Journal Article

ReducedDOCK4expression leads to erythroid dysplasia in myelodysplastic syndromes

Bartenstein, Matthias, Artz, Andrew, Le Beau, Michelle M., Unnikrishnan, Madhu, Torregroza, Ingrid, List, Alan F., McGraw, Kathy L., Yu, Yiting, Yajnik, Vijay, Liu, Ting-Chun, Quenon, Thomas, Pellagatti, Andrea, Anastasi, John, Duggan, Ryan, Bhagat, Tushar, Sundaravel, Sriram, Boultwood, Jacqueline, Verma, Amit, Liu, Hui, Karmakar, Subhradip, Wickrema, Amittha, Steidl, Ulrich, Ebenezer, David L., Evans, Todd

2015

Overview

Anemia is the predominant clinical manifestation of myelodysplastic syndromes (MDS). Loss or deletion of chromosome 7 is commonly seen in MDS and leads to a poor prognosis. However, the identity of functionally relevant, dysplasia-causing, genes on 7q remains unclear. Dedicator of cytokinesis 4 (DOCK4) is a GTPase exchange factor, and its gene maps to the commonly deleted 7q region. We demonstrate thatDOCK4is underexpressed in MDS bone marrow samples and that the reduced expression is associated with decreased overall survival in patients. We show that depletion ofDOCK4levels leads to erythroid cells with dysplastic morphology both in vivo and in vitro. We established a novel single-cell assay to quantify disrupted F-actin filament network in erythroblasts and demonstrate that reduced expression ofDOCK4leads to disruption of the actin filaments, resulting in erythroid dysplasia that phenocopies the red blood cell (RBC) defects seen in samples from MDS patients. Reexpression of DOCK4 in −7q MDS patient erythroblasts resulted in significant erythropoietic improvements. Mechanisms underlying F-actin disruption revealed thatDOCK4knockdown reduces ras-related C3 botulinum toxin substrate 1 (RAC1) GTPase activation, leading to increased phosphorylation of the actin-stabilizing protein ADDUCIN in MDS samples. These data identifyDOCK4as a putative 7q gene whose reduced expression can lead to erythroid dysplasia.

• Publisher: National Academy of Sciences