Journal of Medical Genetics最新文献

Deleterious variants in the BRSK2 gene, which encodes a serine/threonine kinase crucial for neuronal polarisation and brain development, have recently been linked to the pathogenesis of autism spectrum disorder (ASD). However, comprehensive clinical descriptions of individuals with pathogenic BRSK2 variants remain limited, and the molecular and cellular consequences of these mutations are poorly understood. This case report provides a detailed clinical, cognitive and molecular characterisation of a male patient with ASD harbouring a de novo BRSK2 frameshift variant, who developed catatonia, developmental regression and cognitive decline during early adolescence. To assess the functional impact of the variant, induced pluripotent stem cells (iPSCs) and iPSC-derived neural organoids were generated from the patient. Molecular analyses revealed a significant reduction in BRSK2 transcript and protein levels. Sequencing of BRSK2 mRNA showed exclusive expression from the wild-type allele, consistent with degradation of the mutant transcript via nonsense-mediated decay. These findings broaden the mutational and phenotypic spectrum associated with BRSK2-related neurodevelopmental disorders and provide functional evidence supporting the pathogenicity of the identified variant. Furthermore, this report demonstrates the role of BRSK2 in complex neuropsychiatric features-such as catatonia and cognitive deterioration, which remain underreported in the existing literature-and emphasises the importance of longitudinal cognitive and behavioural monitoring in individuals with BRSK2 mutations.

Duchenne muscular dystrophy (DMD) is a severe X-linked myopathy characterised by progressive skeletal and cardiac muscle degeneration, loss of ambulation, respiratory failure and premature mortality. Although corticosteroids and gene therapies have improved disease management, they are limited by significant side effects, mutation specificity and delivery challenges, underscoring the need for an alternative or an adjunctive strategy. Emerging evidence identifies autophagy dysregulation as a critical secondary pathological mechanism in DMD, contributing to impaired clearance of damaged organelles and toxic protein aggregates, exacerbating muscle atrophy and fibrosis.This review aims to acknowledge current insights into autophagy regulation in healthy muscle and its disruption in DMD, explore its crosstalk with key pathological pathways such as nuclear factor kappa B signalling, mitochondrial dysfunction and endoplasmic reticulum stress and critically evaluate emerging therapeutic strategies targeting autophagy.Autophagy, a fundamental cellular recycling process, is suppressed in DMD by hyperactivation of the Akt-mTOR pathway and dysregulated calcium homeostasis. This leads to mitochondrial dysfunction, oxidative stress and activation of inflammatory cascades. Recent preclinical studies highlight the therapeutic potential of pharmacological and dietary autophagy modulators, including rapamycin, 5-aminoimidazole-4-carboxamide ribonucleotide, low protein diets, SRT2104 and Givinostat, which improve autophagic flux, restore mitochondrial integrity and attenuate fibrosis. Lifestyle interventions and combinatorial approaches further underscore the importance of integrating multimodal strategies.Further research should focus on longitudinal studies to optimise therapeutic timing, validate dynamic biomarkers (LC-II, p62, miRNAs) and leverage artificial intelligence with multiomics integration for precision therapies. Targeting autophagy and its interconnected pathways holds promise for transforming DMD management and improving patient outcomes.

Background: Desmin (DES) is a major intermediate filament protein involved in the structural integrity and function of striated muscles. Pathogenic mutations in DES are predominantly missense variants, causing isolated cardiomyopathy and combinations of myopathy and cardiomyopathy. In-frame insertions are very rare and usually classified as variants of uncertain significance or likely pathogenic due to limited predictive and/or experimental evidence.

Methods: This study describes a novel heterozygous in-frame insertion in exon 6 of DES (RefSeq NM_001927.4:c.1059_1061dup) identified in an Argentine family with myofibrillar myopathy (MFM). This mutation results in the duplication of a glutamic acid residue at position 353 (NP_001918.3:p.(Glu353dup)), in the 2B subdomain of the central rod domain. Clinical, computational and functional analyses were performed to study the pathogenicity of this variant.

Results: Clinically, the index patient exhibited hallmark MFM features, including progressive muscle weakness, atrophy and fatty muscle replacement. In silico analyses of molecular dynamics revealed that p.Glu353dup alters DES dimer assembly by stabilising an aberrant coiled-coil conformation, a mechanism not previously proposed for DES mutations. Functional studies in HEK293T cells and C2C12 myocytes suggested that the p.Glu353dup variant induces aberrant DES aggregation, confirming its detrimental effect on filament organisation.

Conclusion: These findings are consistent with the idea that p.Glu353dup is a pathogenic variant, supported by clinical studies, in silico protein modelling and functional evidence, highlighting the impact of in-frame insertions on DES filament homeostasis. By providing computational and experimental evidence, this study expands our understanding of desminopathies and offers new perspectives for pathogenicity assessment of uncertain DES variants.

Background: MECOM encodes a developmental and haematopoietic transcription factor associated with a rare early-onset syndrome including bone marrow failure, skeletal and other congenital anomalies. Heterozygous de novo variants are the primary cause. We previously identified MECOM as a candidate gene for paediatric pulmonary arterial hypertension (PAH) using trio exome sequencing.

Methods: To test the role of MECOM in paediatric PAH and further define the clinical phenotype of MECOM-associated syndrome, we queried GeneMatcher and screened rare disease databases for individuals with predicted deleterious MECOM variants. We analysed the clinical spectrum of patients, performed protein modelling of genetic variants and assessed cardiopulmonary expression.

Results: We identified 15 individuals with MECOM variants, including 11 unrelated probands and 8 de novo variants. 11 individuals had severe or mild thrombocytopenia, 9 had skeletal issues, 8 had cardiac anomalies, 6 had PAH and 10 had additional conditions. Three were diagnosed in utero and died in the neonatal period. All missense variants map to the zinc finger 6 or zinc finger 8/9 region, a known hotspot for MECOM-associated syndrome. Protein modelling predicted that both regions are DNA-binding, and that the variants may interfere with binding to a VEGFR2/KDR enhancer. Data from LungMAP showed that MECOM is primarily expressed in pulmonary arterial endothelial cells.

Conclusion: Rare MECOM variants are associated with early-onset syndromic PAH. PAH monitoring should be considered for all individuals with rare MECOM variants. We speculate that the pathogenetic mechanism for PAH and cardiac defects may be impaired VEGFR2/KDR signalling.

Background: Biallelic pathogenic variants in PNKP are associated with microcephaly and early-onset seizures (MCSZ), ataxia with oculomotor apraxia type 4 and Charcot-Marie-Tooth disease type 2B2.

Methods: We describe the clinical and neuroimaging features of 27 new patients with PNKP variants. All patients presented with early-onset seizures, congenital microcephaly and intellectual disability. In addition, we compared our results with data in the literature.

Results: Twenty-five patients presented with the classic MCSZ phenotype, while two showed a more severe clinical phenotype. The brain imaging features of the 25 patients varied significantly, but widening of the frontal lobe gyri with frontal hypoplasia and prominent cerebellar folia (consistent with atrophy) could point to PNKP-related microcephaly . In contrast, the two patients with severe phenotype showed additional brain MRI features of white matter loss and pontocerebellar hypoplasia fulfilling the criteria of microlissencephaly. Exome sequencing identified seven different PNKP variants, including two novel ones. The c.1253_1269dup p.(Thr424GlyfsTer49) and c.1381_1383dup p.(Asn461dup) variants, each was recurrent in 10 patients (37%), while the c.1381_1383del p.(Asn461del) variant was recurrent in four patients (14.8%). Haplotype analysis confirmed that the p.Asn461dup variant has a founder effect in our population. No genotype-phenotype correlation was observed in our cohort.

Conclusion: Our results provide 'microlissencephaly' as an emerging distinct phenotype linked to PNKP variants. As such, PNKP variants could be associated with four overlapping subgroups that lie along a unifying phenotypic continuum.

Background: Tau-tubulin kinase 1 (TTBK1) is a neuron-enriched kinase implicated in τ phosphorylation and neurodegeneration. Human phenotypes associated with constitutional TTBK1 variants remain undefined.

Methods: Two siblings with a severe neurodevelopmental phenotype were assessed using quartet exome sequencing, segregation analysis and standardised clinical and neuroimaging evaluations.

Results: Both children exhibited profound global developmental delay, non-ambulation, axial hypotonia with lower-limb spasticity and proportionate postnatal growth failure with microcephaly. Epilepsy was present in the older sibling. Brain MRI showed a thin brainstem and corpus callosum, periventricular T2 hyperintensities and mild cerebellar atrophy in the older sibling and external hydrocephalus in the younger. Exome sequencing identified a homozygous frameshift variant in TTBK1 (NM_032538.3:c.1899del; p.Thr634Argfs*39) that segregated with the disease. The variant was absent from population databases and predicted to cause loss-of-function. According to the American College of Medical Genetics and Genomics criteria, it fulfils PVS1 and PM2_P.

Conclusion: We report the two siblings with a neurodevelopmental disorder due to a biallelic TTBK1 loss-of-function variant, establishing TTBK1 as critical for human neurodevelopment. Together with preclinical data, these findings underscore its role in motor and cognitive circuits. Additional cases and functional studies will be essential to delineate the clinical spectrum and mechanistic basis of TTBK1 deficiency.

Background: Chromosome 19 is the most gene-dense chromosome in the human genome, with a high frequency of segmental duplications that predispose it to genomic rearrangements. While deletions of chromosome 19 have been associated with various clinical conditions, duplications remain poorly characterised. Here, we report three cases involving 19p13.11 duplication and describe the associated clinical phenotype.

Methods: We describe three unrelated individuals with microduplications at 19p13.11 identified either via clinical whole-exome sequencing or chromosomal microarray. The probands underwent detailed clinical genetic evaluations, and CNVs were confirmed with parental testing when available. Sequencing reads were aligned to the GRCh37/hg19 human genome build.

Results: All three probands exhibited neurodevelopmental delays, attention-deficit/hyperactivity disorder and speech delay. Additional overlapping features included joint hypermobility, short stature and craniofacial anomalies. Patient-specific manifestations included haematological abnormalities, musculoskeletal asymmetries and cardiac findings. Duplicated regions spanned 1.2-1.6 Mb and encompassed 41-49 protein-coding genes. Patients 2 and 3 have CNVs that overlap 76% with those of Patient 1. Several genes have predicted high triplosensitivity scores and are associated with autosomal dominant neurodevelopmental and skeletal disorders. Patient 1, with the largest duplication, had more extensive systemic involvement, likely reflecting the broader gene dosage effect.

Conclusion: This is the first comprehensive clinical and molecular characterisation of 19p13.11 duplications, suggesting a recurring multisystem phenotype driven by gene dosage sensitivity. These findings support the inclusion of 19p13.11 duplications in diagnostic evaluations for neurodevelopmental and multisystem disorders.

Background: Parent/patient-reported (PRD) datasets provide ready access to phenotypic data for monogenic neurodevelopmental disorders, yet their concordance with clinical data is unclear.

Methods: In the GenROC study, 547 children (mean age 7.6 years, balanced sex ratio) had parallel parent-reported web questionnaires and clinician-reported (CRD) Human Phenotype Ontology proformas. We compared the two sources per participant by system, gene and gene group and overall for quantity, detail and similarity.

Results: 547 probands were analysed ranging in age from infancy to 16 years (mean 7.6) with similar gender distribution. PRD provided more terms for dental, gastroenterology, immunology and respiratory systems and for vision (p<0.001 for all) and to a lesser degree for cardiac (p=0.0012). CRD provides more detail than PRD for most gene subgroups, combined systems and for neurology (p<0.001). Similarity scores were low overall per participant (mean 0.38 for combined). Similarity scores were highest for cardiac (mean 0.74) and lowest for Ear/Nose/Throat(ENT) (mean 0.34). There was minimal difference in similarity scores across gene groups or between the top 10 genes-scaffold adaptor gene groups had the highest (mean 0.43) as did STXBP1 (mean 0.5) and CACNA1A (0.49). CRD is more similar to published syndrome phenotypes for syndromic genes.

Conclusions: Parents reported more common childhood phenotypes, such as asthma and dental issues, while clinicians provided clinical phenotype descriptors, such as brain morphology and seizure semiology. It is important to understand the differences when designing studies and using datasets to appreciate their strengths and limitations.

Background: The disruption of neural progenitor proliferation is a key mechanism underlying primary microcephaly, yet how cell cycle arrest leads to progenitor loss remains only partially understood. Cyclin-dependent kinases, CDK4 and CDK6, are central regulators of the G₁/S transition, but their role in cellular stress responses during neurodevelopment remains unclear.

Methods: We studied fibroblasts from affected individuals in two families: siblings homozygous for a CDK4 frameshift (p.Glu94Argfs*65) presenting with microcephaly and pontine hypoplasiaand a child homozygous for a CDK6 missense variant (p.Thr154Ile) with microcephaly, brain atrophy, neutropenia and ovarian failure.

Results: Loss-of-function variants in CDK4 and CDK6, core G₁/S regulators, impaired proliferation and induced mitochondrial stress responses and apoptosis. Mutant fibroblasts exhibited significantly reduced DNA synthesis and cell cycle progression, along with increased mitochondrial activity, elevated reactive oxygen species and increased apoptosis. Mitochondrial responses differed by gene: CDK4 deficiency caused mitochondrial hyperpolarisation, while CDK6 deficiency resulted in depolarisation, suggesting differences in mitochondrial apoptotic dynamics. Both variants affected mTOR pathway signalling, linking cell cycle kinase loss to disrupted metabolic regulation.

Conclusion: These findings uncover a previously unrecognised mitochondrial stress response accompanying proliferative failure, offering mechanistic insight into how cell cycle arrest could lead to neural progenitor depletion and brain growth disorders. More broadly, our results connect cyclin-dependent kinase dysfunction with mitochondrial homeostasis in neurodevelopment, highlighting shared pathways with neurodegeneration and cancer.