Sox9 induces testis development in XX transgenic mice

Mutations in SOX9 are associated with male-to-female sex reversal in humans. To analyze Sox9 function during sex determination, we ectopically expressed this gene in XX gonads. Here, we show that Sox9 is sufficient to induce testis formation in mice, indicating that it can substitute for the sex-determining gene Sry

Amplification of R-spondin1 signaling induces granulosa cell fate defects and cancers in mouse adult ovary

R-spondin1 is a secreted regulator of WNT signaling, involved in both embryonic development and homeostasis of adult organs. It can have a dual role, acting either as a mitogen or as a tumor suppressor. During ovarian development, Rspo1 is a key factor required for sex determination and differentiation of the follicular cell progenitors, but is downregulated after birth. In human, increased RSPO1 expression is associated with ovarian carcinomas, but it is not clear whether it is a cause or a consequence of the tumorigenic process. To address the role of Rspo1 expression in adult ovaries, we generated an Rspo1 gain-of-function mouse model. Females were hypofertile and exhibited various ovarian defects, ranging from cysts to ovarian tumors. Detailed phenotypical characterization showed anomalies in the ovulation process. Although follicles responded to initial follicle-stimulating hormone stimulation and developed normally until the pre-ovulatory stage, they did not progress any further. Although non-ovulated oocytes degenerated, the surrounding follicular cells did not begin atresia. RSPO1-induced expression not only promotes canonical WNT signaling but also alters granulosa cell fate decisions by maintaining epithelial-like traits in these cells. This prevents follicle cells from undergoing apoptosis, leading to the accumulation of granulosa cell tumors that reactivates the epithelial program from their progenitors. Taken together, our data demonstrate that activation of RSPO1 is sufficient in promoting ovarian tumors and thus supports a direct involvement of this gene in the commencement of ovarian cancers

All Small Nuclear RNAs (snRNAs) of the [U4/U6.U5] Tri-snRNP Localize to Nucleoli; Identification of the Nucleolar Localization Element of U6 snRNA

Previously, we showed that spliceosomal U6 small nuclear RNA (snRNA) transiently passes through the nucleolus. Herein, we report that all individual snRNAs of the [U4/U6.U5] tri-snRNP localize to nucleoli, demonstrated by fluorescence microscopy of nucleolar preparations after injection of fluorescein-labeled snRNA into Xenopus oocyte nuclei. Nucleolar localization of U6 is independent from [U4/U6] snRNP formation since sites of direct interaction of U6 snRNA with U4 snRNA are not nucleolar localization elements. Among all regions in U6, the only one required for nucleolar localization is its 3′ end, which associates with the La protein and subsequently during maturation of U6 is bound by Lsm proteins. This 3′-nucleolar localization element of U6 is both essential and sufficient for nucleolar localization and also required for localization to Cajal bodies. Conversion of the 3′ hydroxyl of U6 snRNA to a 3′ phosphate prevents association with the La protein but does not affect U6 localization to nucleoli or Cajal bodies