MAL/SRF complex is involved in platelet formation and megakaryocyte migration by regulating MYL9 (MLC2) and MMP9.
Megakaryoblastic leukemia 1 (MAL) is a transcriptional coactivator of serum response factor (SRF). In acute megakaryoblastic leukemia, the MAL gene is translocated and fused with the gene encoding one twenty-two (OTT). Herein, we show that MAL expression increases during the late differentiation steps of neonate and adult human megakaryopoiesis and localized into the nucleus after Rho GTPase activation by adhesion on collagen I or convulxin. MAL knockdown in megakaryocyte progenitors reduced the percentage of cells forming filopodia, lamellipodia, and stress fibers after adhesion on the same substrates, and reduced proplatelet formation. MAL repression led to dysmorphic megakaryocytes with disorganized demarcation membranes and alpha granules heterogeneously scattered in the cytoplasm. Gene expression profiling revealed a marked decrease in metalloproteinase 9 (MMP-9) and MYL9 expression after MAL inhibition. Luciferase assays in HEK293T cells and chromatin immunoprecipitation in primary megakaryocytes showed that the MAL/SRF complex directly regulates MYL9 and MMP9 in vitro. Megakaryocyte migration in response to stromal cell-derived factor 1, through Matrigel was considerably decreased after MAL knockdown, implicating MMP9 in migration. Finally, the use of a shRNA to decrease MYL9 expression showed that MYL9 was involved in proplatelet formation. MAL/SRF complex is thus involved in platelet formation and megakaryocyte migration by regulating MYL9 and MMP9.
Gilles
Laure
L
Inserm, U790, Villejuif, France.
Bluteau
Dominique
D
Boukour
Siham
S
Chang
Yunhua
Y
Zhang
Yanyan
Y
Robert
Thomas
T
Dessen
Philippe
P
Debili
Najet
N
Bernard
Olivier A
OA
Vainchenker
William
W
Raslova
Hana
H
D000328:Adult; D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism*; D024722:Cardiac Myosins / Q000235:genetics*; D002454:Cell Differentiation; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005312:Fetal Blood / Q000166:cytology; D022001:Focal Adhesions; D020869:Gene Expression Profiling; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D020780:Matrix Metalloproteinase 9 / Q000235:genetics*; D008533:Megakaryocytes / Q000166:cytology / Q000502:physiology*; D046912:Multiprotein Complexes; D018994:Myosin Light Chains / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D015514:Oncogene Proteins, Fusion / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D026362:Serum Response Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D034061:Thrombopoiesis; D015534:Trans-Activators; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D004268:DNA-Binding Proteins; C431575:MRTFA protein, human; D046912:Multiprotein Complexes; D018994:Myosin Light Chains; D015514:Oncogene Proteins, Fusion; D034741:RNA, Small Interfering; C476858:SRF protein, human; D026362:Serum Response Factor; D015534:Trans-Activators; C107184:myosin light chain 2; D020780:Matrix Metalloproteinase 9; D024722:Cardiac Myosins; D020741:rho GTP-Binding Proteins