Rhox6 regulates the expression of distinct target genes to mediate mouse PGCLC formation and ESC self-renewal.

Background: Mouse embryonic stem cells (mESCs) not only retain the property of self-renewal but also have the ability to develop into primordial germ cell-like cells (PGCLCs). However, knowledge about the mechanisms of transcriptional regulation is still limited. Rhox6, a member of the homeobox family that is located on the X chromosome, is highly expressed within PGCLCs in vivo and in vitro. However, the detailed effects of Rhox6 on PGCLC specification and mESC maintenance remain unclear.

Results: In this study, we found that overexpression of Rhox6 favors the formation of PGCLCs, while depletion of Rhox6 inhibits the generation of PGCLCs. Mechanistically, Rhox6 directly induces the expression of Nanos3 during the specification of PGCLCs. Subsequently, downregulation of Nanos3 expression is sufficient to decrease the ability of Rhox6 to induce PGCLC formation. Moreover, we found that depletion of Rhox6 expression facilitates the self-renewal of mESCs. High-throughput sequencing revealed that suppression of Rhox6 transcription significantly increases the expression of pluripotency genes. Functional studies further demonstrated that Rhox6 directly represses the transcription of Tbx3. Therefore, knockdown of the expression of the latter impairs the self-renewal of mESCs promoted by Rhox6 downregulation.

Conclusions: Our study reveals that overexpression of Rhox6 is beneficial for PGCLC generation through induction of Nanos3, while downregulation of Rhox6 contributes to mESC self-renewal by increasing Tbx3. These findings help elucidate the early development of mouse embryos.