Rare causes of the uncommon AKU inheritance in this family have to be considered, ranging from the coincidence of undetectable HGD mutations to a dominant mutation of a second, hitherto unknown AKU gene.
The data formally establish the homogentisate 1,2 dioxygenase gene (HGD) as the molecular cause of alkaptonuria and allow for the development of molecular carrier tests in populations at risk.
The identification of these mutations in this study further expands the spectrum of known HGD gene mutations and contributes to prenatal molecular diagnosis of AKU.
There was, interestingly, no difference in serum levels or absolute urinary excretion of HGA, or clinical symptoms, indicating that protein intake is more important than differences in HGD variants for the amounts of HGA that accumulate in the body of AKU patients.
To assess the involvement of the recently identified human homogentisate 1,2-dioxygenase gene (HGO) in alkaptonuria (AKU) in two unrelated patients with ochronosis of the conjunctiva, sclera, and cornea.
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.
We describe three novel mutations (R58fs, R330S, and H371R) and one common AKU mutation (M368V), detected by mutational and polymorphism analysis of the HGO gene in five Finnish AKU pedigrees.
We show that HGO maps to the same location described for AKU, illustrate that HGO harbours missense mutations that cosegregate with the disease, and provide biochemical evidence that at least one of these missense mutations is a loss-of-function mutation.