Dynamin-2 deficiency causes age- and sex-dependent neutropenia and myelodysplasia in mice

Abstract

The dynamins are a family of ubiquitously expressed GTPase proteins, best known for their role in membrane remodeling. Their contribution to hematopoiesis is incompletely recognized. Individuals with Charcot-Marie-Tooth disease with dynamin-2 mutations often develop neutropenia. We previously reported that dynamin (DNM) inhibition impairs SDF1a-mediated migration in megakaryocytes. Here, we report on conditionally Dnm2 deleted mice in hematopoietic tissues using the Vav-Cre murine strain. Homozygous Dnm2 deletion in blood tissues is embryonic lethal. Dnm2het male mice only developed a slightly decreased hemoglobin level. Dnm2het female mice developed leukopenia by 40 weeks of age and neutropenia by 65 weeks of age. Flow cytometry revealed decreased lineage-negative cells and granulocyte-monocyte progenitors in Dnm2het female mice. Immunohistochemical staining of bone marrow for mature neutrophils with Ly6G was decreased and myelodysplastic features were present in the bone marrow of Dnm2het female mice. A linear distribution of Ly6G+ bone marrow cells along blood vessels was observed in fewer Dnm2het mice than in controls, suggesting that the migration pattern in the marrow is altered. Marrow neutrophils treated with dynamin inhibitor dynasore showed increased cell surface CXCR4, suggesting that abnormal migration results in marrow neutrophil retention. Dnm2het female mice also developed splenomegaly secondary to germinal center hyperplasia at younger ages, suggesting perturbed immunity. In summary, female mice with bone marrow Dnm2 haploinsufficiency developed neutropenia as they aged with decreased granulocyte progenitor production and migration defects. Our studies indicate a potential mechanism for the development of chronic idiopathic neutropenia, a disease that predominantly presents in middle-aged women.