Tbx1 regulates brain vascularization.
The transcription factor TBX1 is the major gene involved in 22q11.2 deletion syndrome (22q11.2DS). Using mouse models of these diseases, we have previously shown that TBX1 activates VEGFR3 in endothelial cells (EC), and that this interaction is critical for the development of the lymphatic vasculature. In this study, we show that TBX1 regulates brain angiogenesis. Using loss-of-function genetics and molecular approaches, we show that TBX1 regulates the VEGFR3 and DLL4 genes in brain ECs. In mice, loss of TBX1 causes global brain vascular defects, comprising brain vessel hyperplasia, enhanced angiogenic sprouting and vessel network disorganization. This phenotype is recapitulated in EC-specific Tbx1 conditional mutants and in an EC-only 3-dimensional cell culture system (matrigel), indicating that the brain vascular phenotype is cell autonomous. Furthermore, EC-specific conditional Tbx1 mutants have poorly perfused brain vessels and brain hypoxia, indicating that the expanded vascular network is functionally impaired. In EC-matrigel cultures, a Notch1 agonist is able to partially rescue microtubule hyperbranching induced by TBX1 knockdown. Thus, we have identified a novel transcriptional regulator of angiogenesis that exerts its effect in brain by negatively regulating angiogenesis through the DLL4/Notch1-VEGFR3 regulatory axis. Given the similarity of the phenotypic consequences of TBX1 mutation in humans and mice, this unexpected role of TBX1 in murine brain vascularization should stimulate clinicians to search for brain microvascular anomalies in 22q11.2DS patients and to evaluate whether some of the anatomical and functional brain anomalies in patients may have a microvascular origin.
Institute of Genetics and Biophysics 'ABT'.
Sara
S
Cioffi
Stefania
S
Martucciello
Filomena Gabriella
FG
Fulcoli
Marchesa
M
Bilio
Rosa
R
Ferrentino
Edoardo
E
Nusco
Elizabeth
E
Illingworth
D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D004062:DiGeorge Syndrome / Q000235:genetics* / Q000473:pathology*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009389:Neovascularization, Pathologic / Q000235:genetics; D010641:Phenotype; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*; D040321:Vascular Endothelial Growth Factor Receptor-3 / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D020825:T-Box Domain Proteins; C108625:TBX1 protein, human; C491573:Tbx1 protein, mouse; C064045:delta protein; C581309:FLT4 protein, human; D040321:Vascular Endothelial Growth Factor Receptor-3