The Bromodomain testis-specific gene (Brdt) characterization and expression in gilthead seabream, Sparus aurata, and European seabass, Dicentrarchus labrax

Abstract

Multiple genes and transcription factors are involved in regulation and control of the complex process of sex determination and differentiation of fish species. Also more, several hormonal factors and some environmental conditions can also be adequate spawning strategies and stimuli for inducing reproduction of fish species. Brdt gene belongs to the bromodomain-extraterminal domain (BET) family of transcriptional coregulators. In mammals, Brdt gene is almost exclusively expressed in testis. Furthermore, Brdt protein is involved in elongating spermatids, and is required for proper spermatogenesis and male fertility. However, from our understanding of fish species, the role of this gene as key, during gametogenesis, still remains unknown. In this study, two Brdt mRNA transcripts were isolated from two teleostean fish species, gilt-head seabream and European seabass. In both species the shorter form lacked a functional C-terminal domain, which may involve a different function as transcriptional regulator. The pattern of Brdt expression showed that the highest levels occurred in the gonads. Significantly lower levels of expression were detected in brain, pituitary and different organ systems (heart, kidney, gills, among other somatic tissues) from both studied species. In situ hybridization approach evidenced that Brdt mRNA expression was restricted to specific cell-types of the germ line, during both oogenesis and spermatogenesis processes.

Soya isoflavones, genistein and daidzein, induce differential transcriptional modulation in the ovary and testis of zebrafish Danio rerio

“…The inter-and intra-specific differences indicated in BRDT expression levels in different species of fish (including zebrafish in the present study; i.e. higher levels of BRDT in the ovaries than in the testes) suggest a different role of BRDT protein during both spermatogenesis and oogenesis, as a transcriptional regulator and/or for chromatin remodeling and compaction depending on the species, as reported in mammals and fish (Taniguchi 2016, Úbeda-Manzanaro et al 2016. In the present study, in the zebrafish testes, basal expression levels of BRDT transcripts increased significantly with exposure to daidzein (at 10 mg l −1 ), but not with exposure to the same dose of genistein.…”

“…Most genes involved in reproduction, hatching, development and epigenetic processes (e.g. oestrogens and receptors, choriogenins, HEs, apoptotic and epigenetic markers, bromodomains) express constitutively at high or moderate levels in the gonads and during the early stages of development and life, as has been reported in different species of fish including zebrafish (Segner et al 2003, Chandrasekar et al 2010, Úbeda-Manzanaro et al 2016, Sarasquete et al 2018a, González-Rojo et al 2019. All these findings corroborate the maternal origin of mRNA transcripts and their transfer to the progeny, since the oocyte is the starting point of a new generation.…”

“…brain, pituitary, musculature, heart, kidney, spleen, intestine, gills), while in the gonochoric sea bass Dicentrarchus labrax, similar and elevated expression levels of BRDT were registered in both gonads, and very low levels of expression were recorded in the other organs and tissues. In addition, a constitutive expression of BRDT has been described in both spermatocytes and spermatids, which could be related to the role of BRDT in the termination of meiosis-I as well as in genome condensation or as a transcriptional regulator during these spermatogenetic states (Úbeda-Manzanaro et al 2016). Interestingly, Kurtz et al (2009) reported that histone acetylation (e.g.…”

“…In addition, bromodomain and extraterminal domain (BET) proteins can also maintain this structural role and participate in chromatin remodelling during oogenesis (Paillisson et al 2007, Berkovits & Wolgemuth 2013, Bao & Bedford 2016, Taniguchi 2016. In fish, the role of the BRDT gene and proteins, which play a key role in hatching, development and differentiation, as well as embryogenesis and gametogenesis of males and females, is much less known and appears to be much more complex and variable than in other vertebrates (Úbeda-Manzanaro et al 2016, Sarasquete et al 2018a). This complexity is potentially due to different strategies and reproductive behaviors, environmental and hormonal sensi-tivity or to the remarkable neuroendocrine and sexual plasticity of the fish (Devlin & Nagahama 2002, Segner et al 2003, Piferrer & Guiguen 2008, Ribas et al 2017.…”

Blocking the Bromodomains Function Contributes to Disturbances in Alga Chara vulgaris Spermatids Differentiation

“…The results of previous immunofluorescent and ultrastructural analyses showed that blocking the removal of histones, during the exchange of these proteins into protamines, hindered the proper course of spermiogenesis [3,28]. The studies of spermatogenesis concerning Brdt gene in two fish species, which have different methods of nuclear protein exchange, revealed variations in this gene expression which could indicate a different role of Brdt protein [29]. The exchange of nucleoproteins in one of these species (Dicentrarchus labrax) follows the same scheme as in Chara [30].…”