Lack of Sertoli cell differentiation and testis cord formation in XY Gadd45g^−/− gonads.

<p>(A–L) Confocal optical slices of whole mount immunostained B6 gonads (dashed outline), showing expression of Sertoli cell markers SOX9 (nuclear, blue) and AMH (cytoplasmic, red) and the germ/endothelial cell marker Pecam1 (membrane, green). (A) From 12.5 dpc, wild type male gonads can be distinguished morphologically from female gonads (B) by the appearance of testis cord structures containing SOX9-expressing Sertoli cells. (C) In Gadd45g^−/− XY gonads, only transient SOX9 expression was observed in a small number of somatic cells at 12.5 dpc. (D–F) and (J–L) are enlarged details of the images above. (G) At 13.5 dpc, all germ cells in male gonads are enclosed in testis cords and interact closely with a surrounding single layer of SOX9- and AMH-positive Sertoli cells. (H,I,K,L) No testis cord formation or AMH expression was induced in Gadd45g^+/+ XX (H,K) or in Gadd45g^−/− XY (I,L) gonads.