Submitted March 19, 2008
Accepted April 14, 2008
Mutations in EKLF/KLF1 form the molecular basis of the rare blood group In(Lu) phenotype
Belinda K. Singleton*, Nicholas M. Burton, Carole Green, R. Leo Brady, and David J. Anstee
Bristol Institute for Transfusion Sciences, National Blood Service, Bristol, United Kingdom
Department of Biochemistry, University of Bristol, Bristol, United Kingdom
* Corresponding author; email: belinda.singleton{at}nbs.nhs.uk.
Comparison of normal erythroblasts and erythroblasts from individuals with the rare In(Lu) type of Lu(a-b-) blood group phenotype revealed increased transcription levels for 314 genes and reduced levels for 354 genes in In(Lu) cells. Many erythroid-specific genes (including ALAS2, SLC4A1) had reduced transcript levels suggesting the phenotype resulted from a transcription factor abnormality. A search for mutations in erythroid transcription factors revealed mutations in the promoter or coding sequence of EKLF in 21 of 24 individuals with the In(Lu) phenotype. In all cases the mutant EKLF allele occurred in the presence of a normal EKLF allele. Nine different loss of function mutations were identified. One mutation abolished a GATA1 binding site in the EKLF promoter (-124T>C). Two mutations (Leu127X; Lys292X) resulted in premature termination codons, two (Pro190LeufsX47; Arg319GlufsX34) in frameshifts and four in amino acid substitution of conserved residues in zinc finger domain 1 (His299Tyr) or domain 2 (Arg328Leu; Arg328His; Arg331Gly). Individuals with the In(Lu) phenotype have no reported pathology indicating that one functional EKLF allele is sufficient to sustain human erythropoiesis. These data provide the first description of inactivating mutations in human EKLF and the first demonstration of a blood group phenotype resulting from mutations in a transcription factor.
