A novel mutation which represents the fifth non-pathogenic polymorphism in the coding sequence of the arylsulfatase A gene

Novel mutations in the arylsulfatase A gene in eight Italian families with metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease caused by arylsulfatase A (ARSA) deficiency. We analysed the ARSA gene in eight unrelated Italian families with different clinical variants of MLD and identified three novel mutations: two Ser406Gly, (Glu329Ter) associated with late infantile MLD and one (Leu52Pro) with juvenile MLD. Only one family carried a pseudodeficiency allele (Asn350Ser). The IVS2+1G>A mutation occurred in four families. We also identified three polymorphisms, all in heterozygosis: Thr391Ser was present in five families, Trp193Cys in four families, and Ala210Ala in one family. We could identify 100% of the alleles causing MLD in the families, involving 12 different mutations, resulting in improved prognosis and genetic counselling.

Identification of 12 novel mutations and two new polymorphisms in the arylsulfatase A gene: haplotype and genotype-phenotype correlation studies in Spanish metachromatic leukodystrophy patients

Arylsulfatase A (ARSA) deficiency is the main cause of metachromatic leukodystrophy (MLD), a lysosomal disorder with no specific treatment. In view of the importance of genetic counseling, analyses of mutations and polymorphisms, including the ARSA pseudodeficiency allele, were carried out in 18 unrelated Spanish MLD patients. A systematic search allowed us to identify 100% of the alleles involving 17 different mutations, 12 of which are novel: G32S, L68P, R84W, P94A, G99V, P136S, W193X, H227Y, R288H, G308D, T327I, and IVS6-12C-->G. Two new polymorphisms, 2033C>T and 2059C>T, were identified in intron 6 which, in combination with two polymorphisms previously described (2161C>G and 2213C>G), gave rise to four different haplotypes in the control population. In addition, we also studied polymorphism 842G>T. Linkage disequilibrium was detected between mutations IVS2+1G-->A, D255H, and T327I and specific haplotypes, suggesting a unique origin for these mutations. Moreover, mutation T327I was always associated with the T allele of the new rare variant A210A (893C>T). The distribution of mutation D255H (frequency 19.4%) among patients with different MLD clinical presentation revealed a clear genotype-phenotype correlation paralleling that reported for mutation IVS2+1G-->A (frequency 25%). Among the novel mutations, only P136S and R288H occurred on a background of the ARSA pseudodeficiency allele. Screening 182 normal chromosomes identified a frequency of 8.8% of this allele; moreover, we identified two unrelated subjects with the polyA- mutation in the absence of the N350S mutation, and this infrequent haplotype reinforced the heterogeneity of conditions with ARSA deficiency.