GM1-gangliosidosis: chromosome 3 assignment of the beta-galactosidase-A gene (beta GALA)

The structural gene (beta GALA) coding for lysosomal beta-galactosidase-A (EC 3.2.1.23) has been assigned to human chromosome 3 using man--mouse somatic cell hybrids. Human beta-galactosidase-A was identified in cell hybrids with a species-specific antiserum to human liver beta-galactosidase-A. The antiserum precipitates beta-galactosidase-A from human tissues, cultured cells, and cell hybrids, and recognizes cross-reacting material from a patient with GM1 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 beta GALA assignment except chromosome 3. Concordant segregation of chromosomes and enzymes in 16 cell hybrids demonstrated assignment of beta GALA to chromosome 3; all other chromosomes were excluded. The evidence suggests that GM1 gangliosidosis is a consequence of mutation at this beta GALA locus on chromosome 3.