Search Results (348)

Background/Objectives: X-linked Alport syndrome (XLAS) arises from pathogenic variants in COL4A5. Truncating variants are generally classified as severe, but whether clinically meaningful heterogeneity exists within this group remains unclear. This study aimed to establish a novel Col4a5 knock-in mouse model based on a clinical variant and to determine whether truncating mutation position influences disease severity. Methods: A de novo COL4A5 frameshift variant, c.2440delG, was identified in a patient with severe early-onset XLAS. A Col4a5-G814fs knock-in mouse was generated by CRISPR/Cas9 on the C57BL/6J inbred mouse strain background and compared with the established Col4a5-G5X nonsense model using survival analysis, serial functional measurements, kidney histopathology, transmission electron microscopy, and RNA sequencing. Results: The Col4a5-G814fs knock-in mouse was successfully generated and showed loss of glomerular α5(IV) collagen chain expression. Compared with G5X mice, G814fs mice exhibited shorter survival (median 141 vs. 161.5 days, p = 0.0004), earlier onset of proteinuria, and more severe kidney functional decline. By 16 weeks, G814fs mice also showed more severe glomerular basement membrane abnormalities and more extensive glomerulosclerosis. RNA sequencing revealed a shared inflammatory gene signature in both models, together with selective upregulation of genes related to the PPAR signaling pathway and fatty acid metabolism in G814fs kidneys. Conclusions: This study reports a novel de novo COL4A5 frameshift variant and establishes the first Col4a5-G814fs knock-in mouse model. Direct comparison with the G5X model shows that distinct truncating COL4A5 mutations can be associated with substantially different disease severity, providing a useful platform for future mechanistic and therapeutic studies in XLAS. Full article

Background/Objectives: Amelogenesis imperfecta (AI) is a heterogeneous group of rare hereditary conditions mainly affecting the quantity and/or quality of tooth enamel. Its phenotypic expression is diverse, as is the mutational spectrum of the AI-causing genes and mutations. Integrins are cell-surface receptors that mediate adhesion between cells and between cells and the extracellular matrix. Among these, mutations in integrin αvβ6 have been shown to cause AI; however, phenotypic variation exists between the knockout mouse model and human cases, as well as among different human AI families. Methods: We recruited AI families and performed mutational analysis using whole exome sequencing. Results: We identified compound heterozygous ITGB6 mutations in two families. In Family 1, a paternally transmitted nonsense mutation (NM_000888.5: c.1060C>T, p.(Gln354*)) and a maternally transmitted missense mutation (NM_000888.5: c.2312A>G, p.(Asn771Ser)) were identified; in Family 2, a paternal missense mutation (NM_000888.5: c.1693T>C, p.(Cys565Arg)) and a maternal frameshift mutation (NM_000888.5: c.2091delC, p.(Asn698Metfs*13)) were identified, each causing AI in the respective proband. Both probands exhibited generalized hypoplastic and hypomineralized AI, but no other extraoral symptoms. Conclusions: This report will not only expand the known mutational spectrum of the ITGB6 gene but also provide evidence for the genotype–phenotype correlations, thereby improving our understanding of the functional role of ITGB6 during amelogenesis. Full article

Lumpy skin disease virus (LSDV) is a large DNA capripoxvirus that causes LSD, a disease that has major economic impact. Since 1989, several sporadic outbreaks were reported in Israel, with the latest outbreaks in 2012, 2019 and 2023. Although considered genetically stable, LSDV shows a high degree of genetic recombination events and genetic variations. In particular, in-frame nonsense mutations were suggested to act as one of the main evolutionary drivers of outbreaks. Whole-genome sequencing of LSDV isolates from the 2019 and 2023 outbreaks was used for genomic analysis using various bioinformatics tools to characterize the genomic evolution, recombination events and micro-evolutionary forces shaping LSDV in Israel by comparing isolates. Comparative genomic analysis revealed substantial nucleotide substitutions in the 2019 and 2023 isolates relative to the 2012 isolate. Specifically, increased nucleotide mismatches, inter-genic deletion, enhanced APOBEC editing signatures and elevated codon usage. Additionally, numerous mutations were recognized, leading to structural disruptions in specific viral proteins and possible RNA instability. In conclusion, this analysis supports that nucleotide substitutions, codon selection pressure and APOBEC-associated editing had driven local microevolution of LSDV during the years between outbreaks despite the absence of clinical indications and major vaccination campaigns. Furthermore, genomic evidences of recombination events between the 2012 and 2019 isolates suggests that these processes may have contributed to the emergence of the variant identified during the 2023 outbreak. Full article

Background: Duchenne muscular dystrophy (DMD) is a rare, disabling, and life-threatening X-linked recessive disorder caused by mutations in the dystrophin gene. The current standard of care is treatment with corticosteroids, which aim to decrease inflammation-induced muscle damage and delay disease progression. Here, we aim to describe clinical, genetic, and diagnostic characteristics and evaluate current management practices of DMD patients in the Kingdom of Saudi Arabia (KSA). Methods: This was an ambispective (prospective and retrospective) observational multicenter study evaluating characteristics of patients aged 1–14 years with genetically confirmed DMD in the KSA. The variables of interest were demographics, genetic mutations, clinical characteristics, and initial management. The relationship between the age at diagnosis, initial management plan (standard of care), and age at initiation of treatment on disease outcomes was also evaluated. Results: A total of 226 patients (181 in the retrospective part and 45 in the prospective part) were enrolled. The most common type of genetic mutation was large deletions (134 patients, 59.3%). The median age of first symptom was 2.7 years (IQR: 2.0–4.6 years) and the median age at diagnosis was 7.0 years (IQR: 4.8–8.5 years). Among these patients, the most common initial symptoms were difficulty in walking (87.7%) and waddling gait (41%). The initial management plan for DMD patients involved medication (75.6%) and physical therapy (71.0%). The most frequently prescribed initial medications were vitamin D (82%) and corticosteroids (62.3%). In total, 6/226 patients (2.6%) received ataluren; they all had identified nonsense mutations. The median age of corticosteroid initiation was 7.1 years (IQR: 5.7–8.7). The median age at loss of ambulation (LoA) was 9.8 years (IQR: 8.0–11.4 years) in the non-treated patients; it was 10.1 years (IQR: 9.3–11.2 years) in the steroid-only group and 10.8 years (10.8, 10.8) in the combined ataluren and steroid treatment group. Discussion: Age of diagnosis and age of treatment initiation is relatively late in the KSA. However, early diagnosis and early treatment onset is associated with better clinical outcomes, mainly a delay in LoA. Therefore, there is an urgent need for raising awareness and enhancing early screening in the KSA. Full article

Background: Genetic causes of growth failure should be suspected in patients born small for gestational age (SGA) who fail to show postnatal catch-up growth, present with severe short stature (SS), and exhibit a poor or absent response to growth hormone (rhGH) therapy. Mutations in the insulin-like growth factor 1 receptor (IGF1R) gene are associated with impaired growth, intrauterine growth restriction (IUGR), low birth weight and/or length, and postnatal SS. Case Description: A 9-year-old boy, born SGA for birth length, was evaluated for severe SS. Common causes of SS were excluded. At 9 years and 7 months of age, his height was 112.6 cm (−3.99 SDS), weight 18 kg (−3.79 SDS), and BMI 14.2 kg/m² (−1.8 SDS); pubertal development was Tanner stage 1. The target height was 158 cm (−2.62 SDS). Bone age was delayed by approximately one year compared with chronological age. Serum IGF-1 levels were within the upper-normal range for age. GH therapy (0.035 mg/kg/day) was initiated due to the lack of catch-up growth in an SGA subject. After three years of treatment, the height gain was only 0.5 SDS. IGF-1 levels showed a transient treatment-related increase, followed by persistent normalization during ongoing therapy. Next-generation sequencing (NGS) analysis identified novel heterozygous paternal nonsense variant in the IGF1R gene: c.3498C>G (p.Tyr1166Ter). At 12 years of age, impaired fasting glucose and reduced glucose tolerance were detected; consequently, it was decided to discontinue rhGH therapy, also in light of the IGF1R mutation and the lack of height recovery. Conclusions: This case underlines the critical role of genetic testing in the evaluation of patients born SGA. The coexistence of SGA status and an IGF1R gene mutation may provide a clear explanation for both the poor response to rhGH therapy and the increased risk of alterations in glucose metabolism. An extensive narrative review of the literature on growth outcomes and glucose metabolism abnormalities during GH treatment in SGA patients carrying IGF1R variants was also performed. Full article

Background/Objectives: Coffin–Lowry syndrome (CLS) is a rare X-linked disease caused by pathogenic variants in the RPS6KA3 gene. It is generally characterized by syndromic intellectual disability and distinctive facial features, skeletal abnormalities, stimulus-induced drop attacks in males, and variable manifestations in females. Methods: We report clinical and genetic findings in a series of 10 cases, eight males and two females, evaluated at the Regional Centre of Medical Genetics Dolj—Emergency Clinical County Hospital Craiova. Results: Genetic testing identified 10 de novo variants in the RPS6KA3 gene consisting of six missense mutations, one nonsense variant, one frameshift, and two variants in non-coding or intronic regions. Case management requires multidisciplinary coordination and is limited to resources mostly available in reference centers. Conclusions: CLS highlights the importance of molecular diagnosis in rare genetic disorders, particularly when clinical features are subtle or atypical. These findings have practical implications for clinical management, suggesting the need for comprehensive genetic screening and individualized care approaches. Full article

Introduction: Congenital central hypoventilation syndrome (CCHS) is a rare disorder characterized by an impaired ventilatory response to hypercapnia and hypoxia, particularly during sleep, and frequently associated with autonomic dysfunction. It is caused by pathogenic variants in the PHOX2B gene. Although CCHS is typically diagnosed in the neonatal period, milder forms may present later in infancy or childhood, often triggered by respiratory infections. Case presentation: We report the case of 16-month-old male diagnosed with CCHS following an episode of hypoxemic–hypercapnic respiratory failure during respiratory syncytial virus (RSV) infection. His medical history included neonatal respiratory distress requiring oxygen therapy and recurrent wheezing. At 15 months, he developed acute respiratory distress with severe hypercapnia (PaCO₂ 70 mmHg), requiring admission to the Pediatric Intensive Care Unit and invasive mechanical ventilation. Persistent sleep-related hypercapnia and hypoxemia prompted evaluation for central hypoventilation, confirmed by means of transcutaneous capnography and nocturnal pulse oximetry. Genetic testing revealed a de novo nonsense mutation in exon 1 of PHOX2B (p.Tyr14Ter). Brain magnetic resonance imaging showed diffuse white matter changes suggestive of gliosis. Further investigations identified early-onset systemic hypertension, requiring antihypertensive therapy. The patient was discharged on nocturnal non-invasive ventilation and enrolled in a neurodevelopmental rehabilitation program. Conclusions: This case highlights the phenotypic variability of CCHS and the importance of considering this diagnosis in children presenting with unexplained hypercapnia and sleep-related hypoxemia. It underscores the need for comprehensive autonomic evaluation, including blood pressure monitoring. The p.Tyr14Ter variant may allow partial protein function, potentially accounting for the relatively mild phenotype. Full article

Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular disease (NMD) caused by loss-of-function mutations in the DMD gene. RNA-based therapies, especially antisense oligonucleotides (ASO)-mediated exon skipping and adenosine deaminase acting on RNA (ADAR)-guided RNA editing, have emerged as complementary approaches that modulate pre-mRNA splicing or correct transcripts without altering genomic DNA. Current phosphorodiamidate morpholino oligomer (PMO) drugs targeting exons 51, 53, and 45 provide mutation-class-specific benefit. At the same time, next-generation delivery strategies (e.g., peptide-conjugated PMOs (PPMOs), antibody–oligonucleotide conjugates (AOC), and endosomal-escape vehicles) aim to improve skeletal, cardiac, and diaphragm exposure. In parallel, RNA editing strategies offer a route to correct select nonsense or missense variants at the base level and may, in principle, restore near-native dystrophin expression. Meaningful translation of these modalities requires predictive large-animal models. A genome-edited microminipig (MMP) bearing DMD exon-23 mutations faithfully recapitulates hallmark features of human DMD. That includes early locomotor deficits, elevated serum creatine kinase (CK) and cardiac troponin T, progressive myocardial fibrosis, and a decline in left-ventricular ejection fraction (LVEF), while maintaining a manageable lifespan of approximately 30 months suitable for long-term studies. In particular, the MMP model provides a practical platform for addressing the persistent challenge of efficient therapeutic delivery to the heart and diaphragm through longitudinal dosing, imaging, and biopsy. In this review, we synthesize clinical progress in exon skipping, outline the promise of RNA editing, and integrate recent insights from Duchenne muscular dystrophy model for microminipigs (DMD-MMPs) as an advanced surrogate for preclinical development and translational evaluation. Full article

Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular disorder caused by loss-of-function mutations in the dystrophin gene, leading to progressive muscle degeneration, motor decline, respiratory compromise, and cardiomyopathy. Diagnosis typically occurs in early childhood following recognition of motor delays, markedly elevated creatine kinase, and confirmatory genetic testing. Over the past decade, the therapeutic landscape for DMD has expanded substantially, evolving from exclusively supportive care to patient-centric multifaceted treatment paradigms, including corticosteroids, mutation-specific therapies, small molecule disease-modifying approaches, and gene replacement strategies. Despite these advances, no currently available therapy restores full-length dystrophin or completely halts disease progression. This review provides a clinically oriented comprehensive overview of currently Food and Drug Administration (FDA)-approved medications for DMD, with particular emphasis on corticosteroids, exon-skipping therapies, nonsense mutation readthrough agents, recently approved gene therapy, and select ongoing gene therapy trials. We summarize mechanisms of action, clinical efficacy, safety considerations, regulatory status, and highlight the challenges of integrating these therapies into longitudinal care. Through illustrative clinical vignettes, we highlight the real-world complexity of treatment selection, shared decision-making, and longitudinal care planning in contemporary DMD management. Full article

Background/Objectives: Human induced pluripotent stem cell (hiPSC) models provide a unique platform for testing the effect of genomic variants identified in patients with inherited diseases. In Alström syndrome, a rare multisystem disorder mainly caused by nonsense mutations in the ALMS1 gene, patients often present with infantile cardiomyopathy, retinal dystrophy, type 2 diabetes, and hearing loss in addition to obesity. These diverse clinical manifestations highlight the pleiotropic functions of ALMS1 in cellular processes such as ciliary signalling, cell cycle regulation, and tissue homeostasis. In cats, the ALMS1:c.7384G>C missense variant has been associated with cardiomyopathy in the absence of other symptoms of Alström syndrome, raising questions regarding the impact of this variant on cardiac pathology. Methods: To answer these questions, we generated an hiPSC line carrying the human ALMS1:c.10004G>C missense variant, homologous to the ALMS1:c.7384G>C feline variant, as well as an isogenic control, to investigate the impact of this variant on cardiomyocyte differentiation and function. Results: The introduction of the ALMS1:c.10004G>C variant in the homozygous state in hiPSCs resulted in a significant reduction in cardiomyocyte differentiation efficiency. However, the variant did not affect contractile frequency, sarcomere organisation, sarcomere length, or cardiomyocyte cell size. Together, these results suggest that while the ALMS1:c.10004G>C variant impairs cardiomyocyte differentiation, it does not disrupt the structural or functional properties of the hiPSC-derived cardiomyocytes that do form. Conclusions: We have generated and initiated the characterisation of the third ALMS1 mutant hiPSC line and the first line based on a missense variant, but further research is needed on its relevance in modelling ALMS1-related changes. Our results also support the previous recommendation not to use ALMS1:c.7384G>C for the selection of breeding cats until further data confirm its intrinsic pathogenicity. Full article

Background: The most common form of monogenic diabetes is maturity onset diabetes of the young (MODY). This study investigates the molecular basis of MODY type 2 (GCK-MODY) in a group of Italian patients, focusing on the functional characterization of a synonymous variant, c.579G>T (p.Gly193Gly), in the glucokinase gene (GCK). Methods: Clinical evaluation and genetic analysis, including whole exome sequencing and Sanger sequencing, were used to identify the variant in GCK, then functional studies using a minigene approach allowed the functional characterization. Results: This study identified the synonymous variant, along with a nonsense mutation, c.859C>T (p.Gln287Ter), in GCK in two Italian patients. Minigene approach demonstrated that the synonymous variant disrupts splicing at the exon 5 boundary, leading to a frameshift and premature stop codon. Similarly, the nonsense mutation also altered splicing, exacerbating the molecular defect. Conclusions: These findings highlight the importance of functional assays, particularly minigene studies, in interpreting the pathogenicity of synonymous and nonsense variants, especially in genes like GCK where splicing alterations can significantly impact protein function. This study underscores the clinical utility of targeted genetic screening for personalized diabetes management. Full article

Pathological USH2A mutations cause Usher syndrome type II, characterized by progressive retinitis pigmentosa and hearing and balance impairment. This study aims to investigate the cellular mechanisms underlying USH2A-related retinal degeneration using human induced pluripotent stem cell (hiPSC)-derived retinal organoids. The introduction of a homozygous nonsense mutation in the USH2A hotspot exon-13 resulted in normal photoreceptor development but loss of ciliary localization of usherin long form B and its interacting proteins, ADGRV1 and whirlin. Notably, single-cell RNA sequencing revealed unexpected significant transcriptional changes in Müller glial cells (MGCs), suggestive of disruptions in the translation, innate immune response, and endolysosomal system. These findings suggest that, while photoreceptor cells are mildly affected by the exon-13 USH2A mutation, MGCs exhibit major transcriptional changes, potentially contributing to the disease progression and therefore shedding light on potential alternative therapeutic targets. Full article

Nonsense mutations, responsible for ~11% of gene lesions causing human monogenic diseases, introduce premature termination codons (PTCs) that lead to truncated proteins and nonsense-mediated mRNA decay (NMD). In the central nervous system (CNS), these mutations drive severe, progressive neurological conditions such as spinal muscular atrophy, Rett syndrome, and Duchenne muscular dystrophy. Readthrough therapies—strategies to override PTCs and restore full-length protein expression—have evolved from early aminoglycosides to modern precision tools including suppressor tRNAs, RNA editing, and CRISPR-based platforms. Yet clinical translation remains hampered by inefficient CNS delivery, variable efficacy, and the absence of personalized stratification. In this review, we propose a translational framework—the 4 Ds of Readthrough Therapy—to systematically address these barriers. The framework dissects the pipeline into Detection (precision patient identification and biomarker profiling), Delivery (engineered vectors for CNS targeting), Decoding (context-aware molecular correction), and Durability (long-term safety and efficacy). By integrating advances in machine learning, nanocarriers, base editing, and adaptive trial designs, this roadmap provides a structured strategy to bridge the translational gap. We advocate that a synergistic, modality-tailored approach will transform nonsense suppression from palliative care to durable, precision-based cures for once-untreatable neurological disorders. Full article

Biallelic variants in NDUFS6, encoding an accessory subunit of mitochondrial complex I, were initially associated with lethal neonatal mitochondrial encephalopathy and Leigh syndrome. Recent studies have demonstrated that NDUFS6 variants can also cause childhood- or adolescent-onset axonal neuropathy and Charcot–Marie–Tooth (CMT)-like phenotypes, indicating marked clinical heterogeneity. Here, we report a patient with a novel homozygous truncating NDUFS6 variant presenting with a neuropathy-predominant phenotype accompanied by epilepsy, in the absence of neonatal metabolic decompensation. The patient presented with childhood-onset progressive gait abnormality, pes cavus deformity, distal weakness requiring Achilles tendon-release surgery, pyramidal signs, urinary incontinence, and focal epileptiform EEG findings. Brain MRI showed bilateral lenticular nucleus abnormalities. Whole-exome sequencing identified a novel homozygous NDUFS6 nonsense variant (c.130C>T, p.Gln44*). While neuropathy has previously been reported primarily in association with the recurrent splice-site variant c.309+5G>A, our findings demonstrate that truncating NDUFS6 mutations can also underlie a neuropathy-predominant phenotype. Together with previously published cases, our findings support a phenotypic heterogeneity ranging from lethal encephalopathy to neuropathy and reinforce the role of NDUFS6 as a disease-causing gene for inherited peripheral neuropathy. These data support inclusion of NDUFS6 among established neuropathy and Charcot–Marie–Tooth genes. Full article

Background/Objectives: Consanguine families are helpful to identify recessive candidate genes for inherited diseases, but can also show an unusual inheritance pattern of pathogenic mutations. In this case series, we demonstrate this in five consanguine families with epilepsy from Pakistan. Methods: We performed whole exome sequencing of respective index patients, analyzed the data using two different models for inheritance of mutations and determined the segregation pattern of relevant mutations in the families by bi-directional Sanger sequencing. Results: Apart from mutations in classical dominant epilepsy genes (TSC2, DEPDC5, and CACNA1I), pathogenic mutations in rare recessive epilepsy-related genes (PGAP2, NOVA2, and CCDC88C) were also identified. Interestingly, we were able to provide evidence that GALR2 is potentially an additional gene associated with a recessive form of epilepsy. In one family, a homozygous ‘pathogenic’ TRAF3IP1 p. Gly387* nonsense mutation was identified, which, most probably due to stop-codon read-through, did not contribute to the phenotype. Conclusions: Our case series of consanguine families with epilepsy exemplifies the inheritance pattern of mutations in rare recessive epilepsy genes, and shows that mutations in classical epilepsy genes showing dominant or sporadic inheritance can also be relevant. That requires the analysis of whole exome data on the basis of different inheritance models. Full article