The origin of sex reversal in XX goats homozygous for the polled intersex syndrome (PIS) mutation was unclear because of the complexity of the mutation that affects the transcription of both FOXL2 and several long noncoding RNAs (lncRNAs). Accumulating evidence suggested that FOXL2 could be the sole gene of the PIS locus responsible for XX sex reversal, the lncRNAs being involved in transcriptional regulation of FOXL2. In this study, using zinc-finger nuclease-directed mutagenesis, we generated several fetuses, of which one XX individual bears biallelic mutations of FOXL2. Our analysis demonstrates that FOXL2 loss of function dissociated from loss of lncRNA expression is sufficient to cause an XX female-to-male sex reversal in the goat model and, as in the mouse model, an agenesis of eyelids. Both developmental defects were reproduced in two newborn animals cloned from the XX FOXL2(-/-) fibroblasts. These results therefore identify FOXL2 as a bona fide female sex-determining gene in the goat. They also highlight a stage-dependent role of FOXL2 in the ovary, different between goats and mice, being important for fetal development in the former but for postnatal maintenance in the latter.

FOXL2 loss of function in goats leads to the early transdifferentiation of ovaries into testes, then to the full sex reversal of XX homozygous mutants. By contrast, Foxl2 loss of function in mice induces an arrest of follicle formation after birth, followed by complete female sterility. In order to understand the molecular role of FOXL2 during ovarian differentiation in the goat species, putative FOXL2 target genes were determined at the earliest stage of gonadal sex-specific differentiation by comparing the mRNA profiles of XX gonads expressing the FOXL2 protein or not. Of these 163 deregulated genes, around two-thirds corresponded to testicular genes that were up-regulated when FOXL2 was absent, and only 19 represented female-associated genes, down-regulated in the absence of FOXL2. FOXL2 should therefore be viewed as an antitestis gene rather than as a female-promoting gene. In particular, the key testis-determining gene DMRT1 was found to be up-regulated ahead of SOX9, thus suggesting in goats that SOX9 primary up-regulation may require DMRT1. Overall, our results equated to FOXL2 being an antitestis gene, allowing us to propose an alternative model for the sex-determination process in goats that differs slightly from that demonstrated in mice.

Premature ovarian insufficiency (POI) is a frequent pathology that affects women under 40 years of age, characterized by an early cessation of menses and high FSH levels. Despite recent progresses in molecular diagnosis, the etiology of POI remains idiopathic in most cases. Whole-exome sequencing of members of a Colombian family affected by POI allowed us to identify a novel homozygous donor splice-site mutation in the meiotic gene MSH4 (MutS Homolog 4). The variant followed a strict mendelian segregation within the family and was absent in a cohort of 135 women over 50 years of age without history of infertility, from the same geographical region as the affected family. Exon trapping experiments showed that the splice-site mutation induced skipping of exon 17. At the protein level, the mutation p.Ile743_Lys785del is predicted to lead to the ablation of the highly conserved Walker B motif of the ATP-binding domain, thus inactivating MSH4. Our study describes the first MSH4 mutation associated with POI and increases the number of meiotic/DNA repair genes formally implicated as being responsible for this condition.

The conditions for sex reversal in vertebrate species have been studied extensively and have highlighted numerous key factors involved in sex differentiation. We review here the history of the development of knowledge, referring to one example of complete female-to-male XX sex reversal associated with a polled phenotype in the goat. The results and hypotheses concerning this polled intersex syndrome (PIS) are then presented, firstly with respect to the transcriptional regulatory effects of the PIS mutation, and secondly regarding the role of the main ovarian-differentiating factor in this PIS locus, the FOXL2 gene.

In a 46 XY individual, the presence of the Y chromosome harboring the testis-determining factor (SRY) triggers testis determination and differentiation. In a 46 XX individual, the absence of SRY and the activation of genes associated with the female pathway lead to ovarian development. The latter process has long been considered as a default pathway. However, recent studies have cast doubts on this dogma. Here, after a brief overview of the main steps of ovarian development, we focus on three genes WNT4, RSPO1 and FOXL2 that are essential for ovarian determination, differentiation and/or maintenance. Special attention is paid to FOXL2 whose mutations are responsible for the blepharophimosis syndrome, often associated with female infertility, and for cancer. We highlight the cooperation of WNT4, RSPO1 and FOXL2 within a regulatory network and the need for further research to better understand their role in defining and maintaining ovarian identity.

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During embryonic development, mutually antagonistic signaling cascades determine gonadal fate toward a testicular or ovarian identity. Errors in this process result in disorders of sex development (DSDs), characterized by discordance between chromosomal, gonadal, and anatomical sex. The absence of an appropriate, accessible in vitro system is a major obstacle in understanding mechanisms of sex-determination/DSDs. Here, we describe protocols for differentiation of mouse and human pluripotent cells toward gonadal progenitors. Transcriptomic analysis reveals that the in vitro–derived murine gonadal cells are equivalent to embryonic day 11.5 in vivo progenitors. Using similar conditions, Sertoli-like cells derived from 46,XY human induced pluripotent stem cells (hiPSCs) exhibit sustained expression of testis-specific genes, secrete anti-Müllerian hormone, migrate, and form tubular structures. Cells derived from 46,XY DSD female hiPSCs, carrying an NR5A1 variant, show aberrant gene expression and absence of tubule formation. CRISPR-Cas9–mediated variant correction rescued the phenotype. This is a robust tool to understand mechanisms of sex determination and model DSDs.

The PI3K/AKT signaling pathway is known to regulate a broad range of cellular processes, and it is often altered in cancer. We have performed high-throughput analyses of the proteins and transcripts deregulated after Akt1 depletion in primary murine granulosa cells, which are the supporting cells of the oocyte. We found known and novel cellular processes perturbed by AKT1 knock-down. Our results confirm and extend the role of this kinase in critical cellular processes, such as directional migration, and provide a series of new substrate candidates that deserve further investigation.