• Zihni Onur Çalışkaner, Abdullah Abdul Waheed, Merve Tuzlakoğlu Öztürk, Yeşim Oymak, Uygar Halis Tazebay, Nejat Akar, Ayten Kandilci, and Didem Torun Özkan.
• Department of Molecular Biology and Genetics, Faculty of Science, Gebze Technical University, Kocaeli, Turkey
• Turk J Med Sci. 2021 Apr 30; 51 (2): 490-500.

Background/AimMacrothrombocytopenia is an autosomal-dominant disorder characterized by increased platelet size and a decreased number of circulating platelets. The membrane skeleton and the link between actin filaments of the skeleton and microtubules, which consist of alpha and beta tubulin [including the tubulin beta-1 chain (TUBB1)] heterodimers, are important for normal platelet morphology, and defects in these systems are associated with macrothrombocytopenia.Materials And MethodsIn this study, we sequenced the exons of the TUBB1 gene using DNA isolated from the peripheral blood samples of healthy controls (n = 47) and patients with macrothrombocytopenia (n = 37) from Turkey. The TUBB1 expression levels in fractioned blood samples from patients and healthy controls were analyzed by RT-qPCR and Western blot. Microtubule organization of the platelets in the peripheral blood smears of patients, and in mutant TUBB1-transfected HeLa cells, were analyzed by immunofluorescence staining.ResultsA new TUBB1 c.803G>T (p.T178T) variant was detected in all of the control and patient samples. Importantly, we found 3 new heterozygous TUBB1 variants predicting amino acid substitutions: G146R (in 1 patient), E123Q (in 1 patient), and T274M (in 4 patients); the latter variant was associated with milder thrombocytopenia in cancer patients treated with paclitaxel. Ectopic expression of TUBB1 T274M/R307H variant in HeLa cells resulted in irregular microtubule organization.ConclusionFurther clinical and functional studies of the newly identified TUBB1 variants may offer important insights into their pathogenicity in macrothrombocytopenia.This work is licensed under a Creative Commons Attribution 4.0 International License.

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