Tamagawa Katsunori, Makino Takashi, Kawata Masakado
Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Japan.
Genome Biol Evol. 2017 May 1;9(5):1204-1211. doi: 10.1093/gbe/evx083.
As most genes are shared between females and males, DNA methylation is assumed to play a crucial role in sex-biased gene expression. DNA methylation exclusively occurs at CpG dinucleotides, and therefore, we would expect that CpG density around transcription start sites (TSSs) relate to sex-biased gene expression. Here we investigated the relationship between CpG densities around TSSs and the ratio of gene expression levels between sexes in the guppy (Poecilia reticulata), which displays remarkable sexual dimorphisms. We found that genes with sex-biased gene expression had different CpG densities downstream of TSSs compared with genes lacking sex-biased gene expression. Intriguingly, male-biased expression genes with intermediate CpG density downstream of TSSs exhibited greater differences in gene expression between sexes in the gonad and tail. Our findings suggested the possibility that CpGs around TSSs, especially in the downstream regions, play a crucial role in sex-biased gene expression through DNA methylation.
由于大多数基因在雌性和雄性中是共享的，因此推测DNA甲基化在性别偏向性基因表达中起关键作用。DNA甲基化仅发生在CpG二核苷酸处，因此，我们预期转录起始位点（TSSs）周围的CpG密度与性别偏向性基因表达有关。在此，我们研究了孔雀鱼（Poecilia reticulata）中TSSs周围的CpG密度与两性基因表达水平比值之间的关系，孔雀鱼表现出显著的两性异形。我们发现，与缺乏性别偏向性基因表达的基因相比，具有性别偏向性基因表达的基因在TSSs下游具有不同的CpG密度。有趣的是，TSSs下游具有中等CpG密度的雄性偏向性表达基因在性腺和尾巴中的两性基因表达差异更大。我们的研究结果表明，TSSs周围的CpG，尤其是下游区域的CpG，可能通过DNA甲基化在性别偏向性基因表达中起关键作用。
