title: β-1 tubulin R307H SNP alters microtubule dynamics and affects severity of a hereditary thrombocytopenia.
abstract: BACKGROUND
  Single nucleotide polymorphisms (SNPs) in platelet-associated genes partly explain inherent variability in platelet counts. Patients with monoallelic Bernard Soulier syndrome due to the Bolzano mutation (GPIBA A156V) have variable platelet counts despite a common mutation for unknown reasons.
  
  
  OBJECTIVE
  We investigated the effect of the most common SNP (R307H) in the hematopoietic-specific tubulin isotype β-1 in these Bernard Soulier patients and potential microtubule-based mechanisms of worsened thrombocytopenia.
  
  
  METHODS
  Ninety-four monoallelic Bolzano mutation patients were evaluated for the R307H β-1 SNP and had platelet counts measured by three methods; the Q43P SNP was also evaluated. To investigate possible mechanisms underlying this association, we used molecular modeling of β-1 tubulin with and without the R307H SNP. We transfected SNP or non-SNP β-1 tubulin into MCF-7 and CMK cell lines and measured microtubule regrowth after nocodazole-induced depolymerization.
  
  
  RESULTS
  We found that patients with at least one R307H SNP allele had significantly worse thrombocytopenia; manual platelet counting revealed a median platelet count of 124 in non-SNP patients and 76 in SNP patients (both ×10(9)  L(-1) ; P < 0.01). The Q43P SNP had no significant association with platelet count. Molecular modeling suggested a structural relationship between the R307H SNP and microtubule stability via alterations in the M-loop of β tubulin; in vitro microtubule recovery assays revealed that cells transfected with R307H SNP β-1 had significantly impaired microtubule recovery.
  
  
  CONCLUSIONS
  Our data show that the R307H SNP is significantly associated with the degree of thrombocytopenia in congenital and acquired platelet disorders, and may affect platelets by altering microtubule behavior.
authors.affiliation: Department of Medicine, Weill Cornell Medical College, New York, NY, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Basciano
authors.forename: J
authors.initials: J
authors.lastname: Matakas
authors.forename: A
authors.initials: A
authors.lastname: Pecci
authors.forename: E
authors.initials: E
authors.lastname: Civaschi
authors.forename: C
authors.initials: C
authors.lastname: Cagioni
authors.forename: N
authors.initials: N
authors.lastname: Bompiani
authors.forename: P
authors.initials: P
authors.lastname: Burger
authors.forename: P
authors.initials: P
authors.lastname: Christos
authors.forename: J P
authors.initials: JP
authors.lastname: Snyder
authors.forename: J
authors.initials: J
authors.lastname: Bussel
authors.forename: C L
authors.initials: CL
authors.lastname: Balduini
authors.forename: P
authors.initials: P
authors.lastname: Giannakakou
authors.forename: P
authors.initials: P
authors.lastname: Noris
mesh_terms: D001606:Bernard-Soulier Syndrome / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D006801:Humans; D061986:MCF-7 Cells; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D008958:Models, Molecular; D010641:Phenotype; D010976:Platelet Count; D020641:Polymorphism, Single Nucleotide; D011487:Protein Conformation; D055550:Protein Stability; D012720:Severity of Illness Index; D013329:Structure-Activity Relationship; D014162:Transfection; D014404:Tubulin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D005819:Genetic Markers; C578986:TUBB1 protein, human; D014404:Tubulin; D050257:Tubulin Modulators
keywords: Bernard-Soulier syndrome; beta-tubulin; cytoskeleton; microtubules; polymorphism, single nucleotide