Multi-posttranscriptional regulations lessen the repressive effect of SRPK1 on brown adipogenesis

Alternative splicing has been widely demonstrated to function as pivotal regulation in specifying cellular fates and biological functions. The relative expression or cellular localization of a splicing factor constitutes an important mechanism in spatiotemporal programming of cell- and stage-specific splicing profiles. In this study, results of deep RNA-sequencing (RNA-Seq) analyses first revealed the reprogrammed splicing profile and reduced expression of serine/arginine-rich splicing factor protein kinase 1 (SRPK1) throughout the development of brown adipose tissue (BAT). A gradual increase in the exon 10-skipped SRPK1 transcript, a potential target of a nonsense-mediated decay (NMD) mechanism, was noted during brown adipogenesis. Elevated RBM4a constituted the regulatory mechanism that led to skipping of SRPK1 exon 10. Moreover, brown adipogenesis-induced upregulation of microRNA (miR)-485 interfered with SRPK1 expression by targeting its 3'-untranslated region (UTR). Depletion of endogenous SRPK1 enhanced the development of C3H10T1/2 cells toward brown adipocytes. Taking our results together, multiple post-transcriptional regulations reduced SRPK1 expression, which subsequently affected brown adipogenesis.