G M1-gangliosidosis (Type II): Studies on a fibroblast cell strain

Abstract

A fibroblast cell strain was developed from the skin of a patient with the Type II form of G M1-gangliosidosis. β-Galactosidase activity at pH 5 with two synthetic substrates was about 3% of normal. Two abnormal gangliosides were identified: One, as expected, migrated like the G M1-ganglioside of brain; the other behaved like the G M2-ganglioside of brain. The composition and source of this G M2-like ganglioside is postulated. The major neutral glycolipid, tentatively identified as a trihexosylceramide, was present in greater amounts, and incorporated more radioactivity from 14C-galactose, than normal. A glycosaminoglycan fraction labeled with 14C-galactose and not precipitated by CPC was found in great excess. It's elution from a molecular sieve was very similar to that of a non-CPC-precipitable, undersulfated keratan-sulfate-like polysaccharide previously isolated from liver of a patient with Type I G M1-gangliosidosis. Spherical cytoplasmic inclusions stained metachromatically with toluidine blue after fixation in 30% acetic acid. Metachromasia was largely abolished after fixation in absolute methanol. It is probable that the accumulation of specific gangliosides and glycosaminoglycans in the mutant cell strain is related directly to its deficient pH 5 β-galactosidase activity. Limited studies on a cell strain derived from a patient with Type I G M1-gangliosidosis revealed no differences from the Type II strain with respect to the gangliosides stored or the frequency, intensity, and quality of cytoplasmic toluidine blue metachromasia.