Fig. 5. Dhh-Cre expressing progenitors give rise to endoneurial fibroblasts as well as Schwann cells in nerves. Sciatic nerves were dissected from P11 Dhh-Cre⁺LoxpRosa⁺ (A,B) pups as well as Dhh-Cre^–LoxpRosa⁺ (C) littermate controls, processed for bluo-gal staining, and examined by electron microscopy. Endoneurial fibroblasts (f) were identified by their angular shape, long processes (A), and lack of a basal lamina (B). Red arrows indicate bluo-gal crystals in an endoneurial fibroblast; green arrows indicate bluo-gal crystals in Schwann cells. B shows the inset from panel A at a higher magnification to demonstrate the presence of a basal lamina on Schwann cells (black arrows), and the absence of a basal lamina on the fibroblast. Bluo-gal crystals were never observed in littermate control nerves (C). Endoneurial fibroblasts expressed ß-gal at a similar frequency to Schwann cells, whereas perineurial cells were nearly all negative (D).