The microtubule modulator RanBP10 plays a critical role in regulation of platelet discoid shape and degranulation.
Terminally mature megakaryocytes undergo dramatic cellular reorganization to produce hundreds of virtually identical platelets. A hallmark feature of this process is the generation of an elaborate system of branched protrusions called proplatelets. We recently identified RanBP10 as a tubulin-binding protein that is concentrated along polymerized microtubules in mature megakaryocytes. RanBP10 depletion in vitro caused the disturbance of polymerized filaments. Here we study the function of RanBP10 in vivo by generating deficient mice using a gene-trap approach. Mutant mice show normal platelet counts, and fetal liver-derived megakaryocytes reveal only slightly reduced proplatelet formation. However, ultrastructural analysis unveiled a significantly increased geometric axis ratio for resting platelets, and many platelets exhibited disorders in microtubule filament numbers and localization. Mutant mice showed a markedly prolonged bleeding time. Granule release, a process that depends on internal contraction of the microtubule marginal coil, also was reduced. Flow cytometry analysis revealed reduced expression of CD62P and CD63 after PAR4-peptide stimulation. These data suggest that RanBP10 plays an essential role in hemostasis and in maintaining microtubule dynamics with respect to both platelet shape and function.
Labor für Pädiatrische Molekularbiologie der Klinik für Allgemeine Pädiatrie, Charité-Universitätsmedizin, Berlin, Germany.
Stefan
S
Kunert
Imke
I
Meyer
Silke
S
Fleischhauer
Martin
M
Wannack
Janine
J
Fiedler
Ramesh A
RA
Shivdasani
Harald
H
Schulze
D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015550:Cell Degranulation / Q000502:physiology*; D048430:Cell Shape / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015151:Immunoblotting; D008297:Male; D008533:Megakaryocytes / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D015539:Platelet Activation / Q000235:genetics / Q000502:physiology; D010974:Platelet Aggregation / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020662:Guanine Nucleotide Exchange Factors; D008869:Microtubule-Associated Proteins; C546963:RanBP10 protein, mouse; D049452:Green Fluorescent Proteins