Beta-Hydroxysteroid Dehydrogenase Genes in Orange-Spotted Grouper (Epinephelus coioides): Genome-Wide Identification and Expression Analysis During Sex Reversal

Beta-hydroxysteroid dehydrogenases (β-HSDs) are a group of steroidogenic enzymes that are involved in steroid biosynthesis and metabolism, and play a crucial role in mammalian physiology and development, including sex determination and differentiation. In the present study, a genome-wide analysis identified the numbers of β-hsd genes in orange-spotted grouper (Epinephelus coioides) (19), human (Homo sapiens) (22), mouse (Mus musculus) (24), chicken (Gallus gallus) (16), xenopus (Xenopus tropicalis) (24), coelacanth (Latimeria chalumnae) (17), spotted gar (Lepisosteus oculatus) (14), zebrafish (Danio rerio) (19), fugu (Takifugu rubripes) (19), tilapia (Oreochromis niloticus) (19), medaka (Oryzias latipes) (19), stickleback (Gasterosteus aculeatus) (17) and common carp (Cyprinus carpio) (27) samples. A comparative analysis revealed that the number of β-hsd genes in teleost fish was no greater than in tetrapods due to gene loss followed by a teleost-specific whole-genome duplication event. Based on transcriptome data from grouper brain and gonad samples during sex reversal, six β-hsd genes had relatively high expression levels in the brain, indicating that these genes may be required for neurogenesis or the maintenance of specific biological processes in the brain. In the gonad, two and eight β-hsd genes were up- and downregulated, respectively, indicating their important roles in sex reversal. Our results demonstrated that β-hsd genes may be involved in the sex reversal of grouper by regulating the synthesis and metabolism of sex steroid hormones.

Origin of the response to adrenal and sex steroids: Roles of promiscuity and co-evolution of enzymes and steroid receptors

Many responses to adrenal and sex steroids are mediated by receptors that belong to the nuclear receptor family of transcription factors. We investigated the co-evolution of these vertebrate steroid receptors and the enzymes that synthesize adrenal and sex steroids through data mining of genomes from cephalochordates [amphioxus], cyclostomes [lampreys, hagfish], chondrichthyes [sharks, rays, skates], actinopterygii [ray-finned fish], sarcopterygii [coelacanths, lungfishes and terrestrial vertebrates]. An ancestor of the estrogen receptor and 3-ketosteroid receptors evolved in amphioxus. A corticoid receptor and a progesterone receptor evolved in cyclostomes, and an androgen receptor evolved in gnathostomes. Amphioxus contains CYP11, CYP17, CYP19, 3β/Δ5-4-HSD and 17β-HSD14, which suffice for the synthesis of estradiol and Δ5-androstenediol. Amphioxus also contains CYP27, which catalyzes the synthesis of 27-hydroxy-cholesterol, another estrogen. Lamprey contains, in addition, CYP21, which catalyzes the synthesis of 11-deoxycortisol. Chondrichthyes contain, in addition, CYP11A, CYP11C, CYP17A1, CYP17A2. Coelacanth also contains CYP11C1, the current descendent from a common ancestor with modern land vertebrate CYP11B genes, which catalyze the synthesis of cortisol, corticosterone and aldosterone. Interestingly, CYP11B2, aldosterone synthase, evolved from separate gene duplications in at least old world monkeys and two suborders of rodents. Sciurognathi (including mice and rats) and Hystricomorpha (including guinea pigs). Thus, steroid receptors and steroidogenic enzymes co-evolved at key transitions in the evolution of vertebrates. Together, this suite of receptors and enzymes through their roles in transcriptional regulation of reproduction, development, homeostasis and the response to stress contributed to the evolutionary diversification of vertebrates. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.