DDX1 regulates alternative splicing and insulin secretion in pancreatic β cells

DEAD-box helicase 1 (DDX1) is a multifunction protein involved in diverse cellular processes including transcription, viral replication, mRNA/miRNA processing, and tRNA splicing. Here, we report a novel function of DDX1 in mRNA alternative splicing in pancreatic β cells. By performing integrated data analysis of high-throughput RNA sequencing (RNA-Seq), and cross-linking and immunoprecipitation coupled with deep sequencing (CLIP-Seq), we identify hundreds of alternative splicing genes that are targeted by DDX1. These DDX1-targeted alternative splicing genes are mainly associated with calcium ion binding, high voltage-gated calcium channel, and transmembrane transporter. Functionally, silencing DDX1 impairs calcium influx and insulin secretion in the pancreatic β cells. These results reveal an important role for DDX1 in the regulation of gene alternative splicing and insulin secretion in pancreatic β cells. To generate the transcriptomic profile mediated by DDX1, we constructed a DDX1 knockdown INS1 cell line (shDDX1) by stably expression short hairpin RNA (shRNA) targeting DDX1. Three independent preparations of shDDX1 and scramble cells were then RNA-sequenced. High-throughput sequencing was performed on a HiSeq 2500 (Illumina) system with paired ends 125bp in length.