Identification of novel pathways for cardiac development and disease via conditional genetic manipulation of cardioblasts and cardiomyocyte lineages.

摘要

In this "post-genomic" era, much of the leading task is to assign functions to the some 30,000 genes estimated from the human genome project. Toward this end, the laboratory mouse has been an invaluable tool. Because of the high number of genes homologous to human, the mouse has become an essential model system in uncovering the link from gene to function and in modeling human diseases. In the past two decades, the conventional knockout has provided many insights to fundamental questions in basic and applied research in the areas of developmental biology, organogenesis, reproduction, neurobiology, and cardiology. However, traditional gene targeting does have its pitfalls. Often, gene ablation experiments result in embryonic lethality. Even though one might be able to observe the effects of a certain gene, one can never be sure of the developmental consequences or adaptive gene expression changes from knocking out a gene in the germ line of a mouse. To overcome these limitations of conventional knockout, a much tighter spatiotemporal control of genetic manipulation is necessary. To accomplish this, the mouse research community now has an arsenal of strategies for the spatiotemporal control of the expression and/or function of specific recombinases to control when and/or where the gene modification occurs. Utilizing the tamoxifen inducible Cre recombinase technology, the work described here illustrates the power of this approach in tracing a population of cells in the myocardium using a marker that is turned off after cell differentiation and in gene ablation experiments where conventional knockout of the gene results in embryonic lethality. More specifically, conditional marking of isl1+ cells allows the isolation and characterization of a native cardiac progenitor population and conditional gene ablation of the cardiac ryanodine receptor 2 in the postnatal heart permits the investigation of the role of calcium release in progression of heart failure in vivo. This work has lead to the design of novel genetically based models systems to engineer specific mutations in cardioblasts and cardiomyocyte lineages in order to improve our understanding of novel molecular pathways in cardiac development and disease.