Perturbation of hoxb5 signaling in vagal neural crests down-regulates ret leading to intestinal hypoganglionosis in mice.
OBJECTIVE
The enteric nervous system (ENS) controls intestinal peristalsis, and defective development of this system results in hypo/aganglionosis, as seen in Hirschsprung's disease. In the embryo, vagal neural crest cells (NCC) migrate and colonize the intestine rostrocaudally then differentiate into the ganglia of the ENS. Vagal NCC express the homeobox gene Hoxb5, a transcriptional activator, in human and mouse, so we used transgenic mice to investigate the function of Hoxb5 and the receptor tyrosine kinase gene Ret, which is affected in many patients with Hirschsprung's disease, in ENS development.


METHODS
We perturbed the Hoxb5 pathway by expressing a chimeric protein enb5, in which the transcription activation domain of Hoxb5 was replaced with the repressor domain of the Drosophila engrailed protein (en), in vagal NCC. This enb5 transcriptional repressor competes with wild-type Hoxb5 for binding to target genes, exerting a dominant negative effect.


RESULTS
We observed that 30.6% +/- 2.3% of NCC expressed enb5 and that these enb5-expressing NCC failed to migrate to the distal intestine. A 34%-37% reduction of ganglia (hypoganglionosis) and slow peristalsis and, occasionally, absence of ganglia and intestinal obstruction were observed in enb5-expressing mice. Ret expression was markedly reduced or absent in NCC and ganglia, and enb5 blocked Hoxb5 induction of Ret in neuroblastoma cells.


CONCLUSIONS
Our data indicate that Ret is a downstream target of Hoxb5 whose perturbation causes Ret haploinsufficiency, impaired NCC migration, and hypo/aganglionosis, suggesting that Hoxb5 may contribute to the etiology of Hirschsprung's disease.
Lui
Vincent C H
VC
Department of Surgery, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China. vchlui@hkucc.hku.hk
Cheng
William W C
WW
Leon
Thomas Y Y
TY
Lau
Danny K C
DK
Garcia-Barcelo
Maria-Mercedes
MM
Garcia-Bareclo
Maria-Mercedes
MM
Miao
Xiao P
XP
Kam
Mandy K M
MK
So
Man T
MT
Chen
Yan
Y
Wall
Nancy A
NA
Sham
Mai H
MH
Tam
Paul K H
PK
D000818:Animals; D004247:DNA / Q000235:genetics*; D004195:Disease Models, Animal; D015536:Down-Regulation; D017615:Enteric Nervous System / Q000002:abnormalities / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006627:Hirschsprung Disease / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics*; D007422:Intestines / Q000294:innervation* / Q000503:physiopathology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009432:Neural Crest / Q000002:abnormalities / Q000196:embryology / Q000378:metabolism*; D010528:Peristalsis / Q000502:physiology; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014630:Vagus Nerve / Q000002:abnormalities / Q000196:embryology / Q000378:metabolism*
D018398:Homeodomain Proteins; C053925:Hoxb5 protein, mouse; D004247:DNA; D051096:Proto-Oncogene Proteins c-ret