The RNA-binding protein ATXN2 controls cellular processes during megakaryopoiesis.

Megakaryocytes accumulate mRNA during their maturation, which is required for the correct spatio-temporal production of cytoskeletal proteins, membranes and platelet-specific granules, and for the subsequent shedding of thousands of platelets per cell. Gene expression profiling identified the RNA binding protein ATAXIN2 (ATXN2) as a putative novel regulator of megakaryopoiesis. ATXN2 expression is high in CD34+/CD41+ megakaryoblasts and sharply decreases upon maturation to megakaryocytes. ATXN2 associates with DDX6 suggesting that it may mediate repression of mRNA translation during early megakaryopoiesis. Comparative transcriptome and proteome analysis on megakaryoid cells (MEG-01) with differential ATXN2 expression identified ATXN2 dependent gene expression of mRNA and protein involved in processes linked to coagulation. Mice deficient for Atxn2 did not display differences in bleeding times, but expression of key surface receptors on platelets, such as ITGB3 (carries the CD61 antigen) and CD31 (PECAM1), were deregulated and platelet aggregation upon specific triggers was reduced. Comparison in the megakaryocyte cell line (MEG-01) the effect of ATXN2 depletion by small interference RNA (shRNA) after 16 days (Puro selected). Two different shRNA targeting ATXN2 (also confirmed on protein level), one shRNA scrambled and one non-transduced control.