The synaptic proteins β-neurexin and neuroligin synergize with extracellular matrix-binding vascular endothelial growth factor a during zebrafish vascular development.

Objective: The goal of this study was to determine the in vivo functions of the synaptic proteins neurexins and neuroligins in embryonic vascular system development using zebrafish as animal model.
Methods and Results: In the present study, we show that the knockdown of the α-form of neurexin 1a induces balance defects and reduced locomotory activity, whereas β-neurexin 1a and neuroligin 1 morphants present defects in sprouting angiogenesis and vascular remodeling, in particular in the caudal plexus and subintestinal vessels. Coinjection of low doses of morpholinos for β-neurexin 1a and neuroligin 1 together or in combination with morpholinos targeting the -heparin--binding isoforms of vascular endothelial growth factor A (encoded by the VEGFAb gene) recapitulates the observed abnormalities, suggesting synergistic activity of these molecules. Similar coinjection experiments with morpholinos, targeting the enzyme heparan sulfate 6-O-sulfotransferase 2, confirm the presence of a functional correlation between extracellular matrix maturation and β-neurexin 1a or neuroligin 1.
Conclusions: Our data represent the first in vivo evidence of the role of neurexin and neuroligin in embryonic blood vessel formation and provide insights into their mechanism of action.