KLF1 Mutations Are Not Common in Israel but Can Explain Occasional Cases of Elevated HbA2 or Very Elevated Fetal Hemoglobin

Introduction: Mutations in KLF1 (Kruppel Like Factor1) have been noted to cause a number of different phenotypes of erythrocyte abnormalities, as KLF1 is known as a master regulator of many genes expressed in red blood cells. One important manifestation caused by KLF1 mutations is the upregulation of γ- or δ-globin genes, with associated microcytosis, thus mimicking beta thalassemia (β-thal) trait. Such findings cause difficulty in counseling couples referred for prenatal diagnosis of β-thal. KLF1 mutations have been reported to be more frequent in geographic regions where β-thal is common. Therefore we undertook to analyze for the presence of KLF1 mutations in Israeli individuals. Materials and Methods: We selected 100 individuals for analysis belonging to one of 4 different groups: 1. Individuals with isolated elevated HbA2 (n=14), or isolated elevation of HbF (n=13) or elevation of both HbA2 and HbF (n=6), who are not carriers of a β-thal mutation by sequence analysis. 2. Individuals with β-thal trait (n=19) who have a higher HbF (and/or HbA2) than is expected for β-thal trait, who do not have β-thal intermedia on clinical criteria (blood count, peripheral smear, spleen size). These individuals carried one of 8 mutations known to cause β-thal in our region 3. Two patients (pts) with a history of transfusions (one with massive splenomegaly and sickle trait, suspected to have coinherited CDA, and one with β-thal intermedia with HbF elevation unexpectedly high for his mutation (TATA box -28 A to C; HBB:c.-78A>C). This patient had HbF levels ranging from 23-33% and HbA2 ranging from 7.8-8.9% over years of followup from age 39-50 years. 4. Anonymous controls (n=46) who are pts with a hematological malignancy not suspected of carrying a hemoglobinopathy. KLF1 (exons 1, 2 and 3) was amplified using PCR (exon 1: 564 base pair product and exons 2 and 3: 1703 base pair product). PCR products were subjected to DNA sequence analysis using an Applied Biosystems ABI apparatus. The sequence obtained was analyzed using BLAST alignment and deviations from the published sequence were analyzed using the Mutation Taster program. Results: Two pts were found to carry substitutions with possible or proven clinical significance. One pt is heterozygous for a substitution at c.972C>A (codon 324 exon 3, E324D, aspartic acid to glutamine) which has not been previously reported. According to Mutation Taster this substitution may have clinical significance. This pt, who has normal h