title: Uncoupling of the Hippo and Rho pathways allows megakaryocytes to escape the tetraploid checkpoint.
abstract: Megakaryocytes are naturally polyploid cells that increase their ploidy by endomitosis. However, very little is known regarding the mechanism by which they escape the tetraploid checkpoint to become polyploid. Recently, it has been shown that the tetraploid checkpoint was regulated by the Hippo-p53 pathway in response to a downregulation of Rho activity. We therefore analyzed the role of Hippo-p53 pathway in the regulation of human megakaryocyte polyploidy. Our results revealed that Hippo-p53 signaling pathway proteins are present and are functional in megakaryocytes. Although this pathway responds to the genotoxic stress agent etoposide, it is not activated in tetraploid or polyploid megakaryocytes. Furthermore, Hippo pathway was observed to be uncoupled from Rho activity. Additionally, polyploid megakaryocytes showed increased expression of YAP target genes when compared to diploid and tetraploid megakaryocytes. Although p53 knockdown increased both modal ploidy and proplatelet formation in megakaryocytes, YAP knockdown caused no significant change in ploidy while moderately affecting proplatelet formation. Interestingly, YAP knockdown reduced the mitochondrial mass in polyploid megakaryocytes and decreased expression of PGC1α, an important mitochondrial biogenesis regulator. Thus, the Hippo pathway is functional in megakaryocytes, but is not induced by tetraploidy. Additionally, YAP regulates the mitochondrial mass in polyploid megakaryocytes.
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France.|Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.
authors: Anita
authors: A
authors: Roy
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France.|Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.
authors: Larissa
authors: L
authors: Lordier
authors: Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.|Centre Nationale de la Recherche Scientifique (CNRS), UMR 8126, Gustave Roussy, Villejuif, France.
authors: Catherine
authors: C
authors: Pioche-Durieu
authors: Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.|CNRS UMR 8122, Gustave Roussy, Villejuif, France.
authors: Sylvie
authors: S
authors: Souquere
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France.|Assistance Publique des Hôpitaux de Paris (AP-HP), Service d'Hématologie Clinique, Hôpital Henri Mondor, Créteil, France.
authors: Lydia
authors: L
authors: Roy
authors: Gustave Roussy, Villejuif, France.
authors: Philippe
authors: P
authors: Rameau
authors: Gustave Roussy, Unité de Thérapie Cellulaire, Villejuif, France.
authors: Valérie
authors: V
authors: Lapierre
authors: Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.|Centre Nationale de la Recherche Scientifique (CNRS), UMR 8126, Gustave Roussy, Villejuif, France.
authors: Eric
authors: E
authors: Le Cam
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France.|Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.
authors: Isabelle
authors: I
authors: Plo
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France.|Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.
authors: Najet
authors: N
authors: Debili
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France.|Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.
authors: Hana
authors: H
authors: Raslova
authors: Institut National de la Santé et la Recherche Médicale (INSERM) UMR1170, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Villejuif, France William.Vainchenker@gustaveroussy.fr.|Université Paris-Saclay, Villejuif, France.|Gustave Roussy, Villejuif, France.
authors: William
authors: W
authors: Vainchenker
mesh_terms: D015415:Biomarkers; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism; D018797:Cell Cycle Proteins; D002454:Cell Differentiation / Q000235:genetics; D015870:Gene Expression; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D000090683:Hippo Signaling Pathway; D006801:Humans; D008533:Megakaryocytes / Q000166:cytology* / Q000378:metabolism*; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha / Q000235:genetics / Q000378:metabolism; D011123:Polyploidy; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D057891:Tetraploidy; D034061:Thrombopoiesis / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C456659:YY1AP1 protein, human; D017346:Protein Serine-Threonine Kinases; D020741:rho GTP-Binding Proteins