The mec-4 gene is a member of a family of Caenorhabditis elegans genes that can mutate to induce neuronal degeneration 
 Three dominant mutations of mec-4, a gene needed for mechanosensation, cause the touch-receptor neurons of Caenorhabditis elegans to degenerate.
 With deg-1, another C.
 elegans gene that can mutate to induce neuronal degeneration and that is similar in sequence, mec-4 defines a new gene family.
 Cross-hybridizing sequences are detectable in other species, raising the possibility that degenerative conditions in other organisms may be caused by mutations in similar genes.
 All three dominant mec-4 mutations affect the same amino acid.
 Effects of amino-acid substitutions at this position suggest that steric hindrance may induce the degenerative state.
