Methylation Status Of LARP2 and IGSF4 Gene Promoter Region In Hb E/Β-Thalassemia And Β-Thalassemia Major Patients

Abstract

Hypermethylation of LARP2 and IGSF4 in β-thalassemia have been implicated in the pathogenesis of abnormal β-globin chain production.  However, methylation status has not been fully explored in Hb E/β-thalassemia which has variable clinical presentation ranging from mild to severe. This study aimed to compare DNA methylation status of LARP2 and IGSF4 gene promoter of Hb E/β-thalassemia and β-thalassemia major patients who have less clinical variability. DNA were extracted from nucleated red blood cells (NRBCs) from peripheral blood (PB) of 21 Hb E/β-thalassemia and 12 β-thalassemia major patients at Hospital UniversitiSains Malaysia (HUSM) and Hospital Raja Perempuan Zainab II (HRPZII). Methylation status of the promoter region of LARP2 and IGSF4 promoter were examined by using bisulfite sequencing PCR (BSP) and methylated specific PCR (MSP) respectively. The results showed that none were fully methylated in LARP2 promoter region of both patients. Partial methylation was detected in 9 of 21 (43%) of Hb E/β-thalassemia patients and 17% in β-thalassemia. Out of 18 CpGsanalyzed, CpGs 3 and 5 were mostly partially methylated, 36% of Hb E/β-thalassemia and 17% in β-thalassemia major. In IGSF4 promoter region, 75% of β-thalassemia patients were fully methylated while 95% Hb E/ β-thalassemia patients were partially methylated. Significant difference reported between types of thalassemia and IGSF4 methylation status (p<0.05). This study demonstrated that partially methylated IGSF4 and LARP2 are common in Hb E/ β-thalassemia. Partial methylation may either cause down- or up-regulation expression of LARP2 and IGSF4 genes. We speculated that these epigenetic changes may contribute to the large clinical spectrum of Hb E/ β-thalassemia. However, this has yet to be confirmed with further study to correlate the findings with clinical severity parameters. 

Keywords: Methylation; β-thalassemia; LARP2; IGSF4