Brown David M, Brameld John M, Parr Tim
Division of Nutritional Sciences, School of Biosciences, The University of Nottingham, Leicestershire, United Kingdom.
PLoS One. 2014 Dec 3;9(12):e114365. doi: 10.1371/journal.pone.0114365. eCollection 2014.
Due to its similarity to humans, the pig is increasingly being considered as a good animal model for studying a range of human diseases. Despite their physiological similarities, differential expression of the myosin heavy chain (MyHC) IIB gene (MYH4) exists in the skeletal muscles of these species, which is associated with a different muscle phenotype. The expression of different MyHC isoforms is a critical determinant of the contractile and metabolic characteristics of the muscle fibre. We aimed to elucidate whether a genomic mechanism was responsible for the drastically different expression of MYH4 between pigs and humans, thus improving our understanding of the pig as a model for human skeletal muscle research. We utilized approximately 1 kb of the MYH4 promoter from a domestic pig and a human (which do and do not express MYH4, respectively) to elucidate the role of the promoter sequence in regulating the high expression of MYH4 in porcine skeletal muscle. We identified a 3 bp genomic difference within the proximal CArG and E-box region of the MYH4 promoter of pigs and humans that dictates the differential activity of these promoters during myogenesis. Subtle species-specific genomic differences within the CArG-box region caused differential protein-DNA interactions at this site and is likely accountable for the differential MYH4 promoter activity between pigs and humans. We propose that the genomic differences identified herein explain the differential activity of the MYH4 promoter of pigs and humans, which may contribute to the differential expression patterns displayed in these otherwise physiologically similar mammals. Further, we report that both the pig and human MYH4 promoters can be induced by MyoD over-expression, but the capacity to activate the MYH4 promoter is largely influenced by the 3 bp difference located within the CArG-box region of the proximal MYH4 promoter.
由于猪与人类的相似性，它越来越被视为研究一系列人类疾病的良好动物模型。尽管它们在生理上有相似之处，但这些物种的骨骼肌中肌球蛋白重链（MyHC）IIB基因（MYH4）存在差异表达，这与不同的肌肉表型相关。不同MyHC亚型的表达是肌肉纤维收缩和代谢特征的关键决定因素。我们旨在阐明是否存在一种基因组机制导致猪和人类之间MYH4的表达存在巨大差异，从而增进我们对猪作为人类骨骼肌研究模型的理解。我们利用了家猪和人类（分别表达和不表达MYH4）的约1 kb MYH4启动子来阐明启动子序列在调节猪骨骼肌中MYH4高表达中的作用。我们在猪和人类MYH4启动子的近端CArG和E-box区域内鉴定出一个3 bp的基因组差异，该差异决定了这些启动子在肌生成过程中的差异活性。CArG-box区域内细微的物种特异性基因组差异导致该位点的蛋白质-DNA相互作用不同，这可能是猪和人类之间MYH4启动子活性差异的原因。我们认为本文鉴定出的基因组差异解释了猪和人类MYH4启动子的差异活性，这可能导致这些在生理上相似的哺乳动物中出现不同的表达模式。此外，我们报告猪和人类的MYH4启动子都可以被MyoD过表达诱导，但激活MYH4启动子的能力在很大程度上受近端MYH4启动子CArG-box区域内3 bp差异的影响。
