Modeling Dosage-Sensitive Sex Reversal in Mice Figure 2. WISH analysis of the ovary somatic cell marker Wnt4 and the testis Leydig cell marker Ptch1 in E13.5 gonad/mesonephros complexes. Wnt4 was expressed throughout +/+ XX ovaries, as expected (A), and at the anterior and/or posterior poles of +/+ B6 XYAKR gonads in the regions without cords, but not in the central region containing cords (B). Expression was detected at the anterior and/or posterior poles of Wt1+/2 (D) and Sf1+/2 (data not shown) B6 XYAKR ovotestes and throughout Wt1+/2 (data not shown) and Sf1+/2 B6 XYAKR ovaries (F). Wnt4 expression was reduced in B6 Wt1+/2 XX (C) and Sf1+/2 XX (E) ovaries compared to B6 Wt1+/+ XX (A) ovaries. Expression also was reduced in B6 Wt1+/2 mesonephroi (C and D), but not in Sf1+/2 mesonephroi (E and F). Ptch1 expression was restricted to central regions containing testicular cords in +/+ B6 XYAKR gonads (H) and was not detected in +/+ B6 XX ovaries (G), as expected. Expression was not detected in Wt1+/2 and Sf1+/2 B6 XX ovaries (I and K). Ptch1 was expressed in the central regions of Wt1+/2 (J) and Sf1+/2 (data not shown) B6 XYAKR ovotestes but at notably lower levels than in +/+ B6 XYAKR gonads, and it was not expressed in Wt1+/2 (data not shown) and Sf1+/2 (L) XYAKR ovaries. Ptch1 expression was reduced in the anterior region of B6 Wt1+/2 mesonephroi (I and J), but not in Sf1+/2 mesonephroi (K and L). The gonad/mesonephros complex in each panel is oriented with the gonad above the mesonephros and separated by a dotted black line with the anterior (cranial) pole to the left. All images are at 106 magnification. doi:10.1371/journal.pgen.1002569.g002 XYAKR,Sxr gonads was classified as an ovotestis because it lacked cords in a small region at the posterior pole and had disorganized testicular cords in the remainder of the gonad. Of the 8 Sf1+/2 B6 XYAKR,Sxr gonads analyzed, 3 were classified as abnormal testes, with testicular cords throughout the gonad, and 5 were classified as ovotestes due to the absence of testicular cords at the posterior pole. The cords in these 8 gonads also were somewhat disorganized and less differentiated. In contrast, all 17 of the +/+ B6 XYAKR,Sxr gonads examined developed robust, well-organized testicular cords throughout the anterior, center and posterior regions. These data indicate that increasing Sry dosage in Wt1+/2 and Sf1+/2 B6 XYAKR gonads by replacing the YAKR Chr with the YAKR,Sxr Chr dramatically increased the amount of testicular tissue that develops, but did not fully rescue cord differentiation. PLoS Genetics | www.plosgenetics.org 7 April 2012 | Volume 8 | Issue 4 | e1002569