Galactose-1-phosphate Uridyltransferase Gene Research Articles

Determination of The GALT Gene in Galactosemic Cataract Patients in Azerbaijan

Galactosemia is one of the genetic diseases that can be treated thanks to early detection by genetic screening test. Galactosemia is a hereditary metabolic disease. This disease is heterogeneous and controlled by GALT, GALK, GALE and GALM genes. The presented article is dedicated to galactosemic disease among Azerbaijani patients as a result of GALT (galactose-1-phosphate uridyltransferase) gene mutations. This study reviews discusses the type of cataracts associated with galactosemia. The genetics of galactosemic patients are evaluated and details of galactose metabolism are described. This study describes the results of the GALT gene analysis of two Azerbaijanian patients with Galactosemic cataract. In one of the patients the heterzygous form of the same mutation, and the homozygous form in the other patient were found. In this study, control and experimental groups were determined, and DNA extracted from the peripheral blood of patients belonging to both groups was subjected to PCR amplification according to standard protocols and sequenced by Sanger sequence method. The symptoms of the disease were reviewed in these patients. Patients presented with jaundice, diarrhea, vomiting, malnutrition, seizures, allergies and more cataracts in the neonatal period. Commonly, Cataract disease is idiopathic origin. Also, patients with cataracts may have an underlying genetic abnormality of galactose metabolism. Elevated levels of galactose and galactose-1-phosphate and absence of GALT activity were diagnosed in the studied patients. Early biochemical and molecular-genetic diagnosis and genetic counseling of patients and their family members are extremely important in the treatment of galactosemia. We selected 25 cataract patients aged 0-45 years and 25 age and sex-matched controls for the study. Blood samples taken from the experimental and control groups, were biochemically and then molecular-genetically analyzed. Mutations Q188R, K285N and N314D were investigated in patients. Of these mutations, only the N314D mutation was detected in two patients. Both heterozygous and homozygous forms of N314D mutation were detected.

Molecular Characterization of Galactosemia: Identification of Six Novel GALT Gene Mutations

Background: Classic galactosemia (CG) is an inborn error of galactose metabolism caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). This enzyme causes the conversion of uridine diphosphate- glucose (UDP)-glucose and galactose-1-phosphate (Gal-1-P) to glucose-1-phosphate and UDP-galactose. The absence of this enzyme results in the accumulation of the metabolites galactitol and Gal-1-P. The CG is heterogeneous at clinical and molecular levels. Objectives: This study provides some data for the investigation of the introduction of new mutations of the GALT gene that involved the cause of galactosemia in the Iranian population. Methods: In this cross-sectional study, 31 newborns diagnosed with galactosemia were investigated for the mutations of the GALT gene in Tehran province, Iran, from March 2014 to December 2019. The polymerase chain reaction sequencing method was used to analyze the GALT gene. Results: The sequence results showed 11 pathogenic mutations on the GALT gene, including five mutations in exon 10, two mutations in exon 9, two mutations in exon 5, one mutation in exon 6, and one mutation in exon 7. Moreover, six new mutations of the GALT gene were identified in the Iranian population, namely c.442C>T (R148W), c.881T>A (F294Y), c.997C>T (R333W), c.940A>G (N314D), c.1030C>A (Q344K), and c.1018G>A (E340K). Other mutations identified in this study were c.563A>G (Q188R), c.855G>T (K285N), c.626A>C (Y209S), c.404C>T (S135L), and c.958G>A (A320T). The most common mutations in this study were p.Q188R (51.6%), K285N (9.67%), E340K (9.67%), and R148W (6.45%). Conclusions: This study identified 11 different pathogenic mutations of the GALT gene in the Iranian population with galactosemia. The identification of the mutations involved in the development of CG in the Iranian population can play an important role in early diagnosis and intervention. The GALT gene mutations identified in this study can be used as screening markers to identify Iranian children with CG.

AAV-mediated expression of galactose-1-phosphate uridyltransferase corrects defects of galactose metabolism in classic galactosemia patient fibroblasts.

Classic galactosemia (CG) is a rare disorder of autosomal recessive inheritance. It is caused predominantly by point mutations as well as deletions in the gene encoding the enzyme galactose-1-phosphate uridyltransferase (GALT). The majority of the more than 350 mutations identified in the GALT gene cause a significant reduction in GALT enzyme activity resulting in the toxic buildup of galactose metabolites that in turn is associated with cellular stress and injury. Consequently, developing a therapeutic strategy that reverses both the oxidative and ER stress in CG cells may be helpful in combating this disease. Recombinant adeno-associated virus (AAV)-mediated gene therapy to restore GALT activity offers the potential to address the unmet medical needs of galactosemia patients. Here, utilizing fibroblasts derived from CG patients we demonstrated that AAV-mediated augmentation of GALT protein and activity resulted in the prevention of ER and oxidative stress. We also demonstrate that these CG patient fibroblasts exhibit reduced CD109 and TGFβRII protein levels and that these effectors of cellular homeostasis could be restored following AAV-mediated expression of GALT. Finally, we show initial in vivo proof-of-concept restoration of galactose metabolism in a GALT knockout mouse model following treatment with AAV-GALT.

Molecular analysis of GALT gene in Argentinian population: Correlation with enzyme activity and characterization of a novel Duarte-like allele

BackgroundClassical galactosemia is an autosomal recessive inherited metabolic disorder caused by mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. GALT enzyme deficiency leads to the accumulation of galactose-1-phosphate in various organs, causing hepatic, renal and cerebral impairment. Over 300 mutations have been reported in the GALT gene. The aim of this study was to describe molecular characterization of GALT gene in Argentinian patients with decreased GALT activity, and to correlate molecular results with enzyme activity. Methods37 patients with enzyme activity below 6.3 μmol/h/g Hb (35% of normal value) were included. GALT activity was measured on red blood cells. DNA was extracted from peripheral blood. p.Gln188Arg mutation was studied by PCR-RFLP and, on samples negative or heterozygous, GALT gene was sequenced. In vivo splicing analysis of the GALT gene was performed on RNA extracted from leukocytes of one patient. Results14 different sequence variations were identified among 72 unrelated alleles. The two most common disease-causing mutations were p.Gln188Arg (24/72) and p.Lys285Asn (9/72). Three novel mutations were detected. One of them, c.688G>A, caused partial skipping of exon 9 of the GALT gene. Enzyme activity correlated with GALT genotype in 36 of the 37 patients. ConclusionThis is the first report of sequence variations in the GALT gene in the Argentinian population. This study highlights the contribution of the molecular analysis to the diagnosis of Galactosemia and reveals c.688G>A as a novel Duarte-like variant, with a high prevalence in our population.

Classic galactosaemia in the Greek Cypriot population: An epidemiological and molecular study.

Classic galactosaemia is an inherited metabolic disorder of galactose metabolism caused by deficiency of the enzyme galactose‐1‐phosphate uridyltransferase (GALT) resulting from mutations in the GALT gene. The objectives of the present study were the determination of the carrier frequency of classic galactosaemia in the Greek Cypriot population and the molecular characterization of the disease alleles. We performed an epidemiological study involving 528 Greek Cypriots originating from all parts of Cyprus. Carriers were identified by measuring GALT activity in red blood cells and were subsequently subjected to mutation analysis. A total of five mutations were identified in patients and carriers of classic galactosaemia: a large deletion of 8.5 kb previously reported by us (55% of alleles), the known mutations p.Lys285Asn (30%), p.Pro185Ser (5%), and c.820+13A>G (5%), and a novel mutation c.378‐12G>A (5%). Interestingly, the most common mutation in European populations, p.Gln188Arg, was not identified in this Cypriot cohort. The carrier frequency for classic galactosaemia among Greek Cypriots was estimated to be 1:88, predicting a homozygote incidence of 1:31,000 births. The Duarte 1 and Duarte 2 variants were found to be present at a frequency of 5.5% and 2.5%, respectively.

Galactose-1-Phosphate Uridyltransferase Activities in Different Genotypes: A Retrospective Analysis of 927 Samples.

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. 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. 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. 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.

Clinical and molecular spectra in galactosemic patients from neonatal screening in northeastern Italy: Structural and functional characterization of new variations in the galactose-1-phosphate uridyltransferase (GALT) gene

Classical galactosemia is an autosomal recessive inborn error of metabolism due to mutations of the GALT gene leading to toxic accumulation of galactose and derived metabolites. With the benefit of early diagnosis by neonatal screening and early therapy, the acute presentation of classical galactosemia can be prevented. However, despite early diagnosis and treatment, the long term outcome for these patients is still unpredictable because they may go on to develop cognitive disability, speech problems, neurological and/or movement disorders and, in females, ovarian dysfunction. The objectives of the current study were to report our experience with a group of galactosemic patients identified through the neonatal screening programs in northeastern Italy during the last 30years.No neonatal deaths due to galactosemia complications occurred after the introduction of the neonatal screening program. However, despite the early diagnosis and dietary treatment, the patients with classical galactosemia showed one or more long-term complications.A total of 18 different variations in the GALT gene were found in the patient cohort: 12 missense, 2 frameshift, 1 nonsense, 1 deletion, 1 silent variation, and 1 intronic. Six (p.R33P, p.G83V, p.P244S, p.L267R, p.L267V, p.E271D) were new variations. The most common variation was p.Q188R (12 alleles, 31.5%), followed by p.K285N (6 alleles, 15.7%) and p.N314D (6 alleles, 15.7%). The other variations comprised 1 or 2 alleles. In the patients carrying a new mutation, the biochemical analysis of GALT activity in erythrocytes showed an activity of <1%. In silico analysis (SIFT, PolyPhen-2 and the computational analysis on the static protein structure) showed potentially damaging effects of the six new variations on the GALT protein, thus expanding the genetic spectrum of GALT variations in Italy. The study emphasizes the difficulty in establishing a genotype–phenotype correlation in classical galactosemia and underlines the importance of molecular diagnostic testing prior to making any treatment.

Identification of galactose-1-phosphate uridyl transferase gene common mutations in dried blood spots

BackgroundThe California newborn screening program uses newborns' dried blood spots (DBS) to screen for more than 45 genetic disorders. Deficiency of galactose-1-phosphate uridyl transferase (GALT) is one of the metabolic genetic disorders screened using newborn DBS. During follow-up tests, common mutations of the GALT gene have been identified using whole blood samples. To avoid the stress of drawing an additional blood sample from newborns who are identified as presumptive positive for galactosemia, we developed a method to test common mutations in the GALT gene using blood spots. MethodsThis method involves DNA extraction from DBS, followed by polymerase chain reaction (PCR), and single nucleotide extension (SNE). SNE products were detected by capillary electrophoresis. ResultsIn a double-blind study, GALT gene common mutations/variants: IVS2-2A>G, p.S135L, p.T138M, p.Q188R, p.L195P, p.Y209C, p.L218L, p.K285N, and p.N314D were detected in seventy-three DBS which had previously been screened and confirmed as positive in the California Newborn Screening Program. Mutations found using blood spots gave 100% concordance with mutations from previously genotyped whole blood samples. ConclusionsThis blood spot method decreases the genomic test turnaround time of GALT screened positive patients and potentially reduces emotional stress on families required to provide an additional blood draw.

Mutational analysis of the GALT gene in Filipino patients.

Classic galactosemia is an inherited metabolic disorder due to mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. This study describes the results of the GALT gene analysis of four unrelated Filipino patients with Classic Galactosemia. DNA extracted from dried blood spots and peripheral blood of the patients, age one month to two and a half years, underwent PCR-amplification with subsequent bidirectional sequencing of all eleven exons with their flanking intronic regions following standard protocols. Clinical data of these patients were reviewed. The patients presented with jaundice, hepatomegaly, diarrhea, vomiting, poor feeding and seizures during their neonatal period. They were diagnosed with elevated blood galactose and galactose-1-phosphate and absent GALT activity. Four missense mutations were found wherein two were previously reported (p.V168L and p.A345D) and two were novel (p.L116P and p.M178R). The most frequent mutation in our cohort is p.V168L. This study suggests that GALT mutations are ethnic-specific and that galactosemia is a heterogeneous disorder at the molecular level. The importance of early detection, immediate and proper medical management and genetic counseling of the patients and their families cannot be overemphasized.

Galactosemia in the Turkish population with a high frequency of Q188R mutation and distribution of Duarte-1 and Duarte-2 variations

Classical galactosemia is an inherited recessive disorder of galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT), which is caused by mutations in the GALT gene. In this study, 56 Turkish patients diagnosed with galactosemia were screened for GALT gene mutations using Affymetrix resequencing microarrays. Eleven types of mutations were detected in these patients, including two novel mutations (R258G and G310fsX49) and nine recurrent mutations. We detected six patients who were homozygous for the E340* mutation and for N314D, L218L silent substitutions (Duarte-1 variant) in this study. The haplotype E340*, N314D and L218L has been reported only in Turkish patients, which suggests that the E340* mutation is specific for our population and might be spread by a Turk ancestor. In patients, the Duarte-1 allele was found with a frequency of 10.71%, whereas the Duarte-2 allele was not detected. Duarte-1 and Duarte-2 alleles were found to be present at a frequency of 2.3% and 1.4%, respectively, in the screening of 105 healthy individuals. Considering all detected mutations, it is a very important finding that exons 6 and 10 of the GALT gene account for 79% of all mutant alleles in the Turkish population. The most common mutation is Q188R, with a frequency of 55.35%.

Biochemical and molecular characterization of GALT gene from Indian galactosemia patients: Identification of 10 novel mutations and their structural and functional implications

Classical Galactosemia is an autosomal recessive disorder of galactose metabolism caused by severe reduction or absence of the galactose-1-phosphate uridyl transferase (GALT) enzyme. Till date, no reports are available on clinical and molecular spectrum of galactosemia from Indian population. The characterization of underlying GALT gene lesions was performed in 55 unrelated galactosemia patients. The GALT mutational spectrum comprised 16 distinct mutations including 10 previously unreported mutations. N314D was the most common mutation with a frequency of 40% followed by Q188R at 2.7%. The novel GALT gene mutations included 6 missense mutations viz. Y89H, Q103R, P166A, S181F, K285R, R333L; one nonsense mutation, S307X and 3 silent mutations — Q103Q, K210K and H319H. The functional significance of the novel GALT missense mutations was investigated using SNPs&GO and SIFT tools. Further, modeling studies using 3D models of mutant and wild type GALT proteins revealed mutations to exert their effects at the molecular level by altering H-bonds, salt bridges, secondary structure or surface features. The study highlighted the heterogeneity of classical galactosemia in the Indian population and also emphasizes the importance of GALT gene analysis in diagnosis of galactosemia. It also revealed that the Indian GALT mutational profile differs significantly from other populations studied.

Mutation spectrum in the French cohort of galactosemic patients and structural simulation of 27 novel missense variations

BackgroundClassic galactosemia refers to galactose-1-phosphate uridyltransferase (GALT) deficiency and is characterized by long-term complications of unknown mechanism and high allelic heterogeneity of GALT gene. AimTo report molecular characterization of GALT variations in 210 French families, to analyze the structural effects of novel missense variations and to assess informativity of structural data in predicting outcome. MethodsSequencing of exons and intron–exon junctions of GALT gene was completed in unsolved cases by analysis of a long range PCR product. Structural consequences of novel missense variations were predicted using a homology model of GALT protein and a semi-automated analysis which integrates simulation of variations, structural analyses and two web servers dedicated to identify mutation-induced change of protein stability. ResultsForty four novel variations were identified, among them 27 nucleotide substitutions. In silico modeling of these missense variations showed that 12 variations are predicted to impair subunit interactions and/or active site conformation and that 23 variations modify H-bond or salt-bridge networks. Twenty variations decrease the global stability of the protein. Five variations had apparently no structural effect. ConclusionOur results expand the mutation spectrum in GALT gene and the list of GALT variations analyzed at the structural level, providing new data to assess the pathophysiology of galactosemia.

Frequency Distribution of Q188R, N314D, Duarte 1, and Duarte 2 GALT Variant Alleles in an Indian Galactosemia Population

Classical galactosemia is a genetic disorder caused by mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. The Q188R and N314D mutations are the most frequently cited GALT gene mutations. N314D is further associated with two variants, Duarte 1 and Duarte 2. Nevertheless, no reports are available on the clinical and molecular spectrum of galactosemia from the Indian population. The present study was designed to establish the frequency of these two most common mutations and their variants in Indian galactosemia patients so as to determine a single most common mutation/polymorphism for establishing the DNA-based diagnosis of galactosemia. Three alleles were found to be present at a frequency of 0.036 (Q188R), 0.40 (N314D), and 0.39 (D2); no D1 alleles were found. A significantly higher frequency of the Duarte 2 allele in our population suggests the presence of a milder form of galactosemia, which can be well managed by early diagnosis and dietary management.

Molecular and biochemical characterization of the GALT gene in Korean patients with galactose-1-phosphate uridyltransferase deficiency

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. 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. 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. The genetic constitution of the GALT gene is responsible for galactosemia in the Korean population.

Coexistence of Duarte 1 and Duarte 2 variants of galactosemia with extrahepatic biliary atresia

Galactosemia is an autosomal recessive disorder caused by deficient or absent activities of one of the three enzymes involved in the galactose metabolic pathway. The predominant form is classic type galactosemia caused by severe reduction or absence of the galactose- 1-phosphate uridyl transferase (GALT) enzyme. Coexistence of extrahepatic biliary atresia (EHBA) with Duarte 1 and 2 variants of galactosemia has not been described earlier. Here we report a case of EHBA with concordant Duarte 1 and 2 variants of galactosemia in an infant with cholestasis. Genetic analysis of the index patient for galactosemia revealed presence of Duarte 1/Duarte 2 variants of galactosemia with genotype N314D-L218L/N314D-G1105C-GI391A- G1323A-5’UTR-119delGTCA. Clinical evaluation of the patient showed the presence of EHBA. Henceforth, it may be hypothesized that EHBA may have a genetic basis with simultaneous involvement of the GALT gene.

The role of human demographic history in determining the distribution and frequency of transferase-deficient galactosaemia mutations

Classical or transferase-deficient galactosaemia is an inherited metabolic disorder caused by mutation in the human Galactose-1-phosphate uridyl transferase (GALT) gene. Of some 170 causative mutations reported, fewer than 10% are observed in more than one geographic region or ethnic group. To better understand the population history of the common GALT mutations, we have established a haplotyping system for the GALT locus incorporating eight single nucleotide polymorphisms and three short tandem repeat markers. We analysed haplotypes associated with the three most frequent GALT gene mutations, Q188R, K285N and Duarte-2 (D2), and estimated their age. Haplotype diversity, in conjunction with measures of genetic diversity and of linkage disequilibrium, indicated that Q188R and K285N are European mutations. The Q188R mutation arose in central Europe within the last 20 000 years, with its observed east-west cline of increasing relative allele frequency possibly being due to population expansion during the re-colonization of Europe by Homo sapiens in the Mesolithic age. K285N was found to be a younger mutation that originated in Eastern Europe and is probably more geographically restricted as it arose after all major European population expansions. The D2 variant was found to be an ancient mutation that originated before the expansion of Homo sapiens out of Africa.

Negative screening tests in classical galactosaemia caused by S135L homozygosity

Classical galactosaemia is relatively common in Ireland due to a high carrier rate of the Q188R GALT mutation. It is screened for using a bacterial inhibition assay (BIA) for free galactose. A Beutler assay on day one of life is performed only in high risk cases (infants of the Traveller community and relatives of known cases). A 16-month-old Irish-born boy of Nigerian origin was referred for investigation of developmental delay, and failure to thrive. He had oral aversion to solids and his diet consisted of cow's milk and milk-based cereal mixes. He was found to have microcephaly, weight <2nd percentile, hepatomegaly and bilateral cataracts. Coagulation screen was normal and transaminases were slightly elevated. His original newborn screen was reviewed and confirmed to have been negative; urinary reducing substances on three separate occasions were negative. Beutler assay demonstrated "absent" red cell galactose-1-phosphate uridyltransferase (GALT) activity. GALT enzyme activity was <0.5 gsubs/h per gHb confirming classical galactosaemia. Gal-1-P was elevated at 1.88 micromol/gHb. Mutation analysis of the GALT gene revealed S135L homozygosity. S135L/S135L galactosaemia is associated with absent red cell GALT activity but with approximately 10% activity in other tissues such as the liver and intestines, probably explaining the negative screening tests and the somewhat milder phenotype associated with this genotype. The patient was commenced on galactose-restricted diet; on follow-up at 2 years of age, growth had normalized but there was global developmental delay. In conclusion, galactosaemia must be considered in children who present with poor growth, hepatomegaly, developmental delay and cataracts and GALT enzyme analysis should be a first line test in such cases. Non-enzymatic screening methods such as urinary reducing substances and BIA for free galactose are not reliable in S135L homozygous galactosaemia.

Galactosaemia in a Brazilian population: High incidence and cost–benefit analysis

To study the incidence of galactosaemia in the state of São Paulo and the benefit/cost (B/C) ratio of the introduction of neonatal screening for galactosaemia, comparing it with a selective approach. An enzymatic-colorimetric assay was used for the screening of total galactose (TG) in a sample of 10% of the births in São Paulo in one year and positive cases were confirmed by the activity of galactose-1-phosphate uridyltransferase (GALT). Detected and referred cases were genotyped using enzyme restriction studies for Q188R, N314D and S135L mutations of the GALT gene. The economic analysis was determined by calculating the B/C ratio and by analysis of sensitivity as a function of the incidence of the disease detected and the variation of the interest rate in the economy. 59 953 newborns were screened for TG, with 3 cases of galactosaemia being identified (0.26% false positives), corresponding to a frequency of 1:19 984 liveborns (95% confidence interval: 1:7494 to 1:59 953). One classical case and one Duarte 2 variant referred to as a selective approach were confirmed. With an incidence of 1:19 984, the B/C ratio was 1.04 for the 11.75% interest rate in effect in Brazil, with values already decapitalized. With a maximum possible incidence of 1:7494, the B/C ratio was 2.79. There is an economic advantage in introducing neonatal screening for galactosaemia in the national neonatal screening programme. This advantage could increase with a reduction of the current interest rates in the economy.

Low allelic heterogeneity in a sample of Mexican patients with classical galactosaemia

Classical galactosaemia is an autosomal recessive disease of galactose metabolism caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). Galactosaemia is not included in the neonatal screening programme in Mexico and it is necessary to implement methodologies for prompt diagnosis of these patients to establish treatment. To date, more than 190 mutations in the GALT gene have been reported, most in caucasian populations, but there have been no reports of mutations in Latin-American populations. We report here the mutational spectrum in 19 Mexican galactosaemic patients. The most frequent mutations were p.Q188R, p.N314D and IVS2-2A>G, which together represented 71% of detected mutations. The mutation IVS2-2A>G, which has been detected only in Hispanics, was thought to generate a null allele; we identified one patient with a homozygous IVS2-2A>G mutation who showed a mild deficiency of enzyme value in erythrocytes. One patient homozygous for Duarte 2 (p.N314D, IVS5+62G>A) is probably due to a partial uniparental disomy of chromosome 9. In addition, a novel mutation c.336T>C (p.S112R) was detected in one patient with severe enzymatic deficiency. Despite the small number of patients studied, our results suggest that classical galactosaemia shows low allelic heterogeneity in Mexican patients, in contrast what is observed in other Mendelian disorders such as cystinosis or autosomal dominant hypercholesterolaemia. This low allelic heterogeneity might be explained by a "population of origin" effect in the central region of Mexico, as has been described for phenylketonuria.

Newborn screening for classic galactosaemia and primary congenital hypothyroidism in the Nkangala district of Mpumalanga province, South Africa

Objectives: The main objective of this work was to establish the newborn incidence of classic galactosemia and congenital hypothyroidism within the Nkangala district of Mpumalanga. In the process a cost effective protocol for newborn screening of both diseases was developed. Study design and setting: Blood spot specimens were collected from over 30 % of newborn infants in the Nkangala district of Mpumalanga Province in a six month period from June to November 2005. The specimens were subsequently screened for classic galactosemia and hypothyroidism using metabolite quantification assays. GALT (galactose-1-phosphate uridyltransferase) enzyme activity assays were also performed to confirm the reliability of the total galactose assays. Real-time PCR was used to detect commonly occurring mutations in the GALT gene that cause galactosemia. Subjects and outcome measures: Informed consent was obtained from the parents of the newborn infants prior to commencement of screening. Total galactose levels of above 0,9 mg/L and TSH concentrations of above 25,1 mU/L were considered to be indicative of galactosemia and hypothyroidism, respectively. A decrease in the total financial input on the screening protocol was evaluated for significance in cost reduction. Results: The incidence of hypothyroidism was found to be 0.1 % while none of the newborns presented with classic galactosemia. There was up to 20 % reduction in direct input costs of screening when our protocol is applied. Conclusion: Cost effective newborn screening is possible when classic galactosemia and congenital hypothyroidism are screened, simultaneously. Cumulative disease frequency plots confirm the already established fact that hypothyroidism tends to prevail in higher frequencies than classic galactosemia