OBJECTIVE: We examined platelet functions in 4 unrelated patients with filaminopathy A caused by dominant mutations of the X-linked filamin A (FLNA) gene. METHODS AND RESULTS: Patients P1, P2, and P4 exhibited periventricular nodular heterotopia, heterozygozity for truncating FLNA mutations, and thrombocytopenia (except P2). P3 exhibited isolated thrombocytopenia and heterozygozity for a p.Glu1803Lys FLNA mutation. Truncated FLNA was undetectable by Western blotting of P1, P2, and P4 platelets, but full-length FLNA was detected at 37%, 82%, and 57% of control, respectively. P3 FLNA (p.Glu1803Lys and full-length) was assessed at 79%. All patients exhibited a platelet subpopulation negative for FLNA. Platelet aggregation, secretion, glycoprotein VI signaling, and thrombus growth on collagen were decreased for P1, P3, and P4, but normal for P2. For the 2 patients analyzed (P1 and P4), spreading was enhanced and, more markedly, in FLNA-negative platelets, suggesting that FLNA negatively regulates cytoskeleton reorganization. Platelet adhesion to von Willebrand factor under flow correlated with platelet full-length FLNA content: markedly reduced for P1 and P4 and unchanged for P2. Interestingly, von Willebrand factor flow adhesion was increased for P3, consistent with a gain-of-function effect enhancing glycoprotein Ib-IX-V/von Willebrand factor interaction. These results are consistent with a positive role for FLNA in platelet adhesion under high shear. CONCLUSIONS: FLNA mutation heterogeneity correlates with different platelet functional impacts and points to opposite regulatory roles of FLNA in spreading and flow adhesion under shear.
OBJECTIVE: We examined platelet functions in 4 unrelated patients with filaminopathy A caused by dominant mutations of the X-linked filamin A (FLNA) gene. METHODS AND RESULTS:PatientsP1, P2, and P4 exhibited periventricular nodular heterotopia, heterozygozity for truncating FLNA mutations, and thrombocytopenia (except P2). P3 exhibited isolated thrombocytopenia and heterozygozity for a p.Glu1803LysFLNA mutation. Truncated FLNA was undetectable by Western blotting of P1, P2, and P4 platelets, but full-length FLNA was detected at 37%, 82%, and 57% of control, respectively. P3 FLNA (p.Glu1803Lys and full-length) was assessed at 79%. All patients exhibited a platelet subpopulation negative for FLNA. Platelet aggregation, secretion, glycoprotein VI signaling, and thrombus growth on collagen were decreased for P1, P3, and P4, but normal for P2. For the 2 patients analyzed (P1 and P4), spreading was enhanced and, more markedly, in FLNA-negative platelets, suggesting that FLNA negatively regulates cytoskeleton reorganization. Platelet adhesion to von Willebrand factor under flow correlated with platelet full-length FLNA content: markedly reduced for P1 and P4 and unchanged for P2. Interestingly, von Willebrand factor flow adhesion was increased for P3, consistent with a gain-of-function effect enhancing glycoprotein Ib-IX-V/von Willebrand factor interaction. These results are consistent with a positive role for FLNA in platelet adhesion under high shear. CONCLUSIONS:FLNA mutation heterogeneity correlates with different platelet functional impacts and points to opposite regulatory roles of FLNA in spreading and flow adhesion under shear.
Authors: T Khatlani; S Pradhan; Q Da; F C Gushiken; A L Bergeron; K W Langlois; J D Molkentin; R E Rumbaut; K V Vijayan Journal: J Thromb Haemost Date: 2014-11-15 Impact factor: 5.824
Authors: Antonija Jurak Begonja; Fred G Pluthero; Worawit Suphamungmee; Silvia Giannini; Hilary Christensen; Richard Leung; Richard W Lo; Fumihiko Nakamura; William Lehman; Markus Plomann; Karin M Hoffmeister; Walter H A Kahr; John H Hartwig; Hervé Falet Journal: Blood Date: 2015-04-02 Impact factor: 22.113