Analysis of Alkaptonuria (AKU) Mutations and Polymorphisms Reveals that the CCC Sequence Motif Is a Mutational Hot Spot in the Homogentisate 1,2 Dioxygenase Gene ( HGO (original) (raw)
Related papers
JIMD Reports, 2011
Enzymatic loss in alkaptonuria (AKU), an autosomal recessive disorder, is caused by mutations in the homogentisate 1,2 dioxygenase (HGD) gene, which decrease or completely inactivate the function of the HGD protein to metabolize homogentisic acid (HGA). AKU shows a very low prevalence (1:100,000-250,000) in most ethnic groups, but there are countries with much higher incidence, such as Slovakia and the Dominican Republic. In this work, we report 11 novel HGD mutations identified during analysis of 36 AKU patients and 41 family members from 27 families originating from 9 different countries, mainly from Slovakia and France. In Slovak patients, we identified two additional mutations, thus a total number of HGD mutations identified in this small country is 12. In order to record AKU-causing mutations and variants of the HGD gene, we have created a HGD mutation database that is open for future submissions and is available online (http://hgddatabase.cvtisr.sk/). It is founded on the Leiden Open (source) Variation Database (LOVD) system and includes data from the original AKU database (http://www. alkaptonuria.cib.csic.es) and also all so far reported variants and AKU patients. Where available, HGD-haplotypes associated with the mutations are also presented. Currently, this database contains 148 unique variants, of which 115 are reported pathogenic mutations. It provides a valuable tool for information exchange in AKU research and care fields and certainly presents a useful data source for genotypephenotype correlations and also for future clinical trials.
Sequence analysis of the homogentisate 1,2 dioxygenase gene in a family affected by alkaptonuria
Journal of medical genetics, 1999
Sequence analysis of the homogentisate 1,2 dioxygenase gene in a family aVected by alkaptonuria EDITOR-Alkaptonuria (AKU) is a disorder of the catabolism of aromatic amino acids. A defect of homogentisate 1,2 dioxygenase (HGO) leads to an accumulation of homogentisic acid (HGA) and subsequently to deposition of polymerised HGA, a brown-black pigment, in connective tissue, primarily in cartilage. 1 2 This phenomenon is known as ochronosis. It results in debilitating arthropathy which typically becomes manifest in the fourth decade of life. Large amounts of HGA are excreted in the urine and cause its black discolouration upon oxidation. In 1891, homogentisic acid was first isolated by Wolkow and Baumann 3 from the urine of an AKU patient from a remote area of the Black Forest in south western Germany. In 1902, Garrod, aware of this biochemical finding, observed the autosomal recessive mode of inheritance of AKU and thereby showed for the first time that mendelian laws also apply to human genetics. 4 Garrod postulated that AKU results from an enzyme deficiency and introduced the concept of the "inborn error of metabolism". 5 Recently, the human gene encoding HGO was cloned by Fernádez-Cañón et al. 6 Two diVerent mutations of this gene were identified in two unrelated AKU aVected families. These mutations cosegregated with manifest disease and could be shown to abrogate enzymatic activity of HGO protein. 6 Homozygosity for these mutations, therefore, was the cause of AKU in the two families. Two additional mutations in the HGO gene were found to cosegregate with AKU in two Slovakian pedigrees. 7 One of these mutations caused a frameshift in an upstream exon and was thus likely to result in a loss of HGO activity. For an additional mutation, complete cosegregation with AKU was reported in an extensively studied Canarian family. 8 Various diVerent mutations of the HGO gene were found in 14 unrelated AKU patients. 9 We performed sequence analysis of the HGO gene in an AKU aVected family from the Black Forest. AKU with severe ochronosis including involvement of the sclerae was diagnosed at necropsy of a 71 year old farmer (fig 1, No 1). The diagnosis of AKU had not been established during the patient's lifetime. He died of recurrent myocardial infarction. Subsequently, the patient's family underwent physical examination. A sister (fig 1, No 2) and a first cousin (fig 1, No 3) were found to be aVected by the disease. These patients have been suVering from arthritic symptoms of AKU since the fourth decade of life and show the typical discolouration of the urine and the ochronotic pigmentation of the sclerae. However, the condition had until then been misdiagnosed as degenerative polyarthritis. A brother (fig 1, No 4) of patient 1 was healthy as were the three children (fig 1, Nos 5, 6, and 7) of patient 2. Anamnestically, a brother (fig 1, No 8) and a first cousin (fig 1, No 9), who died in 1988 and 1995, respectively, were reported to have suVered from debilitating early onset polyarthropathy and the typical ochronotic involvement of the sclerae. They were very probably affected by AKU. No characteristic AKU symptoms were reported
JIMD reports, 2014
Alkaptonuria (AKU) is a rare autosomal recessive disorder with incidence ranging from 1:100,000 to 1:250,000. The disorder is caused by a deficiency of the enzyme homogentisate 1,2-dioxygenase (HGD), which results from defects in the HGD gene. This enzyme converts homogentisic acid to maleylacetoacetate and has a major role in the catabolism of phenylalanine and tyrosine. To elucidate the mutation spectrum of the HGD gene in patients with alkaptonuria from 42 patients attending the National Alkaptonuria Centre, 14 exons of the HGD gene and the intron-exon boundaries were analysed by PCR-based sequencing. A total of 34 sequence variants was observed, confirming the genetic heterogeneity of AKU. Of these mutations, 26 were missense substitutions and four splice site mutations. There were two deletions and one duplication giving rise to frame shifts and one substitution abolishing the translation termination codon (no stop). Nine of the mutations were previously unreported novel variants. Using computational approaches based on the 3D structure, these novel mutations are predicted to affect the activity of the protein complex through destabilisation of the individual protomer structure or through disruption of protomer-protomer interactions.
Annals of Human Genetics, 2014
Alkaptonuria (AKU) is an autosomal recessive disorder; caused by the mutations in the homogentisate 1, 2-dioxygenase (HGD) gene located on Chromosome 3q13.33. AKU is a rare disorder with an incidence of 1: 250,000 to 1: 1,000,000, but Slovakia and the Dominican Republic have a relatively higher incidence of 1: 19,000. Our study focused on studying the frequency of AKU and identification of HGD gene mutations in nomads. HGD gene sequencing was used to identify the mutations in alkaptonurics. For the past four years, from subjects suspected to be clinically affected, we found 16 positive cases among a randomly selected cohort of 41 Indian nomads (Narikuravar) settled in the specific area of Tamil Nadu, India. HGD gene mutation analysis showed that 11 of these patients carry the same homozygous splicing mutation c.87 + 1G > A; in five cases, this mutation was found to be heterozygous, while the second AKU-causing mutation was not identified in these patients. This result indicates that the founder effect and high degree of consanguineous marriages have contributed to AKU among nomads. Eleven positive samples were homozygous for a novel mutation c.87 + 1G > A, that abolishes an intron 2 donor splice site and most likely causes skipping of exon 2. The prevalence of AKU observed earlier seems to be highly increased in people of nomadic origin.
Mutation spectrum of homogentisic acid oxidase (HGD) in alkaptonuria
Human Mutation, 2009
Alkaptonuria (AKU) is a rare autosomal recessive metabolic disorder, characterized by accumulation of homogentisic acid, leading to darkened urine, pigmentation of connective tissue (ochronosis), joint and spine arthritis, and destruction of cardiac valves. AKU is due to mutations in the homogentisate dioxygenase gene, HGD, that converts homogentisic acid to maleylacetoacetic acid in the tyrosine catabolic pathway. Here we report a comprehensive mutation analysis of 93 patients enrolled in our study, as well as an extensive update of all previously published HGD mutations associated with AKU. Within our patient cohort, we identified 52 HGD variants, of which 22 were novel. This yields a total of 91 identified HGD variations associated with AKU to date, including 62 missense, 13 splice site, 10 frameshift, 5 nonsense and 1 no-stop mutation. Most HGD variants reside in exons 3, 6, 8 and 13. We assessed the potential effect of all missense variations on protein function, using 5 bioinformatic tools specifically designed for interpretation of missense variants (SIFT, POLYPHEN, PANTHER, PMUT and SNAP). We also analyzed the potential effect of splice site variants using two different tools (BDGP and NetGene2). This study provides valuable resources for molecular analysis of alkaptonuria and expands our knowledge of the molecular basis of this disease.
Journal of Inherited Metabolic Disease, 2003
Summary: Alkaptonuria (AKU) is a rare metabolic disorder of phenylalanine catabolism that is inherited as an autosomal recessive trait. AKU is caused by loss-of-function mutations in the homogentisate 1,2-dioxygenase (HGO) gene. The deficiency of homogentisate 1,2-dioxygenase activity causes homogentisic aciduria, ochronosis and arthritis. We present the first molecular study of the HGO gene in Turkish AKU patients. Seven unrelated AKU families from different regions in Turkey were analysed. Patients in three families were homozygous for the R58fs mutation; another three families were homozygous for the R225H mutation; and one family was homozygous for the G270R mutation. Analysis of nine intragenic HGO polymorphisms showed that the R58fs, R225H and G270R Turkish AKU mutations are associated with specific HGO haplotypes. The comparison with previously reported haplotypes associated with these mutations from other populations revealed that the R225H is a recurrent mutation in Turkey, whereas G270R most likely has a Slovak origin. Most interestingly, these analyses showed that the Turkish R58fs mutation shares an HGO haplotype with the R58fs mutation found in Finland, Slovakia and India, suggesting that R58fs is an old AKU mutation that probably originated in central Asia and spread throughout Europe and Anatolia during human migrations.
American Journal of Human Genetics, 2000
Alkaptonuria (AKU) is an autosomal recessive disorder caused by the deficiency of homogentisate 1,2 dioxygenase (HGO) activity. AKU shows a very low prevalence (1:100,000-250,000) in most ethnic groups. One notable exception is in Slovakia, where the incidence of AKU rises to 1:19,000. This high incidence is difficult to explain by a classical founder effect, because as many as 10 different AKU mutations have been identified in this relatively small country. We have determined the allelic associations of 11 HGO intragenic polymorphisms for 44 AKU chromosomes from 20 Slovak pedigrees. These data were compared to the HGO haplotype data available in our laboratory for 180 AKU chromosomes from different European and non-European countries. The results show that common European AKU chromosomes have had only a marginal contribution to the Slovak AKU gene pool. Six of the ten Slovak AKU mutations, including the prevalent G152fs, G161R, G270R, and P370fs mutations, most likely originated in Slovakia. Data available for 17 Slovak AKU pedigrees indicate that most of the AKU chromosomes have their origins in a single very small region in the Carpathian mountains, in the northwestern part of the country. Since all six Slovak AKU mutations are associated with HGO mutational hot spots, we suggest that an increased mutation rate at the HGO gene is responsible for the clustering of AKU mutations in such a small geographical region.
Genetics of alkaptonuria – an overview
Acta Facultatis Pharmaceuticae Universitatis Comenianae, 2015
Alkaptonuria (AKU) is the first described inborn error of metabolism and a classical example of rare autosomal recessive disease. AKU patients carry homozygous or compound heterozygous mutations of the gene coding for enzyme homogentisate dioxygenase (HGD) involved in metabolism of tyrosine. The metabolic block in AKU causes accumulation of homogentisic acid (HGA) that, with advancing age of the patient, leads to severe and painful ochronotic arthropathy.