Hormonal Regulation of Steroid Receptor Coactivator‐1 mRNA in the Male and Female Green Anole Brain

Abstract

Green anole lizards are seasonal breeders, with male sexual behaviour primarily regulated by an annual increase in testosterone. Morphological, biochemical and behavioural changes associated with reproduction are activated by testosterone, generally with a greater effect in the breeding season (BS) than in the nonbreeding season (NBS). The present study investigates the possibility that differences in a steroid receptor coactivator may regulate this seasonal difference in responsiveness to testosterone. In situ hybridisation was used to examine the expression of steroid receptor coactivator-1 (SRC-1) in the brains of gonadally intact male and female green anoles across breeding states. A second experiment examined gonadectomised animals with and without testosterone treatment. Gonadally intact males had more SRC-1 expressing cells in the preoptic area and larger volumes of this region as defined by these cells than females. Main effects of both sex and season (males > females and BS > NBS) were present in cell number and volume of the ventromedial hypothalamus. An interaction between sex and season suggested that high expression in BS males was driving these effects. In hormone-manipulated animals, testosterone treatment increased both the number of SRC-1 expressing cells in and volumes of the preoptic area and amygdala. These results suggest that testosterone selectively regulates SRC-1, and that this coactivator may play a role in facilitating reproductive behaviours across both sexes. However, changes in SRC-1 expression are not likely responsible for the seasonal change in responsiveness to testosterone.

SRC-1 Knockout Exerts No Effect on Amyloid β Deposition in APP/PS1 Mice

“…SRC-1 is the key coactivator for the transcriptional regulation of NRs (Bayele, 2019;Heck et al, 2020). There are studies that have reported that SRC-1 is widely expressed in the brain (Chen et al, 2015;Kerver and Wade, 2015) and modulates many brain functions, such as motor, energy homeostasis, and reproductive behavior (Charlier et al, 2005;Yang et al, 2019) through the effect on cerebellar Purkinje cells (Eijun et al, 2003), hypothalamic neurons (Yang et al, 2019;Heck et al, 2020), and so on. Furthermore, a recent study has shown that SRC-1 is highly expressed in the hippocampus, and hippocampal SRC-1 knockdown mediated by the lentivirus could cause decreased synaptic protein expression and memory impairment (Bian et al, 2018;Chen et al, 2020).…”

Steroid receptor coactivator-1: The central intermediator linking multiple signals and functions in the brain and spinal cord

“…Firstly, it is positively regulated by circulating androgen, since orchidectomy decreased SRC-1 in some brain regions 39 that could be rescued by testosterone in a dose-dependent manner 40 , 41 ; and testosterone increased the number and volumes of SRC-1 expressing cells in the preoptic area and amygdala in the green anole lizards. 42 Secondly, it was regulated by thyroid hormones (TH) in a development- and region-specific manner since in the rat brain, anti-thyroid treatment decreased SRC-1 mRNA in the cortex and dentate gyrus but increased it in CA3. 43 However, in mouse cerebellum, TH treatment resulted in a decrease (61%) of SRC-1 in P14 but not adult.…”

Genetic regulation of sex differences in songbirds and lizards

“…These results suggest that T selectively regulates SRC-1, and that this coactivator may influence the activity of these brain regions important for the display of sexual behaviour. However, changes in SRC-1 expression are probably not responsible for the seasonal change in responsiveness to T [89]. CBP is also expressed at relatively high levels in steroid-sensitive brain regions.…”