Differential microRNA Expression during Myogenic Progenitor Cell Proliferation and Differentiation. Mus musculus

MicroRNAs (miRNAs) are important in the regulation of many biological processes such as growth and development. To evaluate the role of miRNAs in skeletal muscle regeneration, global miRNA expression was measured during muscle cell growth and differentiation. Primary cultures of murine myogenic progenitor cells (MPC) were studied for miRNA expression using quantitative PCR-array. During MPC differentiation or proliferation, 139 or 16 miRNAs, respectively, exhibited significant >2-fold changes. Cluster analysis revealed 5 distinct miRNA expression patterns at different stages of differentiation. Fourteen miRNAs exhibiting >10-fold change during differentiation included miR-1, 10b, 96, 98, 133a, 139-5p, 330, 335-3p, 339-5p, 344, 486, 499, 504, and 598. Ten of these miRNAs were located in introns of protein coding genes, such as miR-499 located in the myosin heavy chain isoform Myh7b. In silico analysis of possible miRNA-mRNA interactions indicated that many of these miRNAs targeted mRNA critically involved in muscle differentiation. Interestingly, several miRNAs targeted different sites in a given mRNA, suggesting coordinated expression of multiple miRNAs to ensure the regulation of essential genes. These results identify differentially expressed miRNAs that could represent new regulatory elements in MPC proliferation and differentiation. Overall design: Myogenic progenitor cell (MPC) growth and differentiation are key elements duing muscle regeneration. Using defined culture conditions to promote proliferation or differentiation, we profiled miRNA expression in primary cultures of murine MPC.

微小RNA（microRNAs，miRNAs）在诸多生命过程（如生长与发育）的调控中发挥关键作用。为探究miRNAs在骨骼肌再生中的功能，本研究检测了肌细胞生长与分化过程中的全基因组miRNA表达水平。本研究采用定量PCR芯片（quantitative PCR-array），对小鼠成肌祖细胞（murine myogenic progenitor cells，MPC）的原代培养物进行miRNA表达分析。在MPC分化与增殖阶段，分别有139种和16种miRNAs的表达量出现显著的2倍以上变化。聚类分析结果显示，在分化的不同阶段存在5种独特的miRNA表达模式。在分化过程中表达量变化超过10倍的14种miRNAs包括：miR-1、10b、96、98、133a、139-5p、330、335-3p、339-5p、344、486、499、504及598。其中10种miRNAs位于蛋白质编码基因的内含子区域，例如miR-499定位于肌球蛋白重链异构体Myh7b的基因内含子中。对miRNA与信使RNA（messenger RNA，mRNA）潜在结合关系的硅基分析结果显示，诸多上述miRNAs的靶标mRNA均与肌肉分化过程密切相关。值得注意的是，部分miRNAs可结合同一mRNA的不同位点，这提示多种miRNAs可协同表达，以实现对关键基因的精准调控。本研究结果筛选出了差异表达的miRNAs，这些miRNAs或可作为MPC增殖与分化过程中的新型调控因子。

实验整体设计：成肌祖细胞（MPC）的生长与分化是骨骼肌再生的核心环节。本研究通过设定特定培养条件分别诱导MPC增殖与分化，对小鼠MPC原代培养物的miRNA表达谱进行了分析。