The WS4 mouse arose spontaneously at the Saitama Research Center, Saitama, Japan. The mutation was shown to be allelic to Ednrbs-l by a non-complementation test. Analysis of a cDNA derived from mutant mice revealed that a deletion of nucleotides encoding 106 amino acids corresponding to exons 2 and 3 had occurred. (J:76584, J:115266)