Search Results (17)

Background/Objectives: Infantile cardiomyopathy is a rare but often life-threatening condition in which monogenic causes are particularly relevant, especially when cardiac disease is preceded by hypotonia or multisystem involvement. Among sarcomeric genes, MYL2, encoding the ventricular regulatory myosin light chain, plays a critical role in myocardial contractility. However, biallelic MYL2-associated disease remains exceptionally rare, and its clinical spectrum is not fully defined. This study aims to describe a novel case and further delineate the phenotype of recessive MYL2-related cardiomyopathy. Methods: We report a male infant with congenital hypotonia and delayed motor development who underwent extensive metabolic, neuromuscular, and neuroimaging evaluation. Trio-based whole-exome sequencing was performed to identify a potential genetic etiology, followed by variant interpretation using standard bioinformatic and ACMG/AMP criteria. Results: The patient developed acute decompensated heart failure at approximately 10 months of age, with severe left ventricular systolic dysfunction and multiorgan failure, and died at 12 months despite maximal intensive care support. Whole-exome sequencing identified a homozygous MYL2 c.413T>A (p.Met138Lys) missense variant. The variant is absent or extremely rare in population databases, affects a highly conserved residue, is predicted to be deleterious by multiple in silico tools, and is compatible with autosomal recessive inheritance, with both parents confirmed as heterozygous carriers. In the context of a phenotype consistent with recessive MYL2-associated disease, these findings support a likely pathogenic interpretation. Conclusions: This case expands the allelic and phenotypic spectrum of recessive MYL2-associated cardiomyopathy and highlights the value of early genomic testing in infants with unexplained hypotonia and rapidly progressive cardiac dysfunction. Molecular diagnosis may aid in prognosis, clinical decision-making, and genetic counseling. Full article

Muscle biopsy has long been regarded as the cornerstone for diagnosing pediatric muscular disorders; however, it is invasive and may be limited by sampling error and inconclusive histopathological findings. This study aimed to evaluate whether whole-exome sequencing (WES) can effectively replace muscle biopsy as a first-line diagnostic approach in children with suspected neuromuscular disorders. Between January 2018 and December 2025, we prospectively enrolled 47 pediatric patients presenting with clinical features suggestive of muscular disorders at a tertiary medical center in Taiwan. The cohort included patients with suspected muscular dystrophies (n = 21), congenital myopathies (n = 23), and multiplex ligation-dependent probe amplification (MLPA)-negative Duchenne muscular dystrophy (DMD; n = 3). All patients underwent WES as the initial diagnostic test without prior muscle biopsy. Trio-based analysis using parental samples was performed in 29.8% of cases. Variant interpretation followed the American College of Medical Genetics and Genomics (ACMG) guidelines. WES identified a definitive molecular diagnosis in 72.3% of patients (34/47). Diagnostic yields varied by subgroup: 100% (3/3) in MLPA-negative DMD, 71.4% (15/21) in muscular dystrophies, and 69.6% (16/23) in congenital myopathies. Pathogenic or likely pathogenic variants were detected in 31 distinct genes, including COL6A1 and COL6A3, which are associated with Ullrich congenital muscular dystrophy. Notably, 58.8% of diagnosed patients (20/34) received molecular diagnoses that differed from their initial clinical impression, encompassing conditions such as ZSWIM6-associated neurodevelopmental disorders, GJB2-related hearing loss, OCRL-associated Lowe syndrome, and various metabolic or syndromic disorders. In all three MLPA-negative DMD cases, WES identified point mutations amenable to mutation-specific therapies. No patient required a muscle biopsy for diagnostic confirmation during the study period. First-tier WES demonstrates high diagnostic utility in pediatric muscular disorders while avoiding invasive muscle biopsy. The high rate of diagnostic reclassification underscores the substantial phenotypic overlap between primary neuromuscular diseases and other neurological or systemic conditions. These findings support the early implementation of genetic testing to enable accurate diagnosis and timely initiation of targeted therapies. Full article

Congenital heart disease (CHD) is the most common congenital anomaly worldwide and poses significant diagnostic challenges due to its structural complexity and frequent association with extracardiac anomalies and genetic abnormalities. While conventional tests such as karyotyping, quantitative fluorescent polymerase chain reaction (QF-PCR), and chromosomal microarray analysis (CMA) are standard first-tier investigations, many cases remain genetically unexplained. Prenatal whole exome sequencing (WES) has emerged as a valuable tool to detect pathogenic single gene variants underlying CHD. This narrative review synthesizes findings from 28 studies involving over 2000 WES-tested fetuses and more than 10,000 CHD cases. The additional diagnostic yield of WES over CMA ranged from 8.0% to 66.7%, with higher yields in syndromic or non-isolated CHD (10–50%) compared to isolated cases (7.1–27.8%). Trio-based WES outperformed proband-only sequencing by improving accuracy, reducing turnaround time, and lowering the rate of variant of uncertain significance (VUS). Prenatal WES not only clarifies genetic etiology but also reveals syndromic diagnoses, allowing CHD to be interpreted within broader multisystem contexts. Integration of phenotypic and genomic data enhances prenatal counseling, prognostication, delivery planning, and postnatal care—advancing precision medicine in fetal cardiology. Full article

Background: Prenatal detection of fetal structural anomalies often prompts chromosomal analysis; however, chromosomal microarray analysis (CMA) has limited diagnostic yield for monogenic disorders. Whole-exome sequencing (WES) has emerged as a powerful tool for identifying single-gene etiologies, particularly in cases with complex neurodevelopmental phenotypes. Case Presentation: We report a female infant presenting with prenatally detected ventriculomegaly and inconclusive chromosomal testing. Prenatal investigations, including karyotyping and genome-wide chromosomal sequencing, identified several copy number variants classified as variants of uncertain significance but failed to establish a definitive diagnosis. Postnatally, the patient developed progressive neurological abnormalities, including microcephaly, facial dysmorphism, dystonic movements, and severe global developmental delay. Trio-based whole-exome sequencing identified a heterozygous de novo pathogenic missense variant in the DDX3X gene (c.976C>T; p.Arg326Cys), establishing the diagnosis of DDX3X-related neurodevelopmental disorder. Conclusions: This case highlights the diagnostic limitations of standard prenatal chromosomal testing in detecting monogenic neurodevelopmental disorders and underscores the critical role of timely genetic counseling and exome sequencing. Earlier selective implementation of WES during pregnancy could have enabled an earlier diagnosis, improved prognostic counseling, and optimized clinical decision-making. Full article

Background and Clinical Significance: Methyltransferase-like protein 5 (METTL5) is a conserved RNA methyltransferase responsible for catalyzing the N6-methyladenosine (m6A) modification of 18S ribosomal RNA, a process critical for ribosome biogenesis and translational regulation. Biallelic variants in METTL5 have been linked to autosomal recessive intellectual developmental disorder-72 (MRT72), typically presenting with microcephaly, intellectual disability, and speech delay. However, the association between METTL5 and isolated attention-deficit/hyperactivity disorder (ADHD) remains underexplored. Case Presentation: We report a 14-year-old Qatari female, born to consanguineous parents, who presented with microcephaly, speech delay, learning difficulties, and inattentive-type ADHD. Trio-based whole-genome sequencing identified a novel homozygous METTL5 variant (c.617G > A; p. Arg206Gln), with both parent’s heterozygous carriers. The variant is extremely rare (gnomAD MAF: 0.0000175) and predicted to be deleterious (CADD: 23.7; SIFT: damaging; PolyPhen-2: probably damaging). Structural modeling localized the change within the SAM-dependent catalytic domain, predicting protein destabilization (ΔΔG = +1.8 kcal/mol). The affected residue is highly conserved (ConSurf score: 8), and protein–protein interaction analysis linked METTL5 with METTL14, METTL16, and ZCCHC4, key regulators of rRNA methylation. Conclusions: In silico evidence suggests that the p. Arg206Gln variant disrupts METTL5 function, likely contributing to the observed neurodevelopmental phenotype, including ADHD. This expands the clinical spectrum of METTL5-related disorders and supports its inclusion in neurodevelopmental gene panels. Full article

Background. Whole-genome sequencing (WGS) enables comprehensive detection of genetic variants but faces limitations in benchmarking due to incomplete reference datasets. Trio-based analysis, leveraging Mendelian inheritance, provides an alternative strategy for validating sequencing results and estimating error rates, particularly in regulatory genomic regions. Methods. We extended the nf-core/sarek WGS pipeline by integrating a module that collects parental and offspring allele information, extracts regulatory genomic regions, and computes Mendelian-consistency scores. The algorithm processes variant calls from parents and children to identify expected versus anomalous inheritance patterns. The module was implemented in C++ and integrated into the Nextflow workflow, supporting automated analysis of trio datasets. Results. The method was validated on two real trio datasets, comparing DeepVariant and HaplotypeCaller as variant callers. For both trios, DeepVariant consistently achieved higher sensitivity and precision, with statistically significant differences confirmed using 95% confidence intervals. These results demonstrate that the proposed approach enables effective benchmarking of variant-calling performance in non-benchmark datasets. Conclusions. The developed method provides a practical and scalable framework for quantifying WGS outcomes from trio data. By incorporating Mendelian-inheritance validation into existing pipelines, researchers can estimate sequencing error rates, compare variant callers, and optimize workflows in regulatory genomic regions. Our findings confirm the superior performance of DeepVariant over HaplotypeCaller for the studied datasets. Full article

Genome-wide paternal uniparental isodisomy mosaicism (GWpUPIDM) is an extremely rare condition characterized by varying proportions of an androgenetic cell line across different tissues. It is primarily associated with severe congenital hyperinsulinism (CHI), Beckwith–Wiedemann syndrome (BWS) stigmata, a high risk (69–79%) of developing neoplasia and, in some cases, additional manifestations of multilocus paternal imprinting disorders (MPIDs). We herein report the first Mexican/Latin American female patient GWpUPIDM presenting with non-syndromic CHI requiring subtotal pancreatectomy and persistent but unexplained asymptomatic diffuse hepatopathy. When she was 8.5 years old, whole-exome sequencing (WES) in blood revealed an unexpectedly high (~92%) proportion of regions of homozygosity. DNA profiling confirmed a single haploid set of paternal chromosomes in both biparental and androgenetic cell lines, with varying proportions of the androgenetic lineage in leukocytes (84%), resected pancreas (74%), buccal cells (47%), and hair follicles (0.7%). Additional WES trio analysis using gDNA from the patient’s buccal cells and blood samples from both parents revealed an allelic frequency of ~75% for the paternally inherited variant NM_000158.4(GBE1):c.555+1G>T [ClinVar:632422; dbSNP:rs759707498]. At age 8.5, the patient exhibited no clinical features of BWS, MPIDs, or neoplasia. However, she presented persistent hepatic abnormalities that warrant further investigation to rule out an unmasked glycogen storage disease type IV (OMIM#232500). Our findings emphasize the critical need for early diagnosis of GWpUPIDM using SNP-based microarray or WES with further confirmation through DNA profiling in patients presenting with CHI, placental mesenchymal dysplasia, BWS stigmata, or other MPID-related conditions, including neoplasia, to facilitate timely cancer surveillance and management. Full article

This trio-based whole-genome sequencing (WGS) study enhances the accuracy of variant detection by leveraging parental genotypes, which facilitates the identification of de novo mutations and population-specific variants. Nonetheless, the comprehensive genetic variation data of the Thai population remain limited, posing challenges to advancing personalized medicine and population-based screening strategies. We establish the genetic variation information of a healthy Thai population by analyzing the sequences of 40 trios, yielding 120 whole genomes (excluding offspring). The resulting dataset encompasses 20.2 million variants, including 1.1 million novel and 19.1 million known variants. Within this dataset, we identify 169 pathogenic variants, of which 56 are classified as rare and 87 are absent from the ClinVar database as of version 2023. These pathogenic variants, particularly the rare and de novo mutations, will likely be of significant interest for genetic association studies. Notably, one pathogenic variant linked to a de novo mutation is found in the SF3B2 gene, which is associated with craniofacial microsomia. With its innovative methodology and comprehensive dataset, our trio-based whole-genome sequencing study provides an invaluable representation of the genetic variations in the Thai population. These data provide a critical foundation for further analyses of the pathogenic variants related to human disease phenotypes in genetic association studies. Full article

One out of every hundred live births present with congenital heart abnormalities caused by the aberrant development of the embryonic cardiovascular system. The conserved zinc finger transcription factor proteins, which include GATA binding protein 5 (GATA5) and GATA binding protein (GATA6) play important roles in embryonic development and their inactivation may result in congenital heart defects (CHDs). In this study, we performed genotypic–phenotypic analyses in two families affected by right-sided CHD diagnosed by echocardiography imaging. Proband A presented with pulmonary valve stenosis, and proband B presented with complex CHD involving the right heart structures. For variant detection, we employed whole-genome single-nucleotide polymorphism (SNP) microarray and family-based whole-exome sequencing (WES) studies. Proband A is a full-term infant who was admitted to the neonatal intensive care unit (NICU) at five days of life for pulmonary valve stenosis (PVS). Genomic studies revealed a normal SNP microarray; however, quad WES analysis identified a novel heterozygous [Chr20:g.61041597C>G (p.Arg237Pro)] variant in the GATA5 gene. Further analysis confirmed that the novel variant was inherited from the mother but was absent in the father and the maternal uncle with a history of heart murmur. Proband B was born prematurely at 35 weeks gestation with a prenatally diagnosed complex CHD. A postnatal evaluation revealed right-sided heart defects including pulmonary atresia with intact ventricular septum (PA/IVS), right ventricular hypoplasia, tricuspid valve hypoplasia, hypoplastic main and bilateral branch pulmonary arteries, and possible coronary sinusoids. Cardiac catheterization yielded anatomy and hemodynamics unfavorable to repair. Hence, heart transplantation was indicated. Upon genomic testing, a normal SNP microarray was observed, while trio WES analysis identified a novel heterozygous [Chr18:c.1757C>T (p.Pro586Leu)] variant in the GATA6 gene. This variant was inherited from the father, who carries a clinical diagnosis of tetralogy of Fallot. These findings provide new insights into novel GATA5/6 variants, elaborate on the genotypic and phenotypic association, and highlight the critical role of GATA5 and GATA6 transcription factors in a wide spectrum of right-sided CHDs. Full article

Schizophrenia (SZ) is a heterogeneous and debilitating psychiatric disorder with a strong genetic component. To elucidate functional networks perturbed in schizophrenia, we analysed a large dataset of whole-genome studies that identified SNVs, CNVs, and a multi-stage schizophrenia genome-wide association study. Our analysis identified three subclusters that are interrelated and with small overlaps: GO:0007017~Microtubule-Based Process, GO:00015629~Actin Cytoskeleton, and GO:0007268~SynapticTransmission. We next analysed three distinct trio cohorts of 75 SZ Algerian, 45 SZ French, and 61 SZ Japanese patients. We performed Illumina HiSeq whole-exome sequencing and identified de novo mutations using a Bayesian approach. We validated 88 de novo mutations by Sanger sequencing: 35 in French, 21 in Algerian, and 32 in Japanese SZ patients. These 88 de novo mutations exhibited an enrichment in genes encoding proteins related to GO:0051015~actin filament binding (p = 0.0011) using David, and enrichments in GO: 0003774~transport (p = 0.019) and GO:0003729~mRNA binding (p = 0.010) using Amigo. One of these de novo variant was found in CORO1C coding sequence. We studied Coro1c haploinsufficiency in a Coro1c^+/− mouse and found defects in the corpus callosum. These results could motivate future studies of the mechanisms surrounding genes encoding proteins involved in transport and the cytoskeleton, with the goal of developing therapeutic intervention strategies for a subset of SZ cases. Full article

Autism spectrum disorder (ASD) is a common condition with lifelong implications. The last decade has seen dramatic improvements in DNA sequencing and related bioinformatics and databases. We analyzed the raw DNA sequencing files on the Variantyx^® bioinformatics platform for the last 50 ASD patients evaluated with trio whole-genome sequencing (trio-WGS). “Qualified” variants were defined as coding, rare, and evolutionarily conserved. Primary Diagnostic Variants (PDV), additionally, were present in genes directly linked to ASD and matched clinical correlation. A PDV was identified in 34/50 (68%) of cases, including 25 (50%) cases with heterozygous de novo and 10 (20%) with inherited variants. De novo variants in genes directly associated with ASD were far more likely to be Qualifying than non-Qualifying versus a control group of genes (p = 0.0002), validating that most are indeed disease related. Sequence reanalysis increased diagnostic yield from 28% to 68%, mostly through inclusion of de novo PDVs in genes not yet reported as ASD associated. Thirty-three subjects (66%) had treatment recommendation(s) based on DNA analyses. Our results demonstrate a high yield of trio-WGS for revealing molecular diagnoses in ASD, which is greatly enhanced by reanalyzing DNA sequencing files. In contrast to previous reports, de novo variants dominate the findings, mostly representing novel conditions. This has implications to the cause and rising prevalence of autism. Full article

Cerebral adrenoleukodystrophy (CALD) is a fatal genetic disease characterized by rapid, devastating neurological decline, with a narrow curative treatment window in the early stage. Non-canonical splice-site (NCSS) variants can easily be missed during genomic DNA analyses, and only a few of them in ABCD1 have been explored. Here, we studied a Chinese patient with clinical features similar to those of early-stage CALD but with a negative molecular diagnosis and a sibling who had presumably died of CALD. Trio-based whole-exome sequencing (trio-WES) and RNA sequencing (RNA-Seq) revealed a novel hemizygote NCSS variant c.901-25_901-9 del in ABCD1 intron 1, resulting in a complex splicing pattern. The in vitro minigene assay revealed that the c.901-25_901-9 del construct contained two aberrant transcripts that caused skipping of exon 2 and a small 48-bp deletion on left of the same exon. We identified a novel NCSS variant, that extends the spectrum of the known ABCD1 variants, and demonstrated the pathogenicity of this gene variant. Our findings highlight the importance of combining RNA-Seq and WES techniques for prompt diagnosis of leukodystrophy with NCSS variants. Full article

Most genetic variants are rare and specific to the population, highlighting the importance of characterizing local population genetic diversity. Many countries have initiated population-based whole-genome sequencing (WGS) studies. Genomic variation within Lithuanian families are not available in the public databases. Here, we describe initial findings of a high-coverage (an average of 36.27×) whole genome sequencing for 25 trios of the Lithuanian population. Each genome on average carried approximately 4,701,473 (±28,255) variants, where 80.6% (3,787,626) were single nucleotide polymorphisms (SNPs), and the rest 19.4% were indels. An average of 12.45% was novel according to dbSNP (build 150). The WGS structural variation (SV) analysis identified on average 9133 (±85.10) SVs, of which 95.85% were novel. De novo single nucleotide variation (SNV) analysis identified 4417 variants, where 1.1% de novo SNVs were exonic, 43.9% intronic, 51.9% intergenic, and the rest 3.13% in UTR or downstream sequence. Three potential pathogenic de novo variants in the ZSWIM8, CDC42EP1, and RELA genes were identified. Our findings provide useful information on local human population genomic variation, especially for de novo variants, and will be a valuable resource for further genetic studies, and medical implications. Full article

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with strong genetic influences. There is an increasing demand for ASD genetic testing beyond the traditionally recommended microarray and syndromic autism testing; however, the current whole genome sequencing (WGS) and whole exome sequencing (WES) methods are lacking an academic standard for WGS variant annotation, reporting, and interpretation, tailored towards patients with ASD and offer very limited interpretation for clinical significance. Using WGS data from six family trios, we demonstrate the clinical feasibility and technical implementation of an evidence-based, fully transparent bioinformatics pipeline and report framework for an ASD-focused WGS genetic report. We confirmed a portion of the key variants with Sanger sequencing and provided interpretation with consideration of patients’ clinical symptoms and detailed literature review. Furthermore, we showed that identification of the genetic contributions of ASD core symptoms and comorbidities may promote a better understanding of the ASD pathophysiology, lead to early detection of associated comorbidities, and facilitate pharmacologic intervention based on pathological pathways inferred from the genetic information. We will make the bioinformatics pipeline and interpretation framework publicly available, in an easily accessible format, after validation with a larger cohort. We hope that the present proposed protocol can serve as a starting point to invite discourse and debate to further improve approaches in WGS-based genetic consultation for patients with ASD. Full article

Objective, the application of genomic sequencing in clinical practice has allowed us to appreciate the contribution of co-occurring pathogenic variants to complex and unclassified clinical phenotypes. Besides the clinical relevance, these findings have provided evidence of previously unrecognized functional links between genes in the context of developmental processes and physiology. Patients and Methods, a 5-year-old patient showing an unclassified phenotype characterized by developmental delay, speech delay, peculiar behavioral features, facial dysmorphism and severe cardiopathy was analyzed by trio-based whole exome sequencing (WES) analysis to identify the genomic events underlying the condition. Results, two co-occurring heterozygous truncating variants in CNOT3 and SMAD6 were identified. Heterozygous loss-of-function variants in CNOT3, encoding a subunit of the CCR4-NOT protein complex, have recently been reported to cause a syndromic condition known as intellectual developmental disorder with speech delay, autism and dysmorphic facies (IDDSADF). Enrichment of rare/private variants in the SMAD6 gene, encoding a protein negatively controlling transforming growth factor β/bone morphogenetic protein (TGFB/BMP) signaling, has been described in association with a wide spectrum of congenital heart defects. We dissected the contribution of individual variants to the complex clinical manifestations and profiled a previously unappreciated set of facial features and signs characterizing IDDSADF. Conclusions, two concomitant truncating variants in CNOT3 and SMAD6 are the cause of the combination of features documented in the patient resulting in the unique multisystem neurodevelopmental condition. These findings provide evidence for a functional link between the CCR4-NOT complex and TGFB/BMP signaling in processes controlling cardiac development. Finally, the present revision provides evidence that IDDSADF is characterized by a distinctive facial gestalt. Full article