Hirschsprung disease (HSCR) is a congenital disorder characterised by intestinal 
obstruction due to an absence of intramural ganglia along variable lengths of 
the intestine. RET is the major gene involved in HSCR. Mutations in the GDNF 
gene, and encoding one of the RET ligands, either alone or in combination with 
RET mutations, can also cause HSCR, as can mutations in four other genes (EDN3, 
EDNRB, ECE1, and SOX10). The rare mutations in the latter four genes, however, 
are more or less restricted to HSCR associated with specific phenotypes. We have 
developed a novel comprehensive mutation detection system to analyse all but 
three amplicons of the RET and GDNF genes, based on denaturing gradient gel 
electrophoresis. We make use of two urea-formamide gradients on top of each 
other, allowing mutation detection over a broad range of melting temperatures. 
For the three remaining (GC-rich) PCR fragments we use a combination of DGGE and 
constant denaturing gel electrophoresis (CDGE). These two dual gel systems 
substantially facilitate mutation scanning of RET and GDNF, and may also serve 
as a model to develop mutation detection systems for other disease genes. In a 
screening of 95 HSCR patients, RET mutations were found in nine out of 17 
familial cases (53%), all containing long segment HSCR. In 11 of 78 sporadic 
cases (14%), none had long segment HSCR. Only one GDNF mutation was found, in a 
sporadic case.