Sequencing and genome-wide mapping of 146 bp mono-nucleosomal DNA from human and bovine sperm

The phenomenon of nucleosome retention in mammalian sperm chromatin is still not clarified yet. The goal of our study was to characterize the binding sites of sperm nucleosomes in the human and bovine genomes, and through this, to clarify whether nucleosome retention in sperm underlies rules of great generality and has a biological function. Comparing two mammalian systems we found that nucleosomes remain mainly in centromeres and in non-coding intergenic and intron regions. In contrast, coding DNA, promoter regions and transcription start and end sites, especially in homeobox genes and in the majority of genes with relevance for organ development and morphogenesis, were nucleosome-free. Overall design: 146 bp mono-nucleosomal DNA was isolated and purified from sperm samples of two fertile bulls (bos taurus), one fertile man and a pool of four fertile donors; each DNA sample was deep sequenced using Illumina GAIIx and genome-wide mapped on respective genome; nucleosome-binding sites were analyzed in a genome-wide comparative manner.

哺乳动物精子染色质中的核小体（nucleosome）保留现象，目前仍未得到明确阐释。本研究旨在对人类与牛基因组中精子核小体的结合位点进行特征解析，并借此阐明：精子中的核小体保留是否遵循高度通用的规则，且具备生物学功能。通过对比两类哺乳动物实验系统，我们发现核小体主要留存于着丝粒（centromere）、非编码基因间区以及内含子区域。与之相反，编码DNA、启动子区域以及转录起始与终止位点——尤其是同源框（homeobox）基因，以及绝大多数与器官发育和形态发生相关的基因——均未结合核小体。实验整体设计如下：从2头可育公牛（Bos taurus）、1名可育男性以及4名可育捐赠者的混合精液样本中，分离纯化得到146 bp单核小体DNA；采用Illumina GAIIx测序平台对每一份DNA样本开展深度测序，并将测序序列全局比对至对应参考基因组；最终以全基因组比较分析的方式，对核小体结合位点进行系统性解析。