DMRT1 Is Required for Mouse Spermatogonial Stem Cell Maintenance and Replenishment

Abstract

Male mammals produce sperm for most of postnatal life and therefore require a robust germ line stem cell system, with precise balance between self-renewal and differentiation. Prior work established doublesex- and mab-3-related transcription factor 1 (Dmrt1) as a conserved transcriptional regulator of male sexual differentiation. Here we investigate the role of Dmrt1 in mouse spermatogonial stem cell (SSC) homeostasis. We find that Dmrt1 maintains SSCs during steady state spermatogenesis, where it regulates expression of Plzf, another transcription factor required for SSC maintenance. We also find that Dmrt1 is required for recovery of spermatogenesis after germ cell depletion. Committed progenitor cells expressing Ngn3 normally do not contribute to SSCs marked by the Id4-Gfp transgene, but do so when spermatogonia are chemically depleted using busulfan. Removal of Dmrt1 from Ngn3-positive germ cells blocks the replenishment of Id4-GFP-positive SSCs and recovery of spermatogenesis after busulfan treatment. Our data therefore reveal that Dmrt1 supports SSC maintenance in two ways: allowing SSCs to remain in the stem cell pool under normal conditions; and enabling progenitor cells to help restore the stem cell pool after germ cell depletion.

DMRT proteins and coordination of mammalian spermatogenesis

“…Deletion of Dmrt1 in putative SSCs using Oct4-CreERT2 caused a progressive loss of SSCs (Zhang et al, 2016) (Figure 3A, B). Deletion of Dmrt1 in SSCs was associated with reduced expression of the SSC maintenance factor PLZF, whose loss can cause a similar progressive failure of spermatogenesis (Buaas et al, 2004; Costoya et al, 2004).…”

“…SSC-specific expression of such a partner could help explain why DMRT1 activates Plzf in SSCs but not in differentiating spermatogonia. In vivo, SSC depletion in Dmrt1 conditional mutants appears to result from differentiation rather than cell death, as no elevation in apoptosis was apparent and lineage tracing allowed mutant germ cells to be followed into spermatogonial differentiation (Zhang et al, 2016). By contrast, in vitro depletion of Dmrt1 in cultured germ line stem cells (GS cells) caused elevated Sox2 expression and apoptosis (Takashima et al, 2013).…”

“…Thus Ngn3 -positive cells have been proposed to function as “potential stem cells” that can, under conditions of stress, serve as SSCs or give rise to SSCs; these cells are functionally distinct from the “actual stem cells” that normally maintain spermatogenesis during steady state (Nakagawa et al, 2007). Lineage-tracing experiments showed that deletion of Dmrt1 in Ngn3 -Cre expressing spermatogonia blocked repopulation of ID4-positive SSCs after their depletion by busulfan treatment (Zhang et al, 2016) (Figure 3C, D). …”

Expression Profile of NOTCH3 in Mouse Spermatogonia

“…Moreover, the self-renewal of SSC is promoted by fibroblast growth factor 2 from Sertoli cells and colony-stimulating factor 1 from Leydig cells and macrophages [Oatley et al, 2009;Ishii et al, 2012;DeFalco et al, 2015]. SSC maintenance is also controlled by intrinsic factors, including PLZF, DMRT1, NANOS2, and ID4 [Costoya et al, 2004;Sada et al, 2009;Oatley et al, 2011;Zhang et al, 2016]. However, the molecular mechanism of SSC maintenance is not yet completely understood.…”

Epigenomic and single-cell profiling of human spermatogonial stem cells

“…While it is generally accepted that A-single spermatogonia have the SSC property, mouse A-paired to A-aligned cells are able to break down to A-single status (16). Furthermore, Ngn3-positive transit amplifying cells have the ability to dedifferentiate into SSCs under an injury-repair based model (17).…”