Analysis of splicing abnormalities in the white matter of myotonic dystrophy type 1 brain using RNA-sequence

Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by the genomic expansions of CTG repeats, in which RNA-binding proteins, such as muscleblind-like protein, are sequestered in the nucleus, and abnormal splicing is observed in various genes. Although abnormal splicing reportedly occurs in the brains of patients with DM1, it is relation to the central nervous system symptoms is unknown. Several imaging studies have indicated substantial white matter (WM) defects in patients with DM1. Here, we performed RNA-sequencing and analysis of CTG repeat lengths in the frontal lobe of patients with DM1, separating the grey matter (GM) and WM, to investigate the splicing abnormalities in the DM1 brain, especially in the WM. The results demonstrated the number of repeats in the GM tended to be increase, with several genes showing similar levels of splicing abnormalities in the GM and WM, suggesting that the WM defects in DM1 are not only caused by aberrant splicing of GM RNA but also of WM RNA, which could be attributed to abnormal splicing of glial cell RNAs. Using RNA-seq data, we compared cortical and white matter splicing differences in the brains of myotonic dystrophy type 1 patients with ALS as disease control.