A Pitx2 -MicroRNA Pathway Modulates Cell Proliferation in Myoblasts and Skeletal-Muscle Satellite Cells and Promotes Their Commitment to a Myogenic Cell Fate

Abstract

The acquisition of a proliferating cell status from a quiescent state as well as the shift between proliferation and differentiation are key developmental steps in skeletal-muscle stem cells (satellite cells) to provide proper muscle regeneration. However, how satellite-cell proliferation is regulated, though, is not fully understood. Here, we report that the c-isoform of the transcription factor Pitx2 increases cell proliferation in myoblasts by down-regulating the miRNAs miR-15b, miR-23b, miR-106b, and miR-503. This Pitx2c-miRNA pathway also regulates cell proliferation in early-activated satellite cells, enhancing the Myf5+ satellite cells and thereby promoting their commitment to a myogenic cell fate. This study reveals unknown functions of several miRNAs in myoblast and satellite-cell behaviour and thus may have future applications in regenerative medicine.