Mutation and haplotype analyses in 26 Spanish Sanfilippo syndrome type A patients: possible single origin for 1091delC mutation

Mucopolysaccharidosis IIIA, also known as Sanfilippo syndrome type A, is an autosomal recessive storage disorder caused by deficiency of sulfamidase. The disease results in severe central nervous system degeneration often with mild somatic features that may delay the clinical diagnosis. Molecular analyses would allow early and unequivocal heterozygote detection, providing a useful tool for genetic counselling. About 40 mutations have been reported in the sulfamidase gene, with a very uneven distribution in different patient populations. We have previously described the high prevalence of mutation 1091delC in a small number of Spanish Sanfilippo A patients. The aim of the present work is to extend the mutational study to a total of 26 unrelated patients and perform haplotype analysis in order to study the origin of some mutations. The whole coding region of the gene was scanned by SSCP analysis and sequencing. This allowed the identification of 14 different mutations, corresponding to 90% of the mutant alleles. Seven of these mutations were only found in this Spanish group of patients, three of which, R150W, R433Q and R433W, are described here for the first time. We have also analyzed four internal polymorphisms and constructed the corresponding haplotypes. Chromosomes bearing mutation 1091delC show a conserved haplotype suggesting a common origin for this mutation. Moreover, all other mutations found twice or more also have conserved haplotypes for those polymorphic markers.

Mutation 1091delC is highly prevalent in Spanish Sanfilippo syndrome type A patients

The gene resposible for Sanfilippo syndrome type A, a lysosomal disorder caused by deficiency of sulfamidase, was recently cloned and more than 40 mutations were identified. This paper presents the mutation analysis and clinical findings in 11 Spanish patients in whom 19 of the 22 mutant alleles have been identified. This is the first report on mutations in Spanish Sanfilippo A patients. Seven different mutations were found, four of which (Q85R, R206P, A354P, and L386R) were not previously described. Mutation 1091delC was the most prevalent, accounting for nearly one-half of the mutated alleles, while mutations R245H and R74C were not found. Haplotype analysis suggests a founder effect as the cause of the high frequency of 1091delC in this population.

Recurrence of the D409H mutation in Spanish Gaucher disease patients: description of a new homozygous patient and haplotype analysis

Gaucher disease results, in most patients, from mutations in the gene encoding glucocerebrosidase. Mutation D409H is the third most frequent in Spanish patients, accounting for 5.7% of all mutated alleles. This allele is associated mainly with the neurological forms of the disease. Recently, homozygosity for the D409H mutation has been associated with a particular phenotype, including specific cardiovascular symptoms. Here we report a second Spanish patient bearing the D409H/D409H genotype with a very early manifestation of the disease. The patient started enzyme replacement therapy at 3 months of age. A common origin for the Spanish D409H alleles was ruled out by haplotype analysis using an internal polymorphism of the glucocerebrosidase gene and two external microsatellite markers.

Reliable co-segregation analysis for prenatal diagnosis and heterozygote detection in Gaucher disease

Mutations in the gene encoding beta-glucocerebrosidase are the main cause of Gaucher disease. The identification of some of these mutations in prenatal tests is a good complement to enzymatic assay and allows diagnosis and, in some cases, prognosis of the disease to be made. DNA analysis is particularly useful for carrier detection since the results of biochemical analyses are often ambiguous. The main drawback of mutation analysis for prenatal diagnosis and carrier detection in Gaucher disease is that rare mutations account for more than 30 per cent of the mutant alleles in most populations. The individual detection of these mutations is too expensive and time-consuming for routine use. Here we present a diagnostic protocol based on co-segregation analysis, using highly polymorphic markers, to be applied when at least one disease allele does not correspond to the most common mutations. Because of the frequency of the N370S mutation and its relevance for prognosis, an improved PCR detection method is included.

Genetic fine localization of the beta-glucocerebrosidase (GBA) and prosaposin (PSAP) genes: implications for Gaucher disease

Mutations in the glucocerebrosidase (GBA) and prosaposin (PSAP) genes are responsible for Gaucher disease, the most prevalent sphingolipidosis. Somatic cell hybrid analysis and in situ hybridization experiments have localized the GBA gene to 1q21 and the PSAP gene to 10q21-q22. We performed pairwise and multi-point linkage analyses between the two genes and several highly polymorphic markers from the Généthon human linkage map. Our results show that six markers cosegregate with the GBA gene (Zmax = 8.73 at theta = 0.00 for marker D1S2714) and define a 3.2-cM interval between D1S305 and D1S2624 as the most probable location for the gene. Three of these markers (D1S2777, D1S303, and D1S2140), as well as the gene encoding pyruvate kinase (PKLR), are contained in a single YAC clone together with the GBA gene. A new polymorphism was identified within the PSAP gene (C16045T) and used for linkage studies. The multi-point analysis places the gene in a 9.8-cM interval between D10S1688 and D10S607. The fine localization of these genes provides a useful tool for cosegregation analysis, indirect molecular diagnosis, and population genetic studies.