1,720,965 research outputs found
Role of neuraminidase - dependent adherence in Bacteroides fragilis attachment to human epithelial cells.
No full textHupf1 and hupf2 knockdown by RNA interference in HEPG2 cells as a model to study nonsense-mediated mRNA decay modulation of coagulation-gene expression
No full textRecurrence of the “deep-intronic” FGG IVS6-320A>T mutation causing quantitative fibrinogen deficiency in the Italian population of Veneto
No full textQuantitative fibrinogen deficiency is a rare bleeding disorder characterized by abnormally low levels of fibrinogen in plasma, generally due to mutations in one of the three fibrinogen genes: FGA, FGB, and FGG, coding for A[alpha], B[beta], and [gamma] chain, respectively. Although the partial defect (hypofibrinogenemia) is due to mutations occurring in the heterozygous state, homozygosity or compound heterozygosity for the same genetic defects give rise to the more severe afibrinogenemia. Mutations responsible for these conditions are scattered throughout the three fibrinogen genes, with only few sites representing relative mutational hot spots. In this study, we report the identification of the FGG IVS6-320A>T mutation in an Italian hypofibrinogenemic patient from Veneto (a region of North-Eastern Italy). This ‘deep-intronic’ mutation, which would go unnoticed by using conventional mutational screening strategies was previously reported in an afibrinogenemic family from Vicenza (a province of Veneto). The geographic clustering of patients carrying the FGG IVS6-320A>T mutation and the results of haplotype analysis suggest the existence of a common founder. This information will be useful to direct future genetic screenings in patients coming from the same geographic area
Mutations leading to premature termination codons in the Von Willebrand factor gene are associated with the decay of the mutant mRNAs
No full textMutations leading to premature termination codons in the Von Willebrand factor gene are associated with allele-specific mRNAs decay
No full textIdentificazione e caratterizzazione della prima mutazione missense nel gene per la catena Aalpha del fibrinogeno responsabile di afibrinogenemia congenita
No full textLa carenza di fattore V (FV) della coagulazione è una rara malattia emorragica (MIM+227400) con una prevalenza nella popolazione generale di 1:1.000.000. Essa può essere distinta in carenza di tipo I (quantitativa), caratterizzata da livelli bassi o non misurabili di antigene per il FV, e carenza di tipo II (qualitativa), con livelli di proteina immunoreattiva
nomali o lievemente ridotti associati a marcata carenza funzionale. La carenza grave di tipo I è un carattere autosomico recessivo mentre la maggior parte dei pazienti con carenza lieve o moderata risulta essere eterozigote. Quasi tutte le mutazioni finora riportate in
letteratura (32) sono state identificate in famiglie singole e causano, in due terzi dei casi, l’introduzione di codoni di stop prematuri (PTC) nel gene F5, che consta di 25 esoni e mappa in posizione 1q23. Lo studio delle basi molecolari della carenza di FV in 5 pazienti non imparentati di diversa origine etnica ha consentito l’identificazione di 5 nuove mutazioni nel
gene F5: una mutazione nonsense Trp1797stop), due mutazioni di splicing (IVS8+6T>C e IVS24+1_+4delGTAG) e due mutazioni missense (Phe523Ser e Ser1970Ile). Analisi mediante RT-PCR su RNA piastrinico hanno consentito di dimostrare che la mutazione Trp1797stop determina la degradazione del corrispondente trascritto, probabilmente a seguito dell’attivazione del pathway NMD (Nonsense-Mediated mRNA Decay). Il ruolo patogenetico delle mutazioni missense e di splicing è in corso di caratterizzazione funzionale mediante l’utilizzo di costrutti minigenici del gene F5 (per analizzare gli eventi di splicing
aberrante) e di vettori di espressione contenenti il cDNA per il FV mutato (per analizzare le conseguenze a livello proteico delle due mutazioni missense)
Alterations of mRNA processing and stability as a pathogenic mechanism in von Willebrand factor quantitative deficiencies
No full textIntroduction: von Willebrand disease (VWD) is an inherited bleeding disorder due to a deficiency or abnormality of von Willebrand factor (VWF), associated with heterogeneous phenotypes. While VWD mutations acting at the protein level have been deeply investigated, fewer data are available on genetic defects affecting VWF mRNA. Aim: The aim of this study was to characterize the molecular mechanism underlying VWD in three patients. Methods: Mutational screening of the patients (P1-3) was accomplished by DNA sequencing of all VWF exons and splicing junctions. Platelet mRNA was analyzed by reverse-transcription (RT)-PCR and real-time RT-PCR. Results: P1 is a compound heterozygote for a c.1534-3C>A transversion in intron 13 and for a nonsense mutation (p.Q77X) in exon 4. P2 is heterozygous for a splicing mutation in intron 9 (c.1109+2T>C). RT-PCR assays on the patient's platelet RNA revealed three mRNA populations: (i) wild type; (ii) lacking exon 9; and (iii) lacking exons 8 and 9. P3 showed a novel homozygous splicing mutation in intron 46 (c.7770+1G>T), producing three different mRNA species: (i) retaining the first 25-bp of intron 46; (ii) skipping exon 46; and (iii) skipping exon 46 while retaining 5-bp of intron 45. Whenever possible, the effect of mutations on the levels of VWF transcripts was analyzed, showing that mRNA variants containing a premature termination codon are downregulated, probably by the nonsense-mediated mRNA decay pathway. Conclusions: The identification of the genetic basis of VWD in three patients confirmed that mutations leading to null alleles in the VWF gene are associated with allele-specific mRNA degradation. © 2010 International Society on Thrombosis and Haemostasis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Congenital hypofibrinogenemia : characterization of two missense mutations affecting fibrinogen assembly and secretion
No full textCongenital hypofibrinogenemia is a rare bleeding disorder characterized by abnormally low levels of fibrinogen in plasma, generally due to heterozygous mutations in one of the three fibrinogen genes (FGA, FGB, and FGG, coding for Aalpha, Bbeta, and gamma chain, respectively). Hypofibrinogenemic patients are usually asymptomatic, whereas individuals bearing similar mutations in the homozygous or compound heterozygous state develop a severe bleeding disorder: afibrinogenemia. The mutational spectrum of these quantitative fibrinogen disorders includes large deletions, point mutations causing premature termination codons, and missense mutations affecting fibrinogen assembly or secretion, distributed throughout the 50-kb fibrinogen gene cluster. In this study, we report the mutational screening of two unrelated hypofibrinogenemic patients leading to the identification of two missense mutations, one hitherto unknown (alphaCys45Phe), and one previously described (gammaAsn345Ser). The involvement of alphaCys45Phe and gammaAsn345Ser in the pathogenesis of hypofibrinogenemia was investigated by in-vitro expression experiments. Both mutations were demonstrated to cause a severe impairment of intracellular fibrinogen processing, either by affecting half-molecule dimerization (alphaCys45Phe) or by hampering hexamer secretion (gammaAsn345Ser)
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