METHYLAMINE ACCUMULATION IN CULTURED-CELLS AS A MEASURE OF THE AQUEOUS STORAGE COMPARTMENT IN THE LABORATORY DIAGNOSIS OF GENETIC LYSOSOMALDISEASES

Intracellular accumulation of the lysosomotropic compound [C-14]methyl amine was used to estimate the size of the lysosomal compartment in fi broblasts cultured from patients with a variety of lysosomal storage d iseases. In previous work from our laboratory, it was shown that methy lamine accumulation was significantly increased in diseases with infan tile or juvenile onset and storage of predominantly water-soluble mate rial such as in the mucopolysaccharidoses, mucolipidoses, and oligosac charidoses. In the present study, methylamine incorporation was abnorm ally increased in cells from patients with glycogenosis type II and wi th Niemann-Pick type C disease, whereas it was normal in other sphingo lipidoses and in the late-infantile and juvenile forms of neuronal cer oid lipofuscinoses. The methylamine test was also checked regarding it s potential use for prenatal diagnostic testing, In model systems with cultured amniotic or chorionic villus cells, lysosomal storage was ex perimentally induced by the cathepsin inhibitor leupeptin and was read ily detected when compared to untreated controls. Cultured amniotic ce lls from a fetus with mucopolysaccharidosis II were found to incorpora te significantly higher amounts of [C-14]methylamine than the normal c ontrols. The results indicate that the methylamine accumulation method is an additional tool in the diagnosis and prenatal diagnosis of lyso somal diseases with abnormal storage of water-soluble material. (C) 19 96 Wiley-Liss, Inc.