1993 — 1995 |
Kubalak, Steven W |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Regional Specificity During in Vitro Cardiac Development @ University of California San Diego |
0.957 |
2000 — 2003 |
Kubalak, Steven W |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Cardiovascular Remodeling Mediated by Rxra Receptors @ Medical University of South Carolina
Cardiovascular defects associated with the formation and remodeling of endocardial cushion tissue accounts for a large proportion of congenital heart disease in the United States each year [1.2]. The molecular mechanisms integrating the processes of proliferation, differentiation, and apoptosis for proper remodeling of the tubular heart to form the four- chambered organ is not clear. The complex processes associated with remodeling of endocardial cushion tissue into valvular structures involves multiple cell lineages of myocardial, endothelial, mesenchymal, neural crest, and epicardial origins. Remodeling events such as epithelial-to- mesenchymal transformation to cushion tissue and myocardialization in the outflow tract and atrioventricular canal are the result of a precise coordination of these processes. The retinoid X-receptor alpha knockout (RXRalpha-KO) mouse model shows considerable promise at clarifying these relationships and aiding in the determination of the causes of congenital heart defects. At embryonic day (E) 13.5, RXRalpha-KO embryos display a spectrum of endocardial fusion tissue and ventricular chamber malformations analogous to human congenital heart defects [3.5]. Preliminary evidence indicates there is a reduced proliferation and increased apoptosis in RXRalpha-KO embryonic hearts. Moreover,, in RXRalpha-KO embryos, we found elevated levels of TGF-beta2 mRNA and protein in the heart. Thus, our hypothesis is that RXRalpha functions to integrate the processes of proliferation, differentiation, and apoptosis during remodeling of cushion tissue in the outflow tract, AV canal, and ventricular myocardium and that TGF-beta2 contributes to these processes in an RXRalpha-dependent manner. The Specific Aims of this proposal are: 1) To test the hypothesis that epithelial-to-mesenchymal cell transformation in the conotruncal and atrioventricular cushions is RXRalpha-dependent. II) To determine the role of RXRalpha in the processes of proliferation and apoptosis during septation of the conotruncus and ventricular chambers. III) To test the hypothesis that disruption of RXRalpha expression during cardiogenesis results in cardiac defects that are TGFbeta2 dependent.
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2000 — 2002 |
Kubalak, Steven W |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Core--Animal @ Medical University of South Carolina
biomedical facility; laboratory mouse; animal colony; laboratory rat; chick embryo; gene targeting; genetically modified animals;
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2006 — 2009 |
Kubalak, Steven W |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Signaling Mechanisms Regulating Cardiac Remodeling @ Medical University of South Carolina
DESCRIPTION (provided by applicant): The long-term goal of our laboratory is to understand signaling mechanisms that underlie both normal and abnormal heart development as well as mechanisms that can cause congenital heart disease. Indeed, 1-2% of newborns have some form of congenital heart disease making it the most common congenital birth defect. Many of these cardiovascular defects are related to the formation and remodeling of endocardial cushion tissue into the valves and membranous septa of the heart. We have documented that the retinoid X receptor alpha null (RXRalpha-/-) mouse is an excellent model system to aid our understanding of how retinoic acid signaling influences heart development. Lethality in the embryonic day (E) 13.5 RXRalpha-/- mouse is marked, in part, by elevated TGFbeta2 and enhanced apoptosis in the outflow tract. TGFbeta2 primarily signals through phosphorylation (p) of Smad2/Smad3. pSmad2 and pSmadS show a striking coincident localization with apoptosis in E13.5 cushion mesenchyme suggesting they play a key role in programmed cell death and remodeling events mediated by TGFbeta2. Preliminary Western blot data demonstrates co-treatment of isolated trypsin-dispersed heart cells with retinoic acid and TGFbeta2 for one hour resulted in a synergistic phosphorylation of Smad2/Smad3 compared to each agent alone. This novel interaction is not due to transcriptional effects of RXRa since the effects were seen after only a one-hour treatment. Conversely, in the RXRalpha-/-, immunohistochemistry shows a lack of nuclear localized pSmad2/pSmad3 in the outflow tract. These data demonstrate a novel and significant crosstalk between the retinoic acid and TGFbeta2 signaling cascades in the developing heart that has not previously been realized. Thus, while long-term transcriptional effects of retinoic acid signaling are well documented, effects of short-term activation of the pathway have not been studied. Thus, we hypothesize that retinoic acid signaling can function in a rapid response manner to modulate TGFbeta2-mediated effects during outflow tract remodeling. Using whole mouse embryo cultures, primary cell cultures, and genetic crosses we propose three aims to test this hypothesis: 1) To determine the influence of retinoic acid on TGFbeta2 signaling in the heart and to assess the role for RXRalpha in these processes. 2) To determine how retinoic acid signaling regulates TGFbeta2-induced apoptosis and remodeling in the outflow tract. 3) To determine if RXRalpha directly interacts with Smad signaling in the outflow tract.
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