Regulation of lymphoid versus myeloid fate choice by Mef2c

Despite recent advances in the identification of lymphoid-restricted progenitors, the transcription factors essential for their generation remain to be identified. Here we describe an unexpected role for the myeloid oncogene Mef2c in multipotent progenitors (MPPs), where it is required for pan-lymphoid differentiation. Mef2c deficiency was associated with profound defects in B, T, NK cell and common lymphoid progenitor production and an enhanced myeloid output. Mef2c deficiency in MPPs leads to downregulation of several key lymphoid regulators and the upregulation of the myeloid factor C/EBPa. Our studies also show that Mef2c is a critical transcriptional target of PU.1 during lymphopoiesis. Thus, Mef2c is a crucial component of the transcriptional network that regulates lymphoid specification and cell fate choice in MPPs. Expression profiles of multipotent progenitor cells (MPPs) from Mef2c deficient (Mx1-Cre Mef2cf/f ) mice where compared to MPPs from control (Mef2cf/f ) mice in triplicate.