G M1 -gangliosidosis: Chromosome 3 assignment of the β -galactosidase-A gene ( β GAL A )

Abstract

The structural gene (βGAL A ) coding for lysosomal β-galactosidase- A (EC 3.2.1.23) has been assigned to human chromosome 3 using man-mouse somatic cell hybrids. Human β-galactosidase-A was identified in cell hybrids with a species-specific antiserum to human liver β-galactosidase-A. The antiserum precipitates β-galactosidase-A from human tissues, cultured cells, and cell hybrids, and recognizes cross-reacting material from a patient with G M1 gangliosidosis. We have analyzed 90 primary man-mouse hybrids derived from 12 separate fusion experiments utilizing cells from 9 individuals. Enzyme segregation analysis excluded all chromosomes for βGAL A assignment except chromosome 3. Concordant segregation of chromosomes and enzymes in 16 cell hybrids demonstrated assignment of βGAL A to chromosome 3; all other chromosomes were excluded. The evidence suggests that G M1 gangliosidosis is a consequence of mutation at this βGAL A locus on chromosome 3.