Research ReportThe distribution of estrogen receptor β mRNA in male and female green anole lizards

Estrogens are critical for a variety of aspects of brain development and adult processes. These steroids act via receptors within specific tissues. Several estrogen receptors (ER) are thought to exist, including ERα and ERβ, which function via classical, genomic mechanisms. These two ERs are found in a variety of species and are critical to diverse functions, including reproductive behaviors. ERβ was discovered more recently than ERα, and very little work has been done on this receptor in reptiles. Currently no data are available on its distribution in the brain in this vertebrate group. Here, we have cloned ERβ in the green anole lizard, mapped its distribution using in situ hybridization, and quantified expression in three brain areas controlling reproductive behaviors-the preoptic area, ventromedial amygdala (AMY), and ventromedial hypothalamus (VMH). ERβ was detected in discrete areas throughout the anole brain, with high levels in limbic regions and motor nuclei in the brainstem. Females had a greater density of ERβ positive cells in the AMY and VMH than males. While the functional consequences of these differences are not clear, they may result in an increased ability to respond to local levels of estradiol. The present work documents that neural ERβ is distributed similarly in reptilian, rodent and avian species, suggesting that it may perform similar roles. However, more work is necessary to elucidate the function of ERβ in this group.

► In this study we cloned ERβ in the green anole lizard. ► We mapped the distribution of ERβ mRNA in the lizard brain. ► ERβ was strongly expressed in the forebrain and brainstem motor nuclei. ► ERβ mRNA was sexually dimorphic in forebrain areas important for reproduction.