PGC-1α基因调控鸡骨骼肌纤维类型转换的分子机制

Skeletal muscle fiber type is one of the major factors that directly affect meat quality. Until now, the molecular mechanism of the conversion of myofiber types is still unkown. Recent work has implicated that the transcriptional coactivator PGC-1α might be the key factor in muscle fiber type conversion and determination, but it's molecular mechanism on chicken skeletal muscle fiber type conversion is unclear. Basing on our former research on PGC-1α gene in chickens, the present project is designed to study the expression differences of PGC-1α gene in different chicken breeds (Qingyuan partridge chickens and Recessive white chickens) and different muscle types (slow muscle fibers and fast muscle fibers) as well as before and after differentiation of myoblast, study the effects on the metabolic and contractile phenotype of skeletal muscle cells after interfering and over-expressing PGC-1α gene, and analyze the regulatory networks between PGC-1α gene and genes on the important signaling pathway in skeletal muscle fiber type conversion, with the methods of functional genomics, cell biology, bioinformatics and etc.. Meanwhile, the effects on the conversion of skeletal muscle fiber types by over-expressing PGC-1α gene in vivo is also studied. Based on the results of these studies, the molecular mechanism of PGC-1α gene on the conversion of skeletal muscle fiber types in chicken will be explored, and the results will provide theoretical basis for the genetic improvement of meat quality traits in chicken.

肌纤维类型是直接影响肉质的重要因素，但肌纤维形成后其类型发生转换的分子机制目前尚不清楚。研究表明，PGC-1α可能是调控肌纤维类型转换的关键因子，但其调控鸡肌纤维类型转换的分子机制仍有待揭示。本项目以课题组前期对鸡PGC-1α基因的研究工作为基础，综合功能基因组学、细胞生物学、生物信息学等研究思路和方法，研究该基因在不同品种鸡（清远麻鸡和隐性白羽鸡）不同类型肌肉组织（快肌和慢肌）及鸡成肌细胞分化前后的表达差异，分析RNAi和过表达PGC-1α基因后，成肌细胞收缩特性和代谢特征的变化，探讨PGC-1α基因与肌纤维类型转换重要信号通路上基因间的网络关系；同时，在体内研究PGC-1α基因对肌纤维类型转换的影响。阐明PGC-1α基因调控肌纤维类型转换的分子机制，为我国鸡肉品质性状遗传改良提供理论依据和技术支撑。

为揭示PGC-1α基因调控鸡骨骼肌纤维类型转换的分子机制，本项目以慢生型清远麻鸡和速生型隐性白羽鸡的两种表型肌肉比目鱼肌（慢肌为主）和趾长伸肌（快肌为主）为研究素材，首先在转录水平和翻译水平上对两个品种鸡两种类型肌肉中6个肌纤维类型相关基因（PGC-1α、PGC-1β、CnAα、CnB1、NFATc3、MEF2C）mRNA和PGC-1α蛋白的发育性表达规律进行研究，并利用Agilent鸡全基因组表达谱芯片筛选清远麻鸡不同表型肌肉的差异表达基因，进一步从细胞水平和在体水平上研究过表达和干扰PGC-1α基因对鸡成肌细胞和肌肉组织中CaN-NFAT信号通路相关基因（CnAα、CnB1、NFATc3、MEF2C）、肌细胞相关标记基因（Pax7、MyoD、MyoG）、肌球蛋白重链基因（SM、FRM、FWM）表达量的变化及成肌细胞中与肌纤维类型变化相关的酶（CS、CK、LDH、CaN）活性的影响。结果表明，PGC-1α等6个肌纤维相关基因mRNA在鸡肌肉组织不同发育阶段广泛表达，表达发育模式具有品种、年龄和部位特异性，但性别间差异均不显著；鸡骨骼肌中PGC-1α的表达与慢肌纤维比例密切相关；PGC-1α对CnAα、MEF2C、SM、Pax7、MyoD、MyoG基因的表达均具有显著的正调控作用，而对FWM基因的表达具有负调控作用，对CnB1 、NFATc3和FRM基因表达作用不显著；成肌细胞中与肌纤维类型转换相关的酶活测定结果表明，PGC-1α能够刺激成肌细胞线粒体合成和氧化代谢。本项目研究结果提示PGC-1α基因通过与肌纤维类型转换重要信号通路CaN信号通路中相关基因协同作用，促进鸡骨骼肌纤维向慢肌纤维转换。