Figure 5

Figure 5 (A) A schematic of mural cell development in cranial vessels during early development from 10 hpf and are distributed at the cerebral base and around the CVP by 24 hpf. Then, specification from pdgfrb^low precursors located in the vicinity of arterial endothelial cells on the BA, PCS, BCA, or CVP into mural cells (green) starts at approximately 36 hpf (a). Specification into mural cells from precursors is also slightly induced around primordial hindbrain channels (PHBCs). After the connection of CtAs to CVP, BCA, PCS, or BA and the start of blood circulation, mural cells emerging at the cerebral base migrate to CtAs. When these cells migrate, cell division frequently take place to entirely cover CtAs (b). Time-lapse imaging of TgBAC(abcc9:Gal4FF)^ncv34Tg;Tg(UAS:GFP);Tg(5xUAS:MYR-mCherry)^ncv504Tg;Tg(kdrl:tagBFP)^mu293Tg shows morphological changes from pericyte-like cells to VSMCs around the PCS (c). Mural cell bodies and plasma membranes are highlighted by GFP (green) and MYR-mCherry (magenta), respectively. This VSMC-like morphological change in the cerebral base precedes the expression of VSMC markers such as acta2 or tagln. This is not always the case in CtA mural cells, however. (B) Mural cells appearing around the CVP are derived from the neural crest, whereas those emerging around the BCA, PCS, and BA have a mesodermal origin. Reflecting the connection routes of vessels and the features of mural cell migration along the vessels, mural cells around the CVP migrate toward AMCtAs (blue) and MMCtAs (yellow); those appearing at the BCA to AMCtAs and MMCtAs; and those emerging around the PCS or BA toward CCtAs (aqua). Therefore, mural cells in the zebrafish forebrain, in the hindbrain, or in the middle tend to become neural crest, mesoderm, or mixed-origin tissues, respectively. Scale bar: 20 μm (c). Choroidal vascular plexus (CVP). Basal communicating artery (BCA). Posterior communicating segment (PCS). Basilar artery (BA). Primordial hindbrain channel (PHBC).