Notch4 reveals a novel mechanism regulating Notch signal transduction

https://doi.org/10.1016/j.bbamcr.2014.03.015Get rights and content
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Highlights

  • The Notch4d1 allele encodes for most of the NOTCH4 extracellular domain.

  • NOTCH4 lacks the capacity to signal in cultured cells.

  • NOTCH4 inhibits signalling through the NOTCH1 receptor.

  • Notch4−/− mice exhibit altered retinal angiogenesis.

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 Notch4d1 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 Notch4d1 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.

Abbreviations

ANK
ankyrin repeat
DSL
Delta, Serrate and Lag-2
JAG1
Jagged1
DLL1
Delta-like 1
DLL4
Delta-like 4
E
embryonic day
EC
extracellular domain
EGF
epidermal growth factor
ER
endoplasmic reticulum
ES
embryonic stem
HD
heterodimerisation domain
IB4
Isolectin B4
ICD
Notch intracellular domain
NA
numerical aperture
LNR
Lin12-Notch repeat
MAEC
Mouse aortic endothelial cells
P
Postnatal day
PEST
proline, glutamate, serine, and tyrosine
RACE
Rapid Amplification of cDNA Ends
RAVE
Rapid Analysis of Vessel Elements
TAD
transcriptional activation domain
TGN
trans-Golgi network

Keywords

Notch4
Retinal angiogenesis
cis-Inhibition
Coculture

Cited by (0)

1

Joint authors.