Isolation of chicken homolog of the FOXL2 gene and comparison of its expression patterns with those of aromatase during ovarian development

Abstract

Mutations in the forkhead transcription factor gene FOXL2 are involved in ovarian failure, which occurs in human BPES syndrome. This syndrome presents a sexually dimorphic expression, specific to the ovary in several vertebrates. We cloned the open reading frame of chicken FOXL2 (cFoxL2) and studied cFoxL2 expression in developing gonads and during adulthood to examine the role of FOXL2 in ovarian differentiation and function in birds. The spatial and temporal dynamics of cFoxL2 and aromatase expression were analyzed in parallel by using real-time quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry in attempt to investigate the possible role of cFoxL2 in the regulation of aromatase. The expression patterns of cFoxL2 and aromatase transcripts were highly correlated during the sex-differentiation period (4.7-12.7 days of incubation). Aromatase and cFoxL2 proteins were colocalized in the medullar part of female gonads on embryonic day 14. Fourteen days after hatching, cFoxL2 protein was mainly detected in granulosa cells of developing follicles. In adult ovary follicular envelopes, apart from granulosa cells, cFoxL2 transcript and protein were detected at lower levels in theca cells where aromatase was present. A high level of cFoxL2 transcription was also observed in maturing and ovulated oocytes. Our results confirm that FoxL2 is an early regulator of ovarian development in birds and may be involved in aromatase transcription regulation. Developmental Dynamics 231:859 -870, 2004.

Characterization of early molecular sex differentiation in rainbow trout, Oncorhynchus mykiss

“…The expression of cyp19a1 is also detected both in theca cells and granulosa cells in the adult ovaries of tilapia (Nakamura et al, 1998). A similar expression of Cyp19 in theca cells is also described in the differentiating ovaries of the chicken (Oreal et al, 2002;Govoroun et al, 2004). We, therefore, suggest that in trout, the presumptive localization of cyp19a1 would be in precursors of theca cells.…”

Foxl2 gene and the development of the ovary: a story about goat, mouse, fish and woman

“…On the contrary, FOXL2 could not be detected neither in the oocyte, nor in the fetal or adult testes. Identical results have been observed in the mouse, goat, chicken and fish [9,10].…”

The progestin levonorgestrel affects sex differentiation in zebrafish at environmentally relevant concentrations

“…In zebrafish, dmrt1 mRNA is expressed in both testes and ovaries, but at markedly higher levels in testes; it plays an important role in early gonadal sex differentiation of male zebrafish (Jørgensen et al, 2008;Schulz et al, 2007). Foxl2 is one of the very few conserved ovarian differentiation genes across vertebrate evolution, with female-specific expression in the differentiating ovaries of mammals (Baron et al, 2005), birds (Govoroun et al, 2004), and fish (Baron et al, 2005;Wang et al, 2007). The gene has been regarded as a potential ovary marker during female sex development in catfish (Sridevi et al, 2012).…”