Differential gene expression in male and female rainbow trout embryos prior to the onset of gross morphological differentiation of the gonads

Abstract

BackgroundThere are large differences between the sexes at the genetic level; these differences include heterogametic sex chromosomes and/or differences in expression of genes between the sexes. In rainbow trout (Oncorhynchus mykiss) qRT-PCR studies have found significant differences in expression of several candidate sex determining genes. However, these genes represent a very small fraction of the genome and research in other species suggests there are large portions of the transcriptome that are differentially expressed between the sexes. These differences are especially noticeable once gonad differentiation and maturation has occurred, but less is known at earlier stages of development. Here we use data from a microarray and qRT-PCR to identify genes differentially expressed between the sexes at three time points in pre-hatch embryos, prior to the known timing of sexual differentiation in this species.ResultsThe microarray study revealed 883 differentially expressed features between the sexes with roughly equal numbers of male and female upregulated features across time points. Most of the differentially expressed genes on the microarray were not related to sex function, suggesting large scale differences in gene expression between the sexes are present early in development. Candidate gene analysis revealed sox9, DMRT1, Nr5a1 and wt1 were upregulated in males at some time points and foxl2, ovol1, fst and cyp19a1a were upregulated in females at some time points.ConclusionThis is the first study to identify sexual dimorphism in expression of the genome during embryogenesis in any fish and demonstrates that transcriptional differences are present before the completion of gonadogenesis.

Gonadal transcriptomic analysis of yellow catfish (Pelteobagrus fulvidraco): identification of sex-related genes and genetic markers

“…It has bipotential fates to form either ovary or testis depending on a sex determination cue in many fish species; the development of gonad is referred as sex differentiation. Gene expression between sexes has a great portion of difference in gonads (19); the characterization of genes involved in sex differentiation could localize candidate genes that may potentially control sex determination. A master sex-determination gene among those candidate genes is thought to control the gonad sex differentiation (63).…”

Large-scale tissue-specific and temporal gene expression profiles in Pengze crucian carp

“…Jørgensen et al, 2008;Kobayashi et al, 2008). We collected the steroid receptor gene expression data reported in European seabass (Blázquez and Piferrer, 2005), fathead minnow (Filby and Tyler, 2005), goldfish (Nelson and Habibi, 2010), rainbow trout (Hale et al, 2011), rare minnow (Wang et al, 2011), and loach (Zhang et al, 2012), and we found that most steroid receptor genes reached the highest expression levels at different time points. The results of the present study showed that steroid receptor genes simultaneously peaked at 48 dph, and were associated with active steroidogenesis from 48 to 60 dph.…”

“…Doublesex and mab-3 related transcription factor 1 (dmrt1) is the sex determination gene in reptiles and birds, and its expression was predominantly detected in testes as compared to ovaries . Forkhead box L2 (foxl2) contains a fork-head DNA-binding domain, and it may play a role in ovarian development and function maintenance (Hale et al, 2011;Raghuveer et al, 2011). Nuclear receptor subfamily 5, group A, member 1d (also called steroidogenic factor 1d, nr5a1b) helps control gene modulation that is related to the development of gonads (ovaries and testes) and adrenal glands (von Hofsten et al, 2005).…”

“…Gene expression profiles in different genders (Hale et al, 2011), tissues, and developmental stages (Ijiri et al, 2008;Shi et al, 2013) may have dual functions in sex determination and differentiation. The present study detected all four gene catalogues associated with tissue-specific and temporal distributions in Pcc.…”

Comparative transcriptome analysis of Nile tilapia (Oreochromis niloticus) in response to alkalinity stress

“…Compared to the traditional cDNA microarrays, RNA-Seq is more sensitive in detecting all the expressed genes (Hale et al, 2011). Since gene expression generally changes very significant under abiotic stress compared to that under control conditions, RNA-Seq has been widely used to profile differential gene expression and pathways under certain environmental stress (Dugas et al, 2011;Teets et al, 2012).…”