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bioRxiv2022

Regulatory heterogeneity of Vegf- and Wnt7-dependent angiogenesis drives phenotypic diversity of brain vasculature

Fenestrated and blood-brain barrier (BBB)-forming endothelial cells constitute major brain capillaries, and this vascular heterogeneity is crucial for region-specific neural function and brain homeostasis. How these capillary types emerge in a brain region-specific manner and subsequently establish intrabrain vascular heterogeneity remains unclear. Here, we show a core angiogenic mechanism critical for fenestrated brain capillary development via a comparative analysis of the zebrafish choroid plexuses (CPs) and circumventricular organs (CVOs), demonstrating capillary-type-selective vascularization mechanisms. We found that zebrafish deficient for Gpr124, Reck, or Wnt7aa exhibit severely-impaired BBB angiogenesis without any apparent defect in fenestrated capillary formation in the CPs and CVOs. Conversely, simultaneous genetic loss of various Vegf combinations revealed remarkable heterogeneity of endothelial requirements for Vegfs-dependent angiogenesis within and across these organs, identifying unexpected interplay of Vegfc/d and Vegfa in fenestrated brain capillary formation. Expression analysis and paracrine activity-deficient vegfc mutant characterization suggest that endothelial cells and non-neuronal specialized cell types present in the CPs and CVOs are major sources of Vegfs responsible for regionally-restricted angiogenic interplay. Thus, local presentations and interplay of Vegfc/d and Vegfa control brain region-specific emergence of fenestrated capillaries, providing insight into fenestrated capillary formation in other organs and also how intra-organ vascular heterogeneity arises.

developmental biology↗

bioRxiv2021

Highly efficient synthetic CRISPR RNA/Cas9-based mutagenesis for cardiovascular phenotypic screening in F0 zebrafish

The zebrafish is a valuable vertebrate model to study cardiovascular formation and function due to the facile visualization and rapid development of the circulatory system in its externally growing embryos. Despite having distinct advantages, zebrafish have paralogs of many important genes, making reverse genetics approaches inefficient since generating animals bearing multiple gene mutations requires substantial efforts. Here, we present a simple and robust synthetic CRISPR RNA/Cas9-based mutagenesis approach for generating biallelic F0 zebrafish knockouts. Using a dual-guide synthetic CRISPR RNA/Cas9 ribonucleoprotein (dgRNP) system, we compared the efficiency of biallelic gene disruptions following the injections of one, two, and three dgRNPs per gene into the cytoplasm or yolk. We show that simultaneous cytoplasmic injections of three distinct dgRNPs per gene into one-cell stage embryos resulted in the most efficient and consistent biallelic gene disruptions. Importantly, this triple dgRNP approach enables efficient inactivation of cell autonomous and cell non-autonomous gene function, likely due to the low mosaicism of biallelic disruptions. In support of this finding, we provide evidence that the F0 animals generated by this method fully phenocopied the endothelial and peri-vascular defects observed in corresponding stable mutant homozygotes. Moreover, this approach faithfully recapitulated the trunk vessel phenotypes resulting from the genetic interaction between two vegfr2 zebrafish paralogs. Mechanistically, investigation of genome editing and mRNA decay indicates that the combined mutagenic actions of three dgRNPs per gene lead to an increased probability of frameshift mutations, enabling efficient biallelic gene disruptions. Therefore, our approach offers a highly robust genetic platform to quickly assess novel and redundant gene function in F0 zebrafish.

developmental biology↗