Paraxial Mesoderm

Abstract

This chapter provides an overview of the paraxial mesoderm which forms blocks of tissue called somites, which give rise to two major divisions: the sclerotome and the dermomyotome. It highlights the spatiotemporal expression of 3'-to-5' Hox genes along the paraxial mesoderm which correlates with a progressive loosening of chromatin structures via epigenetic regulation and with the timing of ingression into the paraxial mesoderm along the anterior-posterior axis. It also discusses the posterior gradient signals of FGFs and Wnts which maintain neuromesoderm progenitor (NMP) cells in the progenitor state. The chapter assesses the central dermomyotome which forms the dermis of the back, including precursors of muscle and brown fat cells. It investigates how tendons are formed through the conversion of the dorsalmost layer of sclerotome cells into syndetome cells by FGFs secreted by the myotome.