The RNA-Binding Protein DND1 Acts Sequentially as a Negative Regulator of Pluripotency and a Positive Regulator of Epigenetic Modifiers Required for Germ Cell Reprogramming

Abstract

The adult spermatogonial stem cell population arises from pluripotent primordial germ cells (PGCs) that enter the fetal testis around embryonic day 10.5 (E10.5). These cells undergo rapid mitotic proliferation, then enter a prolonged period of cell cycle arrest (G1/G0) during which they transition to pro-spermatogonia. In mice homozygous for the Ter mutation in the RNA-binding protein DND1 (DND1Ter/Ter), many germ cells fail to enter G1/G0, and give rise to teratomas, tumors in which many embryonic cell types are represented. To investigate the origin of these tumors, we sequenced the transcriptome of male germ cells in DND1Ter/Ter mutants at E12.5, E13.5, and E14.5, just prior to the formation of teratomas, and correlated this information with direct targets of DND1 identified by DO-RIP-Seq. Consistent with previous results, we found that DND1 controls the down regulation of many genes associated with pluripotency and active cell cycle, including elements of the mTor, Hippo and Bmp/Nodal signaling pathways. However, DND1 targets also include genes associated with male differentiation including a large group of chromatin regulators activated in wild type but not mutant germ cells during the transition between E13.5 and E14.5. These results suggest multiple functions of DND1, and link DND1 to the initiation of epigenetic modifications in male germ cells.