[Controlling the spatiotemporal expression of germ line specific genes by PRC1.6 complex]

Abstract

Polycomb repressive complex 1 (PRC1) is a class of epigenetic regulatory complexes that normally represses gene expression by catalyzing and/or recognizing chromatin modifications. PRC1 mainly functions in stem cell maintenance, cell differentiation, cell cycle regulation and related processes. PRC1 also have aberrant functions which has been implicated in many types of developmental diseases and cancers. Mammalian PRC1 complexes are divided into six subtypes based on their composition and function; subtypes include PRC1.1 to PRC1.6. Each PRC1 subtype regulates a unique collection of target genes. The PRC1.6 complex subtype plays key roles in specifically repressing transcription of genes controlling germ cell development in embryonic stem cells and other somatic cell types. Recent research demonstrates that the PRC1.6 complex is also crucial for the timely activation of the germ line of specific genes during spermatogenesis, which is essential for proper gonad development. In this review, we summarize the identification of molecular functions of each core component of the PRC1.6 complex including how it recognizes and represses germ line specific genes. We also update the biological roles of this complex in regulating the spatiotemporal expression of germ line specific genes during embryonic development, gonad development, and spermatogenesis. Lastly, the crosstalk between the PRC1.6 complex and the other main epigenetic regulatory mechanisms involved in controlling spermatogenesis is discussed. Our discussion of the PRC1.6 complex in regulating germ line specific genes informs the studies of molecular processes of spermatogenesis and contributes to the understanding of the pathogenic mechanisms of male infertility.