Sox6 enhances erythroid differentiation in human erythroid progenitors

Abstract

Sox6 belongs to the Sry (sex-determining region Y)-related high-mobility-groupbox family of transcription factors, which control cell-fate specification of many cell types. Here, we explored the role of Sox6 in human erythropoiesis by its overexpression both in the erythroleukemic K562 cell line and in primary erythroid cultures from human cord blood CD34 ؉ cells. Sox6 induced significant erythroid differentiation in both models. K562 cells underwent hemoglobinization and, despite their leukemic origin, died within 9 days after transduction; primary erythroid cultures accelerated their kinetics of erythroid maturation and increased the number of cells that reached the final enucleation step. Searching for direct Sox6 targets, we found SOCS3 (suppressor of cytokine signaling-3), a known mediator of cytokine response. Sox6 was bound in vitro and in vivo to an evolutionarily conserved regulatory SOCS3 element, which induced transcriptional activation. SOCS3 overexpression in K562 cells and in primary erythroid cells recapitulated the growth inhibition induced by Sox6, which demonstrates that SOCS3 is a relevant Sox6 effector. (Blood. 2011;117(13):3669-3679) IntroductionSox proteins are important transcriptional regulators of different developmental processes in which they control the specification and differentiation of many cell types. [1][2][3] In particular, Sox6, originally isolated from adult mouse testis, 4 is required for the development of the central nervous system, 5-7 for chondrogenesis, 8 and for cardiac and skeletal muscle formation. 9,10 Recently, Sox6 has been demonstrated to be crucial for definitive erythropoiesis, 11-15 a process in which committed progenitors progressively differentiate into burst-forming-unit erythroid cells and colonyforming-unit (CFU) erythroid cells, which in turn give rise to proerythroblasts and erythroblasts and finally to mature, enucleated red blood cells. These differentiation stages are accompanied by profound maturational changes: Within few cell divisions, in parallel with the accumulation of erythroid-specific markers (membrane proteins, enzymes required for the heme biosynthesis pathway, and globins), cells undergo chromatin condensation and enucleate. 16,17 This complex spectrum of maturational steps is controlled at the molecular level by the integration of extrinsic (growth factors; oxygen and iron availability) and intrinsic (growth factor receptors, signaling mediators, transcription factors) signals.Several transcription factors are essential for erythroid commitment and for differential globin gene expression during development; their absence is associated with a wide spectrum of phenotypes ranging from mild perturbation to death because of a complete failure of erythropoiesis. 18,19 Among them, Sox6 recently has been shown to stimulate erythroid cell survival, proliferation, and terminal maturation during definitive murine erythropoiesis. 11,12 Sox6-null mouse fetuses and pups are anemic and have defective red blood cells. Recently, Sox6 has been implicated...

To respond or not to respond to hydroxyurea in thalassemia: a matter of stress adaptation?

“…14 Sox6 indeed activates the BCL-xL gene, 12,13 and in agreement with this, Pourfazad et al show that R-cells have higher levels of BCL-xL than NR-cells and that HU is a strong inducer of BCL-xL. Thus, R-cells are protected from apoptosis due both to increased BCL-xL antiapoptotic activity and to the absence of significant induction of p14/ARF (Figure 1).…”

“…11,12 When over-expressed, however, it stimulates cell differentiation and the expression of all globin genes, although the gamma-globin gene is considerably less activated, presumably due to the specific repressive effect of SOX6. 13 In R-cells, SOX6 is over-expressed, particularly after HU administration. This may contribute to explain the increased propensity to differentiation and hemoglobinization of R-cells, together with the blunted HbF stimulation.…”

Global analysis of induced transcription factors and cofactors identifies Tfdp2 as an essential coregulator during terminal erythropoiesis

“…Based on RNA-sequencing data on R1-R5 populations, which represent consecutive stages of in vivo erythropoiesis from CFU-Es to mature reticulocytes, the majority of transcription factors and cofactors are downregulated during terminal differentiation, while only a small number are upregulated (Figure 1A, Supplemental Figure 1). Several upregulated factors, such as Sox6 and Zfpm1, have previously been shown to be indispensable for erythropoiesis [27, 28]; however, the majority of these induced factors remain to be characterized.…”

Defective erythroid maturation in gelsolin mutant mice

“…+ cells, which are more differentiated erythroblasts and mature erythrocytes ( Figure 1A and 25,26 ). Gelsolin expression was subsequently measured in these three sorted cell populations by quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis, in parallel with that of glycophorin A (GpA) and CD44.…”