Global Gene Expression Analysis Involved In Postnatal Mouse Myocardial Proliferation

Objectives:The traditional view has held that adult mammalian cardiomyocytes may permanently lose their ability to proliferate.Recent studies have confirmed that excising partial cardiomyocytes at the apical portion of the heart in 24-hour-old mice could stimulate cardiomyocytes to repair the damaged region.In addition,a surge of thyroid hormones during pre-adolescence may play an important role in myocardial proliferation.The main purpose of this study is to analyze the whole gene expression profiling of mouse cardiomyocytes on the basis of previous research and to explore the phenomenon of cell proliferation or growth arrest in mouse transcription level in order to discover unknown signal transduction target.Methods:In the present study,we analyzed the differentially expressed genes in global gene expression profiles using 24-hour-old(containing proliferative cardiomyocytes),7-day-old(containing proliferative burst cardiomyocytes),and 10-week-old(containing growth-arrested cardiomyocytes)postnatal mouse hearts.We used the random variance model(RVM)to modify the F test to calculate the level of significant difference(p-value)and the false discovery rate(FDR)to obtain the differentially expressed genes.Furthermore,we performed gene ontology analysis,which matches the functional annotation to each gene based on molecular function database.Subsequently,using Fisher‘s test and multiple comparison tests,we derived the p-value(significance level)of each functional annotation.Using the KEGG,Biocarta,and Reactome databases,we identified the pathways determined by systematical relationship,functions,and genomic information of the differentially expressed genes.Fisher‘s test and the chi-square test were used to calculate the p-value to identify the significant signal transduction pathways.We used series test of cluster to analyze the differentially expressed genes,to accurately and intuitively visualize the genes with the same tendency of expression between 24-hour-,7-day-,and 10-week-old mouse hearts.Using the gene-sample matrix to simulate the regulatory effects between genes,we constructed the dynamic network.Moreover,signal-net analysis,based on the KEGG database of the interactions between different gene products and the theory of network biology,was established to illustrate the inter-gene signaling between the differentially expressed genes.The signal transduction pathways of the cell cycle,cell differentiation,and cell division were constructed to characterize the network involved in the phenomenon of myocardial growth arrest.Results:The present study analyzed the differentially expressed genes in 24-hour-old,7-day-old,and 10-week-oldmouse hearts using global gene expression profiles.We analyzed the phenomenon of myocardial proliferation and growth arrest from multiple perspectives.In gene ontology analysis,the enriched gene function was associated with cell cycle,cell division,mitosis,and metabolic processes with increasing age.In pathway analysis,?cell cycle‘,?PI3K-AKT signaling pathway‘,and ?metabolic pathways‘ were well represented.Notably,the cluster analysis revealed that BMP1,BMP10,CCNE2,E2F1,and IGF1 showed a burst of expression in 7-day-old hearts.Dynamic gene network analysis showed 11 genes as key drivers in shifting cardiomyocytes into a lower proliferation capacity.CCNB1,BUB1,TNNI1,NDC80,DYNLT1?,CCNB2,and CDK2 were down-regulated,and TMOD4,PFKFB2,NAMPT,and GRM1 were up-regulated.More importantly,the cell cycle-associated signal transduction pathway was constructed.We focused on genes including ANAPC1,CDC20,CDK1,MYC,CDC25 C,GADD45?,and BMPs which should play the important roles in the phenomenon of postnatal myocardial cell cycle or cell division arrest.Conclusions:In this study,gene expression profiles were performed to determine the most powerful and functional genes in physiological cardiomyocytes.These data are likely to provide an important reference concerning myocardial proliferation and development.