SH2 domain protein E and ABL signaling regulate blood vessel size.

Blood vessels in different vascular beds vary in size, which is essential for their function and fluid flow along the vascular network. Molecular mechanisms involved in the formation of a vascular lumen of appropriate size, or tubulogenesis, are still only partially understood. Src homology 2 domain containing E (She) protein was previously identified in a screen for proteins that interact with Abelson (Abl)-kinase. However, its biological role has remained unknown. Here we demonstrate that She and Abl signaling regulate vessel size in zebrafish embryos and human endothelial cell culture. Zebrafish she mutants displayed increased endothelial cell number and enlarged lumen size of the dorsal aorta (DA) and defects in blood flow, eventually leading to the DA collapse. Vascular endothelial specific overexpression of she resulted in a reduced diameter of the DA, which correlated with the reduced arterial cell number and lower endothelial cell proliferation. Chemical inhibition of Abl signaling in zebrafish embryos caused a similar reduction in the DA diameter and alleviated the she mutant phenotype, suggesting that She acts as a negative regulator of Abl signaling. Enlargement of the DA size in she mutants correlated with an increased endothelial expression of claudin 5a (cldn5a), which encodes a protein enriched in tight junctions. Inhibition of cldn5a expression partially rescued the enlarged DA in she mutants, suggesting that She regulates DA size, in part, by promoting cldn5a expression. SHE knockdown in human endothelial umbilical vein cells resulted in a similar increase in the diameter of vascular tubes, and also increased phosphorylation of a known ABL downstream effector CRKL. These results argue that SHE functions as an evolutionarily conserved inhibitor of ABL signaling and regulates vessel and lumen size during vascular tubulogenesis

Expression of <i>abl1</i> and <i>abl2</i> in different cell types during zebrafish embryogenesis based on single-cell RNA seq expression atlas.

Data were generated by Daniocell atlas https://daniocell.nichd.nih.gov/ [31]. (TIF)</p

Hybridization chain reaction (HCR) analysis of <i>cldn5b</i> mRNA expression at 24 hpf.

(A,B) cldn5b (purple) and kdrl:GFP fluorescence in the trunk region of she mutant and wild-type sibling embryos. DA, dorsal aorta; PCV, posterior cardinal vein. cldn5b fluorescence is shown in A’,B’. (C) Quantification of cldn5b fluorescence in the DA. p = 0.17, Student’s t-test. Error bars show SEM. Data show combined results from two independent experiments. (TIF)</p

Blood flow in the tail region of wild-type zebrafish embryos.

Wild-type siblings obtained from an incross of sheci26 heterozygous adults in kdrl:GFP; gata1:dsRed background were imaged at 4 dpf using confocal microscopy. (MP4)</p

Numerical original data used for graphs and summary statistics.

Tab numbers in the Excel table match to the figure numbers of corresponding graphs. (XLSX)</p

Blood flow does not affect <i>she</i> expression or <i>she</i> mutant phenotype.

(A,B) In situ hybridization analysis for she expression at 28 hpf in tnnt2 MO-injected embryos and uninjected controls. Trunk region is shown, anterior is to the left. Numbers in the lower right indicate embryos that showed normal expression pattern out of the total number of embryos in 3 replicate experiments. (C-H) DA size analysis at 28 hpf in wt (she+/+) and she-/- sibling embryos, injected with tnnt2 MO, compared to uninjected controls. Embryos were obtained from cross of she+/- parents in kdrl:GFP background and subsequently genotyped. Note that DA diameter is greatly reduced in tnnt2 MO-injected embryos compared to wild-type uninjected embryos, and increased in she mutants, injected with tnnt2 MO compared to wild-type embryos injected with tnnt2 MO. Data are combined from 3 replicate experiments, shown in different color. Mean±SD is shown. The number of embryos analyzed is shown at the bottom of each bar. The same wt+tnnt2 MO embryos were used for comparisons in (G) and (H). *p (TIF)</p

Inhibitors of Abl signaling reduce DA diameter in wild-type and <i>she</i> mutant embryos.

(A-E) Dorsal aorta diameter at 28 hpf is reduced in kdrl:GFP embryos treated with 5 μM Dasatinib or 1 μM GNF-7 compared to controls treated with 0.1% DMSO. (F-H) Embryos treated with 5 μM Dasatinib (F-H, left) or 1 μM GNF-7 (H, right) exhibit narrower DA at 4 dpf compared to controls treated with 1% DMSO (GNF-7) or 2% DMSO (Dasatinib treatments). (I-K) The number of cells in the DA is reduced in embryos at 28 hpf treated with 1 μM GNF-7 compared to control embryos treated with 0.1% DMSO. (L-O) GNF-7 treatment reverses DA enlargement in she mutant embryos. she+/-; kdrl:GFP adults were crossed to obtain she mutant embryos. Embryos were treated starting at 6 hpf with either 0.5 μM GNF-7 or 0.1% DMSO. Embryos were imaged at approximately 55 hpf and subsequently genotyped. DA measurements were performed blinded. Mid-trunk region is shown, anterior is to the left. Note the slightly wider DA (red line) in she-/- mutant embryos compared to wild-type (she+/+) siblings. DA is reduced in both wild-type and she mutant embryos treated with GNF-7. (P) Quantification of DA diameter in wild-type or she mutant embryos treated with GNF-7 or DMSO. In all graphs mean±SD is shown. Data points (shown in different colors) are combined from 2 (left graph C,H,K) or 3 (right graph C,P) independent experiments. Total number of embryos analyzed is shown at the bottom of each bar. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, NS–not significant, Student’s t-test (C,H,K), or one-way ANOVA test, followed by multiple comparisons Fisher’s LSD (P).</p

Diagrams and sequence chromatograms of <i>she</i>^<i>ci26</i> and ^<i>ci30</i> mutations.

(A) sheci26 mutants have a 7 bp deletion. Alignment of wild-type and sheci26 mutant sequences is shown starting with the first coding ATG. (B) Genomic DNA sequence chromatogram of sheci30 mutants. (C) sheci30 mutants carry a 575 bp deletion and 24 bp insertion present between exons 3 and 4 within she gene. (TIF)</p

CRISPR/ Cas9 knockdown of <i>abl1</i> and <i>abl2</i> function results in reduced DA size.

(A) A diagram illustrating the targeting sites of sgRNAs against abl1 and abl2 genes. Each gRNA was more than 90% effective based on DNA sequencing analysis. (B-D) Analysis of DA size in kdrl:GFP embryos at 28 hpf. Note the reduced DA diameter in embryos injected with abl1 and 2 gRNA mixture. Data from two replicate experiments are shown in different colors. Mean±SD is shown. **p (TIF)</p

A proposed model for SHE and ABL signaling during vascular tubulogenesis.

Activated ABL promotes enlarged vascular lumen through a downstream effector P-CRKL which increases endothelial cell proliferation and increases Cldn5 expression, thus affecting tight junctions and cell adhesion. Activated ABL phosphorylates SHE, which then interacts with ABL to dampen its activity resulting in the lumen of appropriate size.</p