Mutation and polymorphism analysis of the human homogentisate 1,2- dioxygenase gene in alkaptonuria patients

Alkaptonuria (AKU), a rare hereditary disorder of phenylalanine and tyrosine catabolism, was the first disease to be interpreted as an inborn error of metabolism. AKU patients are deficient for homogentisate 1,2 dioxygenase (HGO); this deficiency causes homogentisic aciduria, ochronosis, and arthritis. We cloned the human HGO gene and characterized two loss-of- function mutations, P230S and V300G, in the HGO gene in AKU patients. Here we report haplotype and mutational analysis of the HGO gene in 29 novel AKU chromosomes. We identified 12 novel mutations: 8 (E42A, W97G, D153G, S189I, I216T, R225H, F227S, and M368V) missense mutations that result in amino acid substitutions at positions conserved in HGO in different species, 1 (F10fs) frameshift mutation, 2 intronic mutations (IVS9-56G→A, IVS9-17G→A), and 1 splice-site mutation (IVS5+1G→T). We also report characterization of five polymorphic sites in HGO and describe the haplotypic associations of alleles at these sites in normal and AKU chromosomes. One of these sites, HGO-3, is a variable dinucleotide repeat; IVS2+35T/A, IVS5+25T/C, and IVS6+46C/A are intronic sites at which single nucleotide substitutions (dimorphisms) have been detected; and c407T/A is a relatively frequent nucleotide substitution in the coding sequence, exon 4, resulting in an amino acid change (H80Q). These data provide insight into the origin and evolution of the various AKU alleles.This work was supported by the Fundación Jose Antonio de Castro, the Spanish Comisión Interministerial de Ciencia y Tecnología (grants SAL96/0055 and BIO94/0932), and the Fondo de Investigaciones Sanitarias (grant FIS95/0885). The financial support of the Ministero dell'Università e della Ricerca Scientifica e Tecnologica to B. P. is also acknowledged. In addition, this study is based on work supported by the Fundación Conchita Rabago de Jímenez Díaz under a grant awarded to D. B.-V. de B.Peer Reviewe