Fig. 6.

Fig. 6.

Cells of the vascular network are capable of endocytosing injected IgG-Alexa-647, similar to BLECs in control brains. (A-B′) Maximum projection showing BLECs (green) closely associated with meningeal blood vessels (red) at the dorsal tectum opticum (TeO) of a mrc1a:mCitrine; kdrl:mCherry-positive brain dissected from a 6-month-old uninjected control fish (A,A′) or IgG-Alexa-647-injected fish (B,B′). The white arrows mark a large autofluorescent vacuole of a BLEC. The arrowheads highlight small vesicles strongly positive for IgG-Alexa-647 (B,B′), which are not visible in uninjected controls (A,A′). (C) Schematic dorsal view of the head region of an adult zebrafish, indicating the zoomed-in area shown in D and F. (D) Maximum projection showing the dorsal TeO of a mrc1a:mCitrine;kdrl:mCherry-positive brain dissected from a 6-month-old control fish that was injected intracranially with IgG-Alexa-647, showing BLECs (green) and meningeal blood vessels (red). The rectangle indicates the zoomed-in area in E and E′. (E,E′) BLECs take up IgG-Alexa-647 in small vesicles (arrowheads). Large autofluorescent vacuoles are marked with arrows. (F) Maximum projection showing the dorsal TeO of a mrc1a:mCitrine;kdrl:mCherry-positive brain dissected from a 6-month-old fish with ablated BLECs. The fish was injected intracranially with IgG-Alexa-647. The rectangle indicates the zoomed-in area in G and G′. (G,G′) The ectopic network takes up IgG-Alexa-647 intracellularly (arrowheads). Large autofluorescent vacuoles, as observed in BLECs, are not visible in these cells. The fish were imaged at a maximum of 24 h post-injection.