Reproductive status-dependent Kisspeptin and RFamide-related peptide (Rfrp) gene expression in female Damaraland mole-rats

Abstract

Damaraland mole rats (Fukomys damarensis) are cooperatively breeding, subterranean mammals, which exhibit high reproductive skew. Reproduction is monopolized by the dominant female of the group while subordinates are physiologically suppressed to the extent that they are anovulatory. It is thought that in these latter animals normal GnRH secretion from the hypothalamus is disrupted. The RFamide peptides kisspeptin (Kiss1) and RFamid-related peptide-3 (RFRP-3) are considered potent regulators of gonadotropin release. To assess whether these neuropeptides are involved in the mechanism of reproductive suppression we investigated the distribution and gene expression of Kiss1 and Rfrp by means of in situ hybridisation in wild-caught female Damaraland mole-rats with different reproductive status. In both reproductive phenotypes, substantial Kiss1 expression was found in the arcuate nucleus and only few Kiss1-expressing cells were detected in the AVPV, potentially due to low circulating estradiol concentrations in breeding and non-breeding females. Rfrp gene expression occurred in the dorsomedial nucleus, the paraventricular nucleus and the periventricular nucleus. While in female breeders and non-breeders plasma oestradiol levels were low and not significantly different, quantification of the hybridisation signal for both genes revealed significant differences in relation to reproductive status. Reproductively active females had more Kiss1-expressing cells and a higher number of silver grains per cell in the arcuate nucleus when compared to non-reproductive females. This difference was most pronounced in the caudal part of the nucleus. No such differences were found in the AVPV. Furthermore, breeding status was associated with a reduced number of Rfrp-expressing cells in the anterior hypothalamus. This reproductive status-dependent expression pattern of Kiss1 and Rfrp suggests that both neuropeptides play a role in the regulation of reproduction in Damaraland mole-rats. Enhanced long-term negative feedback effects of oestradiol could be responsible for the lower Kiss1 expression in the arcuate nucleus of reproductively suppressed females.

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