Sex-specific co-expression networks and sex-biased gene expression in the salmonid Brook Charr Salvelinus fontinalis

Abstract

21Networks of co-expressed genes produce complex phenotypes associated with functional novelty. Sex 22 differences in gene expression levels or in the structure of gene co-expression networks can cause sexual 23 dimorphism and may resolve sexually antagonistic selection. Here we used RNA-sequencing in the 24 paleopolyploid salmonid Brook Charr Salvelinus fontinalis to characterize sex-specific co-expression 25 networks in the liver of 47 female and 53 male offspring. In both networks, modules were characterized 26 for functional enrichment, hub gene identification, and associations with 15 growth, reproduction, and 27 stress-related phenotypes. Modules were then evaluated for preservation in the opposite sex, and in the 28 congener Arctic Charr Salvelinus alpinus. Overall, more transcripts were assigned to a module in the 29 female network than in the male network, which coincided with higher inter-individual gene expression 30 and phenotype variation in the females. Most modules were preserved between sexes and species, 31including those involved in conserved cellular processes (e.g. translation, immune pathways). However, 32 two sex-specific male modules were identified, and these may contribute to sexual dimorphism. To 33 compare with the network analysis, differentially expressed transcripts were identified between the sexes, 34 finding a total of 16% of expressed transcripts as sex-biased. For both sexes, there was no 35 overrepresentation of sex-biased genes or sex-specific modules on the putative sex chromosome. Sex-36 biased transcripts were also not overrepresented in sex-specific modules, and in fact highly male-biased 37 transcripts were enriched in preserved modules. Comparative network analysis and differential expression 38 analyses identified different aspects of sex differences in gene expression, and both provided new insights 39 on the genes underlying sexual dimorphism in the salmonid Brook Charr. 40 41 42 43 44 45 46 47

Effects of an IgE receptor polymorphism acting on immunity, susceptibility to infection and reproduction in a wild rodent

“…Yang et al, 2006). Sex-biases in the co-expression of genes have also been documented, suggesting that males and females differ not only in their regulation of single genes, but whole networks of interacting genes (Sutherland, Prokkola, Audet, & Bernatchez, 2018;Van Nas et al, 2009). The same polymorphism then, could be expressed as different immune phenotypes, and subsequently have very different consequences for the health of males and females in the wild.…”