Summary
Classic galactosaemia is a potentially lethal inborn error of metabolism that results from profound impairment of galactose-1P uridylyltransferase (GALT). Like many autosomal recessive disorders, classic galactosaemia demonstrates marked allelic heterogeneity; many if not most patients are compound heterozygotes. Owing in part to the fact that most GALT mutations are never observed in patients in the homozygous state, in part to concerns of possible allelic interaction, and in part to the broad range of GALT activity levels associated with the affected, carrier, and control states, definition of the specific functional consequence of individual variant GALT alleles from studies of clinical samples alone can be a challenging task. To overcome this problem we previously developed and applied a null-background yeast system to enable functional analyses of human GALT alleles expressed individually or in defined pairs. We report here the application of this system to characterize three distinct variant alleles of GALT identified within a single family. Of these alleles, one carried a missense mutation (K285N) that has previously been reported and characterized, one carried a nonsense mutation (R204X) that has previously been reported but not characterized, and the third carried a missense substitution (T268N) that was novel. Our studies reported here reconfirm the profound nature of the K285N mutation, demonstrate that the R204X mutation severely compromises both expression and function of human GALT, and finally implicate T268N as one of a very small number of naturally occurring rare but neutral missense polymorphisms in human GALT.
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Antshel K, Epstein I, Waisbren S (2004) Cognitive strengths and weaknesses in children and adolescents homozygous for the galactosemia Q188R mutation: a descriptive study. Neuropsychology 18: 658–664.
Bosch A (2006) Classical galactosaemia revisited. J Inherit Metab Dis. 29: 516–525.
Calderon F, Nelson L, Dobrowolski P, et al (2007) Combination of enzyme analysis, allele-specific PCR and sequencing to detect mutations in the GALT gene. J Inherit Metab Dis. 30: 318.
Christacos N, Fridovich-Keil J (2002) Impact of patient mutations on heterodimer formation and function in human galactose-1P uridylyltransferase. Mol Genet Metab. 76: 319–326.
Elsevier JP, Fridovich-Keil JL (1996) The Q188R mutation in human galactose-1 phosphate uridylyltransferase acts as a partial dominant negative. J Biol Chem 271: 32002–32007.
Elsevier JP, Wells L, Quimby BB, Fridovich-Keil JL (1996) Heterodimer formation and activity in the human enzyme galactose-1 phosphate uridylyltransferase. Proc Natl Acad Sci U S A 93: 7166–7171.
Forges T, Monnier-Barbarino P, Leheup B, Jouvet P (2006) Pathophysiology of impaired ovarian function in galactosaemia. Hum Reprod Update 12: 573–584.
Fridovich-Keil J (2006) Galactosemia: the good, the bad, and the unknown. J Cell Physiol 209: 701–705.
Fridovich-Keil JL, Jinks-Robertson S (1993) A yeast expression system for human galactose-1 phosphate uridylyltransferase. Proc Natl Acad Sci U S A 90: 398–402.
Fridovich-Keil JL, Langley SD, Mazur LA, Lennon JC, Dembure PP, Elsas LJ (1995a) Identification and functional analysis of three distinct mutations in the human galactose-1 phosphate uridyltransferase gene associated with galactosemia in a single family. Am J Hum Genet 56: 640–646.
Fridovich-Keil JL, Quimby BB, Wells L, Mazur LA, Elsevier JP (1995b) Characterization of the N314D allele of human galactose-1 phosphate uridylyltransferase using a yeast expression system. Biochem Mol Med 56: 121–130.
Holden HM, Rayment I, Thoden JB (2003) Structure and function of enzymes of the Leloir pathway for galactose metabolism. J Biol Chem 278: 43885–43888.
Isken O, Maquat L (2007) Quality control of eukaryotic mRNA: safeguarding cells from abnormal mRNA function. Genes Dev. 21: 1833–1856.
Leslie ND, Immerman EB, Flach JE, Florez M, Fridovich-Keil JL, Elsas LJ (1992) The human galactose-1 phosphate uridyl transferase gene. Genomics 14: 474–480.
Nadler H, Chacko C, Rachmeler M (1970) Interallelic complementation in hybrid cells derived from human diploid strains deficient in galactose-1 phosphate uridyl transferase activity. Proc Natl Acad Sci U S A 67: 976–982.
Neitzel H (1986) A routine method for the establishment of permanent growing lymphoblastoid cell lines. Hum Genet. 73: 320–326.
Openo K, Schulz J, Vargas C, et al (2006) Epimerase-deficiency galactosemia is not a binary condition. Am J Hum Genet 78: 89–102.
Riehman K, Crews C, Fridovich-Keil JL (2001) Relationship between genotype, activity, and galactose sensitivity in yeast expressing patient alleles of human galactose-1 phosphate uridylyltransferase. J Biol Chem 276: 10634–10640.
Ross KL, Davis CN, Fridovich-Keil JL (2004) Differential roles of the Leloir pathway enzymes and metabolites in defining galactose sensitivity in yeast. Mol Gen Metab 83: 103–116.
Tyfield L, Reichardt J, Fridovich-Keil J, et al (1999) Classical galactosemia and mutations at the galactose-1 phosphate uridyl transferase (GALT) gene. Hum Mutat 13: 417–430.
Waggoner DD, Buist NRM, Donnell GN (1990) Long-term prognosis in galactosemia: results of a survey of 350 Cases. J Inherit Metab Dis 13: 802–818.
Walter J, Tyfield L (2002) Galactosemia. In: Scriver CR, Beaudet AL, Sly WS, Valle D, eds; Childs B, Kinzler KW, Vogelstein B, assoc, eds. The Metabolic and Molecular Bases of Inherited Disease, 8th edn. New York: McGraw-Hill.
Wang BBT, Xu Y-K, Ng WG, Wong L-JC (1998) Molecular and biochemical basis of galactosemia. Mol Genet Metab 63: 263–269.
Wohlers TM, Christacos NC, Harreman MT, Fridovich-Keil JL (1999) Identification and characterization of a mutation, in the human UDP galactose-4-epimerase gene, associated with generalized epimerase-deficiency galactosemia. Am J Hum Genet 64: 462–470.
Zydowsky LD, Ho SI, Baker CH, McIntyre K, Walsh CT (1992) Overexpression, purification, and characterization of yeast cyclophilins A and B. Protein Sci 1: 961–969.
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Communicating editor: Gerard Berry
Competing interests: None declared
References to electronic databases: Galactosaemia: OMIM 230400. Galactose-1-phosphate uridylyltransferase: EC 2.7.7.12. UDP-glucose/galactose pyrophorylase: EC 2.7.7.10.
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Chhay, J.S., Openo, K.K., Eaton, J.S. et al. A yeast model reveals biochemical severity associated with each of three variant alleles of galactose-1P uridylyltransferase segregating in a single family. J Inherit Metab Dis 31, 97–107 (2008). https://doi.org/10.1007/s10545-007-0786-5
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DOI: https://doi.org/10.1007/s10545-007-0786-5