Age, JAK2(V617F) and SF3B1 mutations are the main predicting factors for survival in refractory anaemia with ring sideroblasts and marked thrombocytosis.

Refractory anaemia with ring sideroblasts (RARS) and marked thrombocytosis (RARS-T) is a provisional entity in the World Health Organisation 2008 classification and has previously been shown to have a high proportion of JAK2(V617F) (Janus Kinase 2) and SF3B1 (Splicing Factor 3B subunit 1) mutations. The purpose of the present study was to analyse the frequency of SF3B1 mutations in a large cohort of 111 patients with RARS-T and 33 patients with RARS and to explore the prognostic impact of SF3B1 mutational status on RARS-T. The frequency of SF3B1 mutations in RARS-T (96/111, 86.5%) and RARS (28/33, 84.8%) was similar. In RARS-T, median survival was better in SF3B1-mutated patients than in SF3B1-non-mutated patients (6.9 and 3.3 years, respectively, P=0.003). RARS can be differentiated from RARS-T by the frequency of JAK2(V617F) (0% vs 48.6%). In RARS-T patients, SF3B1 (P=0.021) and JAK2 mutations (P=0.016) were independent factors for a better prognosis. Altogether, our results confirm that RARS-T is an independent entity that should be recognised by the next World Health Organisation classification. The assessment of SF3B1 mutations is of prognostic interest in RARS-T patients. Younger age, JAK2(V617F) and SF3B1 mutations are the main predicting factors for survival in RARS-T.

Severe impairment of nucleotide synthesis through inhibition of mitochondrial respiration.

Since de-novo synthesis of pyrimidine nucleotides is coupled to the mitochondrial respiratory chain (RC) via dehydroorotic acid dehydrogenase (DHODH), respiratory chain dysfunction should impair pyrimidine synthesis. To investigate this, we used specific RC inhibitors, Antimycin A and Rotenone, to treat primary human keratinocytes and 143B cells, a human osteosarcoma cell line, in culture. This resulted in severe impairment of de novo pyrimidine nucleotide synthesis. The effects of RC inhibition were not restricted to pyrimidine synthesis, but concerned purine nucleotides, too. While the total amount of purine nucleotides was not diminished, they were significantly broken down from triphosphates to monophosphates, reflecting impaired mitochondrial ATP regeneration. The effect of Rotenone was similar to that of Antimycin A. This was surprising since Rotenone inhibits complex I of the respiratory chain, which is upstream of ubiquinone where DHODH interacts with the RC. In order to avoid unspecific effects of Rotenone, we examined the consequences of a mitochondrial DNA mutation that causes a specific complex I defect. The effect was much less pronounced than with Rotenone, suggesting that complex I inhibiton cannot fully explain the marked effect of Rotenone on pyrimidine nucleotide synthesis.

Live now--pay by ageing: high performance mitochondrial activity in youth and its age-related side effects.

Radical oxygen species are a byproduct of normal energy metabolism in mitochondria. The short-lived radicals cause damage to their immediate surrounding, i.e. the mitochondria. While most of this damage will be removed by normal mitochondrial turnover, damage to mitochondrial DNA (mtDNA) can persist and may accumulate with age. Recent evidence indicates that mutant mtDNA molecules can accumulate within individual cells, potentially hampering mitochondrial function.

Detection of point mutations by capillary electrophoresis with temporal temperature gradients.

By combining the advantages of capillary electrophoresis and temperature gradient gel electrophoresis, a method was developed to detect point mutations in polymerase chain reaction (PCR) fragments. Increasing and decreasing temporal temperature gradients were established by means of a computer-controlled Peltier module. Native and denaturing conditions were achieved by cooling to 25 degrees C and heating to 70 degrees C, respectively, a thermostating liquid surrounding the capillary. To separate nucleic acid fragments, a sieving media, containing 4% linear polyacrylamide, 1 x Tris borate EDTA buffer (TBE) and 6 M urea, was found appropriate. Renewal of the sieving matrix before each run significantly improved the reproducibility of fragment separation. The ability of this capillary electrophoresis system to detect point mutations is demonstrated with the human prion-protein gene.

Scanning for mutations in the human prion protein open reading frame by temporal temperature gradient gel electrophoresis.

Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal familial insomnia (FFI) and familial Creutzfeldt-Jakob disease (CJD) are caused by point mutations or octarepeat insertions in the prion protein (PrP) gene. In the present work a method was established that is appropriate for a thorough screening for mutations in the PrP gene and is generally applicable to screenings of any given gene. Temperature gradient gel electrophoresis (TGGE) was modified at two critical steps by UV cross-linking of the DNA strands and by replacing the spatial gradient with a temporal one. The shift of a DNA band in temporal temperature gradient gel electrophoresis (tTGGE) due to a mutation can be calculated as a function of the position of the mutation in the sequence. Appropriate DNA fragments were selected for polymerase chain reaction (PCR) amplification and analysis by tTGGE on the basis that the predicted band shifts amount to more than 10% of the migration distance for all possible mutations. The accuracy of the prediction was tested experimentally with ten known mutations in the human PrP gene, and quantitative agreement between theory and experiment was achieved. Thus, this screening method is also a suitable means to verify the absence of mutations in a given gene segment.

Prions and nucleic acids: search for "residual" nucleic acids and screening for mutations in the PrP-gene.

Studies on prions involve nucleic acid chemistry under two headings: i) do infectious prion particles contain nucleic acids? ii) is it possible by a simple procedure to screen the prion protein (PrP)-gene for mutations? The return refocusing gel electrophoresis technique was developed to detect by sensitive silver staining homogeneous and heterogeneous nucleic acids extracted from highly purified scrapie prion preparations. With this method all kinds of nucleic acids from a length of 13 nucleotides up to several thousand could be recovered and detected with a yield over 90%. Despite extensive nuclease digestion some small polynucleotides remained. The results define clear restrictions for a hypothetical scrapie-specific nucleic acid. If homogeneous in size, such a molecule would be smaller than 80 nucleotides in length at a particle-to-infectivity ratio near unity; if heterogeneous, scrapie-specific nucleic acids would have to include molecules smaller than 240 nucleotides. To detect mutations in the PrP-gene, either known mutations from human prion diseases or artificial ones in transgenic animals, or to screen for not yet identified mutations in patients, a method is required which guarantees detection of mutations which might occur in every single position of the whole PrP-ORF. It will be shown that a combination of PCR and temperature-gradient gel electrophoresis fulfils these requirements. By thermodynamic calculations the shift in the gel electrophoresis due to a mutation can be calculated depending on the position of the mutation. The theoretical results were tested with the mutations known so far.

Temperature-gradient gel electrophoresis for the detection of polymorphic DNA and for quantitative polymerase chain reaction.

In order to detect mutations in a gene, either known mutations from human diseases or artificial ones in transgenic animals, or to screen for not yet identified mutations in patients, a method is required which guarantees detection of mutations which might occur in every single position of the whole open reading frame (ORF). It will be shown that a combination of polymerase chain reaction (PCR) and temperature gradient gel electrophoresis (TOGE) fulfills these requirements. By thermodynamic calculations the shift in the gel electrophoresis due to a mutation can be calculated in dependence on the position of the mutation. The theoretical results were tested with the mutations known so far. The quantitative determination of the copy number of a specific DNA or RNA sequence in a biological specimen (quantitative PCR) can be performed precisely and easily by combining PCR and TGGE. The system uses a quantification strategy of a new type of internal standardization. TGGE is applied to separate homo- and heteroduplexes which correspond respectively to standard and template sequences. The accuracy of this quantification strategy is very high, with a variability of < 15%. In addition to quantification, PCR/TGGE detects PCR artifacts and template mutants.