The review deals with features of sex determination in vertebrates. The mechanisms of sex determination are compared between fishes, amphibians, reptilians, birds, and mammals. We focus on structural and functional differences in the role of sex-determining genes in different vertebrates. Special attention is paid to the role of estrogens in sex determination in nonmammalian vertebrates.
Source/description: Ubiquitin-associated protein 2 (UBAP2) is a novel gene first isolated based on its expression in the human adrenal gland. 1 The full-length protein encoded by this gene contains a ubiquitin-associated domain, a motif found in several proteins having connections to ubiquitin and the ubiquitination pathway. 1 In birds, UBAP2 is represented in two copies located on the Z and W chromosomes. 2 In the recent chicken genome sequence assembly, the GGAZ and especially the GGAW sequences were poorly represented and assembled, so additional evidence for the location of Z-and W-linked loci should help to address this situation. Here, we report the cytogenetic assignment of large-insert clones for the chicken UBAP2 genes.
Sex determination system in birds is characterized by a homo-(Neognatae) and heteromorphic (Paleognatae) sex chromosomes. Heterogametic sex is female (ZZ/ZW system). DMRT1 gene is a gene regarded as a main male sex determining factor in this group of animals. The question remains about the participation of other factors (HEMOGEN, AMH etc.) in appearance of testis, and the role of steroid hormones in formation of ovaries. Complete sex inversion is not typical for species with genotypic sex determination (GSD), although the effect of estrogen metabolites is noted for birds. For birds epigenetic mechanisms of regulation (methylation of DNA and non-coding RNA) have been described for sex controlling genes such as CYP19A1 and DMRT1.
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