Fig. 6. Cell commitment and differentiation in colonies from postnatal EPCs. 25% of GFP+ cells isolated from postnatal NLBs expressed Sox10 (A1,A2) but were negative for MASH1 (B1,B2) or RET (C1,C2). As in the case of foetal EPCs, on day 3 Sox10 expression was detected only in colony-associated cells (D1,D2). At this stage, a subset of cells expressed Mash1 (E1,E2) or Ret (F1,F2) but we detected no TuJ1+ cells (G1,G2). On day 10, Sox10 was expressed in a subset of cells (H2,I2) and all colonies contained PGP9.5+ cells (H1) which were negative for SOX10 (H3; arrow points to a PGP9.5+/SOX10-cell and arrowhead points to a PGP9.5-/SOX10+ cell). Also, at this stage, 89% of the colonies contained GFAP+ cells (I1) which maintained expression of Sox10 (I3; arrows point to GFAP+/SOX10+ cells). Cells expressing high levels of PGP9.5 were negative for MASH1 (J1-J3). Also, GFAP and MASH1 were present on mutually exclusive cells (K1-K3; arrow points to a GFAP+/MASH1-cell). Finally, as for foetal EPC colonies, the highest levels of RET were detected in TuJ1+ cells (L1-L3; arrows in L3) while Ret was not expressed in GFAP+ cells (M1-M3).