Comparative muscle transcriptome of Mali and Hampshire breeds of pigs: a preliminary study

Muscle development is an important priority of pig breeding programs. There is a considerable variation in muscularity between the breeds, but the regulation mechanisms of genes underlying myogenesis are still unclear. Transcriptome data from two breeds of pigs with divergent muscularity (Mali and Hampshire) were integrated with histology, immunofluorescence and meat yield to identify differences in myogenesis during the early growth phase. The muscle transcriptomics analysis revealed 17,721 common, 1413 and 1115 unique transcripts to Hampshire and Mali, respectively. This study identified 908 differentially expressed genes (<i>p</i> &lt; 0.05; log₂FC &gt; ±1) in the muscle samples, of which 550 were upregulated and 358 were downregulated in Hampshire pigs, indicating differences in physiological process related to muscle function and development. Expression of genes related to myoblast fusion (<i>MYMK</i>), skeletal muscle satellite cell proliferation (<i>ANGPT1</i>, <i>CDON</i>) and growth factors (<i>HGF, IGF1, IGF2</i>) were higher in Hampshire than Mali, even though transcript levels of several other myogenesis-related genes (<i>MYF6, MYOG, MSTN</i>) were similar. The number of fibers per fascicle and the expression of myogenic marker proteins (MYOD1, MYOG and PAX7) were more in Hampshire as compared to Mali breed of pig, supporting results of transcriptome studies. The results suggest that differences in muscularity between breeds could be related to the regulation of myoblast fusion and myogenic activities. The present study will help to identify genes that could be explored for their utility in the selection of animals with different muscularities.

肌肉发育是猪育种项目的核心目标之一。不同猪品种的肌肉量存在显著差异，但调控肌发生（myogenesis）的基因机制仍未明确。本研究整合了肌发生特性差异显著的两个猪品种——马利猪（Mali）与汉普夏猪（Hampshire）的转录组（transcriptome）数据，并结合组织学、免疫荧光技术与肉产量指标，解析早期生长阶段的肌发生差异。肌肉转录组学（transcriptomics）分析共鉴定得到17721个共有转录本，汉普夏猪与马利猪分别特有1413和1115个转录本。本研究在肌肉样本中鉴定出908个差异表达基因（differentially expressed genes），筛选标准为p<0.05且log₂折叠变化（log₂FC）>±1，其中汉普夏猪中有550个基因上调、358个基因下调，提示二者在肌肉功能与发育相关的生理过程中存在显著差异。与成肌细胞融合相关的基因（MYMK）、骨骼肌卫星细胞增殖相关基因（ANGPT1、CDON）以及生长因子基因（HGF、IGF1、IGF2）在汉普夏猪中的表达水平均高于马利猪；尽管部分其他肌发生相关基因（MYF6、MYOG、MSTN）的转录水平在两品种间无明显差异。与马利猪相比，汉普夏猪的肌束内纤维数量更多，肌源性标记蛋白（MYOD1、MYOG与PAX7）的表达水平也更高，这与转录组学分析结果相符。研究结果表明，不同猪品种间的肌肉量差异可能与成肌细胞融合及肌发生活性的调控有关。本研究可为筛选适配不同肌肉量特性的育种候选基因提供理论参考。