Biochemical and molecular analysis of Thai patients with gaucher disease

Gaucher disease (GD) is an autosomal recessive disorder caused by the deficiency of lysosomal [beta]-glucosidase, or glucocerebrosidase, an enzyme that participates in the degradation of glycosphingolipids. Deficiency of this enzyme results in the storage of glucocerebrosides in lysosomes of macrophage. Gaucher disease has three phenotypes based on the absence (type 1) or presence and severity (types 2 and 3) of primary CNS involvement. Although many clinical diagnoses of Thai patients with Gaucher disease have been reported, their biochemical and molecular characteristics were not included. We established a glucocerebrosidase activity assayed by fluorimetric method and studied 6 controls, 5 patients with GD and a carrier. We have found a remarkably decreased activity (< 5% of normal) of the glucocerebrosidase in all patients, whereas the mean glucocerebrosidase activity was 11.63+-4.97 nmol/mg protein/h in control group. Mutation analysis, performedby long-template PCR, PCR using specific primers, direct sequencing in all coding regions of the GBA gene and restriction enzyme digestion, showed that L444P is the most common mutant allele found in 4 patients (6 of 10 alleles). Three novel mutations were found including a missense mutation (Y363H), a termination codon mutation (X498A), and a frameshift mutation (IVS6(-1)G>C). mRNA of the IVS6(-1)G>C is expected to be unstable and degraded. In conclusion, we established an enzyme assay to diagnose GD. L444P allele is the most frequent mutation identified in Thai patients and 3 novel mutations were identified. These biochemical and molecular tests will facilitate definite diagnosis of GD and have implications on genetic counseling