Abstract
Sexual size dimorphism is an interesting phenomenon occurred in many fish species. Wildtype zebrafish exhibits a significant sexual dimorphism in body size at the adult stage. Previous studies indicated that sexual size dimorphism was eliminated in stat5b-mutated zebrafish. Herein, the comparative transcriptome analysis was conducted to observe the genes and pathways involved in sexual size dimorphism. The number of male-biased and female-biased genes was much less in the liver of stat5b mutant zebrafish than in wildtype. Gene ontology (GO) enrichment and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis indicated that multiple pathways related to metabolism were affected upon loss of stat5b function. qRT-PCR results also validated that sexually dimorphic expression of a set of genes was lost when stat5b was mutated. Furthermore, the weighted correlation network analysis (WGCNA) detected many candidate genes related to the growth traits and stat5b function, such as greb1, lepr, and igf2b. Our data suggest that stat5b should regulate the sexually dimorphic gene expression in zebrafish liver and add in understanding of the molecular mechanisms underlying sexual size dimorphism in fish species.
Highlights
Sexual size dimorphism, the relative difference in body size and growth rate between male and female of the same species, has been reported in many fish species such as turbot (Scophthalmus maximus), Chinese tongue sole (Cynoglossus semilaevis), tilapia (Oreochromis niloticus) and yellow catfish (Pelteobagrus fulvidraco) (Gui and Zhu, 2012; Mei and Gui, 2015)
The body growth is usually controlled by the GH/IGF axis gene expressed in the hypothalamus-pituitarygonad (HPG) axis (Rosenfeld and Hwa, 2009; Li and Lin, 2010; Rotwein, 2012), and the consequent Jak2/Stat5b signaling pathway activated by GH/GHR signal (Ahmed and Farquharson, 2010; Rotwein, 2012)
To figure out the relationship between differentially expressed genes (DEGs) and growth traits (Supplementary Table S1), we introduced the R package weighted correlation network analysis (WGCNA) according to the previous description (Storey, 2002; Langfelder and Horvath, 2008)
Summary
The relative difference in body size and growth rate between male and female of the same species, has been reported in many fish species such as turbot (Scophthalmus maximus), Chinese tongue sole (Cynoglossus semilaevis), tilapia (Oreochromis niloticus) and yellow catfish (Pelteobagrus fulvidraco) (Gui and Zhu, 2012; Mei and Gui, 2015). The body growth is usually controlled by the GH/IGF axis gene expressed in the hypothalamus-pituitarygonad (HPG) axis (Rosenfeld and Hwa, 2009; Li and Lin, 2010; Rotwein, 2012), and the consequent Jak2/Stat5b signaling pathway activated by GH/GHR signal (Ahmed and Farquharson, 2010; Rotwein, 2012). Stat5b is mainly expressed in the liver and responds to the growth factor signals. GH-induced liver IGF-I gene expression was reduced upon loss of Stat5b function (Davey et al, 2001; Lau-Corona et al, 2017). Stat5b has been reported to be involved in the regulation of body growth and adiposity
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