狼山鸡下丘脑和卵巢组织全基因组DNA甲基化分析

为了获得狼山鸡性腺轴组织基因组DNA甲基化水平和模式等表观遗传信息，试验采用全基因组重亚硫酸盐测序（whole genome bisulfite sequencing，WGBS）技术检测狼山鸡下丘脑和卵巢组织基因组DNA甲基化状态，分析两组织DNA甲基化水平及特异甲基化模式。结果表明，狼山鸡下丘脑和卵巢基因组整体甲基化水平分别为4.35%和3.48%，差异显著（P<0.05）；下丘脑和卵巢中分别检测到6 150 000和10 320 000个甲基化胞嘧啶（mC）位点，其中mCG类型位点分别占69.99%和87.88%，下丘脑中非mCG位点占比约为卵巢中的2.5倍；与各染色体不同，两组织线粒体基因组中mCHH位点占比最高，其次是mCHG位点；卵巢基因组启动子区DNA甲基化水平极显著低于内含子和外显子区（P<0.01），极显著高于基因间区（P<0.01）；下丘脑基因组启动子区DNA甲基化水平与内含子和外显子区相比差异不显著（P>0.05），却显著高于基因间区（P<0.05）；下丘脑基因组各功能元件DNA甲基化水平均显著或极显著高于卵巢基因组（P<0.05；P<0.01）。综上，狼山鸡下丘脑和卵巢组织具有不同的DNA甲基化模式和特征，下丘脑中较高的非mCG位点比例可能在中枢神经系统发育中发挥重要作用，本研究结果为进一步分析鸡卵巢和下丘脑基因组DNA甲基化对其繁殖性能调控机制提供参考依据。

Genome-wide DNA Methylation Analysis of Hypothalamus and Ovary in Langshan Chicken

In order to obtain genome-wide epigenetic information,such as DNA methylation level and patterns of gonad axis tissues in Langshan chicken,the whole genome bisulfite sequencing(WGBS)was used to detect the DNA methylation status across the genome of hypothalamus and ovary tissues.The DNA methylation level and specific methylation pattern of each tissue were also analyzed.The results showed that the global methylation level in the genomes of hypothalamus and ovary were 4.35%and 3.48%,respectively,which were significantly different(P<0.05).6150000 and 10320000 methylated cytosine(mC)sites were detected in the hypothalamus and ovary,with mCG sites accounting for nearly 69.99%and 87.88%,respectively.And the proportion of non-mCG sites in the hypothalamus was about 2.5 times that in the ovary.Different from each chromosome,the mCHH sites accounted for the highest proportion in the mitochondrial genomes of the two tissues,followed by the mCHG sites.DNA methylation level in the promoter region of the ovarian genome was significantly lower than that in the intron and exon(P<0.01),and significantly higher than that in the intergenic region(P<0.01).The methylation level of promoter region in the genome of hypothalamus was not significantly different from those of intron and exon regions(P>0.05),but significantly higher than that in the intergenic region(P<0.05).Methylation levels of all functional elements in the genome of hypothalamus were significantly or extremely significantly higher than those of the ovary genome(P<0.05;P<0.01).Overall,different DNA methylation patterns and characteristics existed in the hypothalamus and ovary tissues of Langshan chicken.A higher proportion of non-mCG sites in hypothalamus might play an important role in the development of central nervous system.The results provided reference for further research on the regulatory mechanism of DNA methylation in chicken ovary and hypothalamus on their reproductive performance.