(A) Representative images of mouse OPCs co-transfected with eGFP and control (empty) vector, or vectors encoding MRF or Sox10 and then cultured for 2 days post transfection in proliferative conditions. Cells are stained for the OPC marker NG2 or OL markers MBP and MOG. Scale bar=50um. (B-C) Quantification of the proportion of transfected cells in each condition expressing MBP (B) and MOG (C) at 2 and 5 days post transfection. **P<0.01, unpaired t-test. Values are means± SEM. (D) Representative spinal cord sections of chicken embryos electroporated with expression constructs for MRF, Sox10 or both genes at E3 (stage 12) along with a GFP construct and allowed to develop until E7. Sections are stained with anti-MBP, with GFP shown to identify electroporated cells. (E) Quantification of the proportion of electroporated cells expressing MBP for each condition; shown are values for individual animals and median values for each condition (red bars). (F-G) Examples of MRF-electroporated neural crest cells ectopically expressing MBP (F); (G) shows triple labeling for GFP, MBP and Sox10. The arrowhead indicates a triple-labeled cell, a GFP/Sox10+, MBP- cell can be seen to the left of the image.