Perlecan gene expression precedes laminin gene expression during differentiation of F9 embryonal carcinoma cells

F9 embryonal cells can be induced to differentiate and synthesize basement membrane proteins. Perlecan and laminin are two basement membrane constituents that have extensive regions of homology. Expression of perlecan and laminin B1 genes was followed during differentiation of F9 cells by measurements of transcription rate and mRNA abundance using nuclear run on assays and Northern hybridizations, respectively. The rate of precursor protein synthesis was determined by immunoprecipitation from lysates of pulse-labeled F9 cells. The results showed that perlecan gene expression responds more rapidly after induction than does laminin B1 gene expression but is ultimately expressed at a substantially lower level than laminin. Thus, the perlecan and laminin genes appear to be regulated by different mechanisms and their gene products are not made in stoichiometric amounts.