No abstract

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with highly heritable heterogeneity. Mutations of CUB and sushi multiple domains 3 (CSMD3) gene have been reported in individuals with ASD. However, the underlying mechanisms of CSMD3 for the onset of ASD remain unexplored. Here, using maleCSMD3-knock out (CSMD3-/-) mice, we found that genetic deletion ofCSMD3produced core autistic-like symptoms (social interaction deficits, restricted interests, repetitive and stereotyped behaviors) and motor dysfunction in mice, indicating thatCSMD3gene can be considered as a candidate for ASD. Moreover, we discovered that ablation ofCSMD3in mice led to abnormal cerebellar Purkinje cells (PCs) morphology in Crus I/II lobules, including aberrant developmental dendritogenesis and spinogenesis of PCs. Furthermore, combiningin vivofiber photometry calcium imaging andex vivoelectrophysiological recordings, we showed that theCSMD3-/-mice exhibited an increased neuronal activity (calcium fluorescence signals) in PCs of Crus I/II lobules in response to movement activity, as well as an enhanced intrinsic excitability of PCs and an increase of excitatory rather than inhibitory synaptic input to the PCs, and an impaired long-term depression (LTD) at the parallel fibers (PF)-PC synapse. These results suggest that CSMD3 plays an important role in cerebellar PCs development. Loss of CSMD3 causes abnormal PCs morphology and dysfunction in the cerebellum, which may underlie the pathogenesis of motor deficits and core autistic-like symptoms inCSMD3-/-mice. Our findings provide novel insight into the pathophysiological mechanisms by whichCSMD3mutations cause impairments in cerebellar function that may contribute to ASD.Significance Statement:Autism spectrum disorder (ASD) is a neurodevelopmental disorder with highly heritable heterogeneity. Advances in genomic analysis have contributed to numerous candidate genes for the risk of ASD. Recently, a novel giant geneCSMD3encoding a protein with CUB and sushi multiple domains (CSMD) has been identified as a candidate gene for ASD. However, the underlying mechanisms ofCSMD3for the onset of ASD remain largely unknown. Here, we unravel that loss ofCSMD3results in abnormal morphology, increased intrinsic excitabilities and impaired synaptic plasticity in cerebellar PCs, subsequently leading to motor deficits and ASD-like behaviors in mice. These results provide novel insight into the pathophysiological mechanisms by whichCSMD3mutations cause impairments in cerebellar function that may contribute to ASD.

Genome sequencing(GS) has been applied in the diagnosis of global developmental delay(GDD)/intellectual disability(ID). However, the performance in those with inconclusive results from chromosomal microarray analysis(CMA) and exome sequencing(ES) is unknown. We recruited 100 pediatric GDD/ID patients from multiple sites in China from February 2018 to August 2020 for GS. Patients have received at least one genomic diagnostic test prior to enrollment. Reanalysis of CMA/ES data was performed. The yield of GS was calculated and explanations for missed diagnoses by CMA/ES were investigated. Clinical utility was assessed by interviewing the parents by phone. The overall diagnostic yield of GS was 23%. Seven families could have been solved with reanalysis of ES data. 13 families were missed by previous CMA/ES due to improper method. Three remained unsolved after ES reanalysis due to allele dropout, complex variants missed by ES, and a CNV in untranslated regions. Follow-up of the diagnosed families revealed that nine families experienced changes in clinical management, including identification of targeted treatments, cessation of unnecessary treatment, and considerations for family planning. GS demonstrated high diagnostic yield and clinical utility in this cohort of undiagnosed GDD/ID patients, detecting a wide range of variant types of different sizes in a single workflow.

Among the hypomyelinating leukodystrophies, Pelizaeus–Merzbacher disease (PMD) is a representative disorder. The disease is caused by different types of PLP1 mutations, among which PLP1 duplication accounts for ~ 70% of the mutations. Previous studies have shown that PLP1 duplications lead to PLP1 retention in the endoplasmic reticulum (ER); in parallel, recent studies have demonstrated that PLP1 duplication can also lead to mitochondrial dysfunction. As such, the respective roles and interactions of the ER and mitochondria in the pathogenesis of PLP1 duplication are not clear. In both PLP1 patients’ and healthy fibroblasts, we measured mitochondrial respiration with a Seahorse XF Extracellular Analyzer and examined the interactions between the ER and mitochondria with super-resolution microscopy (spinning-disc pinhole-based structured illumination microscopy, SD-SIM). For the first time, we demonstrated that PLP1 duplication mutants had closer ER-mitochondrion interfaces mediated through structural and morphological changes in both the ER and mitochondria-associated membranes (MAMs). These changes in both the ER and mitochondria then led to mitochondrial dysfunction, as reported previously. This work highlights the roles of MAMs in bridging PLP1 expression in the ER and pathogenic dysfunction in mitochondria, providing novel insight into the pathogenicity of mitochondrial dysfunction resulting from PLP1 duplication. These findings suggest that interactions between the ER and mitochondria may underlie pathogenic mechanisms of hypomyelinating leukodystrophies diseases at the organelle level.

Background Intellectual disability/developmental delay (ID/DD) is a kind of neurodevelopmental disorders of which the genetic etiologies are to be clarified in majority of the patients. The features of ID/DD patients with hemizygous variants in ATRX in China remains unclear due to the rare reports in worldwide.Methods Clinical data of six Chinese pedigrees with hemizygous variants in ATRX and ID/DD was collected. The information of physical examination, blood tests, metabolism screening of blood and urine, cranial magnetic resonance imaging (MRI), and whole exome sequencing (WES) of each patient was elaboratively analyzed.Result ID/DD patients with hemizygous variants in ATRX in China were characterized by moderate to profound ID/DD, facial malformations (microcephaly, hypertelorism, low nasal bridge and ear deformities), hypotonia and poor malmyelination. Five ARTX variants in six Chinese patients consisted of missense, in-frame deletion and frameshift variants, two of which were novel.Conclusion Six Chinese ID/DD patients were clinically and genetically diagnosed with ATRX mutations related syndrome (ATRX syndrome). And genotype–phenotype correlation was revealed in the participants, which expanded the clinical and genetic spectrum of ATRX syndrome.