Extended Data Figure 8: Zonation of mural cell markers in zebrafish brain.

a, The zonated distribution of tagln and pdgfrb as shown in the three-month-old zebrafish brain using transgenic reporter fish. GFP is expressed from the tagln promoter and RFP from the UAS promoter activated by pdgfrb promoter-driven Gal4FF. Similar to mice, tagln is expressed in a/aaSMCs (white arrows, inset i) whereas pdgfrb marks mural cells along all vessel types, including capillary pericytes (PC). The lower panels show insets at high magnification. Note the lower expression of pdgfrb in the aSMCs of the larger arteries (inset ii). b, GFP expression from a UAS promoter activated by Gal4FF expressed from the abcc9 promoter in forebrain mural cells of a two-month-old zebrafish. Endothelial cells are labelled by DsRed expression from the kdrl (Vegfr2) promoter. Note that, similar to the expression pattern of Abcc9 in mice, fish abcc9 expression is localized mainly to capillary pericytes and venous mural cells, but not to arteries or arterioles (A). Top, a midsagittal view shows GFP-positive pericytes (white arrowheads) on capillary branches, whereas the SMC of the feeding arteriole as well as the upstream artery (A, white arrows) are GFP-negative. Middle, in a ventral view of the capillary network branching off an arteriole (A), numerous GFP-positive pericytes are seen, while the arteriole is negative. An arteriole–capillary transition is indicated by a yellow arrowhead. Dashed line indicates a vascular continuum stretching from the arteriole (A) across capillary branches to a venule (V). Bottom, another midsagittal view illustrates that arterial SMCs (A) lack abcc9 expression. Scale bars, 50 μm.