Expression of insulin-like 3 (INSL3) and differential splicing of its receptor in the ovary of rhesus macaques

BACKGROUND: Although insulin-like 3 (INSL3) has been identified in the gonad of both sexes in many species, there are only limited reports on the distribution of INSL3 and its receptor, relaxin/insulin-like family peptide receptor 2 (RXFP2), in the primate ovary. Since the hormone-receptor pair is believed to play a role in female reproduction, investigating the transcription of INSL3/RXFP2 genes and the spatiotemporal expression of INSL3 in the nonhuman primate may shed light on the functional aspects of the system in humans. METHODS: Database mining, molecular and immunological methods were applied. RESULTS: One single INSL3 transcript and three novel splice variant transcripts of RXFP2 were identified in the ovary of rhesus macaques. While the full-length RXFP2 transcript is barely detectable in granulosa cells during the periovulatory period, INSL3 transcript and protein are highly abundant in theca cells surrounding antral follicles. Moreover, the INSL3 level in follicular fluid is 3-4 times higher than that in female serum which remains low throughout the menstrual cycle. CONCLUSIONS: The presence of INSL3 and its receptor in the ovary implies a potential role of the ligand-receptor pair in female reproduction in nonhuman primates. However, the existence of multiple splice variants of RXFP2 indicates a very complex nature of the hormone-receptor system.