HBS1L-MYB INTERGENIC REGION EXPRESSION IS ASSOCIATED WITH FETAL HEMOGLOBIN LEVEL IN β-THALASSEMIA/HbE ERYTHROBLASTS

Abstract

β-thalassemia/HbE is a hematological disease caused by impairment of β-globin production. The degree of diseases severity depends on several factors including the expression of fetal globin (α2γ2) which can compensate for an accumulation of excess α-globin chains. GWAS analysis were performed to identify loci that are linked to reduction in disease severity. A subset of key loci is located at or near the genes encoding transcription factors functionally associated with globin gene expression. The polymorphisms at the intergenic region between HBS1L and MYB gene or HMIR was shown to be one of the significant severity modifying factor. A set of short transcripts corresponding to the HBS1L-MYB genes intergenic region was found in RNA-seq analyses of K562 erythroid cell line, indicating that this intergenic region is actively transcribed. Recently, the non-coding RNA was shown to play roles in gene transcription control. Quantitative PCR was carried out to determine and quantify the non-coding HBS1L-MYB transcripts in primary human erythroblasts derived from normal individuals and β-thalassemia/HbE patients. Three clusters of HMIR transcripts were identified. Interestingly, erythroblasts from β-thalassemia/HbE patients have significantly lower levels of the HMIR transcripts than those of normal erythroblasts. In order to characterize these HMIR transcripts, the 5ʹ and 3ʹ rapid amplification of cDNA ends (RACE) were carried out to detect the full length of the transcripts. Amplifying results of RACE products show that the 5ʹend of each transcripts are more than 200 base pairs. The clones were selected for DNA sequencing, however, they do not contain HMIR sequences. Hence, these transcripts are the candidate for being a small non-coding RNAs that might responsible for modifying the patient’s severity.