Blood vessel formation and MC recruitment in the CNS do not require HS production by MCs. Overview images of the vasculature from control (A) and EXT1^MCko (E) hindbrains. Whole-mount hindbrains of E11.5 embryos were labeled with isolectin-B4 (blue) and NG2 (red) to detect ECs and MCs, respectively. High-resolution imaging revealed recruitment and attachment of MCs in EXT1^MCko (F) as well as control (B) embryos. Immunostaining with HS (green) confirmed the presence of HS in BM of blood vessels (arrows, D,H); n > 5. Arrows (C-D,G-H) highlight strongest HS expression correlating with MC association to vessels. High-magnification microscopy revealed solid HS expression at the EC-MC interface in vessels of control embryos (arrow, I-J,M-N), lacking in EXT1^MCko vessels (K-L,O-P). Overall vascular plexus in EXT1^MCko hindbrains displays reduced HS expression (L,P); n > 4. Comparison of MC coverage in EXT1^MCko and control hindbrains at the periphery (Q-R) and midline (S-T) shows no differences in MC recruitment and migration; n = 3. In contrast, Pdgfrb^−/− hindbrains (V) lack MC coverage compared with control littermates (U); n = 2.