Tob1 is expressed in developing and adult gonads and is associated with the P-body marker, Dcp2

Tob1 is a member of the BTG/TOB family of proteins with established antiproliferative function. In Danio rerio and Xenopus laevis, the Tob1 gene is expressed from the one-cell stage through to early gastrula stages, followed in later development by discrete expression in many tissues including the notochord and somites. In both mouse and human, Tob1 is expressed in many adult tissues including the testis and ovary; however, the specific cell types are unknown. We examine Tob1 gene expression in mouse in developing germ cells and in sorted male germ cells (gonocytes, spermatogonia, pachytene spermatocytes and round spermatids) by reverse transcription and droplet digital polymerase chain reaction (RT-ddPCR) and in adult ovary and testis by immunofluorescence with anti-Tob1 protein staining. By RT-ddPCR, Tob1 expression was low in developing male germ cells but was highly expressed in round spermatids. In developing female germ cells undergoing entry into meiosis, it increased 10-fold. Tob1 was also highly expressed in round spermatids and in oocytes in all stages of folliculogenesis. Notably, a marker for P-bodies, Dcp-2, was also highly expressed in round spermatids and all oocyte stages examined. The cytoplasmic presence of Tob1 protein in round spermatids and oocytes and the association of Tob1 protein with Dcp2 in both cell types suggest that Tob1 protein plays a role in post-transcriptional mechanisms.