α-mannosidosis in the guinea pig:: cloning of the lysosomal α-mannosidase cDNA and identification of a missense mutation causing α-mannosidosis

alpha-Mannosidosis is a lysosomal storage disorder caused by deficient activity of the lysosomal alpha-mannosidase. We report here the sequencing and expression of the lysosomal alpha-mannosidase cDNA from normal and alpha-mannosidosis guinea pigs. The amino acid sequence of the guinea pig enzyme displayed 82-85% identity to the lysosomal alpha-mannosidase in other mammals. The cDNA of the alpha-mannosidosis guinea pig contained a missense mutation, 679C > T, leading to substitution of arginine by tryptophan at amino acid position 227 (R227W). The R227W allele segregated with the alpha-mannosidosis genotype in the guinea pig colony and introduction of R227W into the wild-type sequence eliminated the production of recombinant a-mannosidase activity in heterologous expression studies. Furthermore, the guinea pig mutation has been found in human patients. Our results strongly indicate that the 679C > T mutation causes alpha-mannosidosis and suggest that the guinea pig will be an excellent model for investigation of pathogenesis and evaluation of therapeutic strategies for human alpha-mannosidosis. (C) 2001 Elsevier Science B.V. All rights reserved.