Effects of a transient increase or decrease in temperature during in ovo development on epigenetic, transcriptomic and metabolic features of day-old broilers and laying chicks

我们自己和许多其他已发表的研究都有证据表明，孵化温度的调节对家禽的卵外发育有直接影响和持续影响。与产前规划概念和“节俭表型假说”相关的研究主要集中在产前事件可能对以后生活产生的负面影响上（Hales & Barker 1992）。然而，产前“畸变”也可能对适应产后条件产生积极影响。在卵内发育过程中对条件进行有针对性的调节，可能是在健康和福祉、生长和耐热性方面提高生产适应性的一种手段。然而，利用这些编程现象需要对潜在的分子机制有全面的了解。鸟类的卵内发育是研究环境对早期发育及其长期影响的分子途径的一个有价值的模型。在这项研究中，我们的目的是研究在特定的处理期内(胚胎日（ED） 10-13；次级肌纤维和卫星细胞发育阶段对肉鸡和蛋鸡日龄雄性和雌性雏鸡代谢、生化和组织学性状以及基因表达和表观遗传变化的影响。除了生产类型和性别因素外，研究设计还考虑了肌肉类型的影响，检查了仅由糖酵解肌纤维组成的胸肌支原体和也由氧化肌纤维组成的腓肠肌支原体，从而形成了不同的卫星细胞发育生态位。碳水化合物和脂肪相关的能量代谢分析将由整体代谢组和mRNA表达谱补充。将进行比较ATACseq分析，以确定治疗、谱系和性别相关的表观遗传修饰。此外，ATACseq将在单细胞中应用于肉仔鸡和蛋鸡的异种组织中生成原型全基因组染色质接近图谱。目的是揭示通过表观基因组和转录组从基因组到代谢组的基因型-表型图谱的功能关系，以响应孵育温度的变化。卵发育过程中温度的实验调节，结合对代谢表型、基因表达和表观遗传变化的影响的观察，将有助于识别与代谢、健康和福祉以及生产适应性相关的胎儿编程过程中涉及的基因和途径。

There is evidence from our own and numerous other published studies that modulation of incubation temperature has direct effects on in ovo and sustained effects on ex ovo development in poultry. Studies related to the concepts of prenatal programming and the “thrifty phenotype hypothesis” have mainly focused on the negative effects that prenatal events may exert later in life (Hales & Barker 1992). However, prenatal "aberrations" may also have a positive influence on adaptation to postnatal conditions. The targeted modulation of conditions during in ovo development could be a means for improving productive adaptability in terms of health and well-being, growth and thermotolerance. However taking advantage of these programming phenomena requires a comprehensive knowledge of the underlying molecular mechanisms. The in ovo development of birds is a valuable model for studying molecular routes mediating environmental influences on early development and their long-term consequences. In this study, we aim to investigate the effects of increased and decreased incubation temperatures (37.8°C +/- 1°C) within a specific treatment period (embryonic day (ED) 10-13; phase of development of secondary myofibres and satellite cells) on metabolic, biochemical and histological traits, as well as on gene expression and epigenetic changes in male and female day-old chicks of broilers and layers. In addition to the factors of production type and sex, the study design also takes into account the influence of muscle type by examining the M. pectoralis, which consists only of glycolytic muscle fibres, and the M. gastrocnemius, which also consists of oxidative muscle fibres, thus forming different niches of satellite cell development. Analyses of carbohydrate- and fat-related energy metabolism will be complemented by holistic metabolome and mRNA expression profiling. Comparative ATACseq analyses will be performed to identify treatment-, lineage- and sex-associated epigenetic modifications. In addition, ATACseq will be used in single cells to generate prototype genome-wide chromatin accessibility maps in the heterogeneous tissues of the M gastrocnemius of broiler and layer hens. The aim is to uncover functional relationships along the genotype-phenotype map from the genome to the metabolome via the epigenome and transcriptome in response to changes in incubation temperature. Experimental modulation of temperature during in ovo development in combination with observation of its effects on metabolic phenotypes, gene expression and epigenetic changes will allow the identification of genes and pathways involved in fetal programming processes related to metabolism, health and well-being and productive adaptability.