TET2 Plays an Essential Role in Erythropoiesis by Regulating Lineage-Specific Genes via DNA Oxidative Demethylation in a Zebrafish Model

Abstract

Although epigenetic modulation is critical for a variety of cellular activities, its role in erythropoiesis remains poorly understood. Teneleven translocation (TET) molecules participate in methylcytosine (5mC) hydroxylation, which results in DNA demethylation in several biological processes. In this research, the role of TETs in erythropoiesis was investigated by using the zebrafish model, where three TET homologs were identified. These homologs share conserved structural domains with their mammalian counterparts. Zebrafish TETs mediate the conversion of 5mC to hydroxymethylcytosine (5hmC) in zebrafish embryos, and the deletion of TET2 inhibits erythropoiesis by suppressing the expression of the scl, gata-1, and cmyb genes. TET2-upregulated lineage-specific genes and erythropoiesis are closely associated with the occurrence of 5hmC and demethylation in the intermediate CpG promoters (ICPs) of scl, gata-1, cmyb, which frequently occur at specific regions or CpG sites of these ICPs. Moreover, TET2 regulates the formation and differentiation of erythroid progenitors, and deletion of TET2 leads to erythrocyte dysplasia and anemia. Here, we preliminarily proved that TET2 plays an essential role in erythrocyte development by regulating lineage-specific genes via DNA oxidative demethylation. This report is anticipated to broaden current information on hematopoiesis and pathogenesis of hematopoiesis-related diseases.

A Zebrafish Model of Myelodysplastic Syndrome Produced through tet2 Genomic Editing

“…It is well known that morpholinos can produce spurious phenotypes through this mechanism, and most investigators now confirm the specificity of phenotypes in morphants by either repeating the knockdown in p53 m/m embryos or simultaneously knocking down p53 (31,49). This does not appear to have been done in the study by Ge et al (40), providing an additional example of morphant phenotypes that may not accurately reflect the specific role of the gene under investigation.…”

“…We suspect that abnormalities of primitive erythropoiesis observed in the study of Ge and colleagues (40) after morpholino knockdown of tet2 may reflect, at least in part, the nonspecific activation of p53 by the morpholino (48). It is well known that morpholinos can produce spurious phenotypes through this mechanism, and most investigators now confirm the specificity of phenotypes in morphants by either repeating the knockdown in p53 m/m embryos or simultaneously knocking down p53 (31,49).…”

“…Recently, the effect of tet2 loss on embryonic zebrafish hematopoiesis was reported, based on morpholino-mediated tet2 knockdown in embryos, which led to inhibition of erythropoiesis, apparently due to loss of hematopoietic cells expressing the scl, gata-1, and cmyb genes (40). In contrast, in our homozygous tet2 loss-of-function zebrafish mutant embryos, we did not observe any changes in HSPC numbers, as reflected by cmyb and CD41 expression, or any defects in embryonic erythropoiesis or in myeloperoxidase-expressing myeloid cells.…”

Active DNA demethylation at enhancers during the vertebrate phylotypic period

“…17a), as previously reported in a tet3 morpholino study performed in Xenopus laevis embryos 55 . Next, we injected zebrafish embryos with morpholinos targeting all three Tet proteins to generate tet1 - tet2 - tet3 morphants 56 . The triple morphants were severely affected, with the majority displaying embryonic lethality, while the embryos that survived gastrulation (23%) displayed short and blended axes, impaired head structures, small eyes and reduced pigmentation (Supplementary Fig.…”

TET2 is upregulated during erythroid differentiation of CD34+ cells from healthy donors and myelodysplastic syndrome patients

“…Yan et al [9], similarly demonstrated that TET2 inhibition led to MDS-like dyserythropoiesis. Of note, TET2 deletion leads to erythroid dysplasia and anemia in zebrafish model [14], suggesting a conserved function for TET2 in erythrocytes production.…”