Erbb4 regulates the oocyte microenvironment during folliculogenesis.

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders leading to infertility in women affecting reproductive, endocrine and metabolic systems. Recent genomewide association studies on PCOS cohorts revealed a single nucleotide polymorphism (SNP) in the ERBB4 receptor tyrosine kinase 4 gene, but its role in ovary development or during folliculogenesis remains poorly understood. Since no genetic animal models mimicking all PCOS reproductive features are available, we conditionally deleted Erbb4 in murine granulosa cells (GCs) under the control of Amh promoter. While we have demonstrated that Erbb4 deletion displayed aberrant ovarian function by affecting the reproductive function (asynchronous oestrous cycle leading to few ovulations and subfertility) and metabolic function (obesity), their ovaries also present severe structural and functional abnormalities (impaired oocyte development). Hormone analysis revealed an up-regulation of serum luteinizing hormone, hyperandrogenism, increased production of ovarian and circulating anti-Müllerian hormone. Our data implicate that Erbb4 deletion in GCs leads to defective intercellular junctions between the GCs and oocytes, causing changes in the expression of genes regulating the local microenvironment of the follicles. In vitro culture assays reducing the level of Erbb4 via shRNAs confirm that Erbb4 is essential for regulating Amh level. In conclusion, our results indicate a functional role for Erbb4 in the ovary, especially during folliculogenesis and its reduced expression plays an important role in reproductive pathophysiology, such as PCOS development.