MOLECULAR-CLONING, STRUCTURAL ORGANIZATION, SEQUENCE, CHROMOSOMAL ASSIGNMENT, AND EXPRESSION OF THE MOUSE ALPHA-N-ACETYLGALACTOSAMINIDASE GENE

Alpha-N-acetylgalactosaminidase (2-acetamido-2-deoxy-alpha-D-galactosi de acetamidodeoxy-galactohydrolase, NAGA; EC 3.2.1.49) deficiency is a recently recognized autosomal recessive lysosomal disease. As a prere quisite for the generation of an animal model, the mouse NAGA gene was cloned and characterized. The NAGA gene was assigned to mouse chromos ome 15 band E3, syntenic to the region encompassing the human gene, an d NAGA-deficient mutant human cells transfected with the cosmid clone containing the mouse NAGA gene expressed NAGA activity. Comparison of the mouse NAGA nucleotide sequence with the human NAGA sequence predic ted that the mouse NAGA gene contains an open reading frame of 1245 bp , comprising nine coding exons and spanning a genomic region of 8258 b p, and a 3' untranslated region of 0.5 kb. The 5' untranslated region was determined in primer extension studies to be 235 bp in length. Nuc leotide identity between the human and mouse NAGA exons ranged from 67 .4 to 89.5%, with better matches for exons 1-7 than for 8 and 9. The o verall amino acid identity between the mouse and human deduced NAGA po lypeptides was 82.0%, between those of mouse and chicken 72.9%. Homolo gy was found to only one other mouse gene, i.e. the a-galactosidase A (GALA; EC 3.2.1.22) gene. The amino acid identity ranged from 51.6 to 62.1% in the polypeptide regions corresponding to NAGA exons 2-7 and G ALA exons 1-6, but little, if any, in the remainder. These analyses ga ve emphasis to the strong conservation of the NAGA gene and its origin from an ancestor common with the GALA gene, with NAGA exons 8 and 9 a nd GALA exon 7 being the most divergent regions in the evolution of th e two genes. (C) 1998 Elsevier Science B.V. All rights reserved.