Single cell analysis of transfected gene expression in primary heart cultures containing multiple cell types

Transfection experiments involving mixed cell cultures pose special problems because of differential uptake and expression of DNA by different cell types. In order to evaluate the expression of transfected DNA in primary cultures of embryonic myocardial cells, we have used immunofluorescence microscopy to analyze expression of chloramphenicol acetyltransferase (CAT) on a single cell basis. The results show that myocardial cells take up and express transfected DNA approximately 7 times less efficiently than non-myocardial cells. The immunofluorescence analysis allows the biochemical level of CAT activity expressed under control of different transcriptional promoters to be compared on a cell type by cell type basis. Thus, the relative transcriptional strength of two promoters can be estimated for a specific cell type within a heterogeneous population of cells.