Summary
Regulation of the platelet formation process is poorly understood. It has been shown
that p45NF-E2 deficient mice have a profound defect in platelet formation and recently the first
platelet/megakaryocytic gene regulated by NF-E2, thromboxane synthase (TXS), has been
identified. In this study, we investigated TXS expression as a model of a gene regulated
by NF-E2 during MK differentiation. Megakaryocytic cells derived from blood CD34+ cells were purified according to their stage of maturation on the basis of expression
of CD34, CD41a and CD42a, permitting to define different stages in MK differentiation.
By means of real-time quantitative RT-PCR, we could determine that the level of TXS
increased during differentiation in parallel with the expression of c-mpl and GPIIb (CD41). However, amounts of TXS transcripts increased about 1.6-fold more
than that of GPIIb or c-mpl transcripts during maturation. Expression of TXS and MK
specific proteins such as CD41a, CD42a and vWF was also correlated in maturing MKs.
In addition, staining by anti-TXS antibody of proplatelet bearing MKs was not increased
in comparison to that observed in mature MK, suggesting that TXS is not upregulated
during platelet formation. In addition, we investigated whether TXS and cyclooxygenase
could be involved in platelet formation by adding aspirin into the cultures. No significant
decrease of platelet production was observed.
In conclusion, this study shows that TXS is coordinately expressed with the other
platelet proteins during MK differentiation but is not directly involved in platelet
formation.
Keywords
Megakaryocyte - TXS