Molecular Genetics of Alkaptonuria

Abstract

Alkaptonuria (AKU), the first defined human genetic disease with a recessive trait, is caused by mutations within the homogentisate 1,2‐dioxygenase (HGD) gene (3q13.33). This prototypic inborn error of metabolism is characterised by typical bluish‐black pigmentation in connective tissue ochronosis and severe form of osteoarthritis caused by the deposition of ochronotic pigment in the joints. AKU belongs to a group of rare diseases (1:250 000–1:1 000 000), however, several ethnities were reported, where an increased incidence of AKU was observed (Slovakia, Dominican Republic, Jordan and India). Mutation analysis was so far performed in approximately 350 out of more than 650 worldwide reported AKU patients. Rather high heterogeneity was observed with 122 AKU‐causing mutations that are listed together with HGD polymorphisms in the global HGD mutation database (http://hgddatabase.cvtisr.sk/). Because HGD enzyme functions as hexamer, dimer of trimers, genotype/phenotype correlations are difficult to perform in this rare disease.

Key Concepts:

  • Alkaptonuria (AKU) is a prototypic inborn error in the metabolism of phenylalanine and tyrosine, characterised by the inability to metabolise homogentisic acid (HGA).

  • The raised HGA levels in plasma and extracellular fluid lead to ochronosis, the deposition of polymers of HGA as pigment (ochronotic pigment) in connective tissues including cartilage, heart valves and sclera.

  • Ochronosis leads to painful destruction of large weight‐bearing joints as well as fusion of the vertebrae, scoliosis and tendon and ligament ruptures.

  • AKU is caused by homozygous or compound heterozygous mutations in the homogentisate‐1,2‐dioxygenase gene (HGD) mapping to the chromosome 3q13.33.

  • AKU belongs to a group of rare diseases (1:250 000–1:1 000 000), however, several ethnities were reported, where an increased incidence of AKU was observed (Slovakia, Dominican Republic, Jordan and India).

  • In approximately 350 patients reported worldwide so far 122 different HGD mutations have been reported.

  • It was also shown that AKU is caused also by the apparently partial loss‐of‐function mutations, however, the heterozygous carriers of AKU are healthy.

  • HGD haplotype analysis helps to identify the origin of individual AKU‐causing mutations in different countries.

  • The triketone herbicide nitisinone or Orfadin inhibits the 4‐hydroxyphenylpyruvate dioxygenase enzyme, which produces HGA, thus, it can decrease HGA and should therefore potentially be able to modify AKU.

  • It has been shown that AKU is a novel type II AA amyloidosis, which opens new important perspectives for its therapy, since the control of the underlying inflammatory disorder can result in regression of the disease.

  • Research on ochronosis in this monogenic disease can help to elucidate the molecular pathogenesis of the more common varieties of osteoarthritis, particularly the biochemical and structural changes at its initial stages.

Keywords: AKU; alkaptonuria; HGD mutations; HGD mutation database; homogentisate 1,2‐dioxygenase

Figure 1.

Distribution within the HGD gene of 122 AKU mutations reported so far in about 350 families, 30 single nucleotide polymorphisms (SNPs) and 3 simple sequence repeats (SSRs). Variants IVS9‐56G>A** and IVS9‐17G>A** were published as mutations, but Vilboux et al. reported that they are most likely benign variants. Indeed, in the sample of patients variant IVS9‐17G>A has been found in homozygous state in the patient who also carried homozygous mutation P230S in exon 10. Mutations G115fs* (c.413_434+35del57) and V157fs* (c.470‐1_494del25) are caused by genomic deletions that are predicted to cause exon 6 and 8 skipping, respectively, thus leading to frameshift.

Figure 2.

Comparison of the proportions of HGD mutation types as identified worldwide and in Slovakia. Last column indicates the involvement of mutation hot spots.

Figure 3.

Haplotype analysis in family AKU_DB_61 where the segregation of 3 different AKU‐causing mutations can be followed.

Figure 4.

Map showing geographical distribution of the Slovak HGD mutations from 66 Slovak AKU chromosomes. The code used for the mutations is depicted in the right inset. Geographic origin was reconstructed based on the oldest family data available for the AKU patients. The chart in the right lower corner indicates the percentual proportion of individual mutation identified in Slovakia (out of 112 Slovak AKU chromosomes). In grey are indicated mutations that most likely originated in this country.

close

References

Al‐Sbou M and Mwafi N (2010) Nine cases of alkaptonuria in one family in southern Jordan. Rheumatology International 32: 621–625.

Anikster Y, Nyhan WL and Gahl WA (1998) Ntbc and alkaptonuria. American Journal of Human Genetics 63: 920–921.

Beltrán‐Valero de Bernabé D, Granadino B, Chiarelli I et al. (1998) Mutation and polymorphism analysis of the human homogentisate 1,2‐dioxygenase gene in alkaptonuria patients. American Journal of Human Genetics 62: 776–784.

Beltrán‐Valero de Bernabé D, Jimenez FJ, Aquaron R and Rodríguez de Córdoba S (1999) 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). American Journal of Human Genetics 64: 1316–1322.

Braconi D, Laschi M, Taylor A et al. (2010) Proteomic and redox‐proteomic evaluation of homogentisic acid and ascorbic acid effects on human articular chondrocytes. Journal of Cellular Biochemistry 111: 922–932.

Cox TF and Ranganath LR (2011) A quantitative assessment of alkaptonuria: testing the reliability of two disease severity scoring systems. Journal of Inherited Metabolic Disease 34: 1153–1162.

De Jorge EG, Lorda I, Gallardo ME et al. (2002) Alkaptonuria in the dominican republic: identification of the founder AKU mutation and further evidence of mutation hot spots in the hgo gene. Journal of Medical Genetics 39: E40.

den Dunnen JT and Antonarakis SE (2000) Mutation nomenclature extensions and suggestions to describe complex mutations: a discussion. Human Mutation 15: 7–12.

Fernández‐Cañón JM and Peñalva MA (1995) Molecular characterization of a gene encoding a homogentisate dioxygenase from aspergillus nidulans and identification of its human and plant homologues. Journal of Biological Chemistry 270: 21199–21205.

Fernández‐Cañón JM, Granadino B, Beltrán‐Valero de Bernabé D et al. (1996) The molecular basis of alkaptonuria. Nature Genetics 14: 19–24.

Gallagher JA, Taylor AM, Boyde A, Jarvis JC and Ranganath LR (2012) Recent advances in understanding the pathogenesis of ochronosis. Reumatologia 50: 316–323.

Garrod AE (1902) The incidence of alkaptonuria: a study in chemical individuality. Lancet 2: 1616–1620.

Garrod AE (1908) Croonian lectures on inborn errors of metabolism, lecture II: alkaptonuria. Lancet 2: 73–79.

Granadino B, Beltrán‐Valero de Bernabé D, Fernández‐Cañón JM, Peñalva MA and Rodríguez de Córdoba S (1997) The human homogentisate 1,2‐dioxygenase (hgo) gene. Genomics 43: 115–122.

Grasko JM, Hooper AJ, Brown JW, McKnight CJ and Burnett JR (2009) A novel missense HGD gene mutation, K57N, in a patient with alkaptonuria. Clinica Chimica Acta 403: 254–256.

Introne WJ, Perry MB, Troendle J et al. (2011) A 3‐year randomized therapeutic trial of nitisinone in alkaptonuria. Molecular Genetics and Metabolism 103: 307–314.

Janocha S, Wolz W, Srsen S et al. (1994) The human gene for alkaptonuria (aku) maps to chromosome 3q. Genomics 19: 5–8.

Khachadurian A and Feisal KA (1958) Alkaptonuria; report of a family with seven cases appearing in four successive generations, with metabolic studies in one patient. Journal of Chronic Diseases 7: 455–465.

La Du BN (1958) Alkaptonuria. In: Scriver CR, Beauder AL, Sly W and Valle D (eds) The Metabolic and Molecular Bases of Inherited Sisease, pp. 1371–1386. New York: McGraw Hill.

La Du BN, Zannoni VG, Laster L and Seegmiller JE (1958) The nature of the defect in tyrosine metabolism in alcaptonuria. Journal of Biological Chemistry 230: 251–260.

Laschi M, Tinti L, Braconi D et al. (2012) Homogentisate 1,2‐dioxygenase is expressed in human osteoarticular cells: implications in alkaptonuria. Journal of Cellular Physiology 227: 3254–3257.

Magesh R and George Priya Doss C (2012) Computational methods to work as first‐pass filter in deleterious SNP analysis of alkaptonuria. Scientific World Journal 2012: 738423.

Manning K, Fernández‐Cañón JM, Montagutelli X and Grompe M (1999) Identification of the mutation in the alkaptonuria mouse model. Mutations in brief No. 216. Online. Human Mutation 13: 171.

Martin JP Jr and Batkoff B (1987) Homogentisic acid autoxidation and oxygen radical generation: implications for the etiology of alkaptonuric arthritis. Free Radical Biology and Medicine 3: 241–250.

Milch RA (1955) Direct inheritance of alcaptonuria. Metabolism 4: 513–518.

Milch RA (1960) Studies of alcaptonuria: inheritance of 47 cases in eight highly inter‐related dominican kindreds. American Journal of Human Genetics 12: 76–85.

Millucci L, Spreafico A, Tinti L et al. (2012) Alkaptonuria is a novel human secondary amyloidogenic disease. Biochimca et Biophysica Acta 1822: 1682–1691.

Montagutelli X, Lalouette A, Coude M et al. (1994) Aku, a mutation of the mouse homologous to human alkaptonuria, maps to chromosome 16. Genomics 19: 9–11.

Oexle K, Engel K, Tinschert S, Haas D and Lee‐Kirsch MA (2008) Three‐generational alkaptonuria in a non‐consanguineous family. Journal of Inherited Metabolic Disease 31(Suppl. 2): S425–S430.

Phornphutkul C, Introne WJ, Perry MB et al. (2002) Natural history of alkaptonuria. New England Journal of Medicine 347: 2111–2121.

Pollak MR, Chou YH, Cerda JJ et al. (1993) Homozygosity mapping of the gene for alkaptonuria to chromosome 3q2. Nature Genetics 5: 201–204.

Ranganath L, Taylor AM, Shenkin A et al. (2011) Identification of alkaptonuria in the general population: a United Kingdom experience describing the challenges, possible solutions and persistent barriers. Journal of Inherited Metabolic Disease 34: 723–730.

Ranganath LR and Cox TF (2011) Natural history of alkaptonuria revisited: analyses based on scoring systems. Journal of Inherited Metabolic Disease 34: 1141–1151.

Rodríguez JM, Timm DE, Titus GP et al. (2000) Structural and functional analysis of mutations in alkaptonuria. Human Molecular Genetics 9: 2341–2350.

Srsen S and Varga F (1978) Screening for alkaptonuria in the newborn in Slovakia. Lancet 2: 576.

Srsen S, Muller CR, Fregin A and Srsnova K (2002) Alkaptonuria in Slovakia: thirty‐two years of research on phenotype and genotype. Molecular Genetics and Metabolism 75: 353–359.

Suwannarat P, O'Brien K, Perry MB et al. (2005) Use of nitisinone in patients with alkaptonuria. Metabolism 54: 719–728.

Suzuki Y, Oda K, Yoshikawa Y, Maeda Y and Suzuki T (1999) A novel therapeutic trial of homogentisic aciduria in a murine model of alkaptonuria. Journal of Human Genetics 44: 79–84.

Taylor AM, Boyde A, Davidson JS et al. (2012a) Identification of trabecular excrescences, novel microanatomical structures, present in bone in osteoarthropathies. European Cells and Materials 23: 300–308, discussion 308–309.

Taylor AM, Boyde A, Wilson PJ et al. (2011) The role of calcified cartilage and subchondral bone in the initiation and progression of ochronotic arthropathy in alkaptonuria. Arthritis and Rheumatism 63: 3887–3896.

Taylor AM, Preston AJ, Paulk NK et al. (2012b) Ochronosis in a murine model of alkaptonuria is synonymous to that in the human condition. Osteoarthritis and Cartilage 20: 880–886.

Taylor AM, Wlodarski B, Prior IA et al. (2010) Ultrastructural examination of tissue in a patient with alkaptonuric arthropathy reveals a distinct pattern of binding of ochronotic pigment. Rheumatology 49: 1412–1414.

Tinti L, Spreafico A, Braconi D et al. (2010) Evaluation of antioxiodant drugs for the treatment of ochronotic alkaptonuria in an in vitro human cell model. Journal of Cell Physiology 225: 84–91.

Tinti L, Spreafico A, Chellini F, Galeazzi M and Santucci A (2011) A novel ex vivo organotypic culture model of alkaptonuria–ochronosis. Clinical and Experimental Rheumatology 29: 693–696.

Titus GP, Mueller HA, Burgner J et al. (2000) Crystal structure of human homogentisate dioxygenase. Nature Structural Biology 7: 542–546.

Vilboux T, Kayser M, Introne W et al. (2009) Mutation spectrum of homogentisic acid oxidase (hgd) in alkaptonuria. Human Mutation 30: 1611–1619.

Zatkova A (2011) An update on molecular genetics of alkaptonuria (aku). Journal of Inherited Metabolic Disease 34: 1127–1136.

Zatkova A, Beltrán‐Valero de Bernabé D, Polakova H et al. (2000a) High frequency of alkaptonuria in slovakia: evidence for the appearance of multiple mutations in hgo involving different mutational hot spots. American Journal of Human Genetics 67: 1333–1339.

Zatkova A, Chmelikova A, Polakova H, Ferakova E and Kadasi L (2003) Rapid detection methods for five hgo gene mutations causing alkaptonuria. Clinical Genetics 63: 145–149.

Zatkova A, Polakova H, Micutkova L et al. (2000b) Novel mutations in the homogentisate‐1,2‐dioxygenase gene identified in slovak patients with alkaptonuria. Journal of Medical Genetics 37: 539–542.

Zatkova A, Sedlackova T, Radvansky J et al. (2012) Identification of 11 novel homogentisate 1,2‐dioxygenase variants in alkaptonuria patients and establishment of a novel lovd‐based hgd mutation database. Journal of Inherited Metabolic Disorder Reports 4: 55–65.

Further Reading

Linder J, Miteva M and Romanelli P (2010) Pigmentary deposition disorders. In: Smoller BR and Rongioletti F (eds) Clinical and Pathological Aspects of Skin Diseases in Endocrine, Metabolic, Nutritional and Deposition Disease, pp. 171–180. New York: Springer New York.

Obici L, Raimondi S, Lavatelli F, Bellotti V and Merlini G (2009) Susceptibility to AA amyloidosis in rheumatic diseases: a critical overview. Arthritis and Rheumatism 61: 1435–1440.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Zatkova, Andrea(Jan 2013) Molecular Genetics of Alkaptonuria. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0024298]