MUTATION AND POLYMORPHISM ANALYSIS OF THE HUMAN HOMOGENTISATE 1,2-DIOXYGENASE GENE IN ALKAPTONURIA PATIENTS

Alkaptonuria (AKU), a rare hereditary disorder of phenylalanine and ty rosine catabolism, was the first disease to be interpreted as an inbor n error of metabolism. AKU patients are deficient for homogentisate 1, 2 dioxygenase (HGO); this deficiency causes homogentisic aciduria, och ronosis, and arthritis. We cloned the human HGO gene and characterized two loss-of-function mutations, P230S and V300G, in the HGO gene in A KU patients. Here we report haplotype and mutational analysis of the H GO gene in 23 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 conser ved in HGO in different species, 1 (F10fs) frameshift mutation, 2 intr onic mutations (IVS9-56G-->A, IVS9-17G-->A), and 1 splice-site mutatio n (IVS5 + 1G-->T). We also report characterization of five polymorphic sites in HGO and describe the haplotypic associations of alleles at t hese sites in normal and AKU chromosomes. One of these sites, HGO-3, i s a variable dinucleotide repeat; IVS2+35T/A, IVS5+25T/C, and IVS6+46C /A are intronic sites at which single nucleotide substitutions (dimorp hisms) have been detected; and c407T/A is a relatively frequent nucleo tide substitution in the coding sequence, exon 4, resulting in an amin o acid change (H80Q). These data provide insight into the origin and e volution of the various AKU alleles.