Tao Chenyu, Li Juan, Chen Baobao, Chi Daming, Zeng Yaqiong, Liu Honglin
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China.
PLoS One. 2017 Mar 23;12(3):e0174225. doi: 10.1371/journal.pone.0174225. eCollection 2017.
The nucleosome is the basic structural unit of chromosomes, and its occupancy and distribution in promoters are crucial for the regulation of gene expression. During the growth process of porcine oocytes, the "growing" oocytes (SF) have a much higher transcriptional activity than the "fully grown" oocytes (BF). However, the chromosome status of the two kinds of oocytes remains poorly understood. In this study, we profiled the nucleosome distributions of SF and BF with as few as 1000 oocytes. By comparing the altered regions, we found that SF tended toward nucleosome loss and more open chromosome architecture than BF did. BF had decreased nucleosome occupancy in the coding region and increased nucleosome occupancy in the promoter compared to SF. The nucleosome occupancy of SF was higher than that of BF in the GC-poor regions, but lower than that of BF in the GC-rich regions. The nucleosome distribution around the transcriptional start site (TSS) of all the genes of the two samples was basically the same, but the nucleosome occupancy around the TSS of SF was lower than that of BF. GO functional annotation of genes with different nucleosome occupancy in promoter showed the genes were mainly involved in cell, cellular process, and metabolic process biological process. The results of this study revealed the dynamic reorganization of porcine oocytes in different developmental stages and the critical role of nucleosome arrangement during the oocyte growth process.
核小体是染色体的基本结构单位，其在启动子区域的占据情况和分布对于基因表达的调控至关重要。在猪卵母细胞的生长过程中，“生长中的”卵母细胞（SF）比“完全成熟的”卵母细胞（BF）具有更高的转录活性。然而，这两种卵母细胞的染色体状态仍知之甚少。在本研究中，我们对少至1000个卵母细胞的SF和BF的核小体分布进行了分析。通过比较变化区域，我们发现SF比BF更倾向于核小体丢失和更开放的染色体结构。与SF相比，BF在编码区的核小体占据减少，而在启动子区的核小体占据增加。在GC含量低的区域，SF的核小体占据高于BF，但在GC含量高的区域低于BF。两个样本中所有基因转录起始位点（TSS）周围的核小体分布基本相同，但SF的TSS周围的核小体占据低于BF。对启动子中具有不同核小体占据的基因进行GO功能注释表明，这些基因主要参与细胞、细胞过程和代谢过程生物学过程。本研究结果揭示了猪卵母细胞在不同发育阶段的动态重组以及核小体排列在卵母细胞生长过程中的关键作用。
