Mutation of the 1-tubulin gene associated with congenital macrothrombocytopenia affecting microtubule assembly

Department of Hemostasis and Thrombosis, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.
Blood (Impact Factor: 10.45). 11/2008; 113(2):458-61. DOI: 10.1182/blood-2008-06-162610
Source: PubMed

ABSTRACT Congenital macrothrombocytopenia is a genetically heterogeneous group of rare disorders. We identified the first TUBB1 mutation, R318W, in a patient with congenital macrothrombocytopenia. The patient was heterozygous for Q43P, but this single-nucleotide polymorphism (SNP) did not relate to macrothrombocytopenia. Although no abnormal platelet beta1-tubulin localization/marginal band organization was observed, the level of beta1-tubulin was decreased by approximately 50% compared with healthy controls. Large and irregular bleb protrusions observed in megakaryocytes derived from the patient's peripheral blood CD34(+) cells suggested impaired megakaryocyte fragmentation and release of large platelets. In vitro transfection experiments in Chinese hamster ovary (CHO) cells demonstrated no incorporation of mutant beta1-tubulin into microtubules, but the formation of punctuated insoluble aggregates. These results suggested that mutant protein is prone to aggregation but is unstable within megakaryocytes/platelets. Alternatively, mutant beta1-tubulin may not be transported from the megakaryocytes into platelets. W318 beta1-tubulin may interfere with normal platelet production, resulting in macrothrombocytopenia.

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Available from: Ryoji Kobayashi, Sep 29, 2015
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    • "␤1- tubulin is the major isoform of tubulin in MKs and is necessary for PPF (Wang et al., 1986; Schwer et al., 2001). Mutations in ␤1- tubulin (Tubb1) cause autosomal dominant thrombocytopenia in humans (Kunishima et al., 2009). Although pharmacological disruption of the actin cytoskeleton does not prevent PP extension, actin is involved in the bifurcation of PPs which increases PP tip number (Italiano et al., 1999). "
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    ABSTRACT: Platelets are small, anucleate blood cells which play an important role in haemostasis. Thrombocytopenia is a condition where the platelet count falls below 150×10(9)/litre and patients suffering from severe forms of this condition can experience life-threatening bleeds requiring platelet transfusions. Platelets are produced from large progenitor cells called megakaryocytes which are found in the bone marrow. The process of megakaryocyte maturation and the formation of proplatelets are essential steps in the production of mature platelets and both depend heavily on the actin and microtubule cytoskeletons. Understanding these processes is important for the development of in vitro platelet production which will help to treat thrombocytopenia as well as produce model systems for studying platelet-associated disorders. This review will highlight some of the recent advances in our understanding of the role of the cytoskeleton in platelet production, especially the key molecules and signalling pathways that regulate actin and microtubule crosstalk. Copyright © 2015. Published by Elsevier Ltd.
    The international journal of biochemistry & cell biology 07/2015; 66. DOI:10.1016/j.biocel.2015.07.008 · 4.05 Impact Factor
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    • "The principle of benzimidazole resistance is closely associated with point mutations in the β-tubulin genes that change the structure of the fungicide-binding point (Gafur et al. 1998; Albertini et al. 1999; Peres et al. 2004; Chung et al. 2006; Davidson et al. 2006; Ziogas et al. 2009). T274I, R282Q, and Q292E mutations significantly weakened the interactions and binding of the drugs taxol and epothilone (Natarajan and Senapati 2012), while Q43P and R318W mutations had a significant impact on platelet physiology in immune thrombocytopenia (Freson et al. 2005; Kunishima et al. 2009; Navarro- Nunez et al. 2011). The genetics of carbendazim resistance in Aspergillus nidulans (van Tuyl 1977), Ustilago maydis (Ziogas and Girgis 1993) and other fungal species revealed that in most cases it was based on a single gene. "
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    ABSTRACT: The application of fungicides is so critical, especially in greenhouses, to avoid fungal infections. Carbendazim, an inhibitor of tubulin biosynthesis, is the most widely known broad-spectrum benzimidazole fungicide. The application of carbendazim affects other beneficial fungi as well. Paecilomyces lilacinus 36-1 (Pl36-1) is a beneficial fungus used for biological control, and the most effective biocontrol agents of nematode eggs. The Pl36-1 is sensitive to carbendazim (0.3 μg/ml). There is a general consensus that the mechanisms of resistance to carbendazim in the β-tubulin gene have been analyzed in detail. However, no studies were conducted on P. lilacinus strains. In the present study, two carbendazim-resistant mutants of Pl36-1, P50 and P100, were obtained from UV exposure and tested. The β-tubulin gene fragments were cloned and sequenced in the three strains, Pl36-1, P50 and P100. The resistance to carbendazim was developed when amino acid substitutions occurred at β-tubulin gene positions of S145A, T185A and F200Y. The β-tubulin gene was overexpressed in Pl36-1 strains. The β-tubulin expression level of the overexpressed mutant (PL3), quantified by qRT-PCR, was increased 4-folds over its normal level in Pl36-1. In vitro, the PL3 was resistant to carbendazim with maintaining growth, sporulation and pathogenicity rates. Three-year field trial demonstrated that P100 and PL3 strains exhibited carbendazim resistance combined with high nematode reduction and yield improvement.
    European Journal of Plant Pathology 05/2015; 143(1):57-68. DOI:10.1007/s10658-015-0665-0 · 1.49 Impact Factor
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    • "Mks were normally represented in proband BM biopsy, and in vitro development of patient Mks was normal. However , Mks presented an abnormal morphology consistent with impaired proplatelet extension and release (Kunishima et al, 2009). In addition to the in vitro studies on PPF referenced above, other in vivo evidences support the role of b1 tubulin in regulating platelet number and size. "
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    ABSTRACT: Our knowledge of the cellular and molecular mechanisms of platelet production has greatly expanded in recent years due to the opportunity to culture in vitro megakaryocytes and to create transgenic animals with specific genetic defects that interfere with platelet biogenesis. However, in vitro models do not reproduce the complexity of the bone marrow microenvironment where megakaryopoiesis takes place, and experience shows that what is seen in animals does not always happen in humans. So, these experimental models tell us what might happen in humans, but does not assure us that these events really occur. In contrast, inherited thrombocytopenias offer the unique opportunity to verify in humans the actual effects of abnormalities in specific molecules on platelet production. There are currently 20 genes whose defects are known to result in thrombocytopenia and, on this basis, this review tries to outline a model of megakaryopoiesis based on firm evidence. Inherited thrombocytopenias have not yet yielded all the information they can provide, because nearly half of patients have forms that do not fit with any known disorder. So, further investigation of inherited thrombocytopenias will advance not only the knowledge of human illnesses, but also our understanding of human platelet production.
    British Journal of Haematology 01/2014; 165(2). DOI:10.1111/bjh.12752 · 4.71 Impact Factor
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