The effect of DNA hydroxymethylase Tet2 on γ globin activation in the treatment of β-thalassemia / 中华内科杂志

ABSTRACT

Objective To study the function of ten-eleven translocation 2 (Tet2) in γglobin gene expression in patients with β-thalassemia.Methods Gamma globin expression was induced by 5-azacytidine and Tet2 gene expression was knocked down by short hairpin RNA (shRNA) in a human immortalized myelogenous leukemia K562 cell line.The global 5-hydroxymethylcytosine (5hmC) level was measured by an ELISA kit.5hmC level of γglobin gene was quantified by sulfite sequencing.The mRNA level of Tet2,γglobin,and related transcription factors Nfe4 and Klfl were quantified by real-time PCR.Results Tet2 knockdown resulted in a decreased global 5hmC level from 0.14％ to 0.03％ as of the control group in K562 cells.The expression of γ globin was enhanced after 5-azacytidine treatment in vitro.However,γglobin mRNA level in Tet2 knockdown cells was only 55％ as that in control group.The CG sites on γ globin gene were unmethylated.As Tet2 was down-regulated,the expression levels of Nfe4 and Klf1 decreased by about 80％ and increased to 3.5 folds,respectively.Conclusions Tet2 appears to maintain 5hmC level and facilitates γ globin gene activation.Moreover,Tet2 more likely regulates γglobin expression via affecting transcription factors rather than the gene itself.Thus,Tet2 could be a potential therapeutic target for β thalassemias.