Fig. 4. FGFR isoforms and FGFs are developmentally regulated during SMG formation. RT-PCR analysis of FGFR family isoforms (A) and ligands (B) during submandibular gland development is shown with quantitation of the changes shown in the bar graph. The results include receptor/ligand isoforms not present on the Atlas arrays and cDNA from E12 and E13 mouse SMGs. The number of PCR cycles was optimized for each gene so that no products were saturated. Differences in expression levels were quantitated.