Search Results (1,904)

Leigh syndrome is a rare, progressive mitochondrial disorder of childhood. Early diagnosis is often challenging due to nonspecific clinical manifestations. We report a 1-month-old male infant initially referred for suspected congenital muscular torticollis who ultimately received a diagnosis of Leigh syndrome. Despite unremarkable perinatal history, he subsequently developed persistent feeding difficulties, recurrent vomiting, failure to thrive, and global developmental delay. Early neurological assessment revealed poor repertoire patterns on General Movement Assessment. The Neonatal Oral-Motor Assessment Scale (NOMAS) demonstrated dysfunctional oral-motor control, whereas the video fluoroscopic swallowing study (VFSS) revealed aspiration during swallowing. Brain MRI revealed symmetric basal ganglia lesions. Expanded whole-exome sequencing identified a pathogenic MT-ATP6 m.8993T>G variant with high heteroplasmy level (>90% in blood), confirming the diagnosis of Leigh syndrome. The variant was maternally inherited, although neither the mother nor the older sibling exhibited clinical features of mitochondrial disease. Leigh syndrome can initially manifest with subtle systemic features rather than overt neurological features. Persistent feeding difficulties and growth delay in infancy warrant thorough evaluation, including neuroimaging and comprehensive genomic testing, to enable timely diagnosis and optimize clinical management. Full article

Background: Mullegama–Klein–Martinez syndrome (MKMS; OMIM #301022) is an X-linked cohesinopathy caused by pathogenic variants in STAG2, which encodes a subunit of the cohesin complex responsible for chromosomal segregation and transcriptional regulation. Individuals typically present with developmental delay, microcephaly, dysmorphic features, and variable congenital anomalies, though complex cardiac malformations are uncommon. Case Presentation: We report a female infant presenting on the first day of life with complex congenital heart disease, including pulmonary atresia, double-outlet right ventricle, large subaortic ventricular septal defect, and patent ductus arteriosus. She exhibited intrauterine growth restriction, mild craniofacial dysmorphism, and left upper-extremity hypotonia. Stepwise genetic evaluation revealed a de novo likely pathogenic STAG2 frameshift variant, c.2972_2975dup (p.His992Glnfs*11), identified by rapid trio whole-exome sequencing. This variant truncates the C-terminal domain critical for cohesin binding. A 3D structural model generated by SWISS-MODEL demonstrated disruption of β-strand and loop conformations within this domain, consistent with loss of cohesin complex stability. Conclusions: This case expands the phenotypic spectrum of STAG2-related MKM and highlights the role of STAG2 in cardiac development. Recognition of such presentations supports the inclusion of STAG2 in the differential diagnosis for complex congenital heart disease and underscores the diagnostic utility of rapid trio exome sequencing in neonatal care. The utility of 3D protein modeling to illustrate structural consequences of truncating variants provides valuable insight into variant pathogenicity and supports precision diagnosis in cohesinopathies. Full article

Background/Objectives: Family history is a known risk factor for multiple myeloma (MM) and its precursor condition, monoclonal gammopathy of undetermined significance (MGUS). Previous genome-wide association studies (GWASs) have identified 35 common loci associated with MM risk and 21 associated with MGUS. The objective of this study was to identify less common and rare genetic loci predisposing to MM/MGUS through whole-exome sequencing (WES)-based linkage analysis. Methods:Multipoint linkage analysis was conducted using the Multipoint Engine for Rapid Likelihood Inference (MERLIN) with the Lander–Green algorithm on germline WES data from 79 pedigrees with 2 or more affected relatives (120 MM, 86 MGUS, and 21 unaffected). Genome-wide linkage was evaluated using 12,946 independent single-nucleotide variants (linkage disequilibrium r² < 0.05). Results: Significant linkage was observed at chromosome 6q22.33–q24.2 by the non-parametric model (logarithm-of-odds (LOD) = 3.3) and suggestive linkage by the dominant parametric model (heterogeneity LOD (HLOD) = 2.5). Fourteen rare variants within this region were prioritized using family-specific partial LOD scores and in silico functional prediction tools. Nine of these variants, REPS1, THEMIS, TAAR6, AHI1, VNN1, VNN3, MTFR2/FAM54A, LAMA2, and PHACTR2, overlapped immune-regulatory regions in blood cell lines and were not previously identified in GWASs. Conclusions: This study demonstrates the utility of applying a linkage analysis framework to familial WES data for identifying genomic regions and candidate genes that may contribute to MM/MGUS predisposition. These findings provide new insight into the inherited risk and etiology of familial MM and MGUS. Full article

Background: Genetic variants in Pre-B cell Leukemia Factor 1 (PBX1) transcription factor (TF) have been associated with Congenital Anomalies of the Kidney and Urinary Tract (CAKUT). This study aims to functionally characterize a novel missense variant in a 4-year-old patient presenting with horseshoe kidney with preserved function, in the absence of a positive familial history. Methods: Clinical exome sequencing was performed on a 4-year-old child, followed by Sanger sequencing and family segregation studies to validate the identified variant. Functional assays to study the protein expression, molecular interactions and localization were then performed. Results: Genetic analysis identified a novel de novo variant [c.712C>T, p.(Arg238Trp), NM_002585.3], mapping in the first nuclear localization signal (NLS) of PBX1. When introduced in HEK293T cells, PBX1^c.712C>T did not affect protein expression, which was comparable to the wild-type (WT) counterpart. Similar results were obtained when modeling a missense variant [c.863G>A; p.(Arg288Gln)], located in the second NLS of the protein, previously reported in the literature but never functionally characterized. As a TF, PBX1 may work in association with MEIS and PKNOX1/2 cofactors, but none of the two variants modified the interactions with its cofactor PKNOX1. However, both variants significantly affected the nuclear localization of PBX1, increasing its retention in the cytoplasm while limiting its availability in the nucleus. Conclusions: In conclusion, we identified a novel de novo heterozygous missense variant in PBX1 that impairs nuclear localization of the protein, potentially limiting its role as a TF and possibly explaining the clinical phenotype of the patient. Full article

Background: Intellectual disability (ID) is a heterogeneous condition caused by diverse genetic factors, including single-nucleotide variants (SNVs) and copy number variants (CNVs). Whole-exome sequencing (WES) and clinical exome sequencing (CES) have become essential tools for identifying pathogenic variants; however, their relative diagnostic performance in ID has not been fully characterized. Methods: Children diagnosed with ID or related neurodevelopmental disorders underwent WES or CES. Identified variants were classified according to ACMG/AMP and ClinGen guidelines, with segregation analysis performed when parental samples were available. Diagnostic yields were compared across demographic, prenatal, and phenotypic subgroups. A multidimensional semi-quantitative scoring system encompassing 15 clinical domains (e.g., age at onset, neuro-motor function, seizures, MRI findings, vision, and dysmorphic features) was developed. Z-scores were calculated for each parameter, followed by hierarchical cluster analysis (HCA) and correlation modeling to define genotype–phenotype associations and pathway-level clustering. Results: A broad spectrum of pathogenic and likely pathogenic variants across multiple genes and biological pathways was identified in our study. CNV-associated cases frequently exhibited prenatal anomalies or multisystem phenotypes associated with large chromosomal rearrangements. Monogenic variants and their corresponding phenotypic profiles were identified through clinical exome sequencing (CES) and whole-exome sequencing (WES). Phenotypic HCA based on Z-scores revealed three major biological groups of patients with coherent genotype–phenotype relationships: Group 1, severe multisystem neurodevelopmental disorders dominated by transcriptional and RNA-processing genes (POLR1C, TCF4, HNRNPU, NIPBL, ACTG1); Group 2, intermediate epileptic and metabolic forms associated with ion-channel and excitability-related genes (SCN2A, PAH, IQSEC2, GNPAT); and Group 3, milder or focal neurodevelopmental phenotypes involving myelination and signaling-related genes (NKX6-2, PLP1, PGAP3, SMAD6, ATP1A3). Gene distribution significantly differed among these biological categories (χ² = 54.566, df = 34, p = 0.0141), confirming non-random, biologically consistent grouping. Higher Z-scores correlated with earlier onset and greater neurological severity, underscoring the clinical relevance of the multidimensional analytical framework. Conclusions: This study highlights the genetic complexity and clinical heterogeneity of intellectual disability and demonstrates the superior diagnostic resolution of WES and CES. Integrating multidimensional phenotypic profiling with genomic analysis enhances genotype–phenotype integration and enables data-driven phenotype stratification and pathway-based re-analysis. This combined diagnostic and analytical framework offers a more comprehensive approach to diagnosing monogenic ID and provides a foundation for future predictive and functional studies. Full article

Background: Pyridoxine-dependent epilepsy (PDE) is a rare disorder characterized by seizures resistant to conventional treatments but responsive to pyridoxine therapy. Typically caused by biallelic variants in ALDH7A1, PNPO, or PLPBP, a few patients present a similar clinical phenotype but without confirmed molecular diagnoses. We report a child with a 13-year PDE diagnosis and normal intellectual development, whose seizures recurred after pyridoxine withdrawal but resolved with reintroduction, despite unremarkable whole-exome sequencing results. Methods: Following negative results from WES, optical genome mapping (OGM) and whole-genome sequencing (WGS) were performed to highlight any potential structural variants involving known PDE-associated genes. Results: OGM and WGS revealed a recurrent 16p11.2 BP4-5 duplication, inherited from his healthy father, along with a de novo chromothripsis-type unbalanced t(1;18)(p22.3;q12.3), affecting several genes not currently associated with epilepsy (RIT2, PIK3C3, COL24A1, LRRC8D, DIPK1A, and DPYD), with RIT2 being a plausible candidate for the neurological phenotype due to its neuron-specific expression along with a likely reshuffling of topologically associating domains (TADs) involving SYT4, an epilepsy-candidate gene. Discussion: While the molecular data do not pinpoint a single gene or locus as the cause of seizures in this case, a key aspect of our patient’s phenotype is true pyridoxine dependence, rather than just pyridoxine responsiveness. We propose that the genomic complexity associated with the chromothriptic t(1;18) and the 16p11.2 BP4-5 duplication may create a unique metabolic environment in which pyridoxine-dependent pathways are disrupted through unconventional mechanisms. The preservation of cognitive function in our case has been observed in small groups of PDE patients, especially those diagnosed and treated early. This may indicate a distinct phenotypic subgroup that warrants further genetic investigation. Full article

Weaver syndrome is a rare congenital overgrowth disorder caused by pathogenic EZH2 variants. This study reports a novel EZH2 variant associated with atypical manifestations, including severe bilateral camptodactyly and complex brain malformations. A 4-year-old Taiwanese female exhibited classical Weaver syndrome features including macrosomia, macrocephaly, hypertelorism, and developmental delay, plus atypical findings of severe bilateral camptodactyly and complex brain malformations. Neuroimaging revealed corpus callosum dysgenesis with rostral agenesis and genu hypoplasia, bilateral frontal lobe hypoplasia, and an arachnoid cyst. The patient demonstrated global developmental delay with marked motor impairment but less severely affected speech and cognition, consistent with mild intellectual disability. Whole-exome sequencing identified a novel de novo pathogenic variant in EZH2: c.449T>C (p.Ile150Thr), affecting a highly conserved amino acid within the SANT domain. This case broadens the clinical spectrum of Weaver syndrome by highlighting severe camptodactyly and complex brain malformations as possible EZH2-related manifestations. The corpus callosum dysgenesis suggests a wider role of EZH2 in neurodevelopment than previously recognized. The novel SANT domain variant may explain the severe phenotypic presentation. The novel EZH2 variant c.449T>C (p.Ile150Thr) expands the molecular and phenotypic spectrum of Weaver syndrome. These findings underscore the importance of comprehensive neuroimaging and molecular genetic testing in suspected cases, particularly atypical presentations. Full article

Background: Multiple Sclerosis (MS) is a chronic, autoimmune, multifactorial, and complex disorder of the central nervous system (CNS), affecting more than 2 million individuals globally. Genome-wide association studies (GWAS) have explained only a small fraction of its high heritability, highlighting the need for alternative approaches to identify rare genetic variants that contribute to its etiology. To address this, we performed whole-exome sequencing (WES) in a multi-affected family. Methods: WES was performed in a MS multigenerational family comprising two affected sisters, their two healthy brothers, and one affected son. Results: Bioinformatics analysis identified 47 co-segregating rare variants. Three missense variants in genes involved in inflammation, autoimmunity, and demyelinization were identified as the most promising candidates: c.443 C>T, p.Pro148Leu in the RTN4 gene, c.1678 T>G, p.Phe560Val in the JAK2 gene, and c.3449 A>G, p.Tyr1150Cys in the DUOX2 gene. Protein modeling and in silico tools suggest that the three selected variants may have a significant impact on protein function. Conclusions: We identified novel candidate genes for MS in a multiplex family, providing evidence for an oligogenic model of disease susceptibility. Further replication and functional studies are required to validate these preliminary results. Full article

Background: Inherited retinal dystrophies (IRDs) include a clinically and genetically diverse array of conditions resulting in progressive visual impairment. The PROM1 gene is crucial for the development and maintenance of photoreceptors. Variants in PROM1 are linked to a wide phenotypic spectra of IRDs; however, the correlation between genotype and phenotype is not fully elucidated. Comprehending these relationships is essential for enhanced diagnostic precision, patient guidance, and formulation of focused treatments. Objective: This study aims to examine the genotype–phenotype associations in patients with PROM1-associated IRDs. Clinical variability and inheritance patterns linked to different pathogenic variants are examined, aiming to clarify their different behaviors. Methods: We performed a retrospective investigation of patients identified as affected by PROM1-related IRDs. Thorough ophthalmologic assessments, including retinography, fundus autofluorescence, optical coherence tomography (OCT), and electrodiagnostic testing (EDT), were conducted. Genetic testing was performed via targeted gene panels or whole-exome sequencing. Variants were categorized based on ACMG criteria, and inheritance patterns were determined by familial segregation analysis. Clinical characteristics were analyzed among genotypic groups to ascertain potential phenotype–genotype relationships. Results: All patients had pathogenic or likely pathogenic PROM1 mutations. Both autosomal dominant and autosomal recessive inheritance patterns were identified. Dominant pathogenic variants were predominantly linked to late-onset cone-rod dystrophy or macular dystrophy, whereas biallelic variants frequently resulted in early-onset severe rod–cone dystrophy characterized by fast vision deterioration. A group of patients with the same genotypes displayed significant phenotypic variability, indicating the potential impact of modifier genes or environmental influences. Truncating mutations in the N-terminal region were significantly associated with earlier illness onset and greater functional impairment. Conclusions: PROM1-related IRDs demonstrated significant clinical and genetic heterogeneity, with the route of inheritance and type of variant affecting disease severity and progression. Our findings underscore the significance of thorough genotypic and phenotypic characterization in afflicted individuals. A deeper comprehension of PROM1-related IRD disease pathways can enhance prognosis, direct clinical care, and facilitate the advancement of genotype-based therapy strategies. Full article

Nephrotic syndrome (NS) is a common type of kidney disease in children, marked by protein loss in urine, swelling, and low blood protein levels. It is more severe and prevalent in children of African descent, particularly in steroid-resistant forms. Many cases are primary and linked to mutations in genes such as NPHS1, NPHS2, and WT1. While whole-exome sequencing (WES) has advanced the identification of genetic causes globally, its application in African settings remains limited, leaving many cases undiagnosed. This review explores the potential of WES in improving NS diagnosis among African paediatric populations. A literature search was conducted using PubMed, Scopus, and Medline for studies published between 2015 and 2025 focusing on the application of WES in paediatric NS among individuals of African descent. From the 12 articles retrieved, three met the inclusion criteria. These publications reported variants in NPHS1, NPHS2, WT1, PLCE1, COL4A3, COL4A5, TRPC6, and LAMB2 among South African and Egyptian cohorts. WES remains underutilised in African NS research, hindered by limited resources, cost, and underrepresentation in genomic databases. Nonetheless, preliminary evidence suggests WES may contribute to improving diagnosis and guiding treatment through the identification of population-specific pathogenic variants. Increased investment in genomic infrastructure is important for maximising potential benefits and improving diagnostic capabilities. Full article

Background/Objectives: Immune checkpoint inhibitors (ICIs) are frontline treatment for advanced Merkel Cell Carcinoma (MCC), regardless of viral status. Frontline ICIs provide durable benefit to only half of patients, highlighting a need for alternative therapies. In this study, the objective is to leverage whole exome sequencing (WES) and transcriptome sequencing (WTS) to distinguish genomic alterations associated with ICI response. Investigate differential genomic alterations between virus-positive (VP) and virus-negative (VN)-MCC to identify novel therapeutic targets. Methods: A total of 95 MCC cases underwent WES and WTS. Utilizing computational pipelines applied to WES, we identified viral status and tumor mutational burden (TMB). RNA-seq data was used to characterize the immune microenvironment. Results: Of 95 MCC cases, 57 (60%) were VP-MCC and 38 (40%) were VN-MCC. Median TMB was higher in VN-MCC (27.5 vs. 1 Muts/Mb). Mutations in TP53, RB1, NOTCH1, KMTD2, KMT2C, and PIK3CA were primarily found in VN-MCC. MAPK Pathway Activity Score, NK cell infiltration, and the immune checkpoint gene CD276 in VN-MCC tumors were upregulated. No overall survival (OS) difference was identified between VP and VN-MCC, even after ICIs. Conclusions: MCC oncogenesis and treatment response transcend viral status. While mutational analysis confirms previous findings, assessment of the transcriptome and tumor microenvironment suggests alternate therapeutic targets. Full article

Somatic variant calling is a critical step in cancer genome analysis, but the performance of available tools can vary depending on their underlying algorithms and filtering strategies. We compared three widely used variant callers—Mutect2, Strelka2, and FreeBayes—for their performance in somatic single-nucleotide variant (SNV) detection using both synthetic and real whole-exome sequencing (WES) data. Synthetic data were generated by introducing 4709 SNVs into a variant-free BAM file, while real data consisted of tumor and matched normal WES samples from five ovarian cancer (OC) patients. All callers were run using the nf-core/sarek pipeline with default settings and appropriate filtering. In the synthetic dataset, all tools showed high precision (~99.9%), with Mutect2 achieving the highest recall (63.1%), followed by Strelka2 (46.3%) and FreeBayes (45.2%). In real samples, FreeBayes detected the most variants, and only 5.1% of SNVs were shared across all three tools. We then integrated calls with SomaticSeq in consensus mode (Mutect2 + Strelka2) and kept variants with stronger allelic signals—showing higher VAFs and, typically, higher coverages relative to single-caller only. Caller-exclusive variants showed significant differences in allele frequency and sequencing depth. These results highlight substantial variability in SNV detection across tools. While all showed high specificity, differences in sensitivity and variant profiles underscore the need for context-specific caller selection or ensemble approaches in cancer genomics. Full article

Adaptor Protein-1 (AP-1) is a heterotetrameric essential for intracellular vesicular trafficking and polarized localization of somato-dendritic proteins in neurons. Variants in the AP1G1 gene, encoding the gamma-1 subunit of adaptor-related protein complex 1 (AP1γ1), have recently been associated with Usmani–Riazuddin syndrome (USRISD, MIM#619467), a very rare human genetic disorder characterized by intellectual disability (ID), speech and neurodevelopmental delays. Here we report a novel variant (c.196G>A; p.Gly66Arg) identified by exome sequencing analysis in a young girl showing overlapping clinical features with USRIS, such as motor and speech delay, intellectual disability and abnormal aggressive behavior. In silico analysis of the missense de novo variant suggested an alteration in AP1G1 protein folding. Patient’s fibroblasts have been studied with immunofluorescence techniques to analyze the intracellular distribution of AP-1. Zebrafish are widely regarded as an excellent vertebrate model for studying human disease pathogenesis, given their transparent embryonic development, ease of breeding, high genetic similarity to humans, and straightforward genetic manipulation. Leveraging these advantages, we investigated the phenotype, locomotor behavior, and CNS development in zebrafish embryos following the microinjection of human wild-type and mutated AP1G1 mRNAs at the one-cell stage. Knockout (KO) of the AP1G1 gene in zebrafish led to death at the gastrula stage. Lethality in the KO AP1G1 fish model was significantly rescued by injection of the human wild-type AP1G1 mRNA, but not by transcripts encoded by the Gly66Arg missense allele. The phenotype was also not rescued when ap1g1−/− zebrafish embryos were co-injected with both human wild-type and mutated mRNAs, supporting the dominant-negative effect of the new variant. In this study, we defined the effects of a new AP1G1 variant in cellular and animal models of Usmani–Riazzudin syndrome for future therapeutic approaches. Full article

The rapid evolution of sequencing technologies has profoundly advanced precision oncology. Whole-exome sequencing (WES), whole-genome sequencing (WGS), and whole-transcriptome sequencing (RNA-Seq) enable comprehensive characterization of tumor biology by detecting actionable mutations, gene fusions, splice variants, copy number alterations, and pathway dysregulation. These approaches also provide critical insights into biomarkers such as homologous recombination deficiency (HRD), tumor mutational burden (TMB), and microsatellite instability (MSI), which are increasingly essential for guiding therapeutic decisions. Importantly, comprehensive genomic profiling not only refines patient stratification for targeted therapies but also sheds light on tumor–immune interactions and the tumor microenvironment, paving the way for more effective immunotherapeutic combinations. WGS is considered the gold standard for detecting germline mutations and complex structural variants, while WES remains central for detecting somatic driver mutations that guide targeted therapies. RNA-Seq complements these methods by capturing gene expression dynamics, identifying clinically relevant fusions, and revealing mechanisms of resistance. Together with advances in bioinformatics and artificial intelligence, these tools translate molecular data into actionable strategies for patient care. This review integrates insights from WGS, WES, and RNA-Seq with an overview of FDA- and EMA-approved targeted therapies, organized by tumor type, and highlights the molecular signaling pathways that drive cancer development and treatment. By bridging genomic profiling with regulatory-approved therapies, we outline current advances and future perspectives in delivering personalized cancer care. Full article

Background/Objectives: Non-syndromic tooth agenesis (NSTA) is a congenital condition that causes the absence of one or more teeth without accompanying systemic abnormalities, which significantly affects quality of life. Genetic factors, including mutations in several specific genes, contribute to the pathogenesis of NSTA. This study investigates a novel EVC2 mutation in a patient with NSTA and explores its potential pathogenic mechanism, with the aim of enriching the spectrum of pathogenic genes. Methods: Whole-exome sequencing (WES) was performed on peripheral blood samples from a patient diagnosed with NSTA. Bioinformatics analysis was utilized to identify the mutation and assess its potential impact on protein structure and function. Molecular dynamics simulations were conducted to analyze structural alterations in the EVC2 protein. The binding affinity between EVC2, EVC, and Smoothened (SMO) was to determine the effect of mutation on protein–protein interaction. Protein localization and expression were analyzed using immunofluorescence and Western blotting. Reverse transcription quantitative PCR (RT-qPCR) was employed to evaluate downstream signaling pathway alterations. Results: A novel EVC2 mutation (c.1657_1660delinsA, p.Glu553_leu554delinsMet) was identified in the proband, and the mutation was maternally inherited. Molecular dynamics simulations revealed that the mutation resulted in a decrease in α-helical content and significant conformational changes in the protein structure. This led to reduced binding affinity between EVC2 and its ligands EVC and SMO, destabilizing the structural integrity of the protein complex. Despite these structural changes, EVC2 protein localization and expression were unaffected. Furthermore, a downregulation of GLI1 and SHH expression was observed, indicating impaired Hedgehog (Hh) signaling. The downregulation of the Hh signaling pathway impairs the tooth development process and may lead to the occurrence of tooth agenesis. Conclusions: A novel EVC2 mutation was identified in a patient with NSTA. Based on molecular dynamics simulations, it is hypothesized that this EVC2 variant could contribute to the pathogenesis of NSTA by impairing the EVC2-EVC-SMO complex formation, which may lead to downregulation of downstream GLI1 and SHH. These findings provide new insights into the molecular mechanisms underlying EVC2-mediated NSTA, suggesting that disruption of Hh signaling may represent a critical pathogenic mechanism. Full article