title: Differential expression of estrogen receptor alpha in the embryonic adrenal-kidney-gonadal complex of the oviparous lizard, Calotes versicolor (Daud.).
abstract: Estrogen signalling is critical for ovarian differentiation in reptiles with temperature-dependent sex determination (TSD). To elucidate the involvement of estrogen in this process, adrenal-kidney-gonadal (AKG) expression of estrogen receptor (ERα) was studied at female-producing temperature (FPT) in the developing embryos of the lizard, Calotes versicolor which exhibits a distinct pattern of TSD. The eggs of this lizard were incubated at 31.5±0.5°C (100% FPT). The torso of embryos containing adrenal-kidney-gonadal complex (AKG) was collected during different stages of development and subjected to Western blotting and immunohistochemistry analysis. The ERα antibody recognized two protein bands with apparent molecular weight ∼55 and ∼45kDa in the total protein extracts of embryonic AKG complex of C. versicolor. The observed results suggest the occurrence of isoforms of ERα. The differential expression of two different protein isoforms may reveal their distinct role in cell proliferation during gonadal differentiation. This is the first report to reveal two isoforms of the ERα in a reptile during development. Immunohistochemical studies reveal a weak, but specific, cytoplasmic ERα immunostaining exclusively in the AKG during late thermo-sensitive period suggesting the responsiveness of AKG to estrogens before gonadal differentiation at FPT. Further, cytoplasmic as well as nuclear expression of ERα in the medulla and in oogonia of the cortex (faint activity) at gonadal differentiation stage suggests that the onset of gonadal estrogen activity coincides with sexual differentiation of gonad. Intensity and pattern of the immunoreactions of ERα in the medullary region at FPT suggest endogenous production of estrogen which may act in a paracrine fashion to induce neighboring cells into ovarian differentiation pathway.
authors.affiliation: Molecular Endocrinology and Development Laboratory, Department of Zoology, Karnatak University, Dharwad 580 003, India. Electronic address: ls_doddamani@yahoo.com.
authors.forename: L S
authors.initials: LS
authors.lastname: Inamdar
authors.affiliation: Molecular Endocrinology and Development Laboratory, Department of Zoology, Karnatak University, Dharwad 580 003, India.
authors.forename: B S
authors.initials: BS
authors.lastname: Khodnapur
authors.affiliation: Molecular Endocrinology and Development Laboratory, Department of Zoology, Karnatak University, Dharwad 580 003, India.
authors.forename: R S
authors.initials: RS
authors.lastname: Nindi
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Dasari
authors.affiliation: Molecular Reproduction, Development and Genetics Division, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: P B
authors.initials: PB
authors.lastname: Seshagiri
mesh_terms: D000311:Adrenal Glands / Q000196:embryology* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D047108:Embryonic Development; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D006066:Gonads / Q000196:embryology* / Q000378:metabolism; D007150:Immunohistochemistry; D007668:Kidney / Q000196:embryology* / Q000378:metabolism; D008116:Lizards / Q000254:growth & development*; D011960:Receptors, Estrogen / Q000378:metabolism; D012733:Sex Differentiation
chemical_list: D047628:Estrogen Receptor alpha; D011960:Receptors, Estrogen
keywords: Adrenal–kidney–gonadal (AKG) complex; Estrogen receptor (ERα); Immunohistochemistry; Lizard embryo; Ovarian differentiation; Western blotting