Page 33 - Haematologica August 2018

Hematopoiesis
CARD10, a CEBPE target involved in granulocytic differentiation
Pavithra Shyamsunder,1* Haresh Sankar,1 Anand Mayakonda,1 Lin Han,1,2 Hazimah Binte Mohd Nordin,1 Teoh Weoi Woon,1
Mahalakshmi Shanmugasundaram,1 Pushkar Dakle,1 Vikas Madan1*# and H. Phillip Koeffler1,3,4#
1Cancer Science Institute of Singapore, National University of Singapore, Singapore; 2Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore; 3Cedars-Sinai Medical Center, Division of Hematology/Oncology, UCLA School of Medicine, Los Angeles, CA, USA and 4Department of Hematology-Oncology, National University Cancer Institute of Singapore (NCIS), National University Hospital, Singapore
ABSTRACT
Maturation of granulocytes is dependent on controlled gene expression by myeloid lineage restricted transcription factors. CEBPE is one of the essential transcription factors required for granulocytic differentiation. Identification of downstream targets of CEBPE is vital to understand better its role in terminal granulopoiesis. In this study, we have identified Card10 as a novel target of CEBPE. We show that CEBPE binds to regulatory elements upstream of the murine Card10 locus, and expression of CARD10 is significantly reduced in Cebpe knock-out mice. Silencing Card10 in a human cell line and in murine primary cells impaired granulopoiesis, affecting expression of genes involved in myeloid cell development and function. Taken togeth- er, our data demonstrate for the first time that Card10 is expressed in granulocytes and is a direct target of CEBPE with functions extending to myeloid differentiation.
Introduction
Precise levels of progenitor cell proliferation versus lineage-committed differentia- tion is central to the balanced functioning of the hematopoietic system.1,2 Transcription factors are fundamental elements directing differentiation during hematopoietic development.3 The lineage and stage-restricted expression pattern of these factors underlines the need for precise regulation of their function. Major tran- scription factors regulating myeloid development include PU.1, GFI1, IRF8, RUNX1, SCL, TAL1 and the members of C/EBP family. Each of these lineage restricted factors are known to drive the expression of a panel of target genes.4-10
CEBPE is a member of the CCAAT/enhancer binding protein (C/EBP) family of transcription factors involved in hematopoietic cell development and induction of several inflammatory mediators.11,12 CEBPE is expressed in a stage-specific manner during myeloid differentiation and regulates transition from the promyelocyte to the myelocyte.13 This transcription factor is essential for secondary and tertiary granule formation in granulocytes.14 Germline mutations of the CEBPE gene have been detected in patients with neutrophil-specific granule deficiency. Their neu- trophils display atypical bilobed nuclei, lack expression of granule proteins and these patients often have frequent bacterial infections.15,16 Cebpe knock-out mice resemble this clinical phenotype displaying a block in terminal differentiation and absence of secondary granule proteins. Cebpe KO mice develop normally, except that they fail to produce functional neutrophils and eosinophils. Neutrophils from these mice have impaired chemotaxis, bactericidal activity and mice typically die of infections between 3 and 5 months of age.9 The lack of secondary granule proteins in granulocytes from these mice impairs their responses to inflammatory signals characterized by an increase in circulating immature neutrophils and recurrent pyo- genic infections.17
Ferrata Storti Foundation
Haematologica 2018 Volume 103(8):1269-1277
#VM and HPK share senior authorship
Correspondence:
csips@nus.edu.sg or csivm@nus.edu.sg
Received: February 4, 2018. Accepted: May 14, 2018. Pre-published: May 17, 2018.
doi:10.3324/haematol.2018.190280
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/103/8/1269
©2018 Ferrata Storti Foundation
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