Dayan Jonathan, Uni Zehava
Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem, 7610001, Rehovot, Israel.
BMC Genomics. 2024 Dec 4;25(1):1180. doi: 10.1186/s12864-024-11103-6.
Chicken embryos emerge from their shell by the piercing movement of the hatching muscle. Although considered a key player during hatching, with activity that imposes a substantial metabolic demand, data are still limited. The study provides a bioenergetic and transcriptomic analyses during the pre-post-hatching period.
Weight and morphology alongside content determination of creatine and glycogen were analysed. Transcriptome identified differentially expressed genes and enriched biological processes associated with hatching muscle development, catabolism, and energy provision. Using gene set enrichment, we followed the dynamics of gene-sets involved in energy pathways of oxidative phosphorylation, protein catabolism, glycolysis/gluconeogenesis, and glycogen metabolism.
Results show several significant findings: (A) Creatine plays a crucial role in the energy metabolism of the hatching muscle, with its concentration remaining stable while glycogen concentration is depleted at hatch and placement. (B) The hatching muscle has the capacity for de-novo creatine synthesis, as indicated by the expression of related genes (AGAT, GAMT). (C) Transcriptome provided insights into genes related to energy pathways under conditions of pre-hatch oxygen and post-hatch glucose limitations (oxidative phosphorylation: NDUF, MT-ND, SDH, UQCR, COX, MT-CO, ATP5, MT-ATP; glycolysis/gluconeogenesis: FBP,G6PC, PFKM; glycogen metabolism: PPP1, PYGL, GYG1). (D) The post-hatch upregulation of protein catabolic processes genes (PSMA, RNF, UBE, FBX), which align with the muscle's weight dynamics, indicates a functional shift from movement during hatching to lifting the head during feeding.
There is a dynamic metabolic switch in the hatching muscle during embryo-to-hatchling transition. When glycogen concentration depletes, energy supply is maintained by creatine and its de-novo synthesis. Understanding the hatching muscle's energy dynamics is crucial, for reducing hatching failures in endangered avian species, and in domesticated chickens.
鸡胚胎通过破壳肌的穿刺运动破壳而出。尽管破壳肌在孵化过程中被视为关键因素，其活动会带来大量代谢需求，但相关数据仍然有限。本研究对孵化前后阶段进行了生物能量学和转录组分析。
分析了体重、形态以及肌酸和糖原的含量测定。转录组鉴定了与破壳肌发育、分解代谢和能量供应相关的差异表达基因及富集的生物学过程。利用基因集富集分析，我们追踪了参与氧化磷酸化、蛋白质分解代谢、糖酵解/糖异生和糖原代谢等能量途径的基因集动态变化。
结果显示了几个重要发现：（A）肌酸在破壳肌的能量代谢中起关键作用，其浓度保持稳定，而糖原浓度在孵化和放置时耗尽。（B）如相关基因（AGAT、GAMT）的表达所示，破壳肌具有从头合成肌酸的能力。（C）转录组提供了在孵化前缺氧和孵化后葡萄糖受限条件下与能量途径相关基因的见解（氧化磷酸化：NDUF、MT-ND、SDH、UQCR、COX、MT-CO、ATP5、MT-ATP；糖酵解/糖异生：FBP、G6PC、PFKM；糖原代谢：PPP1、PYGL、GYG1）。（D）孵化后蛋白质分解代谢过程基因（PSMA、RNF、UBE、FBX）的上调，与肌肉的重量动态变化一致，表明功能从孵化时的运动转变为进食时抬头。
在胚胎到幼雏的转变过程中，破壳肌存在动态代谢转换。当糖原浓度耗尽时，肌酸及其从头合成维持能量供应。了解破壳肌的能量动态对于减少濒危鸟类和家鸡的孵化失败至关重要。
