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

Abstract Alpha- N- acetylgalactosaminidase(2-acetamido-2-deoxy- α - d - galactosideacetamidodeoxy-galactohydrolase, NAGA; EC 3.2.1.49) deficiency is a recently recognized autosomal recessive lysosomal disease. As a prerequisite for the generation of an animal model, the mouse NAGA gene was cloned and characterized. The NAGA gene was assigned to mouse chromosome 15band E3, syntenic to the region encompassing the human gene, and NAGA-deficient mutant human cells transfected with the cosmidclone containing the NAGA gene expressed NAGA activity. Comparison of the mouse NAGA nucleotide sequence with the human NAGA sequence predicted that the NAGA gene contains an open reading frame of 1245 bp, comprising nine exonsand spanning a genomic region of 8258 bp, and a 3′ untranslated regionof 0.5 kb. The 5′ untranslated regionwas determined in primer extensionstudies to be 235 bp in length. Nucleotide identity between the human and mouse NAGA exonsranged from 67.4 to 89.5%, with better matches for exons1–7 than for 8 and 9. The overall amino acid identity between the mouse and human deduced NAGA polypeptides was 82.0%, between those of mouse and chicken 72.9%. Homology was found to only one other mouse gene, i.e. the α-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 exons2–7 and GALA exons1–6, but little, if any, in the remainder. These analyses gave emphasis to the strong conservation of the NAGA gene and its origin from an ancestor common with the GALA gene, with NAGA exons8 and 9 and GALA exon7 being the most divergent regions in the evolution of the two genes.