Zygotic dab2 mutants do not show lymphatic defects but exhibit elevated numbers of BLECs. (a) Schematic representation of a wild type trunk vasculature at 2dpf indicating the zoomed in area in b and c (red rectangle). (b, c) Maximum projection of confocal images of wild type (b) and homozygous dab2 mutants (c) with PL cells (white asterisk) positioned at the HM at 2dpf. The PCV (arrowhead) and ISVs (arrow) are marked as reference structures. (d) Schematic representation of the wild type trunk vasculature at 5dpf. (e, f) Maximum projection of confocal images of flt4:mCitrine-positive embryos at 5dpf. Wild type fish (e) and homozygous dab2 mutants (f) have formed the TD (white asterisks) dorsally to the PCV (arrowhead) as well as the DLLV (red asterisks). (g) Schematic drawing of a zebrafish head at 5dpf (dorsal view) with BLECs depicted in red, highlighting the area shown in (h) and (i). (h,i) Maximum projection of confocal images taken at 5dpf. Note the lyve1:dsRed signal in BLECs (red) and the fli1a:nEGFP expression marking all endothelial nuclei. While BLECs are visible in both, siblings (h) and homozygous dab2 mutants (i), dab2 mutants occasionally show a second row of BLECs (arrowheads). (j) Quantification of BLECs reveals a significant increase in BLEC numbers in dab2 mutants (Unpaired t test; siblings vs. dab2 -/- p = 0.0418). BLEC, brain lymphatic endothelial cell; DLLV, dorsal longitudinal lymphatic vessel; dpf, days post fertilization; HM, horizontal myoseptum; ISV, intersegmental vessel; PCV, posterior cardinal vein; PL, parachordal lymphangioblast; TD, thoracic duct; DA, dorsal aorta.
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