Our laboratory is interested in the molecular genetics of vascular diseases. We utilize several approaches, including molecular and cellular biology studies, genetic studies in mice, and clinical investigations in patients with vascular diseases. Our focus is on the genetics and genomics of vascular remodeling during common, complex cardiovascular diseases and during premature aging syndromes. Vascular proliferative diseases are characterized by smooth muscle cell (VSMC) proliferation and migration. We have completed our studies of KIS (kinase interacting with stathmin) which targets two regulators of cell proliferation and migration, the cyclin-dependent kinase inhibitor p27Kip1 and the microtubule destabilizing protein stathmin. We found that phosphorylation of p27Kip1 by KIS leads to cell-cycle progression and now further identify the target sequence and the physiological relevance of stathmin phosphorylation by KIS in VSMCs. Our studies demonstrated that vascular wound repair in KIS-/- mice results in accelerated neointima formation, which is composed predominantly of VSMCs. Deletion of KIS led to increased migratory activity of VSMCs accompanied by increased cytoplasmic tubulin destabilizing activity, whereas proliferation of VSMCs was abolished due to delayed nuclear export and degradation of p27Kip1. This pro-migratory phenotype was the result of increased stathmin protein levels due to a lack of stathmin phosphorylation by KIS at serine 38 and diminished stathmin protein degradation. Down-regulation of stathmin in KIS-/-VSMCs fully restored the phenotype, and stathmin-/- mice demonstrated normal responses to vascular injury. These data suggest tha KIS protects against excessive neointima formation by stathmin-mediated inhibition of VSMC migration and that VSMC migration represents a major mechanism of vascular wound repair, constituting a relevant target and mechanism for therapeutic interventions. We also completed studies on endothelial cell differentiation from precursor stem cells. In murine embryonic stem cells, the onset of vascular endothelial growth factor receptor 2 (VEGRF-2) expression identifies endothelial precursors. The objective of our study was to identify a single population of endothelial precursors with common identifying features from murine stem cells. We found that expression of the VEGF coreceptor neuropilin-1 (NRP-1) coincides with expression of Brachyury and VEGFR-2 and identifies endothelial precursors in murine stem cells before CD31 or CD34 expression. When sorted and differentiated, VEGFR-2(+)NRP-1(+) cells form endothelial-like colonies that express CD31 and CD34 7-fold more efficiently than NRP-1 cells. Antagonism of both the VEGF and samaphorin binding functions of NRP-1 impairs the differentiation of vascular precursors to endothelial cells. Hence, the onset of NRP-1 expression identifies endothelial precursors in murine stem cells, which are the origin of a single population of murine endothelial precursors in development to endothelial cells. We are investigating the genomics of coronary restenosis, which is the recurrence of a coronary artery occlusion following stent placement due to VSMC proliferation. The genetic analyses include mRNA expression profiling, genome-wide association study, linkage analysis, and integrative analyses. The goal is to identify genomic profiles of patients with recurrent restenosis, so as to advance our understanding of VSMC -driven remodeling diseases and to target potential molecular therapies. Finally, a major area of investigation is the Hutchinson-Gilford progeria syndrome (HGPS), caused by the production of progerin, a mutant form of the nuclear architectural protein lamin A. The syndrome is characterized by premataure aging, most notably cardiovascular disease that eventually leads to death from myocardial infarction or stroke, usually in their second decade of life. In collaboration with Dr. Francis Collins'laboratory, we have characterized the cardiovascular phenotype of a mouse model for HGPS, which has lead to the development of potential progeria therapies, such as the farnesyltransferase inhibitors (FTIs). We are investigating mechanisms of VSMC proliferation, cell renewal and cell death in double and single copy transgenic progerin mice, which express the human progerin protein. Specifically, these studies focus on cell cycle checkpoints, defects in VSMC regeneration, VSMC migration defects and impaired vascular remodeling. Additional studies, in collaboration with Dr. Leslie Gordon, Brown University, investigate the pathology of the coronary arteries, other components of the cardiovascular system, and other organs in two HGPS children. Primary findings include VSMC drop out in the coronary arteries and aorta, vascular stiffening due to adventitial hyperplasia of the adventitia, and organ fibrosis. These findings provide new insights into this rare disease and vascular remodeling in general.
| Akyürek, Levent M; Boehm, Manfred; Olive, Michelle et al. (2010) Deficiency of cyclin-dependent kinase inhibitors p21Cip1 and p27Kip1 accelerates atherogenesis in apolipoprotein E-deficient mice. Biochem Biophys Res Commun 396:359-63 |
| Cimato, Thomas; Beers, Jeanette; Ding, Shunli et al. (2009) Neuropilin-1 identifies endothelial precursors in human and murine embryonic stem cells before CD34 expression. Circulation 119:2170-8 |
| Capell, Brian C; Olive, Michelle; Erdos, Michael R et al. (2008) A farnesyltransferase inhibitor prevents both the onset and late progression of cardiovascular disease in a progeria mouse model. Proc Natl Acad Sci U S A 105:15902-7 |
| Langenickel, Thomas H; Olive, Michelle; Boehm, Manfred et al. (2008) KIS protects against adverse vascular remodeling by opposing stathmin-mediated VSMC migration in mice. J Clin Invest 118:3848-59 |
