Ablation of neural progenitors results in cortical vessel regression independent of defects in pericyte recruitment.

<p>(A–H) Vessel morphology from E15.5 to E18.5. IB4 staining (in green) revealed no obvious defects at E15.5 (A and B) but significant defects at E16.5 (C and D), E17.5 (E and F), and E18.5 (G and H). (I–J) Quantification of vessel density and branching frequency from E15.5–17.5. Significant decreases (*) in both parameters were observed at E16.5 (<i>p</i> = 0.03 and 0.0003, <i>n</i> = 3) and E17.5 (<i>p</i> = 0.7×10⁻⁵ and 0.007, <i>n</i> = 5), but not at E15.5 (<i>p</i> = 0.52 and 0.25, <i>n</i> = 4). (K–N) Pericyte investment of vessels. Desmin staining (in red) surrounds CD31⁺ (in green) vessels similarly in mutants (L), as in controls (K). Boxed areas in (K and L) are shown in two right panels. PDGFRβ⁺ (in green) cells (some highlighted by arrowheads) were also associated with IB4⁺ (in red) vessels similarly in mutants (N), as in controls (M). PDGFRβ staining in boxed areas are shown as insets. (O) Quantification of PDGFRβ⁺ pericyte density. Pericytes along all vessels were quantified. No significant differences were observed (<i>p</i> = 0.62, <i>n</i> = 4). (P–Q′) Collagen IV staining. Collagen IV⁺ (in red) empty sleeves (arrowheads in Q′) were frequently observed in mutants (Q–Q′), in contrast to controls (P–P′). (R–S) Vessel perfusion. Neonates were perfused trans-cardially using 1% FITC-dextran (in green) followed by IB4 (in red) staining. Many vessels in mutant brains (S) were not well perfused (arrowhead in S), in contrast to those in controls (R). Scale bar (in D): 200 µm for (A–H), (K–N), and (R–S), 80 µm for (P–Q′).