Blocking ALK4/5/7 or ALK5 in E11.5 XY gonads, but not E12.5 testes, permits germ cell entry into meiosis.

<p>Immunofluorescence analysis of: A–C) E11.5 XY and XX gonads cultured for 72 hours or 96 hours in the presence of DMSO, SB431542 or ALK5i-I. STRA8 (A), SYCP3 (B) and γH2AX-P (C) staining is in red, while MVH or DPPA4 (green) staining marks the germ cells. DAPI (blue) is included as a nuclear marker. Scale bars; 200 μm. D) TUNEL staining of E11.5 gonads cultured for 72 hours in the presence of DMSO or SB431542. Red staining marks TUNEL positive cells, while germ cells are marked by DPPA4 staining in green. DAPI (blue) is included as a nuclear marker. Scale bars; 200 μm. <b>E</b>) E12.5 testes cultured for 72 hours in the presence of DMSO or SB431542. γH2AX-P staining is in red, while MVH (green) staining marks the germ cells. DAPI (blue) is included as a nuclear marker. Scale bars 50 μm.