title: Notch4 reveals a novel mechanism regulating Notch signal transduction.
abstract: Notch4 is a divergent member of the Notch family of receptors that is primarily expressed in the vasculature. Its expression implies an important role for Notch4 in the vasculature; however, mice homozygous for the Notch4(d1) knockout allele are viable. Since little is known about the role of Notch4 in the vasculature and how it functions, we further investigated Notch4 in mice and in cultured cells. We found that the Notch4(d1) allele is not null as it expresses a truncated transcript encoding most of the NOTCH4 extracellular domain. In cultured cells, NOTCH4 did not signal in response to ligand. Moreover, NOTCH4 inhibited signalling from the NOTCH1 receptor. This is the first report of cis-inhibition of signalling by another Notch receptor. The NOTCH4 extracellular domain also inhibits NOTCH1 signalling when expressed in cis, raising the possibility that reported Notch4 phenotypes may not be due to loss of NOTCH4 function. To better address the role of NOTCH4 in vivo, we generated a Notch4 null mouse in which the entire coding region was deleted. Notch4 null mice exhibited slightly delayed vessel growth in the retina, consistent with our novel finding that NOTCH4 protein is expressed in the newly formed vasculature. These findings indicate a role of NOTCH4 in fine-tuning the forming vascular plexus.
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia. Electronic address: a.james@victorchang.edu.au.
authors.forename: A C
authors.initials: AC
authors.lastname: James
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia; School of Biotechnology and Biomolecular Sciences, Faculty of Science, UNSW, Sydney, Australia. Electronic address: j.szot@victorchang.edu.au.
authors.forename: J O
authors.initials: JO
authors.lastname: Szot
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia. Electronic address: k.iyer@victorchang.edu.au.
authors.forename: K
authors.initials: K
authors.lastname: Iyer
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia. Electronic address: j.major@victorchang.edu.aua.
authors.forename: J A
authors.initials: JA
authors.lastname: Major
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia. Electronic address: sharonchapman2201@gmail.com.
authors.forename: S E
authors.initials: SE
authors.lastname: Pursglove
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW, Sydney, Australia. Electronic address: g.chapman@victorchang.edu.au.
authors.forename: G
authors.initials: G
authors.lastname: Chapman
authors.affiliation: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Sydney, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW, Sydney, Australia; School of Biotechnology and Biomolecular Sciences, Faculty of Science, UNSW, Sydney, Australia. Electronic address: s.dunwoodie@victorchang.edu.au.
authors.forename: S L
authors.initials: SL
authors.lastname: Dunwoodie
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002135:Calcium-Binding Proteins; D002460:Cell Line; D004622:Embryo, Mammalian; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D041681:NIH 3T3 Cells; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D000074562:Receptor, Notch4; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C519665:DLL4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051881:Receptor, Notch1; D000074562:Receptor, Notch4; D051880:Receptors, Notch; D011993:Recombinant Fusion Proteins; C073572:Notch4 protein, mouse; D049452:Green Fluorescent Proteins
keywords: Coculture; Notch4; Retinal angiogenesis; cis-Inhibition