Molecular Cloning, Characterization, and Chromosome Mapping of Reptilian Estrogen Receptors

Abstract

In many vertebrates, steroid hormones are essential for ovarian differentiation during a critical developmental stage as well as promoting the growth and differentiation of the adult female reproductive system. Although studies have been extensively conducted in mammals and a few fish, amphibians, and bird species, the molecular mechanisms of sex steroid hormone (estrogens) action have been poorly examined in reptiles. Here, we evaluate hormone receptor and ligand interactions in two species of snake, the Okinawa habu (Protobothrops flavoviridis, Viperidae) and the Japanese four-striped rat snake (Elaphe quadrivirgata, Colubridae) after the isolation of cDNAs encoding estrogen receptor α (ESR1) and estrogen receptor β (ESR2). Using a transient transfection assay with mammalian cells, the transcriptional activity of reptilian (Okinawa habu, Japanese four-striped rat snake, American alligator, and Florida red-belly freshwater turtle) ESR1 and ESR2 was examined. All ESR proteins displayed estrogen-dependent activation of transcription via an estrogen-response element-containing promoter; however, the responsiveness to various estrogens was different. Further, we determined the chromosomal locations of the snake steroid hormone receptor genes. ESR1 and ESR2 genes were localized to the short and long arms of chromosome 1, respectively, whereas androgen receptor was localized to a pair of microchromosomes in the two snake species examined. These data provide basic tools that allow future studies examining receptor-ligand interactions and steroid endocrinology in snakes and also expands our knowledge of sex steroid hormone receptor evolution.

Evaluation of Seasonal Serum Level of Estradiol and Progesterone Hormones in Iranian Female Caucasian Viper

“…In many vertebrates the steroid hormones are very important for ovary differentiation, growth and development and also necessary for growth promotion and female's reproductive system differentiation [10]. The steroid hormones play an important role in reproductive biology of vertebrates including reptiles.…”

“…Progesterone is produced by granulosa cells in ovary follicles, in productive female reptiles, male's adrenal glands and non-productive females [9]. Estradiol-17 (E2) is the main estrogen in blood circulation and is essential for natural ovary growth in many vertebrates [10,13]. There is relationship between reproductive events and the concentration of steroids hormones in free range pit vipers (Viperidae, Crotalinae), of the New world species.…”

Characterization of evolutionary trend in squamate estrogen receptor sensitivity

“…Cross-species comparative analyses from wide spectrum of vertebrates, including reptiles, revealed species difference in ERα sensitivity in response to various ligands. Snakes displayed the lowest recorded EC 50 values in all studied vertebrates, followed by other reptile and avian species ( Katsu et al, 2008a andKatsu et al, 2010a;Naidoo et al, 2008). The biological implication of such species difference is yet to be elucidated, and lowered EC 50 values may indicate a reptilespecific evolutionary trend.…”

“…3A; Table 2) (Katsu et al, 2008a, Katsu et al, 2008b, Katsu et al, 2010aand Katsu et al, 2010bMiyagawa et al, 2014 andNaidoo et al, 2008 (Miyagawa et al, 2014). Hence, multiple sequence alignment of the LBD was conducted with the investigated tetrapod ERα orthologs, with inclusion of human ERα-LBD as well (Fig.…”

Integrative and comparative reproductive biology: From alligators to xenobiotics

“…Guillette appreciated the importance of cloning and characterizing reptilian ESRs (including ESR1, ERa and ESR2, ERb) and was involved with characterizing these receptors in several species (Katsu et al, 2004, 2008, 2010, 2006; Kohno et al, 2008). These in vitro characterization projects have revealed important insight into the function and sensitivity of these receptors across various species and have also provided a framework in which to screen chemicals for receptor interaction prior to further in ovo experiments (Kohno and Guillette, 2013).…”