Loss of NEDD4 causes complete XY gonadal sex reversal in mice

Gonadal sex determination in vertebrates: rethinking established mechanisms

Sex determination and differentiation are fundamental processes that are not only essential for fertility but also influence the development of many other organs, and hence, are important for species diversity and survival. In mammals, sex is determined by the inheritance of an X or a Y chromosome from the father. The Y chromosome harbours the testis-determining gene SRY, and it has long been thought that its absence is sufficient for ovarian development. Consequently, the ovarian pathway has been treated as a default pathway, in the sense that ovaries do not have or need a female-determining factor. Recently, a female-determining factor has been identified in mouse as the master regulator of ovarian development. Interestingly, this scenario was predicted as early as 1983. In this Review, we discuss the model predicted in 1983, how the mechanisms and genes currently known to be important for sex determination and differentiation in mammals have changed or supported this model, and finally, reflect on what these findings might mean for sex determination in other vertebrates.

Postnatal Ovarian Transdifferentiation in the Absence of Estrogen Receptor Signaling Is Dependent on Genetic Background

Normal ovarian function requires the expression of estrogen receptors α (ESR1) and β (ESR2) in distinct cell types within the ovary. The double estrogen receptor knockout (αβERKO) ovary had the appearance of seminiferous tubule-like structures that expressed SOX9; this phenotype was lost when the animals were repeatedly backcrossed to the C57BL/6J genetic background. A new line of ERKO mice, Ex3αβERKO, was developed for targeted disruption on a mixed genetic background. Histological examination of the ovaries in the Ex3αβERKO showed the appearance of seminiferous tubule-like structures in mice aged 6 to 12 months. These dismorphogenic regions have cells that no longer express granulosa cell-specific FOXL2, while other cells express Sertoli cell-specific SOX9 as examined by immunohistochemistry. Whole ovarian gene expression analysis in Ex3αERKO, Ex3βRKO, and Ex3αβERKO found many genes differentially expressed compared to controls with one Esr1 and Esr2 allele. The genes specific to the Ex3αβERKO ovary were compared to other models of postnatal ovarian transdifferentiation, identifying 21 candidate genes. To examine the genetic background contributions, DNA was isolated from αβERKO mice that did not show ovarian transdifferentiation and compared to DNA from Ex3αβERKO using Mouse Diversity Array. A genomic region putatively associated with transdifferentiation was identified on Chr18 (5-15 M) and genes in this region were compared to the genes differentially expressed in models of ovarian transdifferentiation. This work demonstrates the importance of ESRs in maintaining granulosa cell differentiation within the ovary, identifies several potential gene candidates, and suggests that genetic background can be a confounding factor.

Sex-biased adaptive immune regulation in cancer development and therapy

The cancer research field is finally starting to unravel the mystery behind why males have a higher incidence and mortality rate than females for nearly all cancer types of the non-reproductive systems. Here, we explain how sex - specifically sex chromosomes and sex hormones - drives differential adaptive immunity across immune-related disease states including cancer, and why males are consequently more predisposed to tumor development. We highlight emerging data on the roles of cell-intrinsic androgen receptors in driving CD8+ T cell dysfunction or exhaustion in the tumor microenvironment and summarize ongoing clinical efforts to determine the impact of androgen blockade on cancer immunotherapy. Finally, we outline a framework for future research in cancer biology and immuno-oncology, underscoring the importance of a holistic research approach to understanding the mechanisms of sex dimorphisms in cancer, so sex will be considered as an imperative factor for guiding treatment decisions in the future.