The role of RXFP2 in mediating androgen-induced inguinoscrotal testis descent in LH receptor knockout mice

Abstract

LH receptor knockout (LhrKO) male mice exhibit a bilateral cryptorchidism resulting from a developmental defect in the gubernaculum during the inguinoscrotal phase of testis descent, which is corrected by testosterone replacement therapy (TRT). In vivo and in vitro experiments were conducted to investigate the roles of the androgen receptor (AR) and RXFP2 signals in regulation of gubernacular development in LhrKO animals. This study demonstrated that AR and RXFP2 proteins were expressed in the gubernaculum during the entire postnatal period. TRT normalized gubernacular RXFP2 protein levels inLhrKO mice. Organ and primary cell cultures of gubernacula showed that 5a-dihydrotestosterone (DHT) upregulated the expression of Rxfp2 which was abolished by the addition of an AR antagonist, flutamide. A single s.c. testosterone injection also led to a significant increase in Rxfp2 mRNA levels in a time-dependent fashion in LhrKO animals. DHT, natural and synthetic insulin-like peptide 3 (INSL3), or relaxin alone did not affect proliferation of gubernacular mesenchymal cells, while co-treatments of DHT with either INSL3 or relaxin resulted in an increase in cell proliferation, and they also enhanced the mesenchymal cell differentiation toward the myogenic pathway, which included a decrease in a mesenchymal cell marker, CD44 and the expression of troponin. These effects were attenuated by the addition of flutamide, siRNA-mediated Rxfp2 knockdown, or by an INSL3 antagonist. Co-administration of an INSL3 antagonist curtailed TRT-induced inguinoscrotal testis descent in LhrKO mice. Our findings indicate that the RXFP2 signaling pathway plays an important role in mediating androgen action to stimulate gubernaculum development during inguinoscrotal testis descent.

Functional link between bone morphogenetic proteins and insulin-like peptide 3 signaling in modulating ovarian androgen production

“…Abiraterone, a potent inhibitor of CYP17A1 enzyme (36), abolished A4 secretion and reduced expression of INSL3 and RXFP2 mRNA by ∼50%, supporting the notion of a mutual, positive autoregulatory loop linking thecal INSL3-RXFP2 signaling and androgen synthesis. Our evidence that ovarian (thecal) expression of RXFP2 is positively regulated by androgens concurs with the recent observation in male mice that testosterone administration to androgen-deficient LHCGR-null mutants upregulated RXFP2 expression in the gubernaculum (37).…”

Genome-Wide Analysis of the World's Sheep Breeds Reveals High Levels of Historic Mixture and Strong Recent Selection

“…Where convincing signals are detected, it can be difficult to clearly identify the target of selection within a region, and even more difficult to establish the link between selection and its morphological consequence. In this study the strongest selection signal was identified immediately adjacent to RXFP2 , a gene involved in reduced bone mass and sexual maturation [47],[48]. Strong evidence supports that RXFP2 was targeted by breeding for the removal of horns, likely to be one of the oldest morphological modifications that accompanied domestication [49],[50].…”

Progress of genome wide association study in domestic animals

“…A genome-wide association study was conducted using 36,000 SNPs and determined the main genetic candidate for horns to be RXFP2 , an autosomal gene with known involvement in determining primary sexual characteristics in humans and mice [37-39]. Evidence from additional SNPs in and around RXFP2 supports a new model of horn-type inheritance in Soay sheep, and for the first time sheep with the same horn phenotype but different underlying genotypes can be identified.…”