Molecular analysis of the aldolase B gene in patients with hereditary fructose intolerance from Spain

Abstract

Hereditary fructose intolerance (HFI) is an autosomal recessive metabolic disorder caused by aldolase (fructosediphosphate aldolase, EC 4.1.2.13) B deficiency.1 The B isoform of aldolase is critical for the metabolism of exogenous fructose by the liver, kidney, and intestine, since it can use fructose-1-phosphate as substrate at physiological concentrations, unlike aldolases A and C. Affected subjects suffer abdominal pain, vomiting, and hypoglycaemia after the ingestion of fructose, sucrose, or sorbitol. Continued ingestion of noxious sugars causes hepatic and renal injury, which eventually leads to liver cirrhosis and sometimes death, particularly in small infants.1 Treatment consists of strict elimination of fructose, sucrose, and sorbitol from the diet immediately after HFI is suspected. This diet exclusion therapy allows for a rapid recovery and, if liver and kidney damage is not irreversible, an uneventful course thereafter. Confirmatory diagnosis is generally made by intravenous fructose tolerance tests and assays of aldolase B activity in hepatic biopsies.Since the gene coding for human aldolase B (ALDOB) was cloned, 2 at least 22 different mutations associated with HFI have been described.3 4 Kinetic analyses of recombinant aldolase B mutants and molecular modelling studies have shown important structure-function implications for several aldolase B residues affected by HFI mutations.5-8 The first HFI mutation identified, termed A149P, 9 is a G→C transversion at the first base of codon 149, which replaces the normal alanine by a proline residue. This missense mutation accounts for more than 50% of mutant alleles in HFI patients from different populations world wide 3 ; the frequency of heterozygous carriers in the United Kingdom has been estimated to be 1.32 ± 0.49%, which allows the prediction of an incidence of HFI associated with the A149P allele of 1 in 23 000 births. 10 The three more common aldolase B mutations, A149P, A174D, and N334K, account for more than 80% of HFI alleles in populations from European countries.4 11 Although there are many reports dealing with the identification of aldolase B mutations associated with HFI in different European populations, studies on the incidence of these mutations in Spanish subjects have not been reported.In this work, we have analysed the molecular defects in the ALDOB gene in 28 HFI patients from Spain. For this purpose, we have performed PCR amplification of the aldolase B coding exons from the probands and subsequent analysis by restriction endonuclease digestion, allele specific oligonucleotide (ASO) hybridisation, and direct sequencing. Our results have allowed us to estimate the frequencies of HFI alleles in Spanish patients, as well as to discover two novel mutations in the ALDOB gene (g.4271C>G and g.1133G>A) that can cause HFI. MATERIALS AND METHODS SubjectsTwenty-eight HFI patients from 21 independent families, referred by hospitals in Spain, were studied. Probands were resident in the following regions: Madrid (11 families), Andalusia (4), Galici...

Different genotypes in a large Italian family with recurrent hereditary fructose intolerance

“…As predicted [6,9], the frequency of the p.A175D mutation was particularly high, compared with recently reported frequencies in Central Europe (15%) or Spain (15.8%) [5,16]. The p.N335K mutation has probably spread from Eastern and/or Central Europe [4,7].…”

“…Our molecular results showed a distribution of the p.A150P mutation that was relatively closer to that of the pan-European population [16], than to that of Italian patients [6,9]. The p.A150P mutation has been described as being more frequent in North Europe than in Italy; however, a frequent mutation reported in the Italian population (c.865delC) has been predicted to be limited to Sicily [6].…”

“…The p.N335K mutation has probably spread from Eastern and/or Central Europe [4,7]. This mutated allele, however, also proved to be relatively common in Italy, with a frequency close to that in Central Europe [5,16].…”

Six novel alleles identified in Italian hereditary fructose intolerance patients enlarge the mutation spectrum of the aldolase B gene

“…1 d) was detected in two unrelated patients, compound heterozygous for the p.Y204X and p.A150P mutations, respectively. Both mutations alter canonical splice acceptor sequences and thereby they should prevent proper maturation of the primary transcript, as already reported for different mutations in the acceptor splicing site of both IVS3 (g.1133G>A) and IVS6 (g.10197G>A) [Sanchez-Gutierrez et al, 2002;Ali et al, 1994].…”

Hereditary fructose intolerance: functional study of two novel ALDOB natural variants and characterization of a partial gene deletion

“…Exons 2-9 encode the type B monomer, a 364-amino acid long polypeptide; four identical monomers assemble to form the mature, tetrameric enzyme. The mutations identified to date in the ALDOB gene of HFI patients consist mainly of subtle/point mutations (missense, nonsense, splicing defects and frameshift mutations) [Stenson et al, 2003;Sanchez-Gutierrez et al, 2002;Davit-Spraul et al, 2008; the Human Gene Mutation Database, http://www.hgmd.org] and only two large intragenic deletions [Cross and Cox, 1990]. Two missense mutations in exon 5, c.448G>C (p.A150P) and c.524C>A…”