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Sex development is an intricate and crucial process in all vertebrates that ensures the continued propagation of genetic diversity within a species, and ultimately their survival. Perturbations in this process can manifest as disorders/differences of sex development (DSD). Various transcriptional networks have been linked to development of the gonad into either male or female, which is actively driven by a set of genes that function in a juxtaposed manner and is maintained through the developmental stages to preserve the final sexual identity. One such identified gene is Chromobox homolog 2 (CBX2), an important ortholog of the Polycomb group (PcG) proteins, that functions as both chromatin modifier and highly dynamic transactivator. CBX2 was shown to be an essential factor for gonadal development in mammals, as genetic variants or loss-of-function of CBX2 can cause sex reversal in mice and humans. Here we will provide an overview of CBX2, its biological functions at molecular level, and the CBX2-dependent transcriptional landscape in gonadal development and DSD.

Trabajo presentado en el 19th International Congress of Developmental Biology, celebrado en Guia (Portugal) del 16 al 20 de octubre de 2022., Identifying genes affecting gonad development is essential to understand the mechanisms causing Variants/Differences in Sex Development. Recently, a DLC3 mutation was associated with male gonadal dysgenesis in 46,XY DSD patients. We show that Cv-c, the Drosophila ortholog of DLC3, is also required to maintain testis integrity during fly development. We found that Cv-c and human DLC3 can perform the same function in fly embryos, as flies with wild type but not mutated DLC3 rescue gonadal dysgenesis, suggesting a functional conservation. Expression of different Cv-c protein variants demonstrated that the StART domain mediates the Cv-c function in the male gonad, independently from the GAP domain activity. This work demonstrates a role for DLC3/Cv-c in male gonadogenesis and highlights a novel StART-mediated function required for gonadal mesoderm-germ cell interaction during testis development.

SUMMARYSex development is an intricate and crucial process in all vertebrates that ensures the continued propagation of genetic diversity within a species, and ultimately their survival. Perturbations in this process can manifest as variations/differences of sex development (VSD/DSD). Primary gonadal somatic cells – the ovarian granulosa cells (GCs) in the case of women – represent the absolute model to investigate mechanism of disease in VSDs. Collection of these cells in humans is laborious and invasive, while classical animal models fail to recapitulate the human phenotype and function. Furthermore, in patients with the most severe forms of VSD gonadal cells are totally absent. It is therefore vital to develop an alternative cell-model. In view of this, we established an efficient method to reprogram donor-derived urinary progenitor cells (UPs) and differentiate iPSCs into granulosa-like cells (GLCs). The UPs presented a less invasive and high-quality cell source, improving the clinical applicability of the model along with utilising a non-integrative reprogramming method that eliminates alteration of the original genome. This novel GLC model closely resembles human GCs in morphology and marker gene expression of GC cell-fate and essential function. These results provide the prospect to generate patient-specific personalised GC models to investigate mechanism of disease in VSDs and could improve understanding of the intricacies in female gonadal development.

Sex development is an intricate and crucial process in all vertebrates that ensures the continued propagation of genetic diversity within a species, and ultimately their survival. Perturbations in this process can manifest as disorders/differences of sex development (DSD). Various transcriptional networks have been linked to development of the gonad into either male or female, which is actively driven by a set of genes that function in a juxtaposed manner and is maintained through the developmental stages to preserve the final sexual identity. One such identified gene is Chromobox homolog 2 (CBX2), an important ortholog of the Polycomb group (PcG) proteins, that functions as both chromatin modifier and highly dynamic transactivator. CBX2 was shown to be an essential factor for gonadal development in mammals, as genetic variants or loss-of-function of CBX2 can cause sex reversal in mice and humans. Here we will provide an overview of CBX2, its biological functions at molecular level, and the CBX2-dependent transcriptional landscape in gonadal development and DSD.

Human sex development relies on differentiation of the gonads, involving many different cells and factors interacting in a very complex process. One of the main obstacles we face when studying gonadal development is the lack of a complete understanding of the mechanisms involved at both molecular and cellular levels, especially in humans. In this chapter, we aim to offer a general view of the challenges and limitations that the currently available cell models face when applied to the study of sex development in humans. Moreover, we analyze the role of induced pluripotent stem cells for the modeling of human gonadal cells, the importance of the origin of the reprograming source, and discuss the potential applications of this technology for sex development research.

Sex development is a complex process involving many genes and hormones. Defects in this process lead to Differences of Sex Development (DSD), a group of heterogeneous conditions not as rare as previously thought. Part of the obstacles in proper management of these patients is due to an incomplete understanding of the genetics programs and molecular pathways involved in sex development and DSD. Several challenges delay progress and the lack of a proper model system for the single patient severely hinders advances in understanding these diseases. The revolutionary techniques of cellular reprogramming and guided in vitro differentiation allow us now to exploit the versatility of induced pluripotent stem cells to create alternatives models for DSD, ideally on a patient-specific personalized basis. View Full-TextKeywords: induced pluripotent stem cells; iPSCs; DSD; cell model; sertoli cell; granulosa cells; germ cells; cellular reprogramming; patient-specific model