Sex-biased expression of microRNAs in Drosophila melanogaster
(Submitted on 11 Dec 2013)
Most animals have separate sexes. The differential expression of gene products, in particular that of gene regulators, is underlying sexual dimorphism. Analyses of sex-biased expression have focused mostly in protein coding genes. Several lines of evidence indicate that microRNAs, a class of major gene regulators, are likely to have a significant role in sexual dimorphism. This role has not been systematically explored so far. Here I study the sex-biased expression pattern of microRNAs in the model species Drosophila melanogaster. As with protein coding genes, sex biased microRNAs are associated with the reproductive function. Strikingly, contrary to protein-coding genes, male biased microRNAs are enriched in the X chromosome whilst female microRNAs are mostly autosomal. I propose that the chromosomal distribution is a consequence of high rates of de novo emergence, and a preference of new microRNAs to be expressed in the testis. I also suggest that demasculinization of the X chromosome may not affect microRNAs. Interestingly, female biased microRNAs are often encoded within protein coding genes that are also expressed in females. These results strongly suggest that the sex-biased expression of microRNAs is mainly a consequence of high rates of microRNA emergence in the X (male bias) or hitch-hiked expression by host genes (female bias).
This is a nice report of sex-biased microRNA evolution in Drosophila. You might want to check out recent publications that call into question the claim that the Drosophila X chromosome is demasculinized for protein-coding genes (http://gbe.oxfordjournals.org/content/4/10/1007), and that MSCI could be driving this pattern (http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001126 and http://www.biomedcentral.com/1741-7007/9/29/)
Thanks for the comment. Actually I originally included your paper in the manuscript but I removed it while making the text more compact. Someone else also pointed me out that this discussion bit should be back, and I agree. Next version will have a more extensive discussion on demasculinization, putting into context your work with Daven. Thanks again for the positive comment.
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