VEGF-B-Neuropilin-1 signaling is spatiotemporally indispensable for vascular and neuronal development in zebrafish.
Physiological functions of vascular endothelial growth factor (VEGF)-B remain an enigma, and deletion of the Vegfb gene in mice lacks an overt phenotype. Here we show that knockdown of Vegfba, but not Vegfbb, in zebrafish embryos by specific morpholinos produced a lethal phenotype owing to vascular and neuronal defects in the brain. Vegfba morpholinos also markedly prevented development of hyaloid vasculatures in the retina, but had little effects on peripheral vascular development. Consistent with phenotypic defects, Vegfba, but not Vegfaa, mRNA was primarily expressed in the brain of developing zebrafish embryos. Interestingly, in situ detection of Neuropilin1 (Nrp1) mRNA showed an overlapping expression pattern with Vegfba, and knockdown of Nrp1 produced a nearly identically lethal phenotype as Vegfba knockdown. Furthermore, zebrafish VEGF-Ba protein directly bound to NRP1. Importantly, gain-of-function by exogenous delivery of mRNAs coding for NRP1-binding ligands VEGF-B or VEGF-A to the zebrafish embryos rescued the lethal phenotype by normalizing vascular development. Similarly, exposure of zebrafish embryos to hypoxia also rescued the Vegfba morpholino-induced vascular defects in the brain by increasing VEGF-A expression. Independent evidence of VEGF-A gain-of-function was provided by using a functionally defective Vhl-mutant zebrafish strain, which again rescued the Vegfba morpholino-induced vascular defects. These findings show that VEGF-B is spatiotemporally required for vascular development in zebrafish embryos and that NRP1, but not VEGFR1, mediates the essential signaling.
Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; Unit of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, 581 83 Linköping, Sweden; yihai.cao@ki.se lasse.jensen@liu.se.
Lasse D
http://orcid.org/0000-0003-2338-357X
LD
Jensen
Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden;
Masaki
M
Nakamura
Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden;
Lars
L
Bräutigam
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou 510060, People's Republic of China;
Xuri
X
Li
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou 510060, People's Republic of China;
Yizhi
Y
Liu
Department of Cardiovascular Sciences, University of Leicester and National Institute for Health Research Leicester, Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester LE3 9QP, United Kingdom.
Nilesh J
NJ
Samani
Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; Unit of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, 581 83 Linköping, Sweden; Department of Cardiovascular Sciences, University of Leicester and National Institute for Health Research Leicester, Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester LE3 9QP, United Kingdom yihai.cao@ki.se lasse.jensen@liu.se.
Yihai
Y
Cao
D000818:Animals; D001808:Blood Vessels / Q000196:embryology*; D055785:Gene Knockdown Techniques; D009474:Neurons / Q000166:cytology*; D039942:Neuropilin-1 / Q000378:metabolism*; D015398:Signal Transduction; D042561:Vascular Endothelial Growth Factor B / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology*
D042561:Vascular Endothelial Growth Factor B; D039942:Neuropilin-1
Neuropilin; VEGF-B; brain development; vasculature; zebrafish