Régulation de l'arrêt des endomitoses et de la différenciation mégacaryocytaire terminale : rôle de p19 INK4D et de MAL
Year: 2009
Type: dissertation
Abstract: Megakaryopoiesis is the System of platelet production divided in three steps: mitosis step, increase in ploidy level by endomitosis, platelet sheeding by cytoplasm fragmentation. My work focused on megakaryopoiesis through the study of two proteins: MAL and p19INK4D (p19). MAL is a transcriptional co-activator of SRF. In acute megakaryoblastic leukemia, the MAL gene is translocated and fused with the gene encoding OTT. We showed that MAL expression increases during the megakaryocyte (MK) differentiation. MAL knockdown in MK progenitors reduced the percentage of cells forming filopodia, lamellipodia and stress fibers, and reduced proplatelet formation. MAL repression led to dysmorphic MK with disorganized demarcation membranes and alpha granules heterogeneously scattered in the cytoplasm. Gene expression profiling revealed a decrease in MMP9 and MYL9 expression after MAL inhibition. Chromatin immunoprecipitation in MK showed that the MAL/SRF complex directly regulates MYL9 and MMP9. MK migration was considerably decreased after MAL knock down, implicating MMP9 in migration. Finally, the use of a shRNA to decrease MYL9 expression showed that MYL9 was involved in proplatelet formation. P19 expression was increased during ploidization. We showed that p19 knockdown led to an increase in the mean ploidy of human MKs. This increase in ploidy was associated with a decrease in the more mature MKpopulation. Inversely, p19 overexpression resulted in a decrease in mean ploidy level. Confirming these results, bone marrow MKs from p19 KO mice exhibited an increase in mean ploidy level. Finally we showed that p19 is directly regulated by the hematopoietic transcription factor AML1.
Author: Laure Gendre-Gilles
Language: English
Subfield: Hematology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W13979251