Galactosemia Mutations Research Articles

Clinical profile and molecular characterization of Galactosemia in Brazil: identification of seven novel mutations.

BackgroundClassical Galactosemia (CG) is an inborn error of galactose metabolism caused by the deficiency of the galactose-1-phosphate uridyltransferase enzyme. It is transmitted as an autosomal recessive disease and is typically characterized by neonatal galactose intolerance, with complications ranging from neonatal jaundice and liver failure to late complications, such as motor and reproductive dysfunctions. Galactosemia is also heterogeneous from a molecular standpoint, with hundreds of different mutations described in the GALT gene, some of them specific to certain populations, reflecting consequence of founder effect.MethodsThis study reviews the main clinical findings and depicts the spectrum of mutations identified in 19 patients with CG, six with Duarte Galactosemia and one with type 2 Galactosemia in Brazil. Some individuals were diagnosed through expanded newborn screening test, which is not available routinely to all newborns.ResultsThe main classical Galactosemia mutations reported to date were identified in this study, as well as the Duarte variant and seven novel mutations - c.2 T > C (p.M1T), c.97C > A (p.R33S), c.217C > T (p.P73S), c.328 + 1G > A (IVS3 + 1G > A), c.377 + 4A > C (IVS4 + 4A > C), c.287_289delACA (p.N97del) and c.506A > C (p.Q169P). This was expected, given the high miscegenation of the Brazilian population.ConclusionsThis study expands the mutation spectrum in GALT gene and reinforces the importance of early diagnosis and introduction of dietary treatment, what is possible with the introduction of Galactosemia in neonatal screening programs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12881-016-0300-8) contains supplementary material, which is available to authorized users.

Analysis of common mutation for GALT gene in newborns with galacatosemia Nineveh governorate

Iraq contains many diseases that have never been counted or examined, including diseases related to food, which has deteriorated in recent years, and has rapid and direct impact especially on the children category, one of these diseases is galactosemia. Classical galactosemia, deficiency of galac tose-1-phosphate uridyltransferase GALT, is characterized by acute symptoms of hepatomegaly, jaundice, sepsis, cataract, vomiting, and diarrhea and growth retardation. Our previous molecular study showed that the most common mutation of the GALT gene is a missense mutation of Q188R (replacement of glutamine-188 by arginine in exon 6 and N314D mutation replacement of aspargen-314 by aspartic acid) in exon 10. The aim of this study was to determine the possibility of diagnosing galacatosemia, and to search for galactosemia mutation Q188R and N314D in Iraqi population. Blood samples were collected from babies admitted to the children's hospitals in Mosul City depending on the clinical symptoms of disease and then serum was taken. Measuring the Galactose-1-Phosphate uridylytransferase GALT enzyme activity and galactose -1- phosphate in serum by ELISA technique was done. DNA samples were analyzed by the polymerase chain reaction followed by digestion with restriction endonuclease HpaΙΙ and AvaΙΙ for Q188R and N314D mutation. The results showed a significant decrease in the level of the GALT enzyme in children with galactosemia 21.7 ± 0.45 and among non-diagnosed children 79.93 ± 1.44 compared with control group 160.33 ± 0.93 as well as a significant decrease in the level of the enzyme among mothers 20.5 ± 1.92 was observed. Gal-1-P level was significantly higher in the cases than that of the control group, while that of the not diagnosed children and mothers groups showed inconsistent difference. Also the result showed absence allele frequency for Q188R mutation and present allele frequency for N314D mutation in Iraqi population. In conclusions It is possible to depend on measurement of Galactose-1-Phosphate as indicator in the diagnosis of Galactosemia in newborn, the main mutation in GALT gene causes galactosemia is N314D in Iraqi population.

Heterozygosity for the Classical Galactosemia Mutation Does Not Affect Ovarian Reserve and Menopausal Age

Female patients with classical galactosemia (galactose-1-phosphate uridyltransferase [GALT] deficiency) frequently suffer from premature ovarian failure, despite treatment with a galactose-restricted diet. Earlier research has suggested an association between heterozygosity for GALT mutations and early menopause. This study evaluates the effect of carriership for classical galactosemia on ovarian reserve and menopausal age. Proven female carriers of classical galactosemia were recruited via the Dutch Galactosemia Society. All 58 participants underwent a structured interview regarding fertility, smoking status, and menopause. To determine ovarian reserve, 42 premenopausal GALT carriers underwent ovarian antral follicle count (AFC) by transvaginal ultrasound and early follicular phase blood sampling for hormonal measurement of follicle-stimulating hormone (FSH), inhibin B, and anti-Müllerian hormone (AMH). These ovarian reserve parameters were compared with a cohort of proven fertile women (n = 166). The mean age at menopause in GALT carriers was 49.7 years, which is not different from the mean age at menopause in the general population in the Netherlands. There was no difference in FSH, inhibin B, and AMH levels or in the AFC (when corrected for age and smoking status) between 42 premenopausal GALT carriers and controls. The authors conclude that there is no evidence that GALT mutation carriership affects ovarian reserve or menopausal age.

Higher frequency of the galactose-1-phosphate uridyl transferase gene K285N mutation in the Slovenian population

Objectives: To analyze a healthy Slovenian population for the frequency of the classical galactosemia allele K285N. Design and methods: DNA was analyzed by means of polymerase chain reaction and restriction fragment length polymorphism. Results: The allele frequency of the K285N mutation in Slovenian population is 0.29%. Conclusions: The allele frequency of the K285N mutation in Slovenian population is higher than in other Caucasian populations. K285N is one of the most frequent classical galactosemia mutations in the Slovenian population.

Molecular detection of galactosemia mutations by PCR-ELISA.

AbstractClassic galactosemia is an autosomal recessive disorder caused by the deficiency of galactose 1-phosphate uridyltransferase, GALT (EC 2.7.7.12) (1). It presents with vomiting and diarrhea in neonates within a few days of milk intake. Most patients develop jaundice and hepatic failure. If untreated, it is potentially lethal. Newborn screening for galactosemia is routine in all states in the USA and in many other countries. Elimination of dietary galactose is the main treatment. However, this does not prevent secondary complications such as growth retardation, mental retardation, dyspraxia, cataracts, ataxia, and ovarian failure later in life (2).KeywordsPolymerase Chain Reaction ProductHybridization ReactionClassic GalactosemiaIntended PrimerPolymerase Chain Reaction Thermal CyclingThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Mutations at the galactose-1-p-uridyltransferase gene in infants with a positive galactosemia newborn screening test.

Newborn screening for galactosemia yields a high number of false-positive results. Confirmatory DNA testing for unknown galactosemia mutations on the initial positive sample using novel techniques of mutation detection tenders itself to reduce the recall rate. The potential benefits of confirmatory DNA testing, however, could be offset by the detection of a high percentage of galactosemia carriers, Duarte/galactosemia compound heterozygotes, and infants with benign sequence changes in the galactose-1-phosphate uridyltransferase (GALT) gene among infants with a positive biochemical screening test. Our aim was to determine the frequency and allelic distribution of all sequence changes in the GALT gene in 110 newborns with a positive total galactose screening test among 43,688 Austrian newborns screened consecutively. We found that only 20 of the 110 probands carried at least one known or novel candidate galactosemia mutation (one galactosemia homozygote, 7 Duarte/galactosemia compounds, 12 carriers) as judged by denaturing gradient gel electrophoresis and cleavage fragment length polymorphism analysis. Four novel galactosemia candidate mutations (Q9H, A46fsdelCAGCT, M129T, L342I) were identified. Sixty-seven probands had no detectable sequence changes and 23 carried only the benign Duarte or Los Angeles variant alleles or silent mutations. We conclude that a rapid and automatable confirmation test for unknown GALT mutations, e.g. on a high-density oligonucleotide array basis, has the potential to lower the recall rate of galactosemia screening in our population by about five-fold from 0.25 to 0.046%. Further research, however, will be required before the development of such a test can be advocated.

Identification of mutations in the galactose-1-phosphate uridyltransferase (GALT) gene in 16 Turkish patients with galactosemia, including a novel mutation of F294Y

Classical galactosemia caused by deficiency of galactose-1-phosphate uridyltransferase (GALT) is a severe autosomal recessive disorder. We report here molecular analysis of 16 unrelated Turkish galactosemia index cases without GALT activity. Almost 84% of all mutant alleles were identified in this study. The most common molecular defect observed in the Turkish population was Q188R (replacement of glutamine-188 by arginine) (57%). In order to facilitate the determination of unknown mutations in the entire coding region of GALT, we established an approach based on GALT cDNA synthesis and direct sequencing. We have identified one novel candidate galactosemia mutation, a T-to-A transversion at the codon 294 (F294Y) in exon 9 in addition to previously reported three missense (M142K K285N, A320T), one stop codon (E340X), and one silent (L218L) mutations in galactosemia patients which reflect considerable genetic heterogeneity in the Turkish population. © 1999 Wiley-Liss, Inc.

Identification of mutations in the galactose-1-phosphate uridyltransferase (GALT) gene in 16 Turkish patients with galactosemia, including a novel mutation of F294Y Communicated by: R.G.H. Cotton Online Citation: Human Mutation, Mutation in Brief #235 (1999) Online http://journals.wiley.com/1059-7794/pdf/mutation/235.pdf

Classical galactosemia caused by deficiency of galactose-1-phosphate uridyltransferase (GALT) is a severe autosomal recessive disorder. We report here molecular analysis of 16 unrelated Turkish galactosemia index cases without GALT activity. Almost 84% of all mutant alleles were identified in this study. The most common molecular defect observed in the Turkish population was Q188R (replacement of glutamine-188 by arginine) (57%). In order to facilitate the determination of unknown mutations in the entire coding region of GALT, we established an approach based on GALT cDNA synthesis and direct sequencing. We have identified one novel candidate galactosemia mutation, a T-to-A transversion at the codon 294 (F294Y) in exon 9 in addition to previously reported three missense (M142K K285N, A320T), one stop codon (E340X), and one silent (L218L) mutations in galactosemia patients which reflect considerable genetic heterogeneity in the Turkish population. © 1999 Wiley-Liss, Inc.

Molecular heterogeneity of classical and Duarte galactosemia: mutation analysis by denaturing gradient gel electrophoresis.

Classical galactosemia is caused by one common missense mutation (Q188R) and by several rare mutations in the galactose-1-phosphate uridyltransferase (GALT) gene. The most common variant of GALT, the Duarte variant, occurs as two types, Duarte-1 (D-1) and Duarte-2 (D-2), both of which carry the sequence change N314D. D-1 increases, whereas D-2 decreases GALT activity. To study the molecular genetics of classical and Duarte galactosemia, we analyzed the GALT mutations in 30 families with classical galactosemia, in 10 families with the D-2 variant and in 3 individuals carrying the D-1 allele by denaturing gradient gel electrophoresis (DGGE). DGGE detected 59 of the 60 classical galactosemia alleles. Q188R accounted for 60%, K285N accounted for 28% of these alleles. Eight novel candidate galactosemia mutations were found. On all D-2 alleles N314D occurred in cis with two intronic sequence changes, on the D-1 alleles in cis with a neutral mutation in exon 7. We conclude that the mutations causing galactosemia are highly heterogeneous and that K285N is a second common galactosemia mutation in our population.

Linkage disequilibrium between a SacI restriction fragment length polymorphism and two galactosemia mutations.

We have identified a novel SacI restriction fragment length polymorphism (RFLP) in the human galactose-1-phosphate uridyl transferase (GALT) gene. This RFLP can be readily typed by the polymerase chain reaction (PCR). The polymorphic allele is found on about 11% of normal chromosomes and is in linkage disequilibrium with the two most common mutations identified in GALT thus far: Q188R and N314D. Q188R is found exclusively on chromosomes with the SacI restriction site, whereas N314D is found only on chromosomes lacking this site. This suggests that these two mutations arose independently in evolution on different chromosomal backgrounds. Galactosemia patients without the Q188R mutation have a frequency of the SacI polymorphism similar to normal controls suggesting that several different galactosemia mutations must be present in them. The SacI RFLP may also be useful in the prenatal diagnosis of galactosemia.

Molecular characterization of galactosemia (Type 1)mutations in Japanese

We characterized two novel mutations of the galactose-1-phosphate uridyltransferase (GALT) gene in two Japanese patients with GALT deficiency and identified N314D and R333W mutations, previously found in Caucasians. One novel missense mutation was an G-to-A transition in exon 8, resulting in the substitution of arginine by histidine at the codon 231 (R231H). GALT activity of the R231H mutant construct was reduced to 15% of normal controls in a COS cell expression system. The other was a splicing mutation, an A-to-G transition at the 38th nucleotide in exon 3 (318A-->G), resulting in a 38-bp deletion in the GALT cDNA by activating a cryptic splice acceptor site. In seven Japanese families (14 alleles for classic form and one allele for Duarte variant) with GALT deficiency, the R231H and 318A-->G mutations were found only on both alleles of the proband. The N314D and R333W mutations were found on one allele each. The Q188R was prevalent in the United States but not in Japanese patients. The N314D mutation was associated with the Duarte variant in Japanese persons, as well as in the United States. We speculate that classic galactosemia mutations appear to differ between Japanese and Caucasian patients. Our limited data set on galactosemia mutations in Japanese suggests that the N314D GALT mutation encoding the Duarte variant arose before Asian and Caucasian people diverged and that classic galactosemia mutations arose and/or accumulated after the divergence of Asian and Caucasian populations.

Molecular characterization of two galactosemia mutations and one polymorphism: implications for structure-function analysis of human galactose-1-phosphate uridyltransferase.

We report here the molecular characterization of two galactosemia mutations, L74P and F171S, and one polymorphism, S135L, in human galactose-1-phosphate uridyltransferase (GALT). Both galactosemia mutations result in reduced enzymatic activity when reconstructed in the cDNA and overexpressed. The polymorphism, in contrast, has near normal activity. Both mutations affect evolutionarily conserved residues, suggesting that they are functionally important, while the polymorphism occurs in a nonconserved domain which is presumably not critical for enzymatic function. The F171S mutation is close to the putative active-site nucleophile. Our data further support the notion of molecular heterogeneity of galactosemia and suggest that galactosemia mutations and GALT polymorphisms may be useful tools in highlighting different functional domains in human GALT.

Characterization of two missense mutations in human galactose-1-phosphate uridyltransferase: Different molecular mechanisms for galactosemia

We report the molecular characterization of two novel galactosemia mutations that exhibit different molecular phenotypes. Both are of the missense type with low or no residual enzyme activity. The R148W mutation results in an unstable protein, although messenger RNA is still produced. In contrast, the L195P mutation produces stable but inactive immunoreactive protein. The R148W mutation alters an amino acid that is not evolutionarily conserved, while the L195P mutation affects a well-conserved residue nine amino acids downstream from the putative active site nucleophile. These mutations provide evidence that different mechanisms can result in galactosemia: destabilizing mutations in any given area of the protein and missense mutations in conserved domains of the enzyme resulting in low or no activity. These two mutant alleles represent the fifth and sixth galactosemia mutations and confirm the hypothesis that galactosemia results from a multiplicity of mutations at the molecular level.

Molecular basis of galactosemia: mutations and polymorphisms in the gene encoding human galactose-1-phosphate uridylyltransferase.

We describe the molecular characterization of two mutations responsible for galactosemia, an inherited disorder of galatose metabolism that causes jaundice, cataracts, and mental retardation in humans. The coding region of galactose-1-phosphate uridylyltransferase (GALT; UDPglucose:alpha-D-galactose-1-phosphate uridylyltransferase, EC 2.7.7.12) was amplified by the polymerase chain reaction from total cDNA of a classic galactosemic individual and was characterized by direct sequencing of the products. Two missense mutations were identified: (i) replacement of valine-44 by methionine and (ii) replacement of methionine-142 by lysine. These mutations led to a drastic reduction in GALT activity when individual mutant cDNAs were overexpressed in a mammalian cell system, although full-length protein is synthesized in this assay. The two galactosemia mutations account for 3 of the 15 galactosemia alleles analyzed. These results suggest that galactosemia is caused by a variety of mutations, which might be responsible for the observed clinical heterogeneity of this disorder. We also present the molecular characterization of two GALT polymorphisms: (i) replacement of leucine-62 by methionine and (ii) replacement of asparagine-314 by aspartate. It appears that galactosemia mutations tend to occur in regions that are highly conserved throughout evolution while the polymorphisms change variable residues.