associated with risk of advanced AMD. Eur. J. Hum. Genet. 2009, 17, 100–104. [Google Scholar] [CrossRef]
- Stanton, C.M.; Yates, J.R.; den Hollander, A.I.; Seddon, J.M.; Swaroop, A.; Stambolian, D.; Fauser, S.; Hoyng, C.; Yu, Y.; Atsuhiro, K.; et al. Complement factor D in age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2011, 52, 8828–8834. [Google Scholar] [CrossRef]
- Chen, W.; Stambolian, D.; Edwards, A.O.; Branham, K.E.; Othman, M.; Jakobsdottir, J.; Tosakulwong, N.; Pericak-Vance, M.A.; Campochiaro, P.A.; Klein, M.L.; et al. Genetic variants near TIMP3 and high-density lipoprotein-associated loci influence susceptibility to age-related macular degeneration. Proc. Natl. Acad. Sci. USA 2010, 107, 7401–7406. [Google Scholar] [CrossRef]
- Fritsche, L.G.; Chen, W.; Schu, M.; Yaspan, B.L.; Yu, Y.; Thorleifsson, G.; Zack, D.J.; Arakawa, S.; Cipriani, V.; Ripke, S.; et al. Seven new loci associated with age-related macular degeneration. Nat. Genet. 2013, 45, 433–439. [Google Scholar] [CrossRef]
- Neale, B.M.; Fagerness, J.; Reynolds, R.; Sobrin, L.; Parker, M.; Raychaudhuri, S.; Tan, P.L.; Oh, E.C.; Merriam, J.E.; Souied, E.; et al. Genome-wide association study of advanced age-related macular degeneration identifies a role of the hepatic lipase gene (LIPC). Proc. Natl. Acad. Sci. USA 2010, 107, 7395–7400. [Google Scholar] [CrossRef]
- Helgason, H.; Sulem, P.; Duvvari, M.R.; Luo, H.; Thorleifsson, G.; Stefansson, H.; Jonsdottir, I.; Masson, G.; Gudbjartsson, D.F.; Walters, G.B.; et al. A rare nonsynonymous sequence variant in C3 is associated with high risk of age-related macular degeneration. Nat. Genet. 2013, 45, 1371–1374. [Google Scholar] [CrossRef]
- Ryu, E.; Fridley, B.L.; Tosakulwong, N.; Bailey, K.R.; Edwards, A.O. Genome-wide association analyses of genetic, phenotypic, and environmental risks in the age-related eye disease study. Mol. Vis. 2010, 16, 2811–2821. [Google Scholar]
- Scheetz, T.E.; Fingert, J.H.; Wang, K.; Kuehn, M.H.; Knudtson, K.L.; Alward, W.L.; Boldt, H.C.; Russell, S.R.; Folk, J.C.; Casavant, T.L. A genome-wide association study for primary open angle glaucoma and macular degeneration reveals novel Loci. PLoS One 2013, 8, e58657. [Google Scholar] [CrossRef]
- Manolio, T.A.; Collins, F.S.; Cox, N.J.; Goldstein, D.B.; Hindorff, L.A.; Hunter, D.J.; McCarthy, M.I.; Ramos, E.M.; Cardon, L.R.; Chakravarti, A.; et al. Finding the missing heritability of complex diseases. Nature 2009, 461, 747–753. [Google Scholar] [CrossRef]
- Li, Y.; Willer, C.; Sanna, S.; Abecasis, G. Genotype imputation. Annu. Rev. Genomics Hum. Genet. 2009, 10, 387–406. [Google Scholar] [CrossRef]
- Marchini, J.; Howie, B. Genotype imputation for genome-wide association studies. Nat. Rev. Genet. 2010, 11, 499–511. [Google Scholar] [CrossRef]
- Seddon, J.M.; Yu, Y.; Miller, E.C.; Reynolds, R.; Tan, P.L.; Gowrisankar, S.; Goldstein, J.I.; Triebwasser, M.; Anderson, H.E.; Zerbib, J.; et al. Rare variants in CFI, C3 and C9 are associated with high risk of advanced age-related macular degeneration. Nat. Genet. 2013, 45, 1366–1370. [Google Scholar] [CrossRef]
- Yaspan, B.L.; Bush, W.S.; Torstenson, E.S.; Ma, D.; Pericak-Vance, M.A.; Ritchie, M.D.; Sutcliffe, J.S.; Haines, J.L. Genetic analysis of biological pathway data through genomic randomization. Hum. Genet. 2011, 129, 563–571. [Google Scholar] [CrossRef]
- Lee, P.H.; O’Dushlaine, C.; Thomas, B.; Purcell, S.M. INRICH: Interval-based enrichment analysis for genome-wide association studies. Bioinformatics 2012, 28, 1797–1799. [Google Scholar] [CrossRef]
- Yang, J.; Li, Y.; Chan, L.; Tsai, Y.T.; Wu, W.H.; Nguyen, H.V.; Hsu, C.W.; Li, X.; Brown, L.M.; Egli, D.; et al. Validation of genome-wide association study (GWAS)-identified disease risk alleles with patient-specific stem cell lines. Hum. Mol. Genet. 2014, 23, 3445–3455. [Google Scholar] [CrossRef]
- Van Lookeren, C.M.; Le Couter, J.; Yaspan, B.L.; Ye, W. Mechanisms of age-related macular degeneration and therapeutic opportunities. J. Pathol. 2014, 232, 151–164. [Google Scholar] [CrossRef]
- Herrup, K. Reimagining Alzheimer’s disease—An age-based hypothesis. J. Neurosci. 2010, 30, 16755–16762. [Google Scholar] [CrossRef]
- Querfurth, H.W.; LaFerla, F.M. Alzheimer’s disease. N. Engl. J. Med. 2010, 362, 329–344. [Google Scholar] [CrossRef]
- Breitner, J.C.; Folstein, M.F. Familial Alzheimer Dementia: A prevalent disorder with specific clinical features. Psychol. Med. 1984, 14, 63–80. [Google Scholar] [CrossRef]
- Breitner, J.C.; Folstein, M.F. Familial nature of Alzheimer’s disease. N. Engl. J. Med. 1984, 311, 192. [Google Scholar]
- Folstein, M. Alzheimer’s disease: Challenge to psychiatry. Hosp. Community Psychiatry 1984, 35, 111. [Google Scholar]
- Pericak-Vance, M.A.; Haines, J.L. Genetic susceptibility to Alzheimer disease. Trends Genet. 1995, 11, 504–508. [Google Scholar] [CrossRef]
- Powell, D.; Folstein, M.F. Pedigree study of familial Alzheimer disease. J. Neurogenet. 1984, 1, 189–197. [Google Scholar] [CrossRef]
- St George-Hyslop, P.H.; Tanzi, R.E.; Polinsky, R.J.; Haines, J.L.; Nee, L.; Watkins, P.C.; Myers, R.H.; Feldman, R.G.; Pollen, D.; Drachman, D.; et al. The genetic defect causing familial Alzheimer’s disease maps on chromosome 21. Science 1987, 235, 885–890. [Google Scholar]
- Levy-Lahad, E.; Lahad, A.; Wijsman, E.M.; Bird, T.D.; Schellenberg, G.D. Apolipoprotein E genotypes and age of onset in early-onset familial Alzheimer’s disease. Ann. Neurol. 1995, 38, 678–680. [Google Scholar] [CrossRef]
- Levy-Lahad, E.; Wasco, W.; Poorkaj, P.; Romano, D.M.; Oshima, J.; Pettingell, W.H.; Yu, C.E.; Jondro, P.D.; Schmidt, S.D.; Wang, K.; et al. Candidate gene for the chromosome 1 familial Alzheimer’s disease locus. Science 1995, 269, 973–977. [Google Scholar] [CrossRef]
- Levy-Lahad, E.; Wijsman, E.M.; Nemens, E.; Anderson, L.; Goddard, K.A.; Weber, J.L.; Bird, T.D.; Schellenberg, G.D. A familial Alzheimer’s disease locus on chromosome 1. Science 1995, 269, 970–973. [Google Scholar] [CrossRef]
- Sherrington, R.; Rogaev, E.I.; Liang, Y.; Rogaeva, E.A.; Levesque, G.; Ikeda, M.; Chi, H.; Lin, C.; Li, G.; Holman, K.; et al. Cloning of a gene bearing missense mutations in early-onset familial Alzheimer’s disease. Nature 1995, 375, 754–760. [Google Scholar] [CrossRef]
- St George-Hyslop, P.; Haines, J.; Rogaev, E.; Mortilla, M.; Vaula, G.; Pericak-Vance, M.; Foncin, J.F.; Montesi, M.; Bruni, A.; Sorbi, S.; et al. Genetic evidence for a novel familial Alzheimer’s disease locus on chromosome 14. Nat. Genet. 1992, 2, 330–334. [Google Scholar] [CrossRef]
- Ridge, P.G.; Mukherjee, S.; Crane, P.K.; Kauwe, J.S. Alzheimer’s disease: Analyzing the missing heritability. PLoS One 2013, 8, e79771. [Google Scholar]
- Pericak-Vance, M.A.; Bebout, J.L.; Gaskell, P.C., Jr.; Yamaoka, L.H.; Hung, W.Y.; Alberts, M.J.; Walker, A.P.; Bartlett, R.J.; Haynes, C.A.; Welsh, K.A.; et al. Linkage studies in familial Alzheimer disease: Evidence for chromosome 19 linkage. Am. J. Hum. Genet. 1991, 48, 1034–1050. [Google Scholar]
- Pericak-Vance, M.A.; Yamaoka, L.H.; Haynes, C.S.; Speer, M.C.; Haines, J.L.; Gaskell, P.C.; Hung, W.Y.; Clark, C.M.; Heyman, A.L.; Trofatter, J.A.; et al. Genetic linkage studies in Alzheimer’s disease families. Exp. Neurol. 1988, 102, 271–279. [Google Scholar] [CrossRef]
- Corder, E.H.; Saunders, A.M.; Strittmatter, W.J.; Schmechel, D.E.; Gaskell, P.C.; Small, G.W.; Roses, A.D.; Haines, J.L.; Pericak-Vance, M.A. Gene dose of apolipoprotein E type 4 allele and the risk of Alzheimer’s disease in late onset families. Science 1993, 261, 921–923. [Google Scholar]
- Corder, E.H.; Saunders, A.M.; Risch, N.J.; Strittmatter, W.J.; Schmechel, D.E.; Gaskell, P.C., Jr.; Rimmler, J.B.; Locke, P.A.; Conneally, P.M.; Schmader, K.E.; et al. Protective effect of apolipoprotein E type 2 allele for late onset Alzheimer disease. Nat. Genet. 1994, 7, 180–184. [Google Scholar] [CrossRef]
- Beecham, G.W.; Martin, E.R.; Li, Y.J.; Slifer, M.A.; Gilbert, J.R.; Haines, J.L.; Pericak-Vance, M.A. Genome-wide association study implicates a chromosome 12 risk locus for late-onset Alzheimer disease. Am. J. Hum. Genet. 2009, 84, 35–43. [Google Scholar] [CrossRef]
- Coon, K.D.; Myers, A.J.; Craig, D.W.; Webster, J.A.; Pearson, J.V.; Lince, D.H.; Zismann, V.L.; Beach, T.G.; Leung, D.; Bryden, L.; et al. A high-density whole-genome association study reveals that APOE is the major susceptibility gene for sporadic late-onset Alzheimer’s disease. J. Clin. Psychiatry. 2007, 68, 613–618. [Google Scholar] [CrossRef]
- Li, H.; Wetten, S.; Li, L.; St Jean, P.L.; Upmanyu, R.; Surh, L.; Hosford, D.; Barnes, M.R.; Briley, J.D.; Borrie, M.; et al. Candidate single-nucleotide polymorphisms from a genomewide association study of Alzheimer disease. Arch. Neurol. 2008, 65, 45–53. [Google Scholar]
- Lambert, J.C.; Ibrahim-Verbaas, C.A.; Harold, D.; Naj, A.C.; Sims, R.; Bellenguez, C.; Jun, G.; Destefano, A.L.; Bis, J.C.; Beecham, G.W.; et al. Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimer’s disease. Nat. Genet. 2013, 45, 1452–1458. [Google Scholar] [CrossRef]
- Naj, A.C.; Jun, G.; Beecham, G.W.; Wang, L.S.; Vardarajan, B.N.; Buros, J.; Gallins, P.J.; Buxbaum, J.D.; Jarvik, G.P.; Crane, P.K.; et al. Common variants at MS4A4/MS4A6E, CD2AP, CD33 and EPHA1 are associated with late-onset Alzheimer’s disease. Nat. Genet. 2011, 43, 436–441. [Google Scholar] [CrossRef]
- Seshadri, S.; Fitzpatrick, A.L.; Ikram, M.A.; Destefano, A.L.; Gudnason, V.; Boada, M.; Bis, J.C.; Smith, A.V.; Carassquillo, M.M.; Lambert, J.C.; et al. Genome-wide analysis of genetic loci associated with Alzheimer disease. JAMA 2010, 303, 1832–1840. [Google Scholar] [CrossRef]
- Gourraud, P.A.; Sdika, M.; Khankhanian, P.; Henry, R.G.; Beheshtian, A.; Matthews, P.M.; Hauser, S.L.; Oksenberg, J.R.; Pelletier, D.; Baranzini, S.E. A genome-wide association study of brain lesion distribution in multiple sclerosis. Brain 2013, 136, 1012–1024. [Google Scholar] [CrossRef]
- Hauser, S.L.; Chan, J.R.; Oksenberg, J.R. Multiple sclerosis: Prospects and promise. Ann. Neurol. 2013, 74, 317–327. [Google Scholar]
- Nylander, A.; Hafler, D.A. Multiple sclerosis. J. Clin. Invest. 2012, 122, 1180–1188. [Google Scholar] [CrossRef]
- Oksenberg, J.R. Decoding multiple sclerosis: An update on genomics and future directions. Expert. Rev. Neurother. 2013, 13, 11–19. [Google Scholar] [CrossRef]
- Compston, A.; Coles, A. Multiple sclerosis. Lancet 2002, 359, 1221–1231. [Google Scholar] [CrossRef]
- Sadovnick, A.D.; Ebers, G.C. Epidemiology of multiple sclerosis: A critical overview. Can. J. Neurol. Sci. 1993, 20, 17–29. [Google Scholar]
- Sawcer, S.; Compston, A. Multiple sclerosis: Light at the end of the tunnel. Eur. J. Hum. Genet. 2006, 14, 257–258. [Google Scholar] [CrossRef]
- Compston, A.; Sawcer, S. Genetic analysis of multiple sclerosis. Curr. Neurol. Neurosci. Rep. 2002, 2, 259–266. [Google Scholar] [CrossRef]
- Sadovnick, A.D. Familial recurrence risks and inheritance of multiple sclerosis. Curr. Opin. Neurol. Neurosurg. 1993, 6, 189–194. [Google Scholar]
- Sadovnick, A.D.; Armstrong, H.; Rice, G.P.; Bulman, D.; Hashimoto, L.; Paty, D.W.; Hashimoto, S.A.; Warren, S.; Hader, W.; Murray, T.J.; et al. A population-based study of multiple sclerosis in twins: Update. Ann. Neurol. 1993, 33, 281–285. [Google Scholar]
- Sadovnick, A.D.; Yee, I.M.; Guimond, C.; Reis, J.; Dyment, D.A.; Ebers, G.C. Age of onset in concordant twins and other relative pairs with multiple sclerosis. Am. J. Epidemiol. 2009, 170, 289–296. [Google Scholar] [CrossRef]
- Sawcer, S.; Ban, M.; Maranian, M.; Yeo, T.W.; Compston, A.; Kirby, A.; Daly, M.J.; de Jager, P.L.; Walsh, E.; Lander, E.S.; et al. A high-density screen for linkage in multiple sclerosis. Am. J. Hum. Genet. 2005, 77, 454–467. [Google Scholar] [CrossRef]
- Haines, J.L.; Ter-Minassian, M.; Bazyk, A.; Gusella, J.F.; Kim, D.J.; Terwedow, H.; Pericak-Vance, M.A.; Rimmler, J.B.; Haynes, C.S.; Roses, A.D.; et al. A complete genomic screen for multiple sclerosis underscores a role for the major histocompatability complex. The Multiple Sclerosis Genetics Group. Nat. Genet. 1996, 13, 469–471. [Google Scholar] [CrossRef]
- Ebers, G.C.; Kukay, K.; Bulman, D.E.; Sadovnick, A.D.; Rice, G.; Anderson, C.; Armstrong, H.; Cousin, K.; Bell, R.B.; Hader, W.; et al. A full genome search in multiple sclerosis. Nat. Genet. 1996, 13, 472–476. [Google Scholar] [CrossRef]
- Haines, J.L.; Bradford, Y.; Garcia, M.E.; Reed, A.D.; Neumeister, E.; Pericak-Vance, M.A.; Rimmler, J.B.; Menold, M.M.; Martin, E.R.; Oksenberg, J.R.; et al. Multiple susceptibility loci for multiple sclerosis. Hum. Mol. Genet. 2002, 11, 2251–2256. [Google Scholar] [CrossRef]
- Haines, J.L.; Terwedow, H.A.; Burgess, K.; Pericak-Vance, M.A.; Rimmler, J.B.; Martin, E.R.; Oksenberg, J.R.; Lincoln, R.; Zhang, D.Y.; Banatao, D.R.; et al. Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group. Hum. Mol. Genet. 1998, 7, 1229–1234. [Google Scholar] [CrossRef]
- Kenealy, S.J.; Herrel, L.A.; Bradford, Y.; Schnetz-Boutaud, N.; Oksenberg, J.R.; Hauser, S.L.; Barcellos, L.F.; Schmidt, S.; Gregory, S.G.; Pericak-Vance, M.A.; et al. Examination of seven candidate regions for multiple sclerosis: Strong evidence of linkage to chromosome 1q44. Genes Immun. 2006, 7, 73–76. [Google Scholar]
- McCauley, J.L.; Zuvich, R.L.; Bradford, Y.; Kenealy, S.J.; Schnetz-Boutaud, N.; Gregory, S.G.; Hauser, S.L.; Oksenberg, J.R.; Mortlock, D.P.; Pericak-Vance, M.A.; et al. Follow-up examination of linkage and association to chromosome 1q43 in multiple sclerosis. Genes Immun. 2009, 10, 624–630. [Google Scholar] [CrossRef]
- Pericak-Vance, M.A.; Rimmler, J.B.; Martin, E.R.; Haines, J.L.; Garcia, M.E.; Oksenberg, J.R.; Barcellos, L.F.; Lincoln, R.; Goodkin, D.E.; Hauser, S.L. Linkage and association analysis of chromosome 19q13 in multiple sclerosis. Neurogenetics 2001, 3, 195–201. [Google Scholar] [CrossRef]
- Gregory, S.G.; Schmidt, S.; Seth, P.; Oksenberg, J.R.; Hart, J.; Prokop, A.; Caillier, S.J.; Ban, M.; Goris, A.; Barcellos, L.F.; et al. Interleukin 7 receptor alpha chain (IL7R) shows allelic and functional association with multiple sclerosis. Nat. Genet. 2007, 39, 1083–1091. [Google Scholar] [CrossRef]
- Hafler, D.A.; Compston, A.; Sawcer, S.; Lander, E.S.; Daly, M.J.; de Jager, P.L.; de Bakker, P.I.; Gabriel, S.B.; Mirel, D.B.; Ivinson, A.J.; et al. Risk alleles for multiple sclerosis identified by a genomewide study. N. Engl. J. Med. 2007, 357, 851–862. [Google Scholar] [CrossRef]
- Beecham, A.H.; Patsopoulos, N.A.; Xifara, D.K.; Davis, M.F.; Kemppinen, A.; Cotsapas, C.; Shah, T.S.; Spencer, C.; Booth, D.; Goris, A.; et al. Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis. Nat. Genet. 2013, 45, 1353–1360. [Google Scholar] [CrossRef]
- Damotte, V.; Guillot-Noel, L.; Patsopoulos, N.A.; Madireddy, L.; El, B.M.; Ban, M.; Baranzini, S.; Barcellos, L.; Beecham, G.; Beecham, A.; et al. A gene pathway analysis highlights the role of cellular adhesion molecules in multiple sclerosis susceptibility. Genes Immun. 2014, 15, 126–132. [Google Scholar] [CrossRef]
- Yan, J.; Greer, J.M. NF-kappa B, a potential therapeutic target for the treatment of multiple sclerosis. CNSNeurol. Disord. Drug Targets 2008, 7, 536–557. [Google Scholar]
- Metacore. Available online: http://thomsonreuters.com/metacore/ (accessed on 7 March 2014).
- Cytoscape. Available online: http://www.cytoscape.org/ (accessed on 7 March 2014).
- Ratnapriya, R.; Chew, E.Y. Age-related macular degeneration-clinical review and genetics update. Clin. Genet. 2013, 84, 160–166. [Google Scholar] [CrossRef]
- ESP. Available online: https://esp.gs.washington.edu/drupal/ (accessed on 7 March 2014).
- 1000Genomes. Available online: http://www.1000genomes.org/ (accessed on 7 March 2014).
- ENCODE. Available online: https://genome.ucsc.edu/ENCODE/ (accessed on 7 March 2014).
- International HapMap Consortium. A haplotype map of the human genome. Nature 2005, 437, 1299–1320. [Google Scholar] [CrossRef]
- HapMap. Available online: http://hapmap.ncbi.nlm.nih.gov/ (accessed on 7 March 2014).
© 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).