engleski

Arylsulfatase A pseudodeficiency mutations in multiple sclerosis

Arylsulfatase A (ASA, EC 3.1.6.1) is a lysosomal enzyme involved in catabolism of sulfatides, major lipid constituents of oligodendrocyte membranes which contribute to maintenance of myelin sheath integrity. Low ASA activities have been reported in healthy individuals and several neuropsychiatric disorders, due to condition termed ASA pseudodeficiency (ASA-PD). Two mutations in the ASA gene, responsible for the majority of ASA-PD alleles, are designated as N350S and 1524+95 A-G mutation. Frequency of these two mutations in the Croatian population has been previously estimated at 6.8 % for N350S and 2.8 % for 1524+95 A-G mutation. A possible contribution of ASA-PD mutations to pathogenesis of multiple sclerosis has been discussed and explained by death of oligodendrocyte subpopulations caused by sulfatide accumulation, leading to exposure of myelin antigens and immune reaction. The aim of this study was to estimate a frequency of N350S and 1524+95 A-G mutations in patients with multiple sclerosis (MS) in comparison with healthy individuals in a control group, using PCR-RFLP method. Genomic DNA was extracted from leukocytes, and two fragments of ASA gene amplified using specific primers and treated with adequate restriction enzymes. In addition, the ASA activity was measured in leukocyte homogenates by spectrophotometric method using p-nitrocatechol sulfate as chromogenic substrate. Genotyping for ASA-PD mutations detected 8 of 41 MS patients as heterozygous carriers for 1524+95 A-G mutation, and 11 of 42 MS patients as heterozygotes for N350S mutation. The frequencies of mutated alleles were higher in MS patients: 9.7 % in MS vs. 2.8 % in controls for the 1524+95 A-G, and 13.1 % in MS vs. 6.8 % in controls for N350S mutation (control frequencies according to previous study). Determination of ASA activity showed slightly lower values in MS patients (99 ± ; 40 nmol h-1 mg-1 ; N=45) in comparison with controls (118 ± ; 30 nmol h-1 mg-1 ; N=29). Measured ASA activities were in the normal range in majority of MS patients (60 – 300 nmol h-1 mg-1) ; however a distribution of obtained results clearly showed a trend toward lower values in MS patients. Presented data indicate that further study on a larger sample is necessary in order to estimate a possible association of different mutations in the ASA gene and consequent alterations of ASA activity with pathogenesis of multiple sclerosis.

pseudodeficiency mutations; arylsulfatase A; multiple sclerosis

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