This work is focused on the clinical problem of cardia hypertrophy. Hypertrophy is associated with hypertension, valve disease, myocardial infarction and other disease states as well as being important in growth and development of the heart. Hypertrophic stimuli trigger a cascade of regulatory events which culminate in an increased mass and structural reorganization that are thought to maintain cardiac output at near """"""""normal"""""""" levels. In pathological hypertrophy, the fetal isoforms of several proteins reappear suggesting that the heart is undergoing a dedifferentiation process. A long term objective is to understand these adaptive mechanisms and examine why they eventually deteriorate leading to heart failure. Cardiac-specific (cs) expression of the alpha-myosin heavy chain (MHC) gene is altered in several forms of hypertrophy making it an ideal model for identifying factors involved in controlling hypertrophy and maintenance of the differentiated state of the heart. The present proposal will test the hypothesis that hypertrophy stimuli alter the level and/or activity of cs regulators resulting in changes in the pattern of gene expression in the heart. Two complementary approaches are proposed here: (1) Identify and characterize the binding of proteins to two potential cs DNA recognition sites and use the site and/or purified factor(s) in procedures to isolate cDNAs which encode the regulatory factors; and (2) Initiate development of an in vitro transcription system which mimics the regulation of the alpha- MHC gene in the heart. Isolated cDNA clones will be used to probe changes in mRNA levels of regulatory factors during hypertrophy and development as well as to provide a possible source of protein for activity studies in the transcription assay. In vitro transcription will provide a tool for assaying biochemical activities, to assess interactions and for purification of regulatory factors. The long term goal is to define an intracellular pathway from hypertrophy stimulus to the transcription of specific genes during pathological hypertrophy. Information obtained form this work will provide insight into cs regulatory mechanisms which are responsible, in part, for maintaining the adult differentiated phenotype of the heart and may also regulate other genes in the heart in response to stress.
