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

来自我们自己和许多其他已发表的研究的证据表明，孵化温度的调节对禽类的卵内和体外发育具有直接和持续的影响。与产前编程和节俭表型假说相关的研究主要集中在产前事件可能在以后的生活中产生的负面影响(Hales&Barker 1992)。然而，出生前的“异常”也可能对适应出生后的条件有积极的影响。在卵子发育过程中对条件进行有针对性的调整，可能是在健康和福祉、生长和耐热性方面改善生产适应性的一种手段。然而，要利用这些编程现象，需要全面了解潜在的分子机制。鸟类的在体发育是研究环境影响早期发育及其长期后果的分子途径的一个有价值的模型。在本研究中，我们旨在研究在特定的处理期间(胚胎10-13天；次级肌纤维和卫星细胞的发育期)内升高和降低孵化温度(37.8°C/-1°C)对肉鸡和蛋鸡的代谢、生化和组织学特性以及基因表达和表观遗传学变化的影响。除了生产类型和性别的因素，研究设计还考虑了肌肉类型的影响，通过检查胸肌和腓肠肌，胸肌只由糖酵解肌肉纤维组成，腓肠肌也由氧化肌肉纤维组成，从而形成不同的卫星细胞发育的生态位。与碳水化合物和脂肪相关的能量代谢分析将得到整体代谢组和mRNA表达谱的补充。将进行ATACseq比较分析，以确定与治疗、血统和性别相关的表观遗传修饰。此外，ATACseq将用于单个细胞，在肉鸡和蛋鸡的M腓肠肌的不同组织中生成全基因组染色质可及性原型图。其目的是揭示随着孵化温度的变化，通过表观基因组和转录组从基因组到代谢组的基因-表型图谱上的功能关系。在卵子发育过程中对温度进行实验调节，结合观察其对代谢表型、基因表达和表观遗传学变化的影响，将有助于识别与新陈代谢、健康和福祉以及生产适应性有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.