Fig. 7. Some myofibroblast progenitors are neural crest derived. Wnt1-Cre mice were mated with ß-actin-flox/stop-ß-gal conditional reporter mice. Sciatic nerves were dissected from the fetuses at E13.5, dissociated and cultured at clonal density. Some cells formed mixed colonies containing neural cells as well as myofibroblasts (A), whereas other colonies contained only neural cells (B), or only myofibroblasts (C). Neural cells were p75⁺ (not shown), had a characteristically spindly morphology, and grew in relatively dense colonies (B). Myofibroblasts were p75^–SMA⁺, were characteristically large and flat, and grew in small, dispersed colonies (C,D). The cultures were stained with X-gal to identify neural crest-derived cells (blue product). Colonies from Cre^–reporter⁺ littermate controls were never X-gal⁺ (A; Table 2), but neural colonies from Cre⁺reporter⁺ mice were usually X-gal⁺ (B; Table 2), as would be expected. Myofibroblast colonies from Cre⁺reporter⁺ mice were sometimes X-gal⁺, indicating neural crest derivation (C). Similar results were obtained using Wnt1-Cre⁺loxpRosa⁺ mice, in which some nerve cells formed ß-gal⁺SMA⁺ myofibroblast colonies (D; see Table 2 for quantification).