Sexually dimorphic transcription of estrogen receptors in cod gonads throughout a reproductive cycle

Abstract

The role of sex steroid regulation in gonadal maturation is a very complex process that is far from being fully understood. Hence, we have investigated seasonal changes in gonadal expression of estrogen receptors (ERs) in Atlantic cod (Gadus morhua L.), a batch spawner, throughout the annual reproductive cycle. Three nuclear ER partial cDNA sequences (esr1, esr2a, and esr2b) were cloned and all esr transcripts were detected mainly in liver and gonads of fish of both sexes. In situ hybridization of esrs along with germ cell (vasa) and gonadal somatic cell markers (gonadal soma-derived factor (gsdf), 3b-hydroxysteroid dehydrogenase (3bhsd), and anti-Mü llerian hormone (amh) for testicular, or gsdf for ovarian somatic cells) showed that all three esrs were preferentially localized within interstitial fibroblasts composed of immature and mature Leydig cells in testis, whereas they were differentially expressed in both follicular cells and oocytes in ovary. Quantitative real-time PCR analysis revealed a sexually dimorphic expression pattern of the three esr paralogs in testis and ovary. A significant increase in esr2a expression was identified in testis and of esr2b in ovary, whereas esr1 transcripts were elevated in both testis and ovary in February and March before the spawning period. The localization and sexually dimorphic expression of esr genes in gonads indicate a direct function of estrogen via ERs in gonadal somatic cell growth and differentiation for Leydig cell in testis and follicular cells in ovary throughout the annual reproductive cycle in Atlantic cod. Key Words" androgen receptor (ar) " Atlantic cod " cytochrome P450 aromatase (cyp19a1a)" estrogen receptor (esr)" sexual maturation

Molecular cloning of ESR2 and gene expression analysis of ESR1 and ESR2 in the pituitary gland of the Chinese alligator ( Alligator sinensis ) during female reproductive cycle

“…And higher ESR2 mRNA levels during spring and autumn active periods also might be due to decreases in estrogen levels. However, changes of ESR1 expression levels during reproductive cycle were consistent with the previous studies in cod (Nagasawa et al, 2014) and Italian wall lizard (Verderame and Limatola, 2010), of which the highest expression of ESR1…”

“…However, in female alligators, the mRNA expression level of ESR1 was higher than that of ESR2 in the hypothalamus and liver, which was consistent with the previous reports in the cod (Nagasawa et al, 2014), Italian wall lizard (Verderame and Limatola, 2010), leopard gecko (Endo et al, 2008) and bovine (Panin et al, 2015).…”

“…Higher expression levels of both ESR genes in the tissues (hypothalamus, pituitary gland, gonad and liver) of male and female alligators that agreed with the results previously found in the killifish, cod, hagfish, four-striped rat snake, pigeon, European starling and rat (Kuiper et al, 1997;Bernard et al, 1999;Katsu et al, 2010;Nagasawa et al, 2014;Zhang et al, 2014;Cotter et al, 2015;Nishimiya et al, 2016). The ESRs mRNA levels in the lung, kidney and pancreas were low.…”

Seasonal cycle of leydig cells in the Japanese Jungle Crow (Corvus macrorhynchos)

“…It has been reported that testosterone levels changed in parallel with spermatogenic activity in the testis. A very recent study suggests that expression of esr genes help in growth and differentiation for Leydig cell in testis throughout the annual reproductive cycle in Atlantic cod (Nagasawa et al 2014).…”

“…Similarly, the interstices between the convoluting seminiferous tubules are packed with areolar connective containing blood capillaries, lymph vessels and interstitial Leydig cells, which secrete testosterone in the breeding season. A very recent study suggests that expression of esr genes help in growth and differentiation for Leydig cell in testis throughout the annual reproductive cycle in Atlantic cod (Nagasawa et al 2014). On the contrary, interstitial tissue of the regressed testes of the nonbreeding season appears more prominent (Loft and Murton, 1973).…”