title: Seasonal changes and sexual dimorphism in gene expression of StAR protein, steroidogenic enzymes and sex hormone receptors in the frog brain.
abstract: The brain of amphibians contains all the key enzymes of steroidogenesis and has a high steroidogenic activity. In seasonally-breeding amphibian species brain steroid levels fluctuate synchronously with the reproductive cycle. Here we report a study of gene expression of StAR protein, key steroidogenic enzymes and sex hormone receptors in the telencephalon (T) and diencephalon-mesencephalon (D-M) of male and female reproductive and post-reproductive Pelophylax esculentus, a seasonally breeding anuran amphibian. Significant differences in gene expression were observed between (a) the reproductive and post-reproductive phase, (b) the two brain regions and (c) male and female frogs. During the reproductive phase, star gene expression increased in the male (both T and D-M) but not in the female brain. Seasonal fluctuations in expression levels of hsd3b1, hsd17b1, srd5a1 and cyp19a1 genes for neurosteroidogenic enzymes occurred in D-M region of both sexes, with the higher levels in reproductive period. Moreover, the D-M region generally showed higher levels of gene expression than the T region in both sexes. Gene expression was higher in females than males for most genes, suggesting higher neurosteroid production in female brain. Seasonal and sex-linked changes were also observed in gene expression for androgen (ar) and estrogen (esr1, esr2) receptors, with the males showing the highest ar levels in reproductive phase and the highest esr1 and esr2 levels in post-reproductive phase; in contrast, females showed the maximum expression for all three genes in reproductive phase. The results are the first evidence for seasonal changes and sexual dimorphism of gene expression of the neurosteroidogenic pathway in amphibians.
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi, 43, 81100 Caserta, Italy. Electronic address: alessandra.santillo@unina2.it.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Santillo
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi, 43, 81100 Caserta, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Falvo
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi, 43, 81100 Caserta, Italy.
authors.forename: Maria Maddalena
authors.initials: MM
authors.lastname: Di Fiore
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi, 43, 81100 Caserta, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Chieffi Baccari
mesh_terms: D000818:Animals; D001001:Anura / Q000378:metabolism*; D001141:Aromatase / Q000235:genetics*; D001921:Brain / Q000378:metabolism; D004027:Diencephalon / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D012739:Gonadal Steroid Hormones / Q000378:metabolism; D008297:Male; D010750:Phosphoproteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011944:Receptors, Androgen / Q000235:genetics*; D011960:Receptors, Estrogen / Q000235:genetics*; D012098:Reproduction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D012727:Sex Characteristics; D054339:Steroidogenic Factor 1 / Q000235:genetics; D013687:Telencephalon / Q000378:metabolism; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D012739:Gonadal Steroid Hormones; D010750:Phosphoproteins; D012333:RNA, Messenger; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D054339:Steroidogenic Factor 1; D000098682:Steroidogenic Acute Regulatory Protein; D001141:Aromatase
keywords: 17β-Hydroxysteroid dehydrogenase; 3β-Hydroxysteroid dehydrogenase; 5α-Reductase; Cytochrome P450 aromatase; Neurosteroidogenesis; Sex hormone receptors