Gaucher disease: genetic heterogeneity within and among the subtypes detected by immunoblotting

Abstract

The genetic heterogeneity of Gaucher disease subtypes and variants was investigated by immunoblotting of fibroblast extracts. For these studies polyclonal and monoclonal antibodies were raised to acid beta-glucosidase preparations containing a single N-terminal amino acid sequence that was colinear with that encoded by the beta-Glc cDNAs. Three forms (Mr approximately equal to 67,000, 64,000-61,000, and 58,000) of cross-reacting immunologic material (CRIM) were observed in control individuals. Decreased amounts of the same CRIM forms were detected in most type 1 Gaucher disease patients, but single CRIM forms of variable molecular weight were observed in several non-Jewish type 1 variants. One or two CRIM forms of variable molecular weight were found in neuronopathic (type 2 and type 3) patients. The amount of CRIM was severely decreased in the majority of the type 2 and type 3 patients; one American black type 2 patient was CRIM negative. With this one exception, one CRIM form was detected in the cell-free culture media from all normal or Gaucher disease fibroblasts that had an Mr approximately 2,000 greater than the highest respective intracellular molecular-weight form. All intra- or extracellular CRIM forms were reduced to a single form after deglycosylation with N-Glycanase. In addition, the radioactivity from [3H]Br-conduritol B epoxide, a specific covalent inhibitor of beta-Glc, localized to the CRIM forms of beta-Glc on immunoblots. These results indicate that all subtypes and variants of Gaucher disease result from mutations that alter the stability and/or processing of beta-Glc. Furthermore, the heterogeneity of the CRIM patterns within and among the variants of Gaucher disease cause the diagnostic usefulness of immunoblotting to be restricted to those families in which the phenotype has been well established.