Gu Zhenzhen, Duan Weiwei, Liu Chenxi, Li Wenrong, Zhang Ning, Han Bin, Liu Mingjun
College of Life Science and Technology, Xinjiang University, Urumqi, China.
Key Laboratory of Genetics Breeding and Reproduction of Grass Feeding Livestock, Ministry of Agriculture and Rural Affairs, Xinjiang Academy of Animal Science, Urumqi, China.
Front Cell Dev Biol. 2025 Sep 1;13:1649640. doi: 10.3389/fcell.2025.1649640. eCollection 2025.
The composition of skeletal muscle fiber types is a crucial determinant of meat quality in livestock. While the transition from embryonic to mature fiber types is known to occur during late gestation, the precise temporal dynamics and molecular mechanisms underlying this process in sheep remain poorly understood. A comprehensive, multi-technique approach is needed to elucidate the critical developmental transitions in myofiber specification.
We systematically investigated muscle fiber type differentiation in the longissimus thoracis et lumborum (LTL) muscle of sheep fetuses at 85, 105, 115, and 135 days of gestation (D85-D135) using an integrated approach combining histological (ATPase staining), protein biochemical (SDS-PAGE and Western blotting), and transcriptomic (RNA-seq) analyses. This multi-omics strategy enabled comprehensive characterization of fiber type composition, myosin heavy chain (MHC) isoform expression, and associated molecular pathways.
Our findings revealed distinct stage-specific developmental patterns. Prior to D105, the number of muscle fibres increased progressively, with fibres predominantly expressing embryonic (MHC-emb) and neonatal (MHC-neo) isoforms. After D105, fibre numbers stabilized and underwent maturation, transitioning to predominantly type I, IIA, and IIB fibres, with type IIA fibres becoming the most abundant (61.2%) by D135. Transcriptome analysis identified D105 as a critical transition point, characterized by the significant downregulation of MYH3 (MHC-emb) and MYH8 (MHC-neo), and the upregulation of mature fibre genes (MYH7, MYH2, and MYH4). Concurrently, we observed increased expression of oxidative metabolism genes (COX7A1, NDUFB6) and enhanced aerobic metabolic capacity in maturing fibers.
This study provides the first integrated multi-omics characterization of muscle fiber type development in late-gestation sheep, identifying D105 as a pivotal transition point in myofiber specification. Our findings reveal coordinated molecular and metabolic changes underlying the transition from embryonic to mature fibre types, with significant implications for understanding ruminant muscle development. These results establish a scientific foundation for improving meat quality through targeted molecular breeding strategies and prenatal nutritional interventions in sheep production systems.
骨骼肌纤维类型的组成是家畜肉质的关键决定因素。虽然已知从胚胎型纤维向成熟型纤维的转变发生在妊娠后期，但绵羊这一过程中精确的时间动态和分子机制仍知之甚少。需要一种全面的多技术方法来阐明肌纤维特化过程中的关键发育转变。
我们采用组织学（ATP酶染色）、蛋白质生化（SDS-PAGE和蛋白质免疫印迹）和转录组学（RNA测序）分析相结合的综合方法，系统地研究了妊娠85、105、115和135天（D85 - D135）绵羊胎儿胸腰最长肌（LTL）中的肌纤维类型分化。这种多组学策略能够全面表征纤维类型组成、肌球蛋白重链（MHC）亚型表达及相关分子途径。
我们的研究结果揭示了不同阶段特异性的发育模式。在D105之前，肌纤维数量逐渐增加，纤维主要表达胚胎型（MHC-emb）和新生型（MHC-neo）亚型。在D105之后，纤维数量稳定并成熟，转变为主要是I型、IIA型和IIB型纤维，到D135时IIA型纤维成为最丰富的类型（61.2%）。转录组分析确定D105为关键转变点，其特征是MYH3（MHC-emb）和MYH8（MHC-neo）显著下调，以及成熟纤维基因（MYH7、MYH2和MYH4）上调。同时，我们观察到成熟纤维中氧化代谢基因（COX7A1、NDUFB6）表达增加，有氧代谢能力增强。
本研究首次对妊娠后期绵羊的肌纤维类型发育进行了综合多组学表征，确定D105为肌纤维特化中的关键转变点。我们的研究结果揭示了从胚胎型纤维向成熟型纤维转变过程中协调的分子和代谢变化，对理解反刍动物肌肉发育具有重要意义。这些结果为通过有针对性的分子育种策略和绵羊生产系统中的产前营养干预来改善肉质奠定了科学基础。
