MSTN与骨骼肌生长发育

尽管肌肉生长抑制素(MSTN)对骨骼肌生长的抑制作用已得到证实,但其抑制骨骼肌细胞生长分化的分子机理还不是十分清楚,这方面仍是目前研究MSTN功能的热点。本文综述了MSTN调控骨骼肌生长发育的各种途径,为进一步深入探讨MSTN调控骨骼肌生长发育的机理提供思路和依据。     

MicroRNA调控猪骨骼肌发育的研究进展

骨骼肌的生长发育是影响猪肉产量和品质的重要因素,其受遗传和营养等众多因素的精细调控。MicroRNA (miRNA)是一种长度约为22 nt的非编码RNA,通过与靶基因的mRNA 3′UTR序列结合,调控其转录后的表达发挥作用。近年来,大量的研究表明miRNA参与机体的生长发育、生殖、疾病等多种生命过程。本文对miRNA在猪骨骼肌发育调控中的作用进行了综述,以期为猪的遗传改良提供参考和借鉴。     

甲基转移酶METTL21C影响鸡骨骼肌细胞成肌的发育

本研究旨在探究甲基转移酶METTL21C在家禽骨骼肌发育分化过程中的作用。采用实时荧光定量PCR (quantitative Real-time PCR, qPCR)检测METTL21C基因在鸡不同组织中的表达情况,绘制其组织表达谱;选取3个时间点,检测其在骨骼肌组织中的表达情况。通过酶消化法从鸡骨骼肌组织中分离得到原代细胞;将METTL21C超表达载体转染至原代鸡骨骼肌细胞,通过qPCR和Western blotting检测Pax7、MyoD、Myf5、MyoG等基因的表达水平。结果显示,METTL21C在心肌和骨骼肌组织中的表达量显著高于其他组织,在胚胎期和幼龄期骨骼肌中的表达呈上升趋势;超表达METTL21C后,成肌相关基因Pax7、MyoD、Myf5、MyoG的表达量显著升高。本研究初步发现甲基转移酶METTL21C具有促进家禽骨骼肌发育分化的作用,为骨骼肌发育的分子机理的研究及相关医学研究提供数据支持。     

微小RNA调控骨骼肌增殖、分化的研究进展

骨骼肌损伤、萎缩等疾病的防治一直是困扰临床医生的难题。这些骨骼肌疾病的康复离不开肌细胞增殖、分化的调节。微小RNA（microRNA）作为基因表达的调节因子,通过对骨骼肌细胞增殖、分化机制的开启、促进和抑制等方式,对骨骼肌发育过程中的初始肌细胞、成肌细胞以及生物体成熟以后的肌卫星细胞的增殖、分化均进行着精细调节。因此,研究microRNA调节骨骼肌增殖、分化的机制已成为科研工作者的当务之急,并具有广阔的应用前景。     

microRNAs调控骨骼肌分化的分子机制

microRNA（miRNA）是一大类广泛存在于真核细胞当中的长度约22nt的内源性单链非编码RNA,通过与靶基因mRNA的3’非翻译区（3’untranslated region,3’UTR）结合在转录后水平调控靶基因的表达。miRNA作为调控基因表达的重要分子在骨骼肌分化调控中的作用越来越受到关注,阐明miRNA在骨骼肌增殖与分化中的作用机制具有重要的理论意义,同时也可为骨骼肌相关疾病的治疗提供新的思路。文章总结了miRNA,尤其是miR-1、miR-133和miR-206等肌肉特异性miRNA,在调控骨骼肌分化过程中作用机制的研究进展,以便于进一步工作的开展。     

内质网应激在骨骼肌生理及病理中的功能研究进展

骨骼肌拥有高度发达的内质网,又被称为肌浆网,不仅可以作为钙泵完成肌肉的兴奋收缩偶联反应,还可对各种生理或病理性刺激迅速做出反应,通过内质网应激反应,激活下游信号通路,赋予骨骼肌应对外界或内在刺激的能力。因此,骨骼肌内丰富的内质网是骨骼肌具有高度可塑性的细胞学基础。大量研究表明,内质网应激广泛参与了骨骼肌的生理和病理进程,本文就内质网应激在骨骼肌成肌分化、萎缩和运动的作用进行了综述。     

骨骼肌质膜修复相关蛋白研究进展

质膜修复(plasma membrane repair, PMR)是细胞存活及正常生理活动的重要保障。骨骼肌细胞易受机械刺激引发质膜损伤,及时有效的质膜修复是维持骨骼肌细胞功能的关键。此外,骨骼肌质膜修复缺陷也是肌营养不良症的主要病理特点。该文从骨骼肌生理和病理角度出发,对参与PMR的相关蛋白进行全面综述,系统梳理了PMR相关蛋白在骨骼肌损伤修复中的特点及协同效应,总结并归纳了骨骼肌PMR的理论模型,为膜修复蛋白在PMR中作用机制的深入研究提供新思路。     

猪骨骼肌快肌肌钙蛋白C2基因的cDNA克隆与表达分析

从人骨骼肌快肌肌钙蛋白C2（TNNC2）基因出发,在dbEST数据库中进行同源性搜索,找到一个有较高同源性且在猪背最长肌中表达EST（BM083186）。通过电子克隆和进一步RT-PCR实验验证,获得猪TNNC2基因全长cDNA序列,其全长843bp,开放阅读框为201～683bp,编码有160个氨基酸。同源性分析结果表明,与人、鼠的骨骼肌快肌肌钙蛋白C2基因cDNA编码区（CDS）同源性分别为93.6％、90.5％,蛋白序列同源性均为97.5%。多种组织的半定量RT-PCR研究表明,该基因在骨骼肌中表达,并且在杜洛克猪背最长肌中的表达比兰塘猪高。     

猪骨骼肌磷酸葡萄糖异构酶的提纯及性质研究

本文报道猪骨骼肌磷酸葡萄糖异构酶（ＧＰＩ．ＥＣ ５．３．１．９）的提纯及其性质。设计了四步提纯法（稀盐溶液抽提、有机溶媒沉淀、透析、葡聚糖Ｇ－１００柱层析），对猪的五种不同解剖部位的骨骼风进行了ＧＰＩ的提纯。结果均得到聚丙烯酰胺凝胶电泳（ＰＡＧＥ）图谱为一条带的产品。提纯效果以猪股二头肌为例：提纯１０．６８倍、活力回收３２．３７％，比活力１．６×１０５单位。对提纯酶性质的研究表明；猪肌提纯的ＧＰＩ由三个亚基组成。分子量约为１２０Ｋｄ，等电点为 ６． ６，最适ｐＨ８．５，最适温度 ３５℃，米氏常数：６．０２ｍｍｏｌ／Ｌ，活化能为３２３７８．４焦耳／Ｋ，ｍｏｌ。免疫电泳实验证实猪肌提纯酶具抗原性。其免疫血清与自牛、兔、鸡、鱼的骨骼肌用同法提纯的ＧＰＩ有交叉免疫反应。免疫血清且对原酶液有抑制作用。猪肌ＧＰＩ与其它数种动物肌肉之ＧＰＩ的ＰＡＧＥ行为、混合电泳行为，等电聚焦行为、氨基酸组成等各方面基本相同，可以认为这是猪肌ＧＰＩ与其它数种动物肌肉的ＧＰＩ为同源蛋白质的佐证。     

Regulation of RNA N6-methyladenosine modification and its emerging roles in skeletal muscle development

N⁶-methyladenosine (m⁶A) is one of the most widespread and highly conserved chemical modifications in cellular RNAs of eukaryotic genomes. Owing to the development of high-throughput m⁶A sequencing, the functions and mechanisms of m⁶A modification in development and diseases have been revealed. Recent studies have shown that RNA m⁶A methylation plays a critical role in skeletal muscle development, which regulates myoblast proliferation and differentiation, and muscle regeneration. Exploration of the functions of m⁶A modification and its regulators provides a deeper understanding of the regulatory mechanisms underlying skeletal muscle development. In the present review, we aim to summarize recent breakthroughs concerning the global landscape of m⁶A modification in mammals and examine the biological functions and mechanisms of enzymes regulating m⁶A RNA methylation. We describe the interplay between m⁶A and other epigenetic modifications and highlight the regulatory roles of m⁶A in development, especially that of skeletal muscle. m⁶A and its regulators are expected to be targets for the treatment of human muscle-related diseases and novel epigenetic markers for animal breeding in meat production.     

MiR-206在骨骼肌发育中的功能

微RNA(microRNA,miRNA)是一类在分子进化中十分保守的非编码RNA,长度约22个核苷酸,一般情况下它在转录后水平抑制基因表达。miRNA在细胞增殖、分化、凋亡等诸多生理过程中发挥着重要作用。有些miRNA具有组织特异性表达,其中miR-206是目前发现的唯一在骨骼肌中特异表达的miRNA,它在调节骨骼肌发生过程中扮演重要角色。miR-206表达异常与一些肌肉相关疾病如肌肉营养不良、肌萎缩性侧索硬化症等有关。此外,在Texel羊中,myostatin基因的一个点突变就产生了一个miR-206和miR-1的靶点,抑制了myostain基因的表达,从而产生了双肌表型。因此,miR-206有可能成为治疗肌肉相关疾病和畜禽改良育种的重要候选分子。     

LncRNA调控骨骼肌发育的分子机制及其在家养动物中的研究进展

骨骼肌是维持机体功能必不可少的组织,与家养动物的产肉率等重要经济性状密切相关。近年来,高通量测序鉴定了大量与骨骼肌生成相关的长链非编码RNA (long non-coding RNA, lncRNA),它们可作为调节因子在表观调控、转录调控以及转录后调控等多个层面调控基因表达。lncRNA通过靶向关键因子参与调控骨骼肌发育的各个环节,包括骨骼肌干细胞增殖、迁移、分化,成肌细胞增殖、分化、肌管融合,肌纤维肥大和纤维类型转换等过程。本文重点归纳了lncRNA在人和小鼠骨骼肌发育中的分子调控机制,介绍了lncRNA的研究方法,综述了lncRNA在家养动物骨骼肌发育中的研究进展,分析了目前家养动物lncRNA研究所面临的困难和挑战,最后展望了未来家养动物lncRNA研究的方向,以期为进一步阐明骨骼肌生长发育的分子调控机制提供参考。     

Lean and obese pig breeds exhibit differences in prenatal gene expression profiles of muscle development

Muscle development in domesticated animals is important for meat production. Furthermore, intramuscular fat content is an important trait of meat intended for consumption. Here, we examined differences in the expression of factors related to myogenesis, adipogenesis and skeletal muscle growth during fetal muscle development of lean (Yorkshire) and obese (Chenghua) pig breeds. At prenatal days 50 (d50) and 90 (d90), muscles and sera were collected from pig fetuses. Histology revealed larger diameters and numbers of myofibers in Chenghua pig fetuses than those in Yorkshire pig fetuses at d50 and d90. Yorkshire fetuses had higher serum concentrations of myostatin (d90), a negative regulator for muscle development, and higher mRNA expression of the growth hormone receptor Ghr (d90), myogenic MyoG (d90) and adipogenic LPL (d50). By contrast, Chenghua fetuses exhibited higher serum concentration of growth hormone (d90), and higher mRNA expression of myogenic MyoD (d90) as well as adipogenic PPARG and FABP4 (d50). Our results revealed distinct expression patterns in the two pig breeds at each developmental stage before birth. Compared with Chenghua pigs, development and maturation of fetal skeletal muscles may occur earlier in Yorkshire pigs, but the negative regulatory effects of myostatin may suppress muscle development at the later stage.     

肌肉生长抑制素调控动物骨骼肌生长机制的研究进展

肌肉生成抑制素（myostatin, MSTN）在动物机体骨骼肌的增殖、分化和生长中起着重要的负调控作用。MSTN基因的过表达会阻碍骨骼肌增殖分化及生长发育,而缺失或表达降低则会导致肌肉肥大,形成双肌现象（double muscle phenomenon, DMP）。MSTN能作用于多个基因及结合多种细胞因子广泛参与生理生化、物质代谢、病理调控等过程,在动物机体生长发育过程中扮演着重要的角色。本文将从MSTN基因的历史渊源、基因定位、时空表达特性、部分相关作用机制等方面进行论述,旨在对MSTN调控动物骨骼肌生长部分机制作梳理,以期为后期研究提供理论依据。     

A computerized mechanical cell stimulator for tissue culture: Effects on skeletal muscle organogenesis

Summary A tissue culture system has been developed which can mechanically stimulate cells growing on a highly elastic plastic substratum in a 24-well cell growth chamber. The collagen-coated substratum to which the cells attach and grow in the Mechanical Cell Stimulator (Model I) can be repetitively stretched and relaxed by stepper motor with linear accuracy of 30 μm. The activity controlling unit is an Apple IIe computer interfaced with the cell growth chamber via optical data links and is capable of simulating many of the mechanical activity patterns that cells are subjected to in vivo. Primary avian skeletal myoblasts proliferate and fuse into multinucleated myotubes in this set-up in a manner similar to normal tissue culture dishes. Under static culture conditions, the muscle cells differentiate into networks of myotubes which show little orientation. Growing the proliferating muscle cells on a unidirectional stretching substratum causes the developing myotubes to orient parallel to the direction of movement. In contrast, growing the cells on a substratum undergoing continuous stretch-relaxation cycling orients the developing myotubes perpendicular to the direction of movement. Neither type of mechanical activity significantly affects the rate of cell proliferation of the rate of myoblast fusion into myotubes. These results indicate that during in vivo skeletal muscle organogenesis, when substantial mechanical stresses are placed on skeletal muscle cells by both continuous bone elongation and by spontaneous contractions, only bone elongation plays a significant role in proper fiber orientation for subsequent functional work. Supported by grants NS16753, AR36266, and RR05818 from the National Institutes of Health, Bethesda, MD.