牛MRFs基因家族研究进展

肌肉调节因子（MRFs）基因家族又叫生肌决定因子（MyoD）基因家族,该家族编码4种肌肉特异性转录因子,分别是MyoD、MyoG、Myf5和Myf6,它们是控制骨骼肌生成的关键调节因子,共同控制肌肉的生成。研究表明,这些肌肉特异性转录因子与肌肉生长和肉质有着密切的关系。近年来,该家族的基因已成为肉用动物研究的热点,在牛上已有一些研究,其中包括遗传变异及功能研究等。在此,本文对牛MRFs家族基因结构与基因定位,MRFs家族的功能,MRFs家族基因遗传多态性研究的现状及其在肉牛育种中的应用进行了综述。     

Caprine sex affects skeletal muscle profile and MRFs expression during postnatal development

The important roles of myogenic regulatory factors (MRFs) have been well addressed in the process of mammalian skeletal myogenesis, while limited research has been performed in small ruminants. Furthermore, the effects of gender on the development of skeletal muscle and MRFs expression remain unknown. In this study, we identified the caprine Myf5, Myf6, MyoD and myogenin genes and quantified their expressions at six different postnatal time points by real‐time RT‐PCR. The sex has a marked effect on the expression differences of Myf5, MyoD and myogenin in the five investigated skeletal muscles, while minor influence on the expression difference of Myf6 except for Semitendinosus and Quadriceps femoris tissues (P < 0.001). The histological sections of muscles revealed a constant increase of muscle fiber diameter with aging but non‐significant differences between genders. We provide novel evidence for MRFs expression in age‐ and gender‐dependent manners, which will contribute to prioritizing these genes as potential candidate genes for trait‐associated study and provide a foundation for understanding the molecular control of skeletal muscle growth in goat species.     

Relationships among muscle fiber type composition,fiber diameter and MRF gene expression in different skeletal muscles of naturally grazing Wuzhumuqin sheep during postnatal development

The aim of this study was to determine the relationships among muscle fiber‐type composition, fiber diameter, and myogenic regulatory factor (MRF) gene expression in different skeletal muscles during development in naturally grazing Wuzhumuqin sheep. Three major muscles (i.e. the Longissimus dorsi (LD), Biceps femoris (BF) and Triceps brachii (TB)) were obtained from 20 Wuzhumuqin sheep and 20 castrated rams at each of the following ages: 1, 3, 6, 9, 12 and 18 months. Muscle fiber‐type composition and fiber diameter were measured using histochemistry and morphological analysis, and MRF gene expression levels were determined using real‐time PCR. In the LD muscle, changes in the proportion of each of different types of fiber (I, IIA and IIB) were relatively small. In the BF muscle, a higher proportion of type I and a 6.19‐fold lower proportion of type IIA fibers were observed (P < 0.05). In addition, the compositions of type I and IIA fibers continuously changed in the TB muscle (P < 0.05). Moreover, muscle diameter gradually increased throughout development (P < 0.05). Almost no significant difference was found in MRF gene expression patterns, which appeared to be relatively stable. These results suggest that changes in fiber‐type composition and increases in fiber size may be mutually interacting processes during muscle development.     

Myf5在不同生长阶段小鼠心肌中的定位与表达

Myf5是生肌调节因子MRFs家族的重要成员,在肌细胞的增殖和发育过程中发挥着重要的调控作用。通过对心肌组织进行HE染色和免疫组化试验,观察心肌纤维细胞核的大小和数量、肌纤维体积和肌纤维之间的间隙变化,了解心肌组织不同发育阶段的显微结构,对比各组的阳性着色部位和着色程度的变化,从而对Myf5因子在不同发育阶段小鼠心肌组织的表达进行初步定性、定量和定位分析。并通过实时荧光定量PCR技术对小鼠的不同发育阶段中的心肌组织的Myf5基因表达做出准确的定量分析。结果表明,在小鼠心肌组织发育的不同阶段,Myf5均显示阳性,幼年鼠表达量最高;Myf5 m RNA表达量幼年鼠最高,性成熟鼠最低,呈现先降低后缓慢上升的趋势,并且幼年阶段与性成熟、体成熟阶段呈现极显著差异,与老年阶段无明显差异。研究表明,Myf5表达与小鼠心肌组织发育具有相关性,可进一步揭示Myf5在心脏发育的病理状况差异性和调控机制。     

五指山猪与长白猪65 d胎儿组织MRFs家族基因的表达研究

 
以五指山猪和长白猪妊娠65 d胎儿腿部骨骼肌、背部骨骼肌、心脏、肝脏、脾脏、肺脏、肾脏、肠、胃、脑10种组织为材料,采用qPCR技术,检测和研究MRFs基因家族成员（包括MyoD1、Myf4、Myf5和Mfy6基因）在以上10种组织中的mRNA表达水平及差异。结果表明：（1）MRFs家族成员除肝、肾、肠组织以外,在五指山猪65 d猪胎儿组织中mRNA表达水平均高于长白猪相应组织中的表达水平（P<0.05）;（2）MRFs家族成员表达水平在腿肌和背肌中的表达普遍偏高,其他组织中表达较低（P<0.05）;（3）2个猪种在以上10种组织中MRFs家族mRNA表达水平的高低分布基本一致,其相对表达量顺序为：腿部骨骼肌＞背部骨骼肌＞肝＞肺＞胃＞脾＞脑＞肾＞肠＞心。