Molecular cloning of doublesex and mab-3-related transcription factor 1, forkhead transcription factor gene 2, and two types of cytochrome P450 aromatase in Southern catfish and their possible roles in sex differentiation

Abstract

To address the roles of doublesex and mab-3-related transcription factor 1 (Dmrt1), forkhead transcription factor gene 2 (Foxl2), and aromatase in sex differentiation of Southern catfish, the cDNA sequences of these genes were isolated from the gonads. Dmrt1a and Dmrt1b were found to be expressed in the gonads, being higher in the testis. A low expression level of Dmrt1b was also detected in the intestine and kidney of the male. Foxl2 was found to be expressed extensively in the brain (B), pituitary (P), gill and gonads (G), with the highest level in the ovary, indicating the possible involvement of Foxl2 in the B-P-G axis. Cytochrome P450 (Cyp)19b was found to be expressed in the brain, spleen, and gonads, while Cyp19a was only expressed in the gonads and spleen. All-female Southern catfish fry were treated with fadrozole (F), tamoxifen (TAM), and 17b-estradiol (E 2 ) respectively, from 5 to 25 days after hatching (dah).The expression levels of these genes were measured at 65 dah. In the F-, TAM-, and FCTAM-treated groups, Dmrt1a and Dmrt1b were up-regulated in the gonad, whereas Foxl2 and Cyp19a were down-regulated, while the expression of Cyp19b in the gonad remained unchanged. Furthermore, downregulation of Foxl2 and Cyp19b was also detected in the brain.In the E 2 -treated group, Dmrt1a and Dmrt1b were downregulated to an undetectable level in the gonad, whereas Foxl2 and Cyp19b were up-regulated in the brain. Consistent with the observed changes in the expressions of these genes, 56, 70, and 80% sex-reversed male individuals were obtained in the F-, TAM-, and FCTAM-treated groups respectively. These results indicate the significant roles of Dmrt1, Foxl2, and Cyp19 in the sex differentiation of Southern catfish.

Effects of sexual steroids on the expression of foxl2 in Gobiocypris rarus

“…E2 could promote the expression of foxl2 but MT could repress the expression of foxl2 in G. rarus. These results were similar to the previous studies in other animals such as rainbow trout (Baron et al, 2004), chicken (Hudson et al, 2005) and catfish (Liu et al, 2007). Androgen could significantly decrease the expression of foxl2a and foxl2b in rainbow trout (Baron et al, 2004).…”

“…Androgen could significantly decrease the expression of foxl2a and foxl2b in rainbow trout (Baron et al, 2004). E2 could up-regulate the expression of foxl2 in rainbow trout (Baron et al, 2004) and southern catfish (Liu et al, 2007), while aromatase inhibitor could repress the expression of foxl2 in chicken (Hudson et al, 2005), rainbow trout (Baron et al, 2004), and southern catfish (Liu et al, 2007). Taken together, the expression of foxl2 is regulated through feedback mechanism by its downstream hormones, estrogen and androgen.…”

“…Aromatase is the key enzyme for synthesis of estrogen (Guiguen et al, 2010), and thus it is important for sex differentiation (Wu et al, 2008). Inhibitors of aromatase can cause sex reversal from female to male in fish (Kitano et al, 2000;Kobayashi et al, 2003;Liu et al, 2007). Foxl2 was expressed predominantly in the brain and gonads of G. rarus.…”

Sexually dimorphic and ontogenetic expression of dmrt1, cyp19a1a and cyp19a1b in Gobiocypris rarus

“…A fragment of dmrt1 which encodes the DM domain of 46 AA (ABF57693) had been reported with testis specific expression in G. rarus detected by RT-PCR (Zhang et al, 2008 expressed in both the ovary and testes in a sexually dimorphic pattern: high expression in the testes, low in the ovary. This result is similar to findings in other fish such as zebrafish (Guo et al, 2005), rainbow trout (Oncorhynchus mykiss) (Marchand et al, 2000), pufferfish (Takifugu rubripes) (Yamaguchi et al, 2006) and southern catfish (Silurus meridionals) (Liu et al, 2007). Strong male-biased expression of dmrt1 may be the general rule (Herpin and Schartl, 2011), although male-restricted expression of dmrt1 has been reported in North African catfish (Clarias gariepinus) (Raghuveer and Senthilkumaran, 2009), Nile tilapia (Oreochromis niloticus) and Japanese ricefish (Oryzias latipes) (Kobayashi et al, 2004).…”

Progress in studies of fish reproductive development regulation

“…Estrogens play an important role in fish sex differentiation, which are regarded as a natural inducer of ovary differentiation [11,53]. The amount of estrogens correlates closely to the expression levels of aromatases.…”