Sertoli cells support germ cell differentiation in XY <i>Rspo1^KOSox9^cKO</i> gonads.

<p>Immunofluorescence (a–i) of GATA1 (Sertoli cell marker, in green), AR (Androgen Receptor) (Sertoli, peritubular myoid and Leydig cell marker, in red), STRA8 (a premeiotic marker, in red), and γH2AX (a meiotic marker, in green) at P10. Counterstain is DAPI (in blue). In situ hybridization (j–l) using a probe for <i>Clu</i> transcripts, another marker for mature Sertoli cells, illustrated as computer–generated bright field superimpositions of the blue counterstain (DAPI) with the hybridization signal (red false color). GATA1, AR and <i>Clu</i> expression show that the Sertoli cells mature in XY controls (a, g, j) and XY <i>Rspo1^KOSox9^cKO</i> testes (c, i, l), and are able to support germ cell differentiation until meiosis initiation as revealed by STRA8 (a, c, d, f) and γH2AX (d, f, g, i) expression. Note that both Sertoli, peritubular myoid and Leydig cells of XY <i>Sox9^cKO</i> mutant gonads normally expressed AR (h). (scale bars: 50 µm). XY (a, d, g, j) <i>Rspo1^+/−; Sox9^flox/flox</i> controls, XY <i>Sox9^cKO</i> gonads (b, e, h, k) and XY <i>Rspo1^KOSox9^cKO</i> (c, f, i, l) gonads.