Thrombocytopenia-associated mutations in MASTL deregulate global phosphorylation and actin cytoskeleton dynamics in platelets

ABSTRACT: MASTL, also known as Greatwall, was originally characterized in flies and Xenopus as a mitotic kinase involved in the maintenance of the mitotic state by inhibiting PP2A-B55 complexes. A specific mutation (E167D) in the human MASTL gene was simultaneously linked to autosomal dominant thrombocytopenia. However, the possible connections between the cell cycle machinery and this human disease remain unexplored. By analyzing genetically-engineered mice with specific ablation of Mastl in megakaryocytes and platelets we report here that Mastl ablation results in defective megakaryocyte maturation and reduced platelet counts. Platelet counts are also reduced in a new Mastl E166D knockin model carrying the thrombocytopenia-associated mutation in the murine locus. Surprisingly, thrombocytopenia in this model is not due to defective megakaryocyte maturation, but a consequence of aberrant activation and reduced survival of platelets. Stimulation of Mastl E166D platelets is characterized by rapid formation of hyper-stabilized pseudopods similarly to cells in which PP2A activity is chemically inhibited. These defects are accompanied by abnormal phosphorylation of multiple components of the actin cytoskeleton and can be rescued both in vitro and in vivo by inhibiting upstream kinases such as PKA, PKC or AMPK. These results suggest that Mastl E166D is a dominant mutation that may contribute to thrombocytopenia by altering the phosphorylation status of several molecular pathways critical in platelet cytoskeletal dynamics. These data reveal an unexpected role of Mastl in the control of cytoskeleton dynamics in a cell-cycle independent manner in nucleus-depleted, terminally differentiated cells.

INSTRUMENT(S): impact

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Blood Platelet, Blood Cell

DISEASE(S): Thrombocytopenia

SUBMITTER: Javier Munoz  

LAB HEAD: Javier Munoz

PROVIDER: PXD009398 | Pride | 2019-11-12

REPOSITORIES: Pride