The specific aims during the last grant-period were to examine the roles of the integrin alpha4beta1 and its cell surface ligand VCAM-1 in muscle differentiation, and to determine how expression of the proteins are regulated in this process. We have made significant progress on each of the original specific aims as shown in detail in the appended manuscripts. During the course of our studies we found that a zinc finger/homeodomain protein (ZEB) acts as a transcriptional repressor and regulates expression of alpha4 during muscle differentiation. In addition to alpha4, ZEB also regulates a number of other muscle genes. The present proposal is to further characterize ZEB and a Drosophila homologue, zfh-1. Results in cell culture and with transgenic mice suggest that myogenesis is under negative regulation by ZEB and the release of this inhibition has a role in regulating the timing of muscle gene expression and thus myogenic differentiation. ZEB is also expressed in tissues in addition to muscle, and experiments with transgenic mice suggest that it plays an important role very early in development. Studies are proposed in cell culture and in transgenic mice to analyze the structure/function of ZEB. We have identified the Drosophila protein zfh-1 as a homologue of ZEB. Zfh-1 represses transcription and regulates myogenesis in Drosophila-overexpression of the protein selectively blocks somatic muscle formation in Drosophila embryos without affecting visceral or heart muscle differentiation. One target of zfh-1 is the myogenic protein MEF2, which is activated directly by twist in somatic muscle cells and is essential for somatic myogenesis. A model is proposed where zfh-1 inhibits somatic myogenesis by blocking twist function and thus MEF2 expression. We suggest that it is a release of this zfh-1 inhibition in somatic muscle cells (by downregulation of expression and loss of function) that defines the onset of somatic myogenesis. Studies are proposed to examine the regions of zfh-1 required for its activity in somatic muscle, and to understand its relationship to other regulators of myogenesis such as twist and MEF2.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR041908-08
Application #
6328838
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Program Officer
Lymn, Richard W
Project Start
1993-09-01
Project End
2003-11-30
Budget Start
2000-12-01
Budget End
2001-11-30
Support Year
8
Fiscal Year
2001
Total Cost
$288,391
Indirect Cost
Name
Washington University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Sheppard, A M; McQuillan, J J; Iademarco, M F et al. (1995) Control of vascular cell adhesion molecule-1 gene promoter activity during neural differentiation. J Biol Chem 270:3710-9
Iademarco, M F; Barks, J L; Dean, D C (1995) Regulation of vascular cell adhesion molecule-1 expression by IL-4 and TNF-alpha in cultured endothelial cells. J Clin Invest 95:264-71
Rosen, G D; Barks, J L; Iademarco, M F et al. (1994) An intricate arrangement of binding sites for the Ets family of transcription factors regulates activity of the alpha 4 integrin gene promoter. J Biol Chem 269:15652-60
Sheppard, A M; Onken, M D; Rosen, G D et al. (1994) Expanding roles for alpha 4 integrin and its ligands in development. Cell Adhes Commun 2:27-43