The aryl hydrocarbon receptor (AHR) transcription factor regulates megakaryocytic polyploidization

• Published in: British journal of haematology Vol. 152; no. 4; pp. 469 - 484
• Main Authors: Lindsey, Stephan, Papoutsakis, Eleftherios T.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.02.2011; Blackwell
• Subjects: Animals; Biological and medical sciences; Blood Platelets - physiology; cell biology; Cell Differentiation - genetics; Gene Expression Regulation - genetics; Gene Knockdown Techniques; haematopoiesis; Hematologic and hematopoietic diseases; Humans; Medical sciences; Megakaryocytes - cytology; Megakaryocytes - metabolism; megakaryocytopoiesis; Mice; Mice, Knockout; Platelet Count; Polyploidy; Receptors, Aryl Hydrocarbon - deficiency; Receptors, Aryl Hydrocarbon - genetics; Receptors, Aryl Hydrocarbon - physiology; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Messenger - genetics; Thrombopoiesis - genetics; thrombopoietin; transcription factors; Transcription Factors - physiology; Tumor Cells, Cultured; Megakaryocytopoiesis; Signal transduction; Aryl hydrocarbon receptor; Polyploidy; Hematology; Hematopoiesis; transcription factors; Cell biology; Megakaryocyte; Transcription factor; Thrombopoietin; haematopoiesis
• ISSN: 0007-1048; 1365-2141
• DOI: 10.1111/j.1365-2141.2010.08548.x

Summary We propose that the aryl hydrocarbon receptor (AHR) is a novel transcriptional regulator of megakaryopoietic polyploidization. Functional evidence was obtained that AHR impacts in vivo megakaryocytic differentiation and maturation; compared to wild‐type mice, AHR‐null mice had lower platelet counts, fewer numbers of newly synthesized platelets, increased bleeding times and lower‐ploidy megakaryocytes (Mks). AHR mRNA increased 3·6‐fold during ex vivo megakaryocytic differentiation, but reduced or remained constant during parallel isogenic granulocytic or erythroid differentiation. We interrogated the role of AHR in megakaryopoiesis using a validated Mk model of megakaryopoiesis, the human megakaryoblastic leukaemia CHRF cell line. Upon CHRF Mk differentiation, AHR mRNA and protein levels increased, AHR protein shifted from the cytoplasm to the nucleus and AHR binding to its consensus DNA binding sequence increased. Protein and mRNA levels of the AHR transcriptional target HES1 also increased. Mk differentiation of CHRF cells where AHR or HES1 was knocked‐down using RNAi resulted in lower ploidy distributions and cells that were incapable of reaching ploidy classes ≥16n. AHR knockdown also resulted in increased DNA synthesis of lower ploidy cells, without impacting apoptosis. Together, these data support a role for AHR in Mk polyploidization and in vivo platelet function, and warrant further detailed investigations.