Intellectual disability/developmental delay is a complex condition with extraordinary heterogeneity. A large proportion of patients lacks a specific diagnosis. Next generation sequencing, enabling identification of genetic variations in multiple genes, has become an efficient strategy for genetic analysis in intellectual disability/developmental delay. Clinical data of 112 Chinese families with unexplained intellectual disability/developmental delay was collected. Targeted next generation sequencing of 454 genes related to intellectual disability/developmental delay was performed for all 112 index patients. Patients with promising variants and their other family members underwent Sanger sequencing to validate the authenticity and segregation of the variants. Fourteen promising variants in genes EFNB1, MECP2, ATRX, NAA10, ANKRD11, DHCR7, LAMA1, NFIX, UBE3A, ARID1B and PTPRD were identified in 11 of 112 patients (11/112, 9.82%). Of 14 variants, eight arose de novo, and 13 are novel. Nine patients (9/112, 8.03%) got definite molecular diagnoses. It is the first time to report variants in EFNB1, NAA10, DHCR7, LAMA1 and NFIX in Chinese intellectual disability/developmental delay patients and first report about variants in NAA10 and LAMA1 in affected individuals of Asian ancestry. Targeted next generation sequencing of 454 genes is an effective test strategy for patients with unexplained intellectual disability/developmental delay. Genetic heterogenicity is significant in this Chinese cohort and de novo variants play an important role in the diagnosis. Findings of this study further delineate the corresponding phenotypes, expand the mutation spectrum and support the involvement of PTPRD in the disease.

Hypomyelinating leukodystrophies (HLDs) are genetic disorders characterized by deficient myelination. While TMEM63A variants are associated with HLD19, the specific lipid alterations in affected brain regions remain to be fully characterized. This study aimed to investigate the spatial distribution of lipid changes in a Tmem63a mutant rat model of hypomyelination. A homozygous Tmem63a c.500G > A p.(G167E) knock-in rat model ( Tmem63a ^G167E/G167E ) was established. Brain sections from Tmem63a ^G167E/G167E and Tmem63a ^WT rats ( n = 3/group) were analyzed using MALDI-MSI for lipid profiling across nine distinct brain regions. Myelin structure was characterized by transmission electron microscopy (TEM) and g-ratio quantification. Statistical analyses included Mann-Whitney U tests for g-ratio distributions and ROC analysis for feature screening. Out of 702 analyzed features, 124 were differentially expressed. Lipids constituted the most altered class (43 features), including 22 glycerophospholipid, 9 fatty acid, 5 sphingolipid, 5 sterol lipid, and 2 prenol lipid species. These alterations were predominantly observed in white matter-rich regions and gray-white matter junctions. TEM revealed thinner and less dense myelin sheaths in Tmem63a ^G167E/G167E rats, with a reduced proportion of optimal g-ratios. This study provides a comprehensive spatial lipidomic characterization in a Tmem63a mutant rat model, revealing significant lipid alterations associated with hypomyelination. These findings offer new insights into the pathology of hypomyelination and highlight specific lipid species for future investigation.

Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability and epileptic seizures, primarily caused by dysfunction of the m

SPTBN1 encodes βII-spectrin, a cytoskeletal protein essential for neuronal structure and function. Pathogenic variants in this gene cause a neurodevel

Mechanically activated (MA) ion channels convert physical forces into electrical signals. Despite the importance of this function, the involvement of mechanosensitive ion channels in human disease is poorly understood. Here we report heterozygous missense mutations in the gene encoding the MA ion channel TMEM63A that result in an infantile disorder resembling a hypomyelinating leukodystrophy. Four unrelated individuals presented with congenital nystagmus, motor delay, and deficient myelination on serial scans in infancy, prompting the diagnosis of Pelizaeus-Merzbacher (like) disease. Genomic sequencing revealed all four individuals carry heterozygous missense variants in the pore-forming domain of TMEM63A. These variants were confirmed to have arisen de novo in three of the four individuals. While the physiological role of TMEM63A is incompletely understood, it is highly expressed in oligodendrocytes and it has recently been shown to be a mechanically activated (MA) ion channel. Using patch clamp electrophysiology, we demonstrated that each of the modelled variants results in strongly attenuated stretch-activated currents when expressed in naïve cells. Unexpectedly, the clinical evolution of all four individuals has been surprisingly favorable, with substantial improvements in neurological signs and developmental progression. In the three individuals with follow-up scans after four years of age, the myelin deficit had almost completely resolved. Our results suggest a previously unappreciated role for mechanosensitive ion channels in myelin development.