Dullard deficiency causes hemorrhage in the adult ovarian follicles.

In mammals, the ovarian follicles are regulated at least in part by bone morphogenetic protein (BMP) family members. Dullard (also known as Ctdnep1) gene encodes a phosphatase that suppresses BMP signaling by inactivating or degrading BMP receptors. Here we report that the Col1a1-Cre-induced Dullard mutant mice displayed hemorrhagic ovarian cysts, with red blood cells accumulated in the follicles, resulting in infertility. Cells expressing Cre driven by Col1a1 2.3-kb promoter and their descendants were found in granulosa cells in the ovary and in Sertoli cells in the testis. DullardmRNA was localized to granulosa cells in the ovary. Genes involved in steroid hormone genesis including Cyp11a1, Hsd3b1 and Star were reduced, whereas expression of Smad6 and Smad7, BMP-inducible inhibitory Smads, was up-regulated in the Dullard mutant ovaries. Tamoxifen-inducible Dullard deletion in the whole body using Rosa26-CreER mice also resulted in hemorrhagic ovarian cysts in 2 weeks, which was rescued by administration of LDN-193189, a chemical inhibitor of BMP receptor kinase, suggesting that the hemorrhage in the Dullard-deficient ovarian follicles might be caused by increased BMP signaling. Thus, we conclude that Dullard is essential for ovarian homeostasis at least in part via suppression of BMP signaling.

Preformed Wolffian duct regulates Müllerian duct elongation independently of canonical Wnt signaling or Lhx1 expression.

The Müllerian duct gives rise to female reproductive organs, such as the oviduct and uterus. During gestation, the Wolffian duct, which generates male reproductive organs and the kidney, is formed, and the Müllerian duct then elongates caudally along the preformed Wolffian duct. Anatomical separation of these two ducts in chick embryos demonstrated that the Wolffian duct is required for Müllerian duct formation. Likewise, a few reports supported this notion in mice, including studies on Wnt9b mutant mice and Wolffian duct-specific Lhx1 deletion. However, anatomical ablation of the Wolffian duct has not been established in mice. In this study, we addressed the importance of the interaction between these two reproductive ducts, by generating mice that specifically expressed a diphtheria toxin subunit in the Wolffian duct. While this genetic ablation of the Wolffian duct resulted in kidney hypoplasia/agenesis in both male and female mutant mice, the female mutant mice lacked the uterus, which is derived from the Müllerian duct. At mid-gestation, the Müllerian duct was truncated at the level where the mutant Wolffian duct was prematurely terminated, meaning that Müllerian duct elongation was dependent on the preformed Wolffian duct. However, Wnt9b expression in the Wolffian duct and the resultant canonical Wnt activity, as well as Lhx1 expression, were not affected in the mutant mice. These results suggest that the Wolffian duct regulates Müllerian duct elongation by currently unidentified mechanisms that are independent of canonical Wnt signaling or Lhx1 expression.

Sall4 Is Transiently Expressed in the Caudal Wolffian Duct and the Ureteric Bud, but Dispensable for Kidney Development.

The kidney, the metanephros, is formed by reciprocal interactions between the metanephric mesenchyme and the ureteric bud, the latter of which is derived from the Wolffian duct that elongates in the rostral-to-caudal direction. Sall1 expressed in the metanephric mesenchyme is essential for ureteric bud attraction in kidney development. Sall4, another member of the Sall gene family, is required for maintenance of embryonic stem cells and establishment of induced pluripotent stem cells, and is thus considered to be one of the stemness genes. Sall4 is also a causative gene for Okihiro syndrome and is essential for the formation of many organs in both humans and mice. However, its expression and role in kidney development remain unknown, despite the essential role of Sall1 in the metanephric mesenchyme. Here, we report that mouse Sall4 is expressed transiently in the Wolffian duct-derived lineage, and is nearly complementary to Sall1 expression. While Sall4 expression is excluded from the Wolffian duct at embryonic (E) day 9.5, Sall4 is expressed in the Wolffian duct weakly in the mesonephric region at E10.5 and more abundantly in the caudal metanephric region where ureteric budding occurs. Sall4 expression is highest at E11.5 in the Wolffian duct and ureteric bud, but disappears by E13.5. We further demonstrate that Sall4 deletion in the Wolffian duct and ureteric bud does not cause any apparent kidney phenotypes. Therefore, Sall4 is expressed transiently in the caudal Wolffian duct and the ureteric bud, but is dispensable for kidney development in mice.