Nine known and five novel mutations in the erythroid transcription factor KLF1 gene and phenotypic expression of fetal hemoglobin in hemoglobin E disorder

Abstract

Hemoglobin E is the most common Hb variant found in South East Asia. Variation of Hb F expression in Hb E syndrome is associated with several genetic modifiers. We report several single nucleotide polymorphisms (SNPs), including nine known and five novel mutations of the Krüppel-like factor 1 (KLF1; an erythroid specific transcription factor) gene and determine their associations with phenotypic expression of Hb F in Hb E disorders. KLF1 mutations were examined using high resolution melting (HRM) assay and DNA sequencing in 575 homozygous Hb E, 278 heterozygous Hb E and 100 normal subjects. Fourteen mutations were mostly observed in subjects with elevated Hb F, including nine known mutations (G176AfsX179, T334R, R238H, −154 (C>T), A298P, S270W, R301H, −148 (G>A) and G335R and five novel mutations (Q217X, Q223X, Y290_S293del, K307N, and M358I). None of them, but the −148 (G>A), were observed in normal controls to have Hb F <1%. Combined KLF1 mutations with other SNPs including Gγ-XmnI, BCL11A and HBS1L-MYB were associated with higher Hb F levels. KLF1 is therefore an important genetic factor associated with increased Hb F and in combination with other modifying factors could explain the phenotypic variation of Hb F expression in this common hemoglobinopathy.