Angiomotin-like protein 1 controls endothelial polarity and junction stability during sprouting angiogenesis.
BACKGROUND
We have previously shown that angiomotin (Amot) is essential for endothelial cell migration during mouse embryogenesis. However, approximately 5% of Amot knockout mice survived without any detectable vascular defects. Angiomotin-like protein 1 (AmotL1) potentially compensates for the absence of Amot as it is 62% homologous to Amot and exhibits similar expression pattern in endothelial cells.


OBJECTIVE
Here, we report the identification of a novel isoform of AmotL1 that controls endothelial cell polarization and directional migration.


RESULTS
Small interfering RNA-mediated silencing of AmotL1 in mouse aortic endothelial cells caused a significant reduction in migration. In confluent mouse pancreatic islet endothelial cells (MS-1), AmotL1 colocalized with Amot to tight junctions. Small interfering RNA knockdown of both Amot and AmotL1 in MS-1 cells exhibited an additive effect on increasing paracellular permeability compared to that of knocking down either Amot or AmotL1, indicating both proteins were required for proper tight junction activity. Moreover, as visualized using high-resolution 2-photon microscopy, the morpholino-mediated knockdown of amotl1 during zebrafish embryogenesis resulted in vascular migratory defect of intersegmental vessels with strikingly decreased junction stability between the stalk cells and the aorta. However, the phenotype was quite distinct from that of amot knockdown which affected polarization of the tip cells of intersegmental vessels. Double knockdown resulted in an additive phenotype of depolarized tip cells with no or decreased connection of the stalk cells to the dorsal aorta.


CONCLUSIONS
These results cumulatively validate that Amot and AmotL1 have similar effects on endothelial migration and tight junction formation in vitro. However, in vivo Amot appears to control the polarity of vascular tip cells whereas AmotL1 mainly affects the stability of cell-cell junctions of the stalk cells.
Zheng
Yujuan
Y
Department of Oncology and Pathology, Cancer Centrum Karolinska, Karolinska Institutet, SE-17176 Stockholm, Sweden.
Vertuani
Simona
S
Nyström
Staffan
S
Audebert
Stéphane
S
Meijer
Inèz
I
Tegnebratt
Tetyana
T
Borg
Jean-Paul
JP
Uhlén
Per
P
Majumdar
Arindam
A
Holmgren
Lars
L
D000595:Amino Acid Sequence; D000091082:Angiomotins; D000091304:Angiopoietin-Like Protein 1; D000818:Animals; D030801:Animals, Genetically Modified; D002417:Cattle; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D018919:Neovascularization, Physiologic / Q000502:physiology*; D054731:PDZ Domains / Q000235:genetics; D020033:Protein Isoforms / Q000378:metabolism; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
C423985:AMOT protein, human; C510063:AMOTL1 protein, human; C511047:Amot protein, mouse; C543121:AmotL1 protein, zebrafish; C449807:Amotl1 protein, mouse; D000091082:Angiomotins; D000091304:Angiopoietin-Like Protein 1; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D020033:Protein Isoforms; D029961:Zebrafish Proteins; C543122:amot protein, zebrafish