On some occasions, mutations of a gene cause different syndromes that may have 
similar phenotypes. For example, mutations of the MITF gene cause Waardenburg 
syndrome type 2 (Tassabehji et al, 1994; Nobukuni et al, 1996) as well as Tietz 
syndrome (Smith et al, 1997). On other occasions, mutations of different genes 
cause an identical syndrome. Molecular analyses of these genes may provide a 
good opportunity to not only understand such syndromes themselves but also the 
biologic aspects of cells relevant to these syndromes. By analyzing the genes 
for Waardenburg syndrome, we showed that PAX3, the gene responsible for 
Waardenburg syndrome type 1, regulates MITF, the gene responsible for 
Waardenburg syndrome type 2. Such epistatic relationships have been shown 
between other genes related to Waardenburg syndrome, and likely to construct a 
cascade. This paper proposes such a cascade, one that involves genes for PAX3, 
MITF, human MyoD, MYF5, c-MET, c-KIT, tyrosinase, TRP-1, human QNR-71, SOX10, 
EDNRB, and EDN3.