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PubMed2025

Clinical characteristic of isolated thrombocytopenia in patients with bone marrow failure-related germline variants: a retrospective study from a single centre.

BACKGROUND: Immune thrombocytopenia (ITP) comprises the majority of thrombocytopenia. Some patients respond poorly to first-line ITP therapy or develop pancytopenia years later. Recent studies link heterozygous germline variants in acquired aplastic anemia (AA), yet their role in isolated thrombocytopenia carrying bone marrow failure-related germline variants (ITGV-BMFs) remains unclear. While whole-exome sequencing (WES) detects these variants, its cost limits routine use. This study compares prognosis and clinical features of isolated thrombocytopenia in patients with ITGV-BMFsand those with classic ITP. METHODS: The clinical data of patients diagnosed with ITGV-BMFs were retrospectively analyzed and compared with those of patients with classic ITP from August 2018 to February 2024. The baseline characteristics, genomic systematically background, previous treatment response as well as their follow-up outcomes were compared. RESULTS: Patients with ITGV-BMFs demonstrated earlier onset age (p < 0.001), lower bleeding scores and CD34%, along with elevated mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and reticulocyte (RET) counts (p < 0.001). Multivariate logistic regression analysis showed that the patients with ITGV-BMFs may possess distinct characteristics, including an earlier age at onset (p = 0.014) and lower bleeding score (p = 0.048). Notably, MCV and RET showed promising performance in receiver operating characteristic (ROC) curve analysis. During the follow-up period, 57.69% (15/26) ITGV-BMFs patients were further confirmed as aplastic anemia (AA, n = 13) or myelodysplastic syndrome (MDS, n = 2), with a median progression-free survival (PFS) of 7.25 years (p < 0.0001). CONCLUSION: ITGV-BMFs may be diagnosed early using elevated MCV and reticulocyte counts, a diagnostic approach that may lead to earlier intervention and improved prognosis.

Humans↗

PubMed2024

Genomic insights from a deeply phenotyped highly consanguineous neurodevelopmental disorders cohort.

PURPOSE: The genetic underpinning of neurodevelopmental disorders (NDDs) in diverse ethnic populations, especially those with high rates of consanguinity, remains largely unexplored. Here, we aim to elucidate genomic insight from 576 well-phenotyped and highly consanguineous (16%) NDD cohort. METHODS: We used chromosomal microarray (CMA; N:247), exome sequencing (ES; N:127), combined CMA and ES (N:202), and long-read genome sequencing to identify genetic etiology. Deep clinical multivariate data were coupled with genomic variants for stratification analysis. RESULTS: Genetic diagnosis rates were 17% with CMA, 29.92% with ES, and 37.13% with combined CMA and ES. Notably, children of consanguineous parents showed a significantly higher diagnostic yield (P < .01) compared to those from nonconsanguineous parents. Among the ES-identified pathogenic variants, 36.19% (38/105) were novel, implicating 35 unique genes. Long-read sequencing of seizure participants unresolved by combined test identified expanded FMR1 trinucleotide repeats. Additionally, we identified 2 recurrent X-linked variants in the G6PD in 3.65% (12/329) of NDD participants. These variants were absent in large-population control cohorts and cohort comprising neurodevelopmental and neuropsychiatric populations of European descendants, indicating a possible associated risk factor potentially resulting from ancient genetic drift. CONCLUSION: This study unveils unique clinical and genomic insights from a consanguinity rich Bangladeshi NDD cohort.

Humans↗

PubMed2026

Expansion of the allelic and phenotypic spectrum of MED25-related developmental disorder: novel compound heterozygous variants with structural domain implications.

MED25-related developmental disorder (Basel-Vanagaite-Smirin-Yosef syndrome) is a rare autosomal recessive disorder, defined by severe neurodevelopmental delay, corpus callosum abnormalities, ocular involvement, epilepsy, and marked facial appearance. MED25 pathogenic variants interfere with the functioning of the Mediator complex, which is responsible for RNA polymerase II transcription. We report a 9-year-old girl who presents with significant global developmental delay, agenesis of the corpus callosum, congenital cataracts, epilepsy, hypotonia, musculoskeletal abnormalities, and typical craniofacial features. Trio-based whole-exome sequencing revealed compound heterozygous variants in MED25: a maternally transmitted truncating variant (c.1366 C > T; p.Gln456*) and a paternally inherited missense variant (c.430 C > T; p.Leu144Phe). The new classification of the missense variant as potentially pathogenic is supported by a systematic ACMG re-evaluation supported by segregation analysis, phenotypic specificity, computational prediction, and structural localization in the MED25 Activator Interaction Domain (ACID). Comparative phenotypic analyses show strong agreement with reported cases but add more data to fine-tune clinical spectrum. This article broadens the allelic and phenotypic spectrum of MED25-related developmental disorder and highlights the need for comprehensive evaluation across molecular, structural, and phenotypic pathways to elucidate variant signature in rare genetic disease models correctly.

Humans↗

PubMed2024

Clinical characterizations and molecular genetic study of two co-segregating variants in PDZD7 and PDE6C genes leading simultaneously to non-syndromic hearing loss and achromatopsia.

BACKGROUND: Autosomal recessive non-syndromic hearing loss (NSHL) and cone dystrophies (CODs) are highly genetically and phenotypically heterogeneous disorders. In this study, we applied the whole exome sequencing (WES) to find the cause of HL and COD in an Iranian consanguineous family with three affected individuals. METHODS: Three members from an Iranian consanguineous family who were suffering from NSHL and visual impairment were ascertained in this study. Comprehensive clinical evaluations and genetic analysis followed by bioinformatic and co-segregation studies were performed to diagnose the cause of these phenotypes. Data were collected from 2020 to 2022. RESULTS: All cases showed congenital bilateral NSHL, decreased visual acuity, poor color discrimination, photophobia and macular atrophy. Moreover, cornea, iris and anterior vitreous were within normal limit in both eyes, decreased foveal sensitivity, central scotoma and generalized depression of visual field were seen in three cases. WES results showed two variants, a novel null variant (p.Trp548Ter) in the PDE6C gene causing COD type 4 (Achromatopsia) and a previously reported variant (p.Ile84Thr) in the PDZD7 gene causing NSHL. Both variants were found in the cis configuration on chromosome 10 with a genetic distance of about 8.3 cM, leading to their co-inheritance. However, two diseases could appear independently in subsequent generations due to crossover during meiosis. CONCLUSIONS: Here, we could successfully determine the etiology of a seemingly complex phenotype in two adjacent genes. We identified a novel variant in the PDE6C gene, related to achromatopsia. Interestingly, this variant could cooperatively cause visual disorders: cone dystrophy and cone-rod dystrophy.

Adult↗

PubMed2026

Myoepithelioma-like tumor of the vulvar region shows a quiet genome and heterogeneous detectable mechanisms of SMARCB1 inactivation: Integrated analysis of two cases and review of the literature.

Myoepithelioma-like tumor of the vulvar region (MELTVR) is a rare SMARCB1-deficient mesenchymal neoplasm of adult women that can mimic malignant vulvar sarcomas, particularly epithelioid sarcoma. Although loss of SMARCB1/INI1 expression is a defining feature, the comprehensive genomic landscape of MELTVR remains poorly characterized. We report two cases of MELTVR and performed integrated histopathologic, immunophenotypic, and molecular analyses, including whole-exome sequencing (WES) with copy number assessment and targeted RNA-based fusion testing using the Archer FusionPlex Sarcoma panel. Histologically, both tumors consisted of relatively uniform epithelioid to short spindle cells in solid nests and cords within focal myxoid stroma, with complete loss of INI1 and positivity for smooth muscle markers and focal ER/EMA expression. Genomic profiling demonstrated a quiet molecular background in both cases, with low tumor mutation burden (0.45 and 1.03 mut/Mb) and no pathogenic SNVs/indels in major cancer-associated genes. One case showed a focal homozygous deletion of the SMARCB1 locus at 22q11.2, whereas the other case exhibited INI1 loss without detectable SMARCB1 mutation or copy number loss, suggesting heterogeneous mechanisms of inactivation. CDKN2A copy number remained neutral in both tumors. No canonical sarcoma-associated gene rearrangements, including EWSR1, FUS, PLAG1, or NR4A3, were identified. Together with a review of previously reported cases, these findings support MELTVR as an SMARCB1-inactivated neoplasm with low genomic complexity and highlight the diagnostic value of NGS-based profiling in excluding malignant mimics and preventing overtreatment.

Humans↗

PubMed2024

Clinical characteristics and genetic analysis of four pediatric patients with Kleefstra syndrome.

BACKGROUND: Kleefstra syndrome spectrum (KLEFS) is an autosomal dominant disorder that can lead to intellectual disability and autism spectrum disorders. KLEFS encompasses Kleefstra syndrome-1 (KLEFS1) and Kleefstra syndrome-2 (KLEFS2), with KLEFS1 accounting for more than 75%. However, limited information is available regarding KLEFS2. KLEFS1 is caused by a subtelomeric chromosomal abnormality resulting in either deletion at the end of the long arm of chromosome 9, which contains the EHMT1 gene, or by variants in the EHMT1 gene and the KMT2C gene that cause KLEFS2. METHODS: This study was a retrospective analysis of clinical data from four patients with KLEFS. Exome sequencing (ES) and Sanger sequencing techniques were used to identify and validate the candidate variants, facilitating the analysis of genotype‒phenotype correlations of the EHMT1 and KMT2C genes. Protein structure modeling was performed to evaluate the effects of the variants on the protein's three-dimensional structure. In addition, real-time quantitative reverse transcription‒polymerase chain reaction (RT‒qPCR) and western blotting were used to examine the protein and mRNA levels of the KMT2C gene. RESULTS: Two patients with KLEFS1 were identified: one with a novel variant (c.2382 + 1G > T) and the other with a previously reported variant (c.2426 C > T, p.Pro809Leu) in the EHMT1 gene. A De novo deletion at the end of the long arm of chromosome 9 was also reported. Furthermore, a patient with KLEFS2 was identified with a novel variant in the KMT2C gene (c.568 C > T, p.Arg190Ter). The RT‒qPCR and western blot results revealed that the expression of the KMT2C gene was downregulated in the KLEFS2 sample. CONCLUSION: This study contributes to the understanding of both KLEFS1 and KLEFS2 by identifying novel variants in EHMT1 and KMT2C genes, thereby expanding the variant spectrum. Additionally, we provide the first evidence of how a KMT2C variant leads to decreased gene and protein expression, enhancing our understanding of the molecular mechanisms underlying KLEFS2. Based on these findings, children exhibiting developmental delay, hypotonia, distinctive facial features, and other neurodevelopmental abnormalities should be considered for ES to ensure early intervention and treatment.

Child↗

PubMed2026

Intramuscular patient-derived xenografts achieve high engraftment rates in gastric cancer: implications for pharmacodynamic testing and genomic biomarker discovery.

BACKGROUND: Gastric cancer (GC) exhibits marked inter-patient heterogeneity, limiting empirical chemotherapy efficacy. Patient-derived xenograft (PDX) models preserve the molecular features of parental tumors and can serve as pharmacodynamic surrogates, but conventional subcutaneous PDX suffers from low engraftment rates. This study evaluated an optimized intramuscular PDX platform for individualized drug testing in GC and applied whole exome sequencing (WES) for biomarker identification (Clinical trial registry: ChiCTR-OOC-17012731). MATERIALS AND METHODS: Ninety-eight treatment-naive GC patients were enrolled between April 2018 and December 2020. Fresh tumor tissues were engrafted into NCG mice by intramuscular transplantation. Drug efficacy was evaluated using tumor cell necrosis rate and Ki-67 expression. WES was performed on 32 engrafted tumorgrafts to characterize driver mutations in fast- and slow-growing subgroups. RESULTS: An engraftment rate of 71.7% (43/60) was achieved, substantially exceeding rates reported in prior studies. Clinical characteristics were independent of engraftment success and outgrowth time (all p > 0.05). Fast- and slow-growing tumorgrafts diverged in frequently altered genes: KMT2C, APOB, CDK12 and MSH2 predominated in fast-growing grafts, whereas TP53, CHD3 and TET2 were enriched in slow-growing grafts. Slow-growing tumorgrafts correlated with longer progression-free survival (p = 0.02). PDX-guided treatment was associated with improved prognosis. CONCLUSIONS: Intramuscular transplantation into NCG mice yields high engraftment rates for GC PDX. PDX-guided chemotherapy selection is associated with favorable outcomes. Driver mutation divergence between fast- and slow-growing tumorgrafts provides candidate prognostic biomarkers.

Animals↗

PubMed2026

A Novel Splice Variant in the COL1A1 Gene Leads to Exon 46 Skipping and Osteogenesis Imperfecta.

BACKGROUND: Osteogenesis imperfecta (OI) is a clinical and genetic disorder characterised by bone fragility, growth deficiency and skeletal deformity. Ninety per cent of OI cases are attributable to autosomal dominant variants in the COL1A1 and COL1A2 genes. METHODS: Candidate variants were identified and verified through trio whole-exome sequencing (trio-WES), copy number variation sequencing (CNV-seq) and Sanger sequencing. Minigene splicing assays were performed in HeLa and HEK293T cells with pcDNA3.1 and pcMINI-C vectors to investigate the function of the candidate variants. A systematic review of COL1A1 splicing variants and the corresponding genotype-phenotype spectrum was performed. RESULTS: Trio-WES revealed a novel heterozygous variant in the C-terminal region of the COL1A1 gene: NM_000088.4:c.3423+5G>A. Sanger sequencing confirmed the variant in both the proband (II-2) and her foetus (III-1) who were clinically suspected of having OI. The c.3423+5G>A variant causes complete skipping of Exon 46, as demonstrated by a minigene splicing assay. We retrieved 419 COL1A1 splicing variants from PubMed, excluded 15 without phenotypic data and 2 linked to Ehlers-Danlos syndrome and stratified the remaining 402 variants into three types on the basis of splice site location: (1) Variants at canonical splicing sites (77.8%, 313/402) mostly cause mild phenotypes, whereas a minority may be severe. (2) Intron variants in other locations, such as splice region variants (17.9%, 72/402), usually cause mild clinical phenotypes, and deep intronic splice variants (0.4%, 2/402) that may result in severe phenotypes. (3) Other variants (3.7%, 15/402), such as exon variants or fragment loss, are extremely rare. We also preliminarily discuss the mechanisms underlying phenotypic variability and the characteristics of C-terminal variants. CONCLUSIONS: This intron variant in COL1A1 was classified as likely pathogenic and was confirmed to disrupt COL1A1 expression. The summary analysis results also revealed a correlation among splicing variants, C-terminal region variants and disease, suggesting that variant location provides a useful framework for prognosis prediction.

Female↗

PubMed2025

Genome sequencing reveals the impact of pseudoexons in rare genetic disease.

PURPOSE: Advancements in sequencing technologies have significantly improved clinical genetic testing; yet, the diagnostic yield remains around 30% to 40%. Emerging technologies are now being deployed to address the remaining diagnostic gap. METHODS: We tested whether short-read genome sequencing could increase the diagnostic yield in individuals enrolled into the UCI-GREGoR research study, who had suspected Mendelian conditions and prior inconclusive testing. Two other collaborative research cohorts, focused on aortopathy and dilated cardiomyopathy, consisted of individuals who were undiagnosed but had not undergone harmonized prior testing. RESULTS: We sequenced 353 families (754 participants) and found a molecular diagnosis in 54 (15.3%) of them. Of these diagnoses, 55.5% were previously missed because the causative variants were in regions not originally interrogated. In 5 cases, they were deep intronic variants, all of which led to abnormal splicing and pseudoexons, as directly shown by RNA sequencing. All 5 of these variants had inconclusive spliceAI scores. In 26% of newly diagnosed cases, the causal variant could have been detected by exome sequencing reanalysis. CONCLUSION: Genome sequencing can overcome limitations of clinical genetic testing, such as the inability to call intronic variants. Our findings highlight pseudoexons as a common mechanism via which deep intronic variants cause Mendelian disease.

Humans↗

PubMed2025

Detection of copy number variations by chromosomal microarray analysis in disorders of sex development of unexplained molecular etiology and association with clinical findings.

PURPOSE: Despite advances in genetic diagnostics, the molecular cause of a significant proportion of DSDs remains unknown. The aim of this study was to identify copy number variations (CNVs) using chromosomal microarray analysis (CMA) technology in DSD patients with previously undetected molecular genetic etiology and to investigate their phenotypic associations with these variations. METHODS: This study included DSD cases without chromosomal abnormalities and without any variants detected by sequence analysis methods, including whole-exome sequencing analysis. We evaluated variant pathogenicity according to the American College of Medical Genetics and Genomics guidelines and recorded the phenotypic findings of the cases. All pathogenic variants were subjected to segregation analysis. RESULTS: Of the 20 patients included in the study, 16 (80%) were classified as 46,XY DSD and 4 (20%) as 46,XX DSD. Initial clinical diagnoses in this 46,XX DSD group included gonadal dysgenesis in two patients (50%) and androgen excess in the remaining two (50%). Among the 46,XY DSD patients, five patients (31.25%) were presumed to be androgen insensitive, nine (56.25%) were diagnosed with defects in androgen biosynthesis, and two (12.5%) had gonadal dysgenesis. CMA detected 38 CNVs in 16 patients (80%), comprising 12 deletions (31.6%) and 26 duplications (68.4%). Three pathogenic CNVs were detected in 3 patients (15%), whereas 27 variants of uncertain significance were identified in 13 patients (65%). CONCLUSION: In selected cases, the diagnostic approach should incorporate CMA to elucidate the molecular etiology of DSD. Furthermore, CMA may prove to be an invaluable tool in the search for new genes responsible for DSD.

Humans↗

PubMed2025

Accurate somatic small variant discovery for multiple sequencing technologies with DeepSomatic.

Somatic variant detection is an integral part of cancer genomics analysis. While most methods have focused on short-read sequencing, long-read technologies offer potential advantages in repeat mapping and variant phasing. We present DeepSomatic, a deep-learning method for detecting somatic small nucleotide variations and insertions and deletions from both short-read and long-read data. The method has modes for whole-genome and whole-exome sequencing and can run on tumor-normal, tumor-only and formalin-fixed paraffin-embedded samples. To train DeepSomatic and help address the dearth of publicly available training and benchmarking data for somatic variant detection, we generated and make openly available the Cancer Standards Long-read Evaluation (CASTLE) dataset of six matched tumor-normal cell line pairs whole-genome sequenced with Illumina, PacBio HiFi and Oxford Nanopore Technologies, along with benchmark variant sets. Across samples, both cell line and patient-derived, and across short-read and long-read sequencing technologies, DeepSomatic consistently outperforms existing callers.

Humans↗

PubMed2026

Genetic Ancestry and Carrier Variant Frequency Enrichment in a Colombian Andean Population: Insights From the Eje Cafetero.

Colombia is one of the most genetically diverse populations in Latin America, and its demographic process has promoted the persistence and local enrichment of deleterious alleles, increasing the frequency of autosomal recessive disorders, particularly in semi-isolated Andean populations such as the Eje Cafetero. However, exome-based reference data from this region remain scarce, limiting ancestry-aware variant interpretation and carrier screening strategies. We aimed to characterize the ancestry proportions of this population using exome data, and to estimate the carrier frequency and distribution of pathogenic and likely pathogenic (P/LP) variants in clinically relevant recessive genes. We conducted a cross-sectional study with whole-exome sequencing (WES) in 316 unrelated individuals from the Colombian Eje Cafetero. P/LP variants were evaluated in 454 genes associated with autosomal recessive disorders. The global ancestry proportions were estimated using a validated panel of 250 exome-compatible ancestry-informative markers. Carrier frequencies were compared against Non-Finnish Europeans (NFE) and Admixed Americans (AMX) from gnomAD v4. The cohort showed predominant European ancestry (mean 51%), followed by Native American (36%) and African (13%) components. We identified 151 carriers of 89 distinct pathogenic variants across autosomal recessive genes. The most frequent variants were SERPINA1 c.863A>T (5.5%), CFTR c.1210-11T>G (3.5%), and PYGM c.1094C>T (1.5%). Also, recurrent variants were significantly enriched compared with both NFE and AMX populations, supporting regional founder effects. This study represents one of the most comprehensive exome-based genetic characterizations of the Colombian Eje Cafetero, revealing ancestry-specific enrichment of clinically relevant autosomal recessive variants driven by founder effects.

Female↗

PubMed2024

Family genetic risk communication and reverse cascade testing in the BabySeq project.

PURPOSE: Genomic sequencing of newborns can initiate disease surveillance and therapy for children and may identify at-risk relatives through reverse cascade testing. We explored genetic risk communication and reverse cascade testing among families of newborns who underwent exome sequencing and were identified as having a risk for an autosomal dominant disease. METHODS: We conducted semistructured interviews with parents of newborns enrolled in the BabySeq Project who had a pathogenic or likely pathogenic variant associated with an autosomal dominant childhood- and/or adult-onset disease returned. We used directed content analysis to derive themes. RESULTS: From 11 families, all first-degree relatives (n = 32, 100%), 29 second-degree relatives (76%), and 26 third-degree relatives (43%) were informed of their risk. All parents (n = 22, 69% of first-degree relatives), 4 (11%) second-degree relatives, and 1 (2%) third-degree relatives underwent cascade testing. Most parents preferred to handle risk communication themselves. Parents with positive cascade testing but no associated symptoms were less inclined to share findings with relatives but highly motivated to share results if the variant's associated disease severity was high, as perceived with adult-onset conditions. One new subtheme, family member traits, was identified and defined as a relative's propensity to anxiety/concern after risk communications but did not diminish risk communication. CONCLUSION: Findings can inform more effective notification and testing practices for families of newborns at risk for hereditary genetic conditions.

Humans↗

PubMed2026

COMMD9-regulated endothelial cell abnormality-induced hypercoagulability is associated with Budd-Chiari syndrome.

BACKGROUND: Budd-Chiari syndrome (BCS) presents diagnostic and treatment challenges owing to its insidious onset. Genetic variants associated with BCS vary geographically; in Asian populations, the condition is primarily caused by membranous obstruction composed of endothelial cells (ECs). A better understanding of the genetic pathogenesis of membranous BCS may offer new insights into disease mechanisms. METHODS: This study employed whole-exome sequencing to identify candidate genes responsible for EC abnormalities in 485 patients with membranous BCS and 329 patients with vascular malformations (VaMs). Functional investigations were conducted to validate the selected genes in vitro and in vivo. RESULTS: Whole-exome data revealed that the frequency of variants in the vascular function-related KLHDC2 exceeded that of JAK2 in BCS. Knockdown of KLHDC2 promoted adhesion and suppressed proliferation of ECs. In addition, 92 genes enriched for rare variants overlapped between BCS and VaMs. Systems biology analysis revealed two gene clusters, including COMMD9, enriched in proteins intolerant to loss-of-function mutations. Furthermore, suppression of COMMD9 impaired EC migration and tube formation, inhibited subintestinal angiogenic sprouting in zebrafish, and elevated EC adhesion. Transcriptomic analysis linked COMMD9 to EC abnormalities via the PI3K-Akt pathway. Commd9 knockdown promoted venous hypercoagulability in vivo following drug or ligation-induced stenosis. CONCLUSIONS: These findings indicate that multiple rare genetic variants, particularly in COMMD9, are involved in the development of membranous BCS by regulating hypercoagulability induced by EC abnormalities. These findings may help guide future clinical research towards improved understanding and treatment of BCS.

Budd–Chiari syndrome↗

PubMed2026

Whole-exome characterization of host genetic variation in HIV-associated genes across the high-prevalence Mizo population, Northeast India.

BACKGROUND: The Mizoram state of Northeast India has one of the highest HIV prevalence rates in Asia, yet the host genetic factors influencing HIV susceptibility in this Tibeto-Burman population remain uncharacterised. METHODS: We performed whole-exome sequencing using Illumina NovaSeq 6000, mean coverage 100X on 76 HIV-negative Mizo individuals. Variants were called using GATK HaplotypeCaller v4.3 against GRCh38p14, annotated with ANNOVAR, and filtered using hard-quality thresholds (QD ≥ 2, SOR ≤ 3, MQ ≥ 40, DP ≥ 10, GQ ≥ 20). The allele frequencies were compared against gnomAD v2.1.1 population databases. Hardy-Weinberg equilibrium was assessed using the Wigginton exact test with Bonferroni correction. RESULTS: Post-quality filtering resulted in 12,011 sample-variants across 2,821 unique positions from 36 HIV-associated loci (33 protein-coding genes, 2 chemokine ligands, and 3 lncRNA targets). Of these, 784 observations (51 unique positions) were high-impact nonsynonymous or loss-of-function variants. ADAR rs2229857 (p.K384R, NM_015840) was the most frequently observed variant (Mizo carrier frequency = 0.895; 95% CI: 0.806-0.946). CXCR1 rs16858808 (p.R335C) showed the greatest population enrichment (Mizo carrier frequency = 0.197; 95% CI: 0.123-0.300; 7.65-fold carrier-frequency enrichment versus gnomAD South Asian; CADD = 15.60). Sixteen of 20 tested variants deviated from Hardy-Weinberg equilibrium after Bonferroni correction (p < 0.0025), predominantly showing excess homozygosity consistent with the endogamous Mizo population. The protective variant CCR5-Δ32 was absent in all the 76 individuals tested. CONCLUSION: This first whole-exome characterization of HIV host genes in the Mizo population identifies CXCR1 rs16858808 as the most population-enriched functional variant and reveals a pervasive endogamy signature. These findings provide a population-specific genetic framework for future HIV susceptibility studies and ART pharmacogenomics research.

Humans↗

PubMed2026

TTC19 and FMNL2 gene variants in a pediatric case of mitochondrial disorder with renal tubular acidosis.

Mitochondrial complex III deficiency caused by pathogenic variants in TTC19 is a heterogeneous disorder typically presenting with progressive neurological involvement in late childhood. Early-onset of disease with predominant renal manifestations are uncommon and may complicate diagnosis. We report a child presenting with developmental delay, failure to thrive, lactic acidosis, and distal renal tubular acidosis (dRTA), raising suspicion of an underlying mitochondrial disorder. Whole exome sequencing (WES) analysis identified a homozygous intron-exon boundary deletion of 31 bp (c.463-19_474del) in TTC19 predicted to disrupt splicing, with functional evidence demonstrating aberrant transcript formation, reduced gene expression, and mitochondrial dysfunction in patient-derived fibroblasts. Based on the biochemical findings, re-analysis of exome data revealed a novel homozygous canonical splice-site variant (c.783-1G>A) in FMNL2. The splicing assay showed the skipping of exon 9, and reduced expression in the fibroblasts. This case expands the clinical spectrum of TTC19-related mitochondrial complex III deficiency with early-onset renal tubular acidosis. While TTC19 is the most plausible primary disease-causing gene, the functional disruption of FMNL2 suggests a potential contributory role or association with the renal phenotype. Hence, these findings highlight the importance of genomic re-analysis along with functional studies in resolving complex multisystem disorders.

Female↗

PubMed2026

Identification of the Genomic Etiology of Unexplained Congenital Problems in Pediatric Patients: First Reported Case With Coffin-Siris Syndrome and Sialuria From India.

Coffin-Siris syndrome (CSS) (OMIM:614608) is a rare genetic disorder characterized by global developmental delay (GDD), speech impediment, coarse facial features, and hypoplastic or absent fifth fingernails/toenails. Genetic variants in the SMARCB1 gene are associated with CSS, benign tumors (schwannomas), and rhabdoid tumor predisposition syndrome. Genetic variants in the GNE gene are associated with the autosomal dominant sialuria (OMIM#269921), a rare inborn error of metabolism resulting in high levels of free sialic acid. Here we present case reports of two siblings: patient 1 (10 years) and patient 2 (2 years). While both siblings showed GDD and dysmorphic features such as hypotelorism and large ears, patient #1 exhibited additional phenotypes. Whole exome sequencing identified a heterozygous pathogenic variant, NM_003073.5:c.1096C>T (p.Arg366Cys), in the SMARCB1 gene in both siblings. In addition, patient 1 harbored a heterozygous likely pathogenic variant, NM_005476.7:c.2086G>A (p.Val696Met), in the GNE gene, which was absent in patient 2. The co-occurrence of the GNE variant may contribute to the increased severity of the phenotype in patient 1. This study is the first report worldwide of the co-occurrence of two extremely rare disorders. These findings highlight the complexity of genomic contributions while also emphasizing the value of genomic sequencing for congenital problems.

Coffin–Siris syndrome↗

PubMed2025

Complex de novo structural variants are an underestimated cause of rare disorders.

Complex de novo structural variants (dnSVs) are crucial genetic factors in rare disorders, yet their prevalence and characteristics in rare disorders remain poorly understood. Here, we conduct a comprehensive analysis of whole-genome sequencing data of 12,568 families, including 13,698 offspring with rare diseases, obtained as part of the UK 100,000 Genomes Project. We identify 1,870 dnSVs, constituting the largest dnSV dataset reported to date. Complex dnSVs (n = 158; 8.4%) emerge as the third most common type of SV, following simple deletions and duplications. We classify 65% of these complex dnSVs into 11 subtypes. Among probands with dnSVs (n = 1,696), 9% exhibit exon-disrupting pathogenic dnSVs associated with the probands' phenotype. Notably, 12% of exon-disrupting pathogenic dnSVs and 22% of de novo deletions or duplications previously identified by array-based or whole-exome sequencing methods are found to be complex dnSVs. We also find distinct genomic properties of de novo deletions depending on the parent of origin. This study highlights the importance of complex dnSVs in the cause of rare disorders and demonstrates the necessity of specific genomic analysis to avoid overlooking these variants.

Humans↗