Fig. 4.

The meningeal blood vasculature in BLEC-depleted fish shows a massive reduction in blood vessel coverage and in the number of vessel branches and junctions, while the average vessel thickness and branch length are increased. (A) Schematic representation of a zebrafish head (dorsal view). Red rectangles mark the analyzed areas (0.166 mm²) per fish. (B,C) Maximum projection of the dorsal TeO (tectum opticum) of 12-month-old mrc1a:mCitrine;kdrl:mCherry-positive zebrafish with either BLECs (control, B) or with a dorsally extending network after BLEC ablation (C). The number of blood vessels is decreased in fish with a dorsal network. (D) Quantitative analysis of blood vessels from 6- to 12-month-old fish, normalized to the control of each age. The area covered by blood vessels is significantly reduced (*P=0.044, Man-Whitney U-test) by 34% in fish with a dorsal network after BLEC ablation. In addition, the number of vessel branches (*P=0.044, Mann–Whitney U-test) and junctions (*P=0.044, Mann–Whitney U-test) is reduced. The average branch length (34%, **P=0.007, unpaired Student's t-test) and the average vessel thickness (14%, *P=0.019, unpaired Student's t-test) are increased in fish with a dorsal network. (E-G) Schematic representation (E) and maximum projections (F,G) of the dorsal TeO of 5-week-old mrc1a:mCitrine;kdrl:mCherry-positive zebrafish with BLECs (control, F) or with ablated BLECs but lacking the vessel network on the dorsal side of the brain (G). The number of blood vessels, the average branch length and the average vessel thickness do not differ in 1- to 3-month-old fish. However, there is a slight decrease in the number of branches (14%, P=0.052, unpaired Student's t-test) and junctions (14%, P=0.069, unpaired Student's t-test) compared to control fish. Results are presented as mean±s.d.