Identification of Region-Specific Gene Isoforms in the Human Brain Using Long-Read Transcriptome Sequencing and Their Correlation with DNA Methylation

Abstract

BackgroundSite specificity is known in neuropsychiatric disorders, and differences in gene expression patterns could potentially explain this mechanism. However, studies using long-read transcriptome sequencing to analyze gene expression in different regions of the human brain have been limited, and none have focused on the hypothalamus, which plays a crucial role in regulating autonomic functions. ResultsWe performed long-read RNA sequencing on 12 samples derived from three different brain regions of the same individuals; the cerebellum, hypothalamus, and temporal cortex. We found that, compared to other regions, many genes with higher expression levels in the cerebellum and temporal cortex were associated with neuronal pathways, whereas those with higher expression levels in the hypothalamus were primarily linked to immune pathways. In addition, we investigated genes with different major isoforms in each brain region, even with similar overall expression levels among regions, and identified several genes, such as GAS7, that express different major isoforms in different regions. Many of these genes are involved in "actin filament-based process" and "cell projection organization" pathways, suggesting that region-dependent isoforms may have distinct roles in dendritic spine and neuronal formation in each region. Furthermore, we investigated the involvement of DNA methylation in these isoforms and found that DNA methylation may be associated with isoforms that have different first exons. ConclusionsOur results provide potentially valuable findings for future research on brain disorders and shed light on the mechanisms underlying isoform diversity in the human brain.