提高肉质已成为现代生猪养殖的主要目标。肌内脂肪含量(IMF)是影响畜肉品质的重要性状,但这种特性背后的分子机制仍不清楚。最近,Choetal.报告发现了影响猪的IMF和红色肉色(a*)的第一个因果突变,即XM_013981330.2:g。-1805__1810del,猪MYH3启动子区中的6bp缺失变体。这项研究的目的是重新评估该突变的因果关系,以用于其潜在的商业应用。根据桑格排序,我们首先在6-bp缺失位点或附近发现了几个新的变异(包括4-bp缺失),在多个品种中形成了四个单倍型。出乎意料的是,6bp缺失等位基因,先前确定为MYH3Q等位基因,因为它对IMF和a*有显著的正效应,不仅在中国本土品种中发现,而且在国际货币基金组织水平相对较低的四个西方商业品种中,包括杜洛克,大白色,长白鱼和Pietrain。更令人惊讶的是,我们发现MYH3Q等位基因和携带它的单倍型对IMF没有显著影响,三种大规模不同猪种群的大理石花纹和颜色评分:异质F6和F7猪和商业杂交Duroc×(长白花×约克郡)猪。在猪卫星细胞中的瞬时转染分析表明,6bp缺失变体对报告基因转录的影响可以忽略不计,但可以减弱MRF(肌生成调节因子)诱导的MYH3启动子载体荧光素酶活性的增加。肌肉中的MYH3蛋白水平在单倍型组中没有显着差异。因此,我们的结果不能支持MYH3中6-bp缺失与IMF性状之间的因果关系,这表明SSC12上IMFQTL的因果突变需要进一步鉴定。
Improving meat quality has become the main goal of modern pig breeding. Intramuscular fat content (IMF) is an important trait influencing meat quality of livestock, but the molecular mechanism behind this trait is still unclear. Recently, Cho et al. reported the discovery of the first causal mutation affecting IMF and red flesh color (a*) in pigs, namely XM_013981330.2:g.-1805_-1810del, a 6-bp deletion variant in the porcine
MYH3 promoter region. The objective of this study was to reassess the causality of this mutation for its potential commercial application. By Sanger sequencing, we firstly identified several new variants (including a 4-bp deletion) at or near the 6-bp deletion site, which formed four haplotypes in multiple breeds. Unexpectedly, the 6-bp deletion allele, previously determined as the MYH3 Q allele because of its significantly positive effect on IMF and a*, was found not only in Chinese indigenous breeds, but also in four western commercial breeds with relatively lower IMF levels, including Duroc, Large White, Landrace and Pietrain. More surprisingly, we found that the
MYH3 Q allele and the haplotypes harboring it had no significant effects on IMF, marbling and color score in three large-scale divergent pig populations: the heterogeneous F6 and F7 pigs and commercial crossbred Duroc × (Landrace × Yorkshire) pigs. Transient transfection analysis in porcine satellite cells showed that the 6-bp deletion variants had a negligible effect on transcription of reporter gene, but could attenuate the MRF (myogenesis regulatory factors)-induced increase in luciferase activity of the
MYH3 promoter vector. The
MYH3 protein level in muscle did not differ significantly among the haplotype groups. Therefore, our results cannot support the causal relationship between the 6-bp deletion in
MYH3 and IMF trait, suggesting that the causal mutation for the IMF QTL on SSC12 needs to be further identified.