Key genetic and epigenetic factors contributed from male germ cell to early embryo: a novel bovine model

成熟精子染色质具有鱼精蛋白/核小体双重结构。最近的研究提示，精子中的体细胞样组蛋白显示出特定的密码(翻译后不同赖氨酸残基上的乙酰化、单甲基化、二甲基化或三甲基化)，并主要与发育相关基因的低甲基化启动子有关。通常的假设是，精子组蛋白及其密码与父亲的单倍体基因组一起传递到卵母细胞，在早期胚胎发育过程中对转录激活至关重要。利用牛生殖细胞和早期胚胎，我们的目标是建立一个可重复的动物模型，用于研究从雄性生殖细胞到早期胚胎的遗传和表观遗传因素。一个易于获得的动物模型将简化受精/早期胚胎发育障碍以及特发性男性因素不育的风险候选基因和机制的评估。在本研究中，我们将致力于以下目标：1)在牛精子中，我们将检测所有与体细胞样组蛋白相关的基因组区域，并从基因本体学的角度评估早期发育的候选基因；2)考虑其启动子甲基化和mRNA表达状况，将在卵母细胞和早期胚胎阶段进一步分析候选基因；3)为了更深入地了解牛生殖细胞和早期胚胎中的表观遗传调控，我们将分析牛生殖细胞和早期胚胎中关键的染色质修饰物和多能基因的mRNA表达；4)对于在牛模型中评估的候选基因，将考虑到人类的生育状况，在人类精子中确定和分析人类的同源基因。

The chromatin of mature spermatozoa is characterized by a dual protamine/nucleosome structure. Recent studies provide hints that somatic-like histones within the sperm exhibit specific 'codes' (posttranslational acetylatlon, mono-, di- or trimethylation on different lysine residues) and associate mainly with hypomethylated promoters of development relevant genes. The common hypothesis is that sperm histones and their 'codes' are transmitted to the oocyte together with the paternal haploid genome and are crucial for transcriptional activation during early embryogenesis. Using bovine germ cells and early embryos, we aim to establish a reproducible animal model for studies regarding genetic and epigenetic factors contributed from male germ cell to early embryo. A well accessible animal model will simplify the evaluation of risk candidate genes and mechanisms for impaired fertilization/early embryogenesis and, thus, for idiopathic male factor infertility. In the present study, the following aims will be addressed; 1) In bovine sperm, we will detect all genomic regions which associate with somatic-like histones and evaluate candidate genes for early development considering gene ontology; 2) The candidate genes will be further analyzed in oocytes and early embryo stages considering their promoter methylation and mRNA expression status; 3) To get a deeper insight in the epigenetic regulation during early embryogenesis, we will analyze the mRNA expression of key chromatin modifiers and pluripotency genes in bovine germ cells and early embryos; 4) For candidate genes evaluated in the bovine model, the human orthologous genes wilt be determined and analyzed in human sperm considering their fertility status.