scholarly journals Kinetic properties of mutant deoxyguanosine kinase in a case of reversible hepatic mtDNA depletion

2007 ◽  
Vol 402 (2) ◽  
pp. 377-385 ◽  
Author(s):  
Bénédicte Mousson de camaret ◽  
Jan-Willem Taanman ◽  
Sylvie Padet ◽  
Maïté Chassagne ◽  
Martine Mayençon ◽  
...  
Keyword(s):  
Stop Codon ◽  
Donor Site ◽  
Residual Activity ◽  
Premature Stop Codon ◽  
Nucleoside Triphosphate ◽  
Kinetic Properties ◽  
Missense Mutations ◽  
Mtdna Depletion ◽  
Deoxyguanosine Kinase ◽  
Phosphate Donor

DGUOK [dG (deoxyguanosine) kinase] is one of the two mitochondrial deoxynucleoside salvage pathway enzymes involved in precursor synthesis for mtDNA (mitochondrial DNA) replication. DGUOK is responsible for the initial rate-limiting phosphorylation of the purine deoxynucleosides, using a nucleoside triphosphate as phosphate donor. Mutations in the DGUOK gene are associated with the hepato-specific and hepatocerebral forms of MDS (mtDNA depletion syndrome). We identified two missense mutations (N46S and L266R) in the DGUOK gene of a previously reported child, now 10 years old, who presented with an unusual revertant phenotype of liver MDS. The kinetic properties of normal and mutant DGUOK were studied in mitochondrial preparations from cultured skin fibroblasts, using an optimized methodology. The N46S/L266R DGUOK showed 14 and 10% residual activity as compared with controls with dG and deoxyadenosine as phosphate acceptors respectively. Similar apparent negative co-operativity in the binding of the phosphate acceptors to the wild-type enzyme was found for the mutant. In contrast, abnormal bimodal kinetics were shown with ATP as the phosphate donor, suggesting an impairment of the ATP binding mode at the phosphate donor site. No kinetic behaviours were found for two other patients with splicing defects or premature stop codon. The present study represents the first characterization of the enzymatic kinetic properties of normal and mutant DGUOK in organello and our optimized protocol allowed us to demonstrate a residual activity in skin fibroblast mitochondria from a patient with a revertant phenotype of MDS. The residual DGUOK activity may play a crucial role in the phenotype reversal.

Mutations of TET2 and JAK2 but Not CBL Are Detectable in a High Portion of Patients with Refractory Anemia with Ring Sideroblasts and Thrombocytosis (RARS-T).

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1766-1766
Author(s):  
Johanna Flach ◽  
Sonja Schindela ◽  
Frank Dicker ◽  
Susanne Schnittger ◽  
Alexander Kohlmann ◽  
...  
Keyword(s):  
Microarray Analysis ◽  
Stop Codon ◽  
Myeloproliferative Neoplasms ◽  
Premature Stop Codon ◽  
Jak2v617f Mutation ◽  
Refractory Anemia ◽  
Missense Mutations ◽  
Myeloid Malignancies ◽  
Ring Sideroblasts ◽  
Equity Ownership

Abstract Abstract 1766 Poster Board I-792 Refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) forms a provisional entity within the category of MDS/MPN-U in the 2008 WHO classification. Although the identification of the JAK2V617F mutation was an important first step in distinguishing this entity from other hematological diseases, further genetic characterization is necessary. We performed comprehensive cytogenetic and molecular genetic investigations including targeted analysis of JAK2V617F, TET2, MPLW515 and CBL, markers known to be altered in MPN, as well as genome-wide single nucleotide polymorphism microarray analysis (SNP-A) in 23 RARS-T patients who fulfilled WHO 2008 diagnostic criteria. The JAK2V617F mutation was detectable in 15 out of 19 analyzed patients (78.9%), four of which were homozygous. However, our patients neither carried a MPLW515 mutation nor mutations in exons 8 or 9 of CBL genes. These genes were recently described to be mainly mutated in myeloproliferative neoplasms. In addition, conventional cytogenetic analysis did not reveal any recurrent cytogenetic abnormalities in RARS-T patients. We also performed SNP microarray analysis in a subset of 10 RARS-T patients. Although we did neither observe recurrent chromosomal gains or losses nor recurring regions of UPD, one patient showed a deletion spanning a 1.3 Mb region on the long arm of chromosome 4 (start: 105,497,200 bp from pter; end: 106,825,780 bp from pter). The deleted region contained TET2, a gene recently found to be altered in many subtypes of myeloid malignancies. To further clarify the 4q24 deletion detected by SNP-A analysis we performed fluorescence in situ hybridization (FISH). 20 out of 100 analyzed interphase nuclei and three metaphases showed only one signal for the probe spanning the TET2 gene in this patient. Interphase FISH with the TET2 probe was performed in nine additional cases not analyzed by SNP arrays due to a lack of material, but no additional case showing a deletion was detected. In addition to FISH, we performed TET2 sequencing in 19/23 RARS-T patients. TET2 mutations were detected in 5/19 patients (26%), of which 3/5 also presented the JAK2V617F mutation, whereas the remaining 2/5 did neither show JAK2V617F nor MPL nor CBL mutations. The five patients showed 6 individually different TET2 mutations. Three were nonsense and two missense mutations. One patient displayed a frameshift mutation leading to a premature stop codon. In summary, RARS-T patients demonstrated a high frequency of both JAK2 and TET2 mutations. Together with the less common MPL mutations described by others RARS-T presents a variety of mutations that overlap with the spectrum of mutations seen in MPN and other myeloid malignancies. Thus, a combination of molecular markers including JAK2 and TET2 should be investigated to more precisely describe RARS-T as an independent disease entity. Disclosures Flach: MLL Munich Leukemia Laboratory: Employment. Schindela:MLL Munich Leukemia Laboratory: Employment. Dicker:MLL Munich Leukemia Laboratory: Employment. Schnittger:MLL Munich Leukemia Laboratory: Equity Ownership. Kohlmann:MLL Munich Leukemia Laboratory: Employment. Weiss:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Equity Ownership.

scholarly journals Erratum: clinical and molecular characteristics of patients with 46,xy dsd due to nr5a1 gene mutations (Probl Endokrinol (Mosk). 2020 Sep 16;66(3):62-69. Russian. doi: 10.14341/probl12445)

2021 ◽  
Vol 67 (6) ◽  
pp. 124-126
Author(s):  
N. Yu. Kalinchenko ◽  
A. A. Kolodkina ◽  
N. Yu. Raygorodskaya ◽  
A. N. Tiulpakov
Keyword(s):  
Stop Codon ◽  
Premature Stop Codon ◽  
Gene Mutations ◽  
Synonymous Substitution ◽  
Molecular Characteristics ◽  
Missense Mutations ◽  
Reading Frame ◽  
Splicing Site

n the article some corrections were needed. Abstract: “Heterozygous SF1 variants were found in 36 out of 310 (11.6%) of cases, among them 15 were not previously described”. has been corrected to read “Heterozygous SF1 variants were found in 36 out of 310 (11.6%) of cases, among them 22 were not previously described”. Results: “Heterozygous SF1 variants were found in 36 out of 310 (11.6%) of cases, among them 15 were not previously described”, has been corrected to read “Heterozygous SF1 variants were found in 36 out of 310 (11.6%) of cases, among them 22 were not previously described”. Among the newly identified variants in the NR1A1 gene, two lead to the premature stop codon -p. Y197X and p. Y25X, two lead to a shift in the reading frame-p. N385fs and p. L245fs, which does not allow us to doubt their pathogenicityAmong the previously undescribed variant changes, 5 missense mutations (p. C283Y, p. C283B, p.H24Q, p.M126K, p.E81K) and 1  synonymous substitution affecting the splicing site (E330E) were evaluated as pathogenic, and 5 others as probably pathogenic.Has been corrected to read: Among the newly identified variants in the NR1A1 gene, two lead to the premature stop codon -p. Y197X and p. Y25X, two lead to a shift in the reading frame — p.N385SfsX10 and p.L245AfsX53, which does not allow us to doubt their pathogenicity Among the previously undescribed variants, 5 missense mutations (p.C283Y, p.С283F, p.H24Q, p.M126K, p.A82T) and 1 synonymous substitution affecting the splicing site (E330E) were predicted as pathogenic, and 5 others as probably pathogenic by calculating pathogenicity. The authors apologize for these errors. 

scholarly journals Band 3 Campinas: A Novel Splicing Mutation in the Band 3 Gene (AE1 ) Associated With Hereditary Spherocytosis, Hyperactivity of Na+/Li+ Countertransport and an Abnormal Renal Bicarbonate Handling

Blood ◽  
1997 ◽  
Vol 90 (7) ◽  
pp. 2810-2818 ◽  
Author(s):  
Paulo R.M. Lima ◽  
José A.R. Gontijo ◽  
José B. Lopes de Faria ◽  
Fernando F. Costa ◽  
Sara T.O. Saad
Keyword(s):  
Hereditary Spherocytosis ◽  
Stop Codon ◽  
Collecting Duct ◽  
Direct Sequencing ◽  
Donor Site ◽  
Premature Stop Codon ◽  
Band 3 ◽  
Base Substitution ◽  
Molecular Defect ◽  
Urinary Acidification

Abstract We have studied the molecular defect underlying band 3 deficiency in one family with hereditary spherocytosis using nonradioactive single strand conformation polimorphism of polymerase chain reaction (PCR) amplified genomic DNA of the AE1 gene. By direct sequencing, a single base substitution in the splicing donor site of intron 8 (position + 1G → T) was identified. The study of the cDNA showed a skipping of exon 8. This exon skipping event is responsible for a frameshift leading to a premature stop codon 13 amino acids downstream. The distal urinary acidification test by furosemide was performed to verify the consequences of the band 3 deficiency in α intercalated cortical collecting duct cells (αICCDC). We found an increased basal urinary bicarbonate excretion, associated with an increased basal urinary pH and an efficient distal urinary acidification. We also tested the consequences of band 3 deficiency on the Na+/H+ exchanger, by the measurement of Na+/Li+ countertransport activity in red blood cells. The Na+/Li+ countertransport activity was increased threefold to sixfold in the patients compared with the controls. It is possible that band 3 deficiency in the kidney leads to a decrease in the reabsorption of HCO−3 in αICCDC and anion loss, which might be associated with an increased sodium-lithium countertransport activity.

scholarly journals Evolution of the human gastrokine locus and confounding factors regarding the pseudogenicity of GKN3

2013 ◽  
Vol 45 (15) ◽  
pp. 667-683 ◽  
Author(s):  
Jessica H. Geahlen ◽  
Carlo Lapid ◽  
Kaisa Thorell ◽  
Igor Nikolskiy ◽  
Won Jae Huh ◽  
...  
Keyword(s):  
Selective Sweep ◽  
Stop Codon ◽  
Genetic Locus ◽  
Donor Site ◽  
Premature Stop Codon ◽  
Population Based ◽  
Splice Donor Site ◽  
Human Populations ◽  
Selective Sweeps ◽  
Gastric Mucous

In a screen for genes expressed specifically in gastric mucous neck cells, we identified GKN3, the recently discovered third member of the gastrokine family. We present confirmatory mouse data and novel porcine data showing that mouse GKN3 expression is confined to mucous cells of the corpus neck and antrum base and is prominently expressed in metaplastic lesions. GKN3 was proposed originally to be expressed in some human populations and a pseudogene in others. To investigate that hypothesis, we studied human GKN3 evolution in the context of its paralogous genomic neighbors, GKN1 and GKN2. Haplotype analysis revealed that GKN3 mimics GKN2 in patterns of exonic SNP allocation, whereas GKN1 appeared to be more stringently selected. GKN3 showed signatures of both directional selection and population based selective sweeps in humans. One such selective sweep includes SNP rs10187256, originally identified as an ancestral tryptophan to premature STOP codon mutation. The derived (nonancestral) allele went to fixation in Asia. We show that another SNP, rs75578132, identified 5 bp downstream of rs10187256, exhibits a second selective sweep in almost all Europeans, some Latinos, and some Africans, possibly resulting from a reintroduction of European genes during African colonization. Finally, we identify a mutation that would destroy the splice donor site in the putative exon3-intron3 boundary, which occurs in all human genomes examined to date. Our results highlight a stomach-specific human genetic locus, which has undergone various selective sweeps across European, Asian, and African populations and thus reflects geographic and ethnic patterns in genome evolution.

scholarly journals Band 3 Campinas: A Novel Splicing Mutation in the Band 3 Gene (AE1 ) Associated With Hereditary Spherocytosis, Hyperactivity of Na+/Li+ Countertransport and an Abnormal Renal Bicarbonate Handling

Blood ◽  
1997 ◽  
Vol 90 (7) ◽  
pp. 2810-2818
Author(s):  
Paulo R.M. Lima ◽  
José A.R. Gontijo ◽  
José B. Lopes de Faria ◽  
Fernando F. Costa ◽  
Sara T.O. Saad
Keyword(s):  
Hereditary Spherocytosis ◽  
Stop Codon ◽  
Collecting Duct ◽  
Direct Sequencing ◽  
Donor Site ◽  
Premature Stop Codon ◽  
Band 3 ◽  
Base Substitution ◽  
Molecular Defect ◽  
Urinary Acidification

We have studied the molecular defect underlying band 3 deficiency in one family with hereditary spherocytosis using nonradioactive single strand conformation polimorphism of polymerase chain reaction (PCR) amplified genomic DNA of the AE1 gene. By direct sequencing, a single base substitution in the splicing donor site of intron 8 (position + 1G → T) was identified. The study of the cDNA showed a skipping of exon 8. This exon skipping event is responsible for a frameshift leading to a premature stop codon 13 amino acids downstream. The distal urinary acidification test by furosemide was performed to verify the consequences of the band 3 deficiency in α intercalated cortical collecting duct cells (αICCDC). We found an increased basal urinary bicarbonate excretion, associated with an increased basal urinary pH and an efficient distal urinary acidification. We also tested the consequences of band 3 deficiency on the Na+/H+ exchanger, by the measurement of Na+/Li+ countertransport activity in red blood cells. The Na+/Li+ countertransport activity was increased threefold to sixfold in the patients compared with the controls. It is possible that band 3 deficiency in the kidney leads to a decrease in the reabsorption of HCO−3 in αICCDC and anion loss, which might be associated with an increased sodium-lithium countertransport activity.

Molecular basis of glutathione reductase deficiency in human blood cells

Blood ◽  
2006 ◽  
Vol 109 (8) ◽  
pp. 3560-3566 ◽  
Author(s):  
Nanne M. Kamerbeek ◽  
Rob van Zwieten ◽  
Martin de Boer ◽  
Gert Morren ◽  
Herma Vuil ◽  
...  
Keyword(s):  
Red Blood Cells ◽  
Glutathione Reductase ◽  
Blood Cells ◽  
Stop Codon ◽  
Residual Activity ◽  
Premature Stop Codon ◽  
Dimerization Domain ◽  
Human Blood Cells ◽  
Glutathione Reductase Deficiency ◽  
Conserved Residue

Abstract Hereditary glutathione reductase (GR) deficiency was found in only 2 cases when testing more than 15 000 blood samples. We have investigated the blood cells of 2 patients (1a and 1b) in a previously described family suffering from favism and cataract and of a novel patient (2) presenting with severe neonatal jaundice. Red blood cells and leukocytes of the patients in family 1 did not contain any GR activity, and the GR protein was undetectable by Western blotting. Owing to a 2246-bp deletion in the patients' DNA, translated GR is expected to lack almost the complete dimerization domain, which results in unstable and inactive enzyme. The red blood cells from patient 2 did not exhibit GR activity either, but the patient's leukocytes contained some residual activity that correlated with a weak protein expression. Patient 2 was found to be a compound heterozygote, with a premature stop codon on one allele and a substitution of glycine 330, a highly conserved residue in the superfamily of NAD(P)H-dependent disulfide reductases, into alanine on the other allele. Studies on recombinant GR G330A revealed a drastically impaired thermostability of the protein. This is the first identification of mutations in the GR gene causing clinical GR deficiency.

scholarly journals Novel loss-of-function mutation in HERC2 is associated with severe developmental delay and paediatric lethality

2020 ◽  
pp. jmedgenet-2020-106873
Author(s):  
Marilena Elpidorou ◽  
Sunayna Best ◽  
James A Poulter ◽  
Verity Hartill ◽  
Emma Hobson ◽  
...  
Keyword(s):  
Autosomal Recessive ◽  
Stop Codon ◽  
Neurodevelopmental Disorder ◽  
Premature Stop Codon ◽  
Homozygous Deletion ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Functional Characterisation ◽  
Mitochondrial Functions ◽  
And Function

BackgroundThe HERC2 gene encodes a 527 kDa E3 ubiquitin protein ligase that has key roles in cell cycle regulation, spindle formation during mitosis, mitochondrial functions and DNA damage responses. It has essential roles during embryonic development, particularly for neuronal and muscular functions. To date, missense mutations in HERC2 have been associated with an autosomal recessive neurodevelopmental disorder with some phenotypical similarities to Angelman syndrome, and a homozygous deletion spanning HERC2 and OCA2 causing a more severe neurodevelopmental phenotype.Methods and resultsWe ascertained a consanguineous family with a presumed autosomal recessive severe neurodevelopmental disorder that leads to paediatric lethality. In affected individuals, we identified a homozygous HERC2 frameshift variant that results in a premature stop codon and complete loss of HERC2 protein. Functional characterisation of this variant in fibroblasts, from one living affected individual, revealed impaired mitochondrial network and function as well as disrupted levels of known interacting proteins such as XPA.ConclusionThis study extends the genotype–phenotype correlation for HERC2 variants to include a distinct lethal neurodevelopmental disorder, highlighting the importance of further characterisation for HERC2-related disorders.

scholarly journals ANGPTL6 genetic variants are an underlying cause of familial intracranial aneurysms

Neurology ◽  
2020 ◽  
pp. 10.1212/WNL.0000000000011125
Author(s):  
Isabel C Hostettler ◽  
Benjamin O’Callaghan ◽  
Enrico Bugiardini ◽  
Emer O’Connor ◽  
Jana Vandrovcova ◽  
...  
Keyword(s):  
Family History ◽  
Genetic Variants ◽  
Intracranial Aneurysms ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Small Subset ◽  
Missense Mutations ◽  
Class Iii ◽  
Exon 2 ◽  
History Of

Background and Purpose:To understand the role of the angiopoietin-like 6 gene (ANGPTL6) in intracranial aneurysms (IA) we investigated its role in a large cohort of familial IAs.Methods:Inclusion of individuals with family history of IA recruited to the Genetic and Observational Subarachnoid Haemorrhage (GOSH) study. The ANGPTL6 gene was sequenced using Sanger sequencing. Identified genetic variants were compared to a control population.Results:We found six rare ANGPTL6 genetic variants in 9/275 individuals with a family history of IA (3.3%), none of them were present in controls: Five missense and one nonsense mutation leading to a premature stop codon. One of these had been previously reported: c.392A>T (p.Glu131Val) on exon 2, another was very close: c.332G>A (p.Arg111His). Two further genetic variants lie within the fibrinogen-like domain of the ANGPTL6 gene, which may influence function or level of the ANGPTL6 protein. The last two missense mutations lie within the coiled-coil domain of the ANGPTL6 protein. All genetic variants were well conserved across species.Conclusion:ANGPTL6 genetic variants are an important cause of IA. Defective or lack of ANGPTL6 protein is therefore an important factor in blood vessel proliferation leading to IA; dysfunction of this protein is likely to cause abnormal proliferation or weakness of vessel walls. With these data, not only do we emphasise the importance of screening familial IA cases for ANGPTL6 and other genes involved in IA, but also highlight the ANGPTL6 pathway as a potential therapeutic target.Classification of Evidence:This is a Class III study showing some specificity of presence of the ANGPTL6 gene variant as a marker of familial intracranial aneurysms in a small subset of those with familial aneurysms.

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