I am particularly interested in dissecting the molecular mechanism of hematopoietic cell migration, including neutrophils and hematopoietic stem cells in physiological settings. Migration is a critical function of hematopoietic cell in which actin cytoskeleton reorganization plays a central role. Because hematopoietic cells are utilized for the therapy of multiple blood diseases and neutrophils are responsible for maintaining an immunocompetence status, understanding the molecular mechanism of normal hematopoietic cell functions is of potential therapeutic importance. The small RHO GTPase family, members of the Ras superfamily, including Rac, RHO and CDC42, play key roles in regulating many of these functions. During my post-doc in the laboratory of Dr David Williams, we have demonstrated that two highly related proteins, Rac1 and Rac2, of the small Rho GTPase family, have distinct functions in the control of hematopoietic cell functions. In particular in neutrophils, we have shown that both Rac1 and Rac2 regulate cell migration but with distinct mechanism (Gu and Filippi et al, Science 2003) both in vitro and in vivo. In addition to this work, we have dissected the sequence/determinant specificity of Rac2 versus Rac1 functions in neutrophils and demonstrated that Rac2 controls its functions, at least in part, by distinct subcellular distributions of these GTPases (Tao et al, Blood 2002, Filippi et al, Nat Immunol 2004), highlighting one important mechanism controlling cellular functions.

My laboratory, in collaboration Dr. Yi Zheng, is now focused on determining the role of CDC42 and RhoA in neutrophil migration and in determining specifically the role of RhoA in hematopoietic stem cell migration and proliferation using gene targeted knock out mice for CDC42 and RhoA and their respective regulator CDC42GAP and 190RhoGAP. These studies will use in vitro and in vivo assays of cell migration as well as immunofluorescence microscopy to study cytoskeleton rearrangement associated with cell migration.

The long term goal of these studies is to identify new molecular targets of potential therapeutic importance.
 

PharmD: University of Rene Descartes, Paris, France, 1998.

Residency: Hematopathology, University of Rene Descartes, Assistance public Hospital of Paris, Paris, France.

Certification: Hematopathology, 2001.

PhD: University of Denis Diderot, Paris, France, 2001.

Mulloy JC, Cancelas JA, Filippi MD, Kalfa TA, Guo F, Zheng Y. Rho GTPases in hematopoiesis and hemopathies. Blood. 2010 Feb 4;115(5):936-47.

Szczur K, Zheng Y, Filippi MD. The small Rho GTPase Cdc42 regulates neutrophil polarity via CD11b integrin signaling. Blood. 2009 Nov 12;114(20):4527-37.

Xu H, Eleswarapu S, Geiger H, Szczur K, Daria D, Zheng Y, Settleman J, Srour EF, Williams DA, Filippi MD. Loss of the Rho GTPase activating protein p190-B enhances hematopoietic stem cell engraftment potential. Blood. 2009 Oct 22;114(17):3557-66.

Gu Y, Harley IT, Henderson LB, Aronow BJ, Vietor I, Huber LA, Harley JB, Kilpatrick JR, Langefeld CD, Williams AH, Jegga AG, Chen J, Wills-Karp M, Arshad SH, Ewart SL, Thio CL, Flick LM, Filippi MD, Grimes HL, Drumm ML, Cutting GR, Knowles MR, Karp CL. Identification of IFRD1 as a modifier gene for cystic fibrosis lung disease. Nature. 2009 Apr 23;458(7241):1039-42.

Monk KR, Wu J, Williams JP, Finney BA, Fitzgerald ME, Filippi MD, Ratner N. Mast cells can contribute to axon-glial dissociation and fibrosis in peripheral nerve. Neuron Glia Biol. 2007 Aug;3(3):233-44.

Daria D, Filippi MD, Knudsen ES, Faccio R, Li Z, Kalfa T, Geiger H. The retinoblastoma tumor suppressor is a critical intrinsic regulator for hematopoietic stem and progenitor cells under stress. Blood. 2008 Feb 15;111(4):1894-902.

Uchida K, Beck DC, Yamamoto T, Berclaz PY, Abe S, Staudt MK, Carey BC, Filippi MD, Wert SE, Denson LA, Puchalski JT, Hauck DM, Trapnell BC. GM-CSF autoantibodies and neutrophil dysfunction in pulmonary alveolar proteinosis.N Engl J Med. 2007 Feb 8;356(6):567-79.

Filippi MD, Szczur K, Harris CE, Berclaz PY. Rho GTPase Rac1 is critical for neutrophil migration into the lung. Blood. 2007 Feb 1;109(3):1257-64.

Szczur K, Xu H, Atkinson S, Zheng Y, Filippi MD. Rho GTPase CDC42 regulates directionality and random movement via distinct MAPK pathways in neutrophils. Blood. 2006 Dec 15;108(13):4205-13.

Wang L, Yang L, Filippi MD, Williams DA, Zheng Y. Genetic deletion of Cdc42GAP reveals a role of Cdc42 in erythropoiesis and hematopoietic stem/progenitor cell survival, adhesion, and engraftment. Blood. 2006 Jan 1;107(1):98-105.