Targeting gene expression to specific cardiovascular cell types in transgenic mice.

Abstract

Transgenic techniques, which allow the introduction of exogenous genes into the genome of experimental animals, promise to bridge the gap between the in vitro observations made by molecular and cellular biologists on cardiac and vascular cells in tissue culture and the physiology and pathology of the whole organ system. One such application of these techniques is tissue targeting: by genetic manipulation to direct expression of a protein--such as a signaling peptide, a growth factor receptor, or an oncogene involved in cell growth--to a tissue where it normally would not be expressed (or where expression is tightly controlled) by fusing it to the transcriptional control sequences of another gene normally expressed in that tissue. In the cardiovascular system, regulatory sequences for cardiomyocyte-specific proteins, vascular endothelium-specific proteins, and smooth muscle-specific proteins can be used to target heterologous genes to their respective tissues in transgenic animals. The effects that such perturbations have on organ physiology and intracellular and intercellular communication can be observed by applying established physiological and molecular approaches. In this review, we highlight some tissue-specific genes from cardiac and vascular cell types whose regulatory sequences may be used to target heterologous proteins; we discuss neutral "reporter" proteins and signal transduction components as paradigms for the application of this technique; and we briefly touch on the potentials and pitfalls of transgenic approaches to molecular physiology.

Caveolin-1/3 Double-Knockout Mice Are Viable, but Lack Both Muscle and Non-Muscle Caveolae, and Develop a Severe Cardiomyopathic Phenotype

“…[41][42][43] Similar studies have been performed by expressing an active mutant of Ras within the heart. 44 These mice manifest cardiac hypertrophy and myofibrillar disarray. Therefore, the complete loss of caveolins in the heart may lead to constitutive activation of G-proteins or Ras signaling, leading to cardiac hypertrophy.…”

Profiling substrate fluxes in the isolated working mouse heart using13C-labeled substrates: focusing on the origin and fate of pyruvate and citrate carbons

“…However, much remains to be learned about the impact of manipulating substrate metabolism on the heart's contractile function and pathophysiological status. Genetically modified mice, especially if they carry inducible cardiomyocyte-specific changes in the expression of a single metabolic gene, have proven to be extremely valuable models for addressing this issue (10,32,37). The dynamic nature of cardiac metabolism and contractile functions requires, however, that investigations be conducted in the intact beating organ.…”

Genetic approaches for changing the heart and dissecting complex syndromes

“…to ubiquitously drive transgene expression in essentially all cells and tissues [17,18], complicating organ specific interpretation of any resulting phenotype. The importance of organ or cell typespecific promoters was quickly appreciated and, with respect to the heart, the development of cardiac-specific promoters greatly enhanced the use of transgenesis in examining abnormalities in the cardiac contractile apparatus [19][20][21][22][23]. The ideal promoter for studying cardiac development and pathology is cardiac-cell type specific and able to drive physiologically relevant levels of expression while being copy number dependent.…”

“…In initial experiments aimed at defining a cardiac-specific promoter, transcriptional cassettes characterized in vitro were found to be relatively inefficient in directing expression in transgenic hearts [23,25]. Direct cardiac injection and testing of putative promoters in transgenic mice were subsequently used to characterize a number of cardiac-specific promoters [20,22,26,27]. For cardiomyocyte-specific expression in the adult heart, the α-myosin heavy chain (MHC) promoter has proven to be the most useful due to its ability to drive high levels of cardiomyocyte-specific expression [12,13,28] in a copy number dependent and position independent manner [24].…”