Dr National Center of Neurology and Psychiatry, Tokyo, Japan
Abstract: Duchenne muscular dystrophy (DMD) is a neuromuscular disease chiefly characterised by progressive muscle weakness due to loss of structural protein, dystrophin (Dp427). Numerous cognitive comorbidities, like autism spectrum disorder (ASD), are observed in 30% of DMD patients due to the cumulative loss of Dp427 and embryonic, brain-specific dystrophin variant, Dp140. Though previous studies in adult mice have linked brain dystrophin to modulating synaptic transmission, its precise cellular localisation and developmental function remain unclear. This is due to the scarcity of embryonic human brain tissue, particularly from DMD patients, and disparities between human-mouse cerebral cortex. To address these challenges, we generated DMD patient-derived induced pluripotent stem cell (iPSC) cerebral organoids to model disease-specific cortical architecture. Bulk qRT-PCR showed that DP140 expression peaks at 100 days of WT organoid culture, mirroring non-disease human mRNA profiling data. Super-resolution microscopy of WT organoids showed distinct localisation of Dp427 and shorter dystrophin in neuroepithelial rosettes, a previously unreported phenotype. DMD iPSC-cerebral organoids exhibited both reduced bulk DP140 and altered dystrophin expression in neural progenitor cells. Additionally, publicly available single cell RNA sequencing data from human embryonic brain showed DMD transcript enrichment in radial glial cells. Together, this suggests a potential role for dystrophin during neurogenesis, whose loss may affect the onset of cognitive comorbidities in DMD. We are currently analysing temporal cortical layer thickness and synaptic markers in DMD patient iPSC-cerebral organoids. We aim to perform cell and axonal migration studies to examine potential disease phenotypes arising from defects in neurogenesis. Single cell RNA sequencing paired with spatial transcriptomics will be done to assess DMD isoform expression and pathway analysis across cell types in our organoids. This will allow us to gain a deeper understanding of human-specific, early molecular defects associated with Dp140 deficiency, potentially opening avenues for novel therapies.
Funding Source: Young Researchers Grant, KAKEN Japan (2024-2027) Defeat Duchenne Canada, The Jesse Davidson Foundation (2024-2027)
