TRANSFECTION OF CARDIAC-MUSCLE - EFFECTS OF OVEREXPRESSION OF C-MYC AND C-FOS PROTOONCOGENE PROTEINS IN PRIMARY CULTURES OF NEONATAL SAT CARDIAC MYOCYTES

1. Studies of cells transfected with specific expression vectors allow functions of specific gene products to be investigated. We first esta blished optimum conditions for transfection of neonatal cardiac myocyt es in primary culture. Increased proto-oncogene expression has been im plicated in the development of cardiac hypertrophy; we therefore wishe d to examine the effects of overexpression of the c-myc and c-fos prot o-oncogenes induced by cell transfection on cell growth. 2. Neonatal r at ventricular myocytes were transfected by electroporation, voltage a nd capacitance settings were optimized and these conditions were then used to transfect expression vectors encoding MYC and FOS proteins int o this cell type. Effects on cell number, DNA synthesis and protein co ntent were determined. 3. Increased expression of c-myc and c-fos in c ells transfected with proto-oncogene expression vectors was confirmed by Northern and Western blotting. Increases in cardiac myocyte cell nu mber, DNA synthesis and total cellular protein were observed in cells transfected with either c-myc or c-fos expression vectors compared wit h cells transfected with non-coding vectors. 4. Overexpression of MYC and FOS proteins results in hyperplastic rather than hypertrophic grow th of the neonatal rat heart, providing evidence for a role of these p roteins in the control of myocardial growth.