Analysis of wt and Sl^17H mutant cDNA expression in stably transfected in stromal cells.Sl/Sl4  stromal cells were transfected with cDNAs encoding the wt-SCF²⁴⁸ (soluble) and wt-SCF²²⁰(MA) or the Sl^17H-SCF²⁴⁸ (soluble) andSl^17H-SCF²²⁰ (MA) mutant isoforms of SCF. SCF-specific primers (upper panel) were used that amplify both the wt and the Sl^17H mutant forms of SCF. For semiquantitative analysis and RNA integrity, actin-specific primers (lower panel) were used. RT-PCR products were examined on a 2.5% ethidium bromide-containing agarose gel. Upper panel, SCF-specific primers. Lane 1, water control; lane 2, parentalSl/Sl4  cell line; lane 3, wt-SCF²⁴⁸(733 bp); lane 4, wt-SCF²²⁰ (623 bp; exon 6); lane 5,Sl^17H-SCF²⁴⁸ (665 bp; exon 8); and lane 6, Sl^17H-SCF²²⁰ (555 bp; exons 6 and 8). Lower panel, actin-specific primers (732 bp). The molecular weight (MW) marker is shown on the left.