Thromb Haemost 2011; 106(04): 693-704
DOI: 10.1160/TH11-02-0126
Platelets and Blood Cells
Schattauer GmbH

Mutations responsible for MYH9-related thrombocytopenia impair SDF-1-driven migration of megakaryoblastic cells

Alessandro Pecci
1   Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia, Italy
,
Valeria Bozzi
1   Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia, Italy
,
Emanuele Panza
2   Department of Gynaecological, Obstetric, and Paediatric Sciences, University of Bologna, Bologna, Italy
3   Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, USA
,
Serena Barozzi
1   Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia, Italy
,
Cristian Gruppi
4   Department of Biochemistry, University of Pavia, Pavia, Italy
,
Marco Seri
2   Department of Gynaecological, Obstetric, and Paediatric Sciences, University of Bologna, Bologna, Italy
,
Carlo L. Balduini
1   Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia, Italy
› Author Affiliations

Financial support: This study was supported by a grant from the Telethon Foundation (GGP06177).
Further Information

Publication History

Received: 23 February 2011

Accepted after major revision: 11 July 2011

Publication Date:
29 November 2017 (online)

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Summary

MYH9-related disease (MYH9-RD) is an autosomal-dominant thrombocytopenia caused by mutations in the gene for the heavy chain of nonmuscle myosin-IIA (NMMHC-IIA). Recent in vitro studies led to the hypothesis that thrombocytopenia of MYH9-RD derives from an ectopic platelet release by megakaryocytes in the osteoblastic areas of bone marrow (BM), which are enriched in type I collagen, rather than in vascular spaces. SDF-1-driven migration of megakaryocytes within BM to reach the vascular spaces is a key mechanism for platelet biogenesis. Since myosin-IIA is implicated in polarised migration of different cell types, we hypothesised that MYH9 mutations could interfere with this mechanism. We therefore investigated the SDF-1-driven migration of a megakaryoblastic cell line, Dami cells, on type I collagen or fibrinogen by a modified transwell assay. Inhibition of myosin-IIA ATPase activity suppressed the SDF-1-driven migration of Dami cells, while over-expression of NMMHC-IIA increased the efficiency of chemotaxis, indicat- ing a role for NMMHC-IIA in this mechanism. Transfection of cells with three MYH9 mutations frequently responsible for MYH9-RD (p.R702C, p.D1424H, or p.R1933X) resulted in a defective SDF-1-driven migration with respect to the wild-type counterpart and in increased cell spreading onto collagen. Analysis of differential localisation of wild-type and mutant proteins suggested that mutant NMMHC-IIAs had an impaired cytoplasmic re-organisation in functional cytoskeletal structures after cell adhesion to collagen. These findings support the hypothesis that a defect of SDF-1-driven migration of megakaryocytes induced by MYH9 mutations contributes to ectopic platelet release in the BM osteoblastic areas, resulting in ineffective platelet production.