BACKGROUND: Hirschsprung's disease (HSCR) is one the most common congenital 
intestinal disease. It leads to aganglionic megacolon in the early childhood. 
Several susceptibility genes have been identified : RET protooncogene and its 
ligand, glial cell derived neutrophic factor (GDNF), Sox 10, Endothelin-3 (EDN3) 
and its receptor B (EDNRB). EDNRB mutations are found in 5% of familial or 
sporadic HSCR. Only few EDNRB mutations found in HSCR have been explored and 
some of them seem to be non fonctional variants.
MATERIALS AND METHODS: The properties of three mutant human endothelin B 
receptor (hETB) (G57S, R319W and P383L) in isolated HSCR were analyzed. Stable 
recombinant cells expressing the three mutants and the wild-type (WT) were 
established. The hETB receptors were characterized for 125I ET-1 binding, ET-1 
induced signaling: calcium transient, AP-1 transcriptional factor activation and 
cAMP accumulation.
RESULTS: Immunofluorescence experiments showed normal cellular distributions of 
the mutant G57S, R319W and WT hETB receptors. In contrast, the P383L hETB mutant 
receptor was concentrated near the nucleus and essentially no ET-1 binding was 
detected. The two other mutants (G57S and R319W) bound ET-1 normally, induced 
calcium transients and activated the AP-1 pathway in the same way as wild type, 
but did not inhibit adenylate cyclase. The G57S hETB mutant even stimulated cAMP 
accumulation which was blocked by pertussis toxin.
CONCLUSION: The absence of the P383L mutant receptor from the membrane clearly 
indicates that this mutation could be involved in HSCR. The G57S and R319W 
mutant receptors, despite their normal coupling to Gaq, have a defect in the 
Galphai signaling pathway and the G57S mutation couples to Galphas. These 
observations allow us to hypothesize that cAMP signaling might be involved in 
the differenciation of neural cells in the bowel.