Croatian Population Data for Arylsulfatase A Pseudodeficiency-Associated Mutations in Healthy Subjects, and in Patients with Alzheimer-Type Dementia and Down Syndrome

Abstract

Background Arylsulfatase A (ASA) is a lysosomal enzyme involved in catabolism of cerebroside sulfate, whose deficiency causes metachromatic leukodystrophy, a rare autosomal recessive disorder characterized by storage of cerebroside sulfate, mainly in the nervous system. Low ASA activities have also been reported in healthy individuals and several neuropsychiatric disorders due to the condition termed ASA pseudodeficiency. The aim of this study was to establish frequency of two mutations associated with ASA pseudodeficiency in healthy individuals in the Croatian population as well as in persons with Alzheimer-type dementia and Down syndrome. Methods Presence of N350S and 1524+95 A→G pseudodeficiency mutations was detected in genomic DNA extracted from leukocytes of healthy subjects ( n = 125) and of patients with Alzheimer-type dementia ( n = 18) and Down syndrome ( n = 21). Arylsulfatase A activity was measured in leukocyte homogenates by spectrophotometry (λ = 515 nm) using p-nitrocatechol sulfate as chromogenic substrate. Results Frequency of N350S mutation and mutation 1524+95 A→G was estimated at 6.8 and 2.8% for healthy controls, 11 and 5.5% for Alzheimer-type dementia, and 12 and 9.5% for Down syndrome, respectively. Arylsulfatase A activity was slightly but not significantly decreased in leukocytes derived from subjects with dementia and Down syndrome in comparison with age-matched control samples. Conclusions Frequency of two mutations associated with ASA pseudodeficiency in the Croatian population is slightly below the range reported for other populations. Additionally, despite the proposed role of arylsulfatase A pseudodeficiency as one of the predisposing factors for neuropsychiatric disorders, our preliminary results did not show significantly higher frequencies of either mutation in Alzheimer-type dementia or Down syndrome.