DNA methylation patterns of β-globin cluster in β-thalassemia patients

Abstract

Background Reactivation of fetal hemoglobin (HbF, α2γ2) holds a therapeutic target for β-thalassemia and sickle cell disease. Although many HbF regulators have been identified, the methylation patterns in β-globin cluster driving the fetal-to-adult hemoglobin switch remains to be determined. Results Here, we evaluated DNA methylation patterns of the β-globin cluster from peripheral bloods of 105 β0/β0 thalassemia patients and 44 normal controls. We also recruited 15 bone marrows and 4 cord blood samples for further evaluation. We identified that the CpG sites in the locus control region (LCR) DNase I hypersensitive site 4 and 3 (HS4-3) regions, and γ- and β-globin promoters displayed hypomethylation in β0/β0-thalassemia patients, especially for the patients with high HbF level, as compared with normal controls. Furthermore, hypomethylations in most of CpG sites of the HS4-3 core regions were also observed in bone marrows (BM) of β0/β0-patients compared with normal controls; and methylation level of γ-globin promoter -50 and + 17 CpG sites showed lower methylation level in patients with high HbF level compared with those with low HbF level and a negative correlation with HbF level among β0-thalassemia patients. Finally, γ-globin promoter + 17 and + 50 CpG sites also displayed significant hypomethylation in cord blood (CB) tissues compared with BM tissues from normal controls. Conclusions Our findings revealed methylation patterns in β-globin cluster associated with β0 thalassemia disease and γ-globin expression, contributed to understand the epigenetic modification in β0 thalassemia patients and provided candidate targets for the therapies of β-hemoglobinopathies.

Epigenetic Regulation of β-Globin Genes and the Potential to Treat Hemoglobinopathies through Epigenome Editing

“…In the γ-globin promoters, CpG sites span a 500 nt region centered on the transcription start site (−162, −53, −50, +6, +17, +50, CpG sites) [ 55 , 56 , 57 ] ( Figure 3 ). Studies in erythroid cells obtained from human hematopoietic stem and progenitor cells (HSPCs) demonstrated that the γ-globin promoters were significantly hypomethylated in cord blood and fetal liver samples compared to adult bone marrow samples [ 55 , 56 , 57 ]. Conversely, the DNA methylation levels of the adult β-globin promoter were higher in fetal cells than in adult samples [ 55 ].…”

“…Conversely, the DNA methylation levels of the adult β-globin promoter were higher in fetal cells than in adult samples [ 55 ]. Moreover, an abnormal DNA hypomethylation pattern in the γ-globin promoters was associated with an increased HbF expression in β-thalassemia patient cells as compared to healthy donors [ 56 ] and in individuals with HPFH mutations [ 58 ]. By contrast, in a non-human primate baboon model, 5hmC levels positively correlated with γ-globin expression, although the 5hmC levels were substantially lower than 5Mc [ 53 ].…”

Estudio de la talasemia β en el laboratorio clínico: estrategias diagnósticas

“…Además, encontramos un elemento regulador distal, conocido como LCR, que desempeña un papel importante en la regulación de la expresión de todos los genes del conjunto. La β-tal se caracteriza por un defecto cuantitativo en la síntesis de las cadenas de globina β subyacente a una marcada heterogeneidad genotípica de las mutaciones del gen (5).…”

Epigenetic Insights and Potential Modifiers as Therapeutic Targets in β–Thalassemia

“…DNA hypomethylation and histone acetylation are effective in inducing γ–globin expression [ 14 ]. Bao et al [ 15 ] described the hypomethylation patterns in the CpG sites around the LCR HS4-HS3 regions of the β–globin cluster as well as the γ– and β–globin promoters in β 0 /β 0 –thalassemia patients, compared with healthy controls. Hypomethylation was associated with high levels of HbF.…”