Alternative pre-mRNA splicing switch controls hESC pluripotency and differentiation

Alternative splicing (AS) of pre-mRNAs is a ubiquitous process in mammals that is tightly regulated in a cell type-and cell state-dependent manner. However, the details of how splicing is regulated to impact specific cell fate decisions remains incompletely understood. A study by Yamazaki and colleagues (pp. 1161-1174) in this issue of Genes & Development provides exciting new insight into the role and regulation of splicing in the maintenance of pluripotency of human embryonic stem cells (hESCs). In brief, they show that AS of several genes is robustly regulated upon differentiation of hESCs. One of these genes, T-cell factor 3 (TCF3), is regulated at least in part through the activity of heterogeneous nuclear ribonucleoproteins H1 and F (hnRNP H/F) to control the mutually exclusive expression of the encoded E12 and E47 transcription regulators. The investigators demonstrate that reduced expression of hnRNP H/F favors expression of E47, which in turn decreases E-cadherin expression to promote hESC differentiation. In contrast, high levels of hnRNP H/F induce expression of E12 to maintain pluripotency. Thus, this work provides at least one new link between AS and control of human stem cell fate and suggests a broader role of splicing in pluripotency.