All three glioma cell lines express the secreted version of SCF (A), and the undifferentiated and neurzalized ES cells express c-kit, the tyrosine kinase receptor for SCF. The ES cells expressed c-kit at 0, 4 and 8 Days of the induction protocol (B). A, Primers specific for the splice variant of SCF that contains exon 6, known to produce secreted SCF, were used in RT-PCR experiments on glioma cell lines N1321, U87, and C6. The predicted 665 bp product is produced by all three cell lines. B, RT-PCR and primers specific for mouse c-kit demonstrated that undifferentiated ES cells and Day 4 and Day 8 neuralized ES cells express c-kit (318 bp PCR product). Primers specific for mouse GAPDH (154 bp PCR product) were used as loading controls and are shown for the corresponding days of induction (taken from the same gel as for c-kit expression). As a negative control reverse transcriptase (RT) was left out of the reaction mixture (- RT). No RT controls in B were pooled samples taken from cells at 0, 4 and 8 Days of induction. In the right column of A and B is shown a low DNA mass ladder (Invitrogen, Cat. # 10068-013).