Sumoylation of CCAAT/enhancer–binding protein α promotes the biased primitive hematopoiesis of zebrafish

Abstract

Hematopoiesis is evolutionarily conserved from zebrafish to mammals, and this includes both primitive and definitive waves during embryogenesis. Primitive hematopoiesis is dominated by erythropoiesis with limited myelopoiesis. Protein sumoylation, a ubiquitination-like posttranslational protein modification, is implicated in a variety of biochemical processes, most notably in transcriptional repression. We show here that the loss of 6 small ubiquitin-related modifier (SUMO) paralogs triggers a sharp upregulation of the myeloid-specific marker mpo and down-regulation of the erythroidspecific marker gata1 in myelo-erythroid progenitor cells ( IntroductionVertebrate hematopoiesis is a successive process involving primitive and definitive waves occurring in anatomically distinct sites. Whereas primitive hematopoiesis predominantly produces erythrocytes and some macrophages, definitive hematopoiesis generates self-renewing pluripotent hematopoietic stem cells capable of giving rise to all blood cell types. 1 The zebrafish (Danio rerio) has emerged as an excellent model organism for the study of hematopoiesis because it combines many advantages of other model organisms. 2,3 In zebrafish, primitive wave originates in 2 intraembryonic sites known as the anterior lateral plate mesoderm (A-LPM) and the posterior lateral plate mesoderm (P-LPM) that subsequently forms the intermediate cell mass (ICM). 4 Whereas the A-LPM is the primary site of production of primitive macrophages, the ICM is the location of multipotential blood progenitors containing predominantly primitive erythrocytes and a few granulocytes. 5 The molecular mechanisms of multipotential progenitor commitment in the ICM remain poorly understood. However, the respective specification of myeloid and erythroid cell lineages of zebrafish myelo-erythroid progenitor cells (MPCs) appear to be controlled by the antagonistic regulation of Gata1 and Pu.1. 6,7 The zebrafish CCAAT/enhancer-binding protein ␣ (C/ebp␣), a master regulator of granulopoiesis, 8 is also expressed, along with pu.1 and gata1, in the hematopoietic progenitors of P-LPM during primitive hematopoiesis. 9 C/ebp␣ is the founding member of a family of transcription factors containing a basic leucine zipper domain. 10 Loss of C/ebp␣ in mice results in the complete absence of mature neutrophils and eosinophils and increased numbers of erythroid progenitors and erythroid cells in the fetal liver. 11,12 C/ebp␣ not only acts as a cell fate switch to induce granulocyte differentiation from bipotential granulocyte-macrophage progenitors, 8 but also determines the hematopoietic cell fate in multipotential progenitor cells by inhibiting erythroid development while promoting myeloid differentiation. 12 In addition, megakaryocyte/erythroid progenitors and common lymphoid progenitors could be redirected to myeloid lineage by ectopic activation of C/ebp␣. 13 C/ebp␣ can be posttranslationally modified by small ubiquitin-related modifier (SUMO), which controls its transactivation activity. 14,15 SUMO is highly cons...

The histone demethylase Jmjd3 regulates zebrafish myeloid development by promoting spi1 expression

“…In addition to the transcriptional regulation, post-translational modifications are also important for myeloid-erythroid lineage choice. It has been reported that hyposumoylation of C/ebpα a leads to expansion of myeloid lineage at the expense of erythroid lineage, suggesting that sumoylation of C/ebpα is important for the differentiation control of erythroid-myeloid progenitors [60]. In this study, we demonstrated that jmjd3 bias the myeloid commitment at the expense of the erythroid commitment.…”

Sumoylation of CCAAT/enhancer-binding protein α is implicated in hematopoietic stem/progenitor cell development through regulating runx1 in zebrafish

“…As our previous studies demonstrated that lack of sumoylation biased primitive hematopoiesis9, here we questioned its role in definitive hematopoiesis. To evaluate the effects of sumoylation on definitive hematopoietic development, the temporal and spatial expression patterns of a panel of HSPC and lineage-specific markers were examined by whole-mount mRNA in situ hybridization (WISH) after antisense MO-mediated knock-down.…”

“…Both C/ebpα-deficient fetal and adult HSPCs exhibit enhanced proliferation and competitive repopulation activities212224, whilst activation of C/ebpα in HSPCs leads to their reduced self-renewal and proliferation23. We have previously shown that zebrafish C/ebpα can be sumoylated, triggering transcriptional repression9. Thus, herein we investigated the potential role of C/ebpα sumoylation in the regulation of HSPC homeostasis.…”

“…Our previous work showed that, a SUMO-C/ebpα fusion protein, mimicking the constitutively sumoylated form of C/ebpα, and a POZ-C/ebpα fusion protein, mimicking the SUMO-mediated repressive form of C/ebpα, could significantly inhibit the transcriptional activity of wide type (WT) C/ebpα9. This allowed us to assess the rescue effects of the fusion proteins in the SUMO-deficient embryos.…”

“…Sumoylation regulates a wide variety of cellular processes such as transcription, DNA repair, trafficking and signal transduction8. Our previous work showed that sumoylation played an important role in the myelo-erythroid progenitor cell (MPC) fate decision during primitive hematopoiesis of zebrafish9. However, the functional role of sumoylation during definitive hematopoiesis is still unknown.…”