Removal of reproductive suppression reveals latent sex differences in brain steroid hormone receptors in naked mole-rats, Heterocephalus glaber. Issue 1 (December 2015)

• Record Type: Journal Article
• Authors: Swift-Gallant, Ashlyn; Mo, Kaiguo; Peragine, Deane; Monks, D.; Holmes, Melissa
• Is Part Of: Biology of sex differences. Volume 6:Issue 1(2015)
• Page Start: 1
• Page End: 9
• Publication Date: 2015-12
• Subjects: Androgen receptor -- Aromatase -- Estradiol -- Estrogen receptor -- Eusocial -- Naked mole-rat -- Progesterone receptor -- Reproductive suppression -- Sex difference -- Testosterone; Biology -- Sex differences -- Periodicals; Sex factors in disease -- Research; Sex differences -- Research -- Periodicals; 612.6
• DOI: 10.1186/s13293-015-0050-x
• Languages: English
• ISSNs: 2042-6410

Abstract

Abstract Background Naked mole-rats are eusocial mammals, living in large colonies with a single breeding female and 1–3 breeding males. Breeders are socially dominant, and only the breeders exhibit traditional sex differences in circulating gonadal steroid hormones and reproductive behaviors. Non-reproductive subordinates also fail to show sex differences in overall body size, external genital morphology, and non-reproductive behaviors. However, subordinates can transition to breeding status if removed from their colony and housed with an opposite-sex conspecific, suggesting the presence of latent sex differences. Here, we assessed the expression of steroid hormone receptor and aromatase messenger RNA (mRNA) in the brains of males and females as they transitioned in social and reproductive status. Methods We compared in-colony subordinates to opposite-sex subordinate pairs that were removed from their colony for either 1 day, 1 week, 1 month, or until they became breeders (i.e., produced a litter). Diencephalic tissue was collected and mRNA of androgen receptor (Ar ), estrogen receptor alpha (Esr1 ), progesterone receptor (Pgr ), and aromatase (Cyp19a1 ) was measured using qPCR. Testosterone, 17β-estradiol, and progesterone from serum were also measured. Results As early as 1 week post-removal, males exhibited increased diencephalicAr mRNA and circulating testosterone, whereas females had increasedCyp19a1 mRNA in the diencephalon. At 1 month post-removal, females exhibited increased 17β-estradiol and progesterone. The largest changes in steroid hormone receptors were observed in breeders. Breeding females had a threefold increase inCyp19a1 and fivefold increases inEsr1 andPgr, whereas breeding males had reducedPgr and increasedAr . Conclusions These data demonstrate that sex differences in circulating gonadal steroids and hypothalamic gene expression emerge weeks to months after subordinate animals are removed from reproductive suppression in their home colony.