Broad screening test for sphingolipid-storage diseases

Background Lipid-storage diseases are collectively important because they c ause substantial morbidity and mortality, and because they may present as d ementia, major psychiatric illness, developmental delay, or cerebral palsy. At present, no single assay can be used as an initial general screen for l ipid-storage diseases. Methods We used a fluorescent analogue of lactosylceramide, called N-{5-(5, 7-dimethylborondipyrromethenedifluoride)-1-pentanoyl}-D-lactosylsphingosine (BODIPY-LacCer), the emission of which changes from green to red wavelengt hs with increasing concentrations in membranes, to examine the intracellula r distribution of the lipid within living cells. Findings During a brief pulse-chase experiment, the fluorescent lipid accum ulated in the lysosomes of fibroblasts from patients with Fabry's disease, GM(1) gangliosidosis, GM(2) gangliosidosis (Tay-Sachs and Sandhoff forms), metachromatic leucodystrophy, mucolipidosis type IV, Niemann-Pick disease ( types A, B, and C), and sphingolipid-activator-protein-precursor (prosaposi n) deficiency. In control cells, the lipid was mainly confined to the Golgi complex. In a masked study, replicate samples of 25 of 26 unique cell line s representing ten different lipid-storage diseases, and 18 of 20 unique ce ll lines representing controls were correctly identified; the sensitivity w as 96.2% (95% CI 80.4-99.9) and the specificity 90.0% (68.3-98.8). Interpretation This method may be useful as an initial general screen for l ipid-storage diseases, and, with modification, could be used for large-scal e automated screening of drugs to abrogate lysosomal storage in various lip idoses. The unexpected accumulation of BODIPY-LacCer in several biochemical ly distinct diseases raises important questions about common mechanisms of cellular dysfunction in these disorders.