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Yuzyuk T, Wilson AR, Mao R, Pasquali M. Galactose-1-Phosphate Uridyltransferase Activities in Different Genotypes: A Retrospective Analysis of 927 Samples. J Appl Lab Med 2019; 3:222-230. [DOI: 10.1373/jalm.2017.025536] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 01/29/2018] [Indexed: 11/06/2022]
Abstract
Abstract
Background
Classic galactosemia is an inherited disorder of galactose metabolism caused by the impaired activity of galactose-1-phosphate uridyltransferase (GALT). Untreated galactosemia is life-threatening; however, early dietary intervention prevents mortality and reduces morbidity associated with this disease. The diagnosis of galactosemia includes the measurement of GALT activity in red blood cells (RBC) and GALT gene analysis. In this study, we evaluate GALT activity in different genotypes using the results of combined biochemical and molecular testing in 927 samples.
Methods
GALT activity in RBC was measured by LC-MS/MS. The analysis of the GALT gene was performed by targeted gene analysis and/or full gene sequencing. Samples were assigned based on the presence of pathogenic (G) or Duarte 2 (D) variants, or their absence (Neg), to G/G, D/G, G/Neg, D/D, D/Neg, and Neg/Neg genotypes. Finite mixture models were applied to investigate distributions of GALT activities in these genotypes. The reference ranges were determined using the central 95% of values of GALT activities.
Results
The ranges of GALT activity in G/G, D/G, G/Neg, D/D, D/Neg, and Neg/Neg genotypes are 0.0 to 0.7 μmol·h−1 gHb−1, 3.1 to 7.8 μmol·h−1 gHb−1, 6.5 to 16.2 μmol·h−1 gHb−1, 6.4 to 16.5 μmol·h−1 gHb−1, 12.0 to 24.0 μmol·h−1 gHb−1, and 19.4 to 33.4 μmol·h−1 gHb−1, respectively.
Conclusions
The GALT activity ranges established in this study are in agreement with the expected impact of the genotype on the enzymatic activity. Molecular findings should be interpreted in view of biochemical results to confirm genotype–phenotype correlation.
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Affiliation(s)
- Tatiana Yuzyuk
- Department of Pathology, University of Utah, Salt Lake City, UT
- ARUP Laboratories, Salt Lake City, UT
| | - Andrew R Wilson
- School of Nursing, University of Utah Health Sciences Center, Salt Lake City, UT
| | - Rong Mao
- Department of Pathology, University of Utah, Salt Lake City, UT
- ARUP Laboratories, Salt Lake City, UT
| | - Marzia Pasquali
- Department of Pathology, University of Utah, Salt Lake City, UT
- ARUP Laboratories, Salt Lake City, UT
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Yuzyuk T, Balakrishnan B, Schwarz EL, De Biase I, Hobert J, Longo N, Mao R, Lai K, Pasquali M. Effect of genotype on galactose-1-phosphate in classic galactosemia patients. Mol Genet Metab 2018; 125:258-265. [PMID: 30172461 DOI: 10.1016/j.ymgme.2018.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/21/2018] [Accepted: 08/22/2018] [Indexed: 11/27/2022]
Abstract
Impaired activity of galactose-1-phosphate uridyltransferase (GALT) causes classic galactosemia (OMIM 230400), characterized by the accumulation of galactose-1-phosphate (GAL1P) in patients' red blood cells (RBCs). Our recent study demonstrated a correlation between RBC GAL1P and long-term outcomes in galactosemia patients. Here, we analyze biochemical and molecular results in 77 classic galactosemia patients to evaluate the association between GALT genotypes and GAL1P concentration in RBCs. Experimental data from model organisms were also included to assess the correlation between GAL1P and predicted residual activity of each genotype. Although all individuals in this study showed markedly reduced RBC GALT activity, we observed significant differences in RBC GAL1P concentrations among galactosemia genotypes. While levels of GAL1P on treatment did not correlate with RBC GALT activities (p = 0.166), there was a negative nonlinear correlation between mean GAL1P concentrations and predicted residual enzyme activity of genotype (p = 0.004). These studies suggest that GAL1P levels in RBCs on treatment likely reflect the overall functional impairment of GALT in patients with galactosemia.
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Affiliation(s)
- Tatiana Yuzyuk
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA.
| | - Bijina Balakrishnan
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | | | - Irene De Biase
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
| | - Judith Hobert
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
| | - Nicola Longo
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA; Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Rong Mao
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
| | - Kent Lai
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Marzia Pasquali
- Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, Salt Lake City, UT, USA
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Yuzyuk T, Viau K, Andrews A, Pasquali M, Longo N. Biochemical changes and clinical outcomes in 34 patients with classic galactosemia. J Inherit Metab Dis 2018; 41:197-208. [PMID: 29350350 DOI: 10.1007/s10545-018-0136-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 12/19/2017] [Accepted: 01/02/2018] [Indexed: 10/18/2022]
Abstract
Impaired activity of galactose-1-phosphate uridyltransferase (GALT) causes galactosemia, an autosomal recessive disorder of galactose metabolism. Early initiation of a galactose-restricted diet can prevent or resolve neonatal complications. Despite therapy, patients often experience long-term complications including speech impairment, learning disabilities, and premature ovarian insufficiency in females. This study evaluates clinical outcomes in 34 galactosemia patients with markedly reduced GALT activity and compares outcomes between patients with different levels of mean galactose-1-phosphate in red blood cells (GAL1P) using logistic regression: group 1 (n = 13) GAL1P ≤1.7 mg/dL vs. group 2 (n = 21) GAL1P ≥ 2 mg/dL. Acute symptoms at birth were comparable between groups (p = 0.30) with approximately 50% of patients presenting with jaundice, liver failure, and failure-to-thrive. However, group 2 patients had significantly higher prevalence of negative long-term outcomes compared to group 1 patients (p = 0.01). Only one of 11 patients >3 yo in group 1 developed neurological and severe behavioral problems of unclear etiology. In contrast, 17 of 20 patients >3 yo in group 2 presented with one or more long-term complications associated with galactosemia. The majority of females ≥15 yo in this group also had impaired ovarian function with markedly reduced levels of anti-Müllerian hormone. These findings suggest that galactosemia patients with higher GAL1P levels are more likely to have negative long-term outcome. Therefore, evaluation of GAL1P levels on a galactose-restricted diet might be helpful in providing a prognosis for galactosemia patients with rare or novel genotypes whose clinical presentations are not well known.
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Affiliation(s)
- Tatiana Yuzyuk
- Department of Pathology, University of Utah, Salt Lake City, UT, USA.
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA.
| | - Krista Viau
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
- Boston Children's Hospital, Boston, MA, USA
| | - Ashley Andrews
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Marzia Pasquali
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Nicola Longo
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, UT, USA
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Leung EKY, Agolini E, Pei X, Melis R, McMillin GA, Friedman PN, Peterson P, Danahey K, O'Donnell PH, Yeo KTJ. Validation of an ExtensiveCYP2D6Assay Panel Based on Invader and TaqMan Copy Number Assays. ACTA ACUST UNITED AC 2017; 1:471-482. [DOI: 10.1373/jalm.2016.021923] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 10/31/2016] [Indexed: 11/06/2022]
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Sartippour MR, Doroudian R, Frampton G, Lorey F, Helmer G, Ho T, Bhandal A. Identification of galactose-1-phosphate uridyl transferase gene common mutations in dried blood spots. Clin Chim Acta 2014; 436:298-302. [DOI: 10.1016/j.cca.2014.06.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 06/07/2014] [Accepted: 06/16/2014] [Indexed: 10/25/2022]
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Choi R, Jo KI, Ko DH, Lee DH, Song J, Jin DK, Ki CS, Lee SY, Kim JW, Lee YW, Park HD. Novel GALT variations and mutation spectrum in the Korean population with decreased galactose-1-phosphate uridyltransferase activity. BMC MEDICAL GENETICS 2014; 15:94. [PMID: 25124065 PMCID: PMC4236512 DOI: 10.1186/s12881-014-0094-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/04/2014] [Indexed: 11/10/2022]
Abstract
BACKGROUND Classic galactosemia (OMIM #230400) is an autosomal recessive metabolic disorder caused by a deficiency of the galactose-1-phosphate uridyltransferase (GALT, EC2.7.7.12) protein due to mutations in the GALT gene. The aim of this study was to provide a comprehensive and updated mutation spectrum of GALT in a Korean population. METHODS Thirteen unrelated patients screened positive for galactosemia in a newborn screening program were included in this study. They showed a reduced GALT enzyme activity in red blood cells. Direct sequencing of the GALT gene and in silico analyses were done to evaluate the impact of novel variations upon GALT enzyme activity. We also reviewed previous reports for GALT mutations in Koreans. RESULTS We identified six novel likely pathogenic variations including three missense (p.Ala101Asp, p.Tyr165His, and p.Pro257Thr), one small deletion/insertion [c.826_827delinsAA (p.Ala276Asn)], one frameshift (p.Asn96Serfs*5), and one splicing (c.378-1G > C) likely pathogenic variations. The most frequent variation was the Duarte variant (c.940A > G, 35.3%), followed by c.507G > C (p.Gln169His, 9.6%), among 34 Korean patients. Other mutations were widely scattered. None of the eight common mutations used for targeted mutation analysis in Western countries including p.Gln188Arg, p.Ser135Leu, p.Lys285Asn, p.Leu195Pro, p.Tyr209Cys, p.Phe171Ser, c.253-2A > G, and a 5 kb deletion, had been found in Koreans until this study. CONCLUSIONS Considering the mutation spectrum in Koreans, direct sequence analysis of entire GALT exons is recommended for accurate diagnosis. The mutations responsible for GALT deficiency in the Korean population were clearly different from those of other populations.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Yong-Wha Lee
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 135-710, Republic of Korea.
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Melis R, Fauron C, McMillin G, Lyon E, Shirts B, Hubley LM, Slev PR. Simultaneous genotyping of rs12979860 and rs8099917 variants near the IL28B locus associated with HCV clearance and treatment response. J Mol Diagn 2011; 13:446-51. [PMID: 21704279 PMCID: PMC3123790 DOI: 10.1016/j.jmoldx.2011.03.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 02/16/2011] [Accepted: 03/22/2011] [Indexed: 01/01/2023] Open
Abstract
Recent genome-wide association studies have identified two host single-nucleotide polymorphisms (SNPs) near the IL28B gene (rs12979860 C/T and rs8099917 T/G) that are associated with sustained virological response in patients infected with the hepatitis C virus. Herein, we describe a rapid multiplexed dual-color fluorescence resonance energy transfer (FRET) probe assay that accurately genotypes for both SNPs simultaneously. A single-nucleotide extension assay was also developed for verification of genotypes. Agreement (100%) was observed in genotype calls between the FRET and single-nucleotide extension methods for both SNPs, yielding 100% analytical sensitivity and specificity. By using the FRET assay, 443 samples of varying ethnic backgrounds were genotyped and six different compound genotypes (rs12979860/rs8099917) were detected in whites, Asians, Middle Easterners, Hispanics, and African Americans, at the following frequencies: CC/TT (39.2%, 78.9%, 40.0%, 33.9%, and 16.8%), CT/TT (20.8%, 0%, 40%, 9.3%, and 37.0%), TT/TT (2.4%, 0%, 0%, 3.4%, and 35.3%), CT/TG (24.0%, 19.7%, 20%, 39.8%, and 3.4%), TT/TG (8.0%, 1.4%, 0%, 3.4%, and 5.9%), and TT/GG (5.6%, 0%, 0%, 10.2%, and 1.7%), respectively. The multiplexed FRET assay can be used to effectively genotype for both SNPs in a single tube, with high analytical sensitivity and specificity.
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Affiliation(s)
- Roberta Melis
- Associated Regional and University Pathologists (ARUP) Institute for Clinical and Experimental Pathology, Salt Lake City, Utah 84108-1221, USA.
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Molecular and biochemical characterization of the GALT gene in Korean patients with galactose-1-phosphate uridyltransferase deficiency. Clin Chim Acta 2010; 411:1506-10. [PMID: 20547145 DOI: 10.1016/j.cca.2010.06.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Revised: 06/04/2010] [Accepted: 06/07/2010] [Indexed: 11/24/2022]
Abstract
BACKGROUND Three different types of galactosemia have been described, and the most common form occurs due to a deficiency in the galactose-1-phosphate uridyltransferase (GALT) enzyme activity. METHODS To investigate the molecular defects of the GALT gene, PCR-direct sequencing was performed with genomic DNA from 18 Korean patients with reduced GALT activity. RESULTS Of the 18 patients tested, 13 (72.2%) had previously reported variants: Duarte variant (12 patients), p.R201H (1 patient), and g.A1962G. In addition, we identified six novel sequence variations by PCR-direct sequencing: five sequence variations in coding regions (p.H31R, p.L116I, p.Q169H, p.H186P and p.R333R), and one in an intron (g.2621A>G). Of 100 normal individuals tested, 4 were heterozygous for the Duarte variant, which indicates a Duarte allele frequency of 2%. Biochemical characteristics of the novel genetic alterations were determined: enzyme activity for exonic alterations and splicing for intron. CONCLUSION The genetic constitution of the GALT gene is responsible for galactosemia in the Korean population.
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Li Y, Ptolemy AS, Harmonay L, Kellogg M, Berry GT. Quantification of galactose-1-phosphate uridyltransferase enzyme activity by liquid chromatography-tandem mass spectrometry. Clin Chem 2010; 56:772-80. [PMID: 20348403 DOI: 10.1373/clinchem.2009.140459] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The diagnosis of galactosemia usually involves the measurement of galactose-1-phosphate uridyltransferase (GALT) activity. Traditional radioactive and fluorescent GALT assays are nonspecific, laborious, and/or lack sufficient analytical sensitivity. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based assay for GALT enzyme activity measurement. METHOD Our assay used stable isotope-labeled alpha- galactose-1-phosphate ([(13)C(6)]-Gal-1-P) as an enzyme substrate. Sample cleanup and separation were achieved by reversed-phase ion-pair chromatography, and the enzymatic product, isotope-labeled uridine diphosphate galactose ([(13)C(6)]-UDPGal), was detected by MS/MS at mass transition (571 > 323) and quantified by use of [(13)C(6)]-Glu-1-P (265 > 79) as an internal standard. RESULTS The method yielded a mean (SD) GALT enzyme activity of 23.8 (3.8) mumol x (g Hgb)(-1) x h(-1) in erythrocyte extracts from 71 controls. The limit of quantification was 0.04 micromol x (g Hgb)(-1) x h(-1) (0.2% of normal control value). Intraassay imprecision was determined at 4 different levels (100%, 25%, 5%, and 0.2% of the normal control values), and the CVs were calculated to be 2.1%, 2.5%, 4.6%, and 9.7%, respectively (n = 3). Interassay imprecision CVs were 4.5%, 6.7%, 8.2%, and 13.2% (n = 5), respectively. The assay recoveries at the 4 levels were higher than 90%. The apparent K(m) of the 2 substrates, Gal-1-P and UDPGlc, were determined to be 0.38 mmol/L and 0.071 mmol/L, respectively. The assay in erythrocytes of 33 patients with classical galactosemia revealed no detectable activity. CONCLUSIONS This LC-MS/MS-based assay for GALT enzyme activity will be useful for the diagnosis and study of biochemically heterogeneous patients with galactosemia, especially those with uncommon genotypes and detectable but low residual activities.
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Affiliation(s)
- Yijun Li
- The Manton Center for Orphan Disease Research, Division of Genetics, Department of Pediatrics, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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Abstract
With the US Food and Drug Administration's recent label change of warfarin to include genetic testing for warfarin sensitivity, manufacturers are developing assays, and laboratories are offering testing. This article describes the genetic variants for which testing is available. Current technologies and assays are compared, including considerations for laboratories in choosing a method. Finally, laboratory issues that apply to all methods, such as quality control and proficiency testing as well as service issues including turn-around-time requirements are discussed.
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Affiliation(s)
- Elaine Lyon
- Department of Pathology, University of Utah, Salt Lake City, Utah, USA.
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