ABSTRACT
The frequency of carriers of the AGUFin mutation, the predominant mutation causing aspartylglucosaminuria in Finland, was determined in a population sample comprising 553 newborns from a delivery hospital in southern Finland, and 607 from a hospital in northern Finland. The AGUFin point mutation was identified from cord blood samples using the PCR-based, solid-phase minisequencing method. Nineteen carriers of the AGUFin mutation were detected, 8 (1:69) in the sample from the southern and 11 (1:55) from the northern population, respectively. The solid-phase minisequencing method proved to be rapid and convenient for the detection of the AGUFin mutation, and can readily be applied in large-scale carrier screening at the population level.
Subject(s)
Amino Acid Metabolism, Inborn Errors/genetics , Aspartylglucosylaminase/genetics , Genetic Carrier Screening , Genetic Testing , Finland , Humans , Infant, Newborn , Point Mutation , Polymerase Chain ReactionABSTRACT
Aspartylglucosaminuria (AGU) is an inherited lysosomal storage disorder caused by the deficiency of aspartylglucosaminidase. We have earlier reported a single missense mutation (Cys163----Ser) to be responsible for 98% of the AGU alleles in the isolated Finnish population, which contains about 90% of the reported AGU patients. Here we describe the spectrum of 10 AGU mutations found in unrelated patients of non-Finnish origin. Since 11 out of 12 AGU patients were homozygotes, consanguinity has to be a common denominator in most AGU families. The mutations were distributed over the entire coding region of the aspartylglucosaminidase cDNA, except in the carboxyl-terminal 17-kDa subunit in which they were clustered within a 46-amino acid region. Based on the character of the mutations, most of them are prone to affect the folding and stability and not to directly affect the active site of the aspartylglucosaminidase enzyme.
Subject(s)
Acetylglucosamine/analogs & derivatives , Aspartylglucosylaminase/genetics , Mutation , Acetylglucosamine/urine , Adolescent , Adult , Alleles , Aspartylglucosaminuria , Base Sequence , Cell Line , Child , Child, Preschool , Chromosome Deletion , Codon/genetics , DNA/genetics , DNA/isolation & purification , DNA Transposable Elements , Fibroblasts/enzymology , Humans , Infant , Leukocytes/enzymology , Molecular Sequence Data , Oligodeoxyribonucleotides , Polymerase Chain Reaction , Polymorphism, Genetic , RNA/genetics , RNA/isolation & purification , RNA SplicingABSTRACT
We have isolated a 2.1 kb cDNA which encodes human aspartylglucosaminidase (AGA, E.C. 3.5.1.26). The activity of this lysosomal enzyme is deficient in aspartylglucosaminuria (AGU), a recessively inherited lysosomal accumulation disease resulting in severe mental retardation. The polypeptide chain deduced from the AGA cDNA consists of 346 amino acids, has two potential N-glycosylation sites and 11 cysteine residues. Transient expression of this cDNA in COS-1 cells resulted in increased expression of immunoprecipitable AGA protein. Direct sequencing of amplified AGA cDNA from an AGU patient revealed a G----C transition resulting in the substitution of cysteine 163 with serine. This mutation was subsequently found in all the 20 analyzed Finnish AGU patients, in the heterozygous form in all 53 carriers and in none of 67 control individuals, suggesting that it represents the major AGU causing mutation enriched in this isolated population. Since the mutation produces a change in the predicted flexibility of the AGA polypeptide chain and removes an intramolecular S-S bridge, it most probably explains the deficient enzyme activity found in cells and tissues of AGU patients.
Subject(s)
Aspartylglucosylaminase/genetics , Carbohydrate Metabolism, Inborn Errors/enzymology , Chromosomes, Human, Pair 4 , DNA/genetics , Mutation , Amino Acid Sequence , Animals , Aspartylglucosaminuria , Aspartylglucosylaminase/urine , Base Sequence , Carbohydrate Metabolism, Inborn Errors/genetics , Cell Line , Cloning, Molecular , Female , Humans , Male , Molecular Sequence Data , Oligonucleotide Probes , Pedigree , Polymerase Chain Reaction , Protein Conformation , RNA/genetics , RNA/isolation & purification , TransfectionSubject(s)
Aspartylglucosaminuria , Aspartylglucosylaminase/genetics , Lysosomal Storage Diseases/genetics , Animals , Aspartylglucosylaminase/isolation & purification , Genes, Recessive , Genetic Therapy/methods , Humans , Intellectual Disability/enzymology , Intellectual Disability/genetics , Lysosomal Storage Diseases/therapy , RatsABSTRACT
Aspartylglucosaminuria (AGU) is caused by deficient activity of the enzyme aspartylglucosaminidase (AGA). The structural gene for AGA has been assigned to the region 4q21-qter of chromosome 4. We have studied the map position of the AGU locus in relation to other marker loci on the long arm of chromosome 4 using linkage analyses. Restriction fragment length polymorphism alleles for the ADH2, ADH3, EGF, FG alpha and FG beta loci and blood group antigens for the MNS locus were determined in a panel of 12 Finnish AGU families. The heterozygous family members were identified by reduced activity of AGA in lymphocytes. Linkage studies were performed using both pairwise and multipoint analyses. Loose linkage of the AGU locus to the FG and MNS loci was observed (z = 1.16, z = 1.39, respectively). Multipoint analysis to the fixed map [ADH-(0.03)-EGF-(0.35)-FG-(0.11)-MNS] suggests that the location of the AGU locus is 0.05-0.30 recombination units distal to MNS (z = 3.03). The order cen-ADH-EGF-FG-MNS-AGU is 35 times more likely than the next best order cen-ADH-EGF-AGU-FG-MNS.
