itgb8 and nrp1a genetically interact to promote normal brain vascular development in zebrafish. (A,B) Zebrafish embryos injected with control MOs or MOs designed to block itgb8 or nrp1a translation (A) or splicing (B). No hemorrhage or other vascular defects were obvious at 3 days post-fertilization in embryos injected with control MOs. However, hemorrhage (arrows) is observed in the heads of fish injected with itgb8 or nrp1a translation or splice blocking MOs. In addition, double injection of itgb8 and nrp1a MOs leads to a higher incidence of cranial hemorrhage (arrows in lower right panels). (C) Quantitation of cerebral hemorrhage phenotypes in embryos injected with single translation blocking (ATG) MOs, splice blocking MOs, or both MOs injected in combination. Numbers of embryos analyzed for each MO are indicated. Translation blocking itgb8 versus itgb8/nrp1a, P=0.0003; translation blocking nrp1a versus nrp1a/itgb8, P=0.002; splice blocking itgb8 versus itgb8/nrp1a, P=0.004; splice blocking nrp1a versus nrp1a/itgb8, P=0.04.