Association study of common KLF1 variants with Hb F and Hb A2 levels in β-thalassaemia carriers of Portuguese ancestry.

Abstract

Kruppel-like factor 1 (KLF1) is an essential erythroid-specific transcription factor. Several reports have shown that KLF1 gene mutations are associated with increased levels of Hb F and Hb A₂. However, scarce population studies have analysed common KLF1 variations. This study examines the potential association with Hb F and Hb A₂ levels in β-thalassemia (β-thal) carriers of Portugueseancestry of the four common KLF1 gene variants: -251C>G (rs3817621) and -148G>A (rs79334031), in the promoter region; and c.115A>C (p.Met39Leu) (rs112631212) and c.304T>C (p.Ser102Pro) (rs2072597), in exon 2. Ninety-two Portuguese β-thal carriers (43 males and 49 females) aged 2 to 77 years old (mean 32.55 years) were engaged in the study. Hb F levels range from 0.2 to 12.5% and Hb A₂ was above the normal level, ranging from 3.6 to 6%. The Hb A₂ and Hb F levels were determined by high-performance liquid chromatography. Single-nucleotide polymorphisms were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Minor allele frequencies for SNPs rs3817621 (G), rs79334031 (A), rs112631212 (C) and rs2072597 (C) were 0.196, 0.016, 0.011 and 0.169, respectively. Basic simple linear regression in the total population showed no significant associations with the levels of Hb F (P>0.05). For the low-frequency variant -148A, a statistically significant association was found with increased levels of Hb A₂ (β = 0.855; P = 0.017). In conclusion, an association signal with Hb A₂ levels was observed for the variant -148A>G (rs79334031). The complex pattern of SNP interactions related to their influence on the KLF1 transcriptional activity mayexplain the absence of association with Hb F levels.