Fig. 7. Activation of myelin gene expression by Sox8, and comparison of ß-galactosidase activities in Sox8^+/lacZ and Sox10^+/lacZ spinal cords. (A) N2A cells were transfected with reporter plasmids in which the luciferase gene was under control of a long (positions -656 to +31) or a short (positions -256 to +31) version of the rat Mbp promoter. Expression plasmids for Sox10 and Sox8 were co-transfected as indicated below the bars. Luciferase activities in extracts from transfected cells were determined in three independent experiments each performed in duplicates. Data are presented as fold inductions ±s.e.m. with the activity of the promoter in the absence of co-transfected Sox protein (-) arbitrarily set to 1. (B) RT-PCR analysis on cDNA obtained from N2A cells inducibly expressing Sox8. - Doxy, no doxycycline (Sox8 absent); + Doxy, doxycycline added (Sox8 present). Transcript levels of Sox8, Plp, Mbp and ß-actin were compared semi-quantitatively using increasing numbers (n, n+3, n+6) of amplification cycles. -, no cDNA added. (C) The amount of ß-galactosidase present per µg extract from Sox8^+/lacZ (white bars) and Sox10^+/lacZ (black bars) spinal cords was determined at 14.5 dpc, 16.5 dpc, 18.5 dpc and in adult mice as indicated below the bars.