A human model for multigenic inheritance: phenotypic expression in Hirschsprung disease requires both the RET gene and a new 9 q31 locus. - Bolk,S.; Pelet,A.; Hofstra,R.WM.; Angrist,M.; Salomon,R.; Croaker,D.; Buys,C.HCM.; Lyonnet,S.; Chakravarti,A. (Proc Natl Acad Sci USA, 2000)