Coordinated expression of 3' hox genes during murine embryonal gut development: an enteric Hox code.
OBJECTIVE
Hox genes are highly conserved developmental control genes that may be organized and expressed in the form of a code required for correct morphogenesis. Little is known about their control of the embryonal gut. However, Hox paralogues 4 and 5, which are expressed at the sites of origin of vagal neural crest cells and splanchnic mesoderm, are likely to be important. We have studied the expression domains of these genes in the gut both spatially and temporally.


METHODS
CD1 mice embryos of embryonic days E8.5-E17.5 were studied. The spatial and temporal expression patterns of messenger RNA of Hoxa4, b4, c4, d4, a5, c5, and b5 homeoprotein were determined by in situ hybridization and immunohistochemistry in whole embryos, whole gastrointestinal tracts, and vibratome sections.


RESULTS
There were different spatial, temporal, and combinatorial expression patterns in different morphological regions: foregut, prececal gut, cecum, and postcecal gut. Two dynamic gradients, rostral and caudal, were coordinated with nested expression domains along the gut primordium. Region-specific domains were present in the stomach and cecum.


CONCLUSIONS
The expression patterns of genes in paralogous groups 4 and 5 suggest that they are organized to form a specific enteric Hox code required for correct enteric development.
Pitera
J E
JE
Gastroenterology Unit, Institute of Child Health, University College London, London, England. J.Pitera@ich.ucl.ac.uk
Smith
V V
VV
Thorogood
P
P
Milla
P J
PJ
D000818:Animals; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D005314:Embryonic and Fetal Development; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000196:embryology*; D051379:Mice; D009132:Muscles / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010750:Phosphoproteins; D011247:Pregnancy; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; C489213:HOXA5 protein, human; C489126:HOXB5 protein, human; C118987:HOXC5 protein, human; D018398:Homeodomain Proteins; C484111:Hoxa4 protein, mouse; C059637:Hoxa5 protein, mouse; C513262:Hoxb4 protein, mouse; C053925:Hoxb5 protein, mouse; C490904:Hoxc4 protein, mouse; C484113:Hoxd3 protein, mouse; C489520:Hoxd4 protein, mouse; D010750:Phosphoproteins; D014157:Transcription Factors