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Haematologica 2019 Volume 104(12):2372-2381
Red Cell Biology & its Disorders
Genetic disarray follows mutant KLF1-E325K expression in a congenital dyserythropoietic anemia patient
1Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA; 2Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA; 3Division of Hematology/Oncology, The Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA; 4Children's Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, USA; 5Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY, USA; 6Dipartimento di Scienze Biomediche e NeuroMotorie, Alma Mater Studiorum, Università di Bologna, Bologna, Italy; 7Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA and 8Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
*ARM and JJB contributed equally as senior authors on this work.
ABSTRACT
Congenital dyserythropoietic anemia type IV is caused by a heterozy- gous mutation, Glu325Lys (E325K), in the KLF1 transcription factor. Molecular characteristics of this disease have not been clarified, part- ly due to its rarity. We expanded erythroid cells from a patient’s peripheral blood and analyzed its global expression pattern. We find that a large num- ber of erythroid pathways are disrupted, particularly those related to mem- brane transport, globin regulation, and iron utilization. The altered genetics lead to significant deficits in differentiation. Glu325 is within the KLF1 zinc finger domain at an amino acid critical for site specific DNA binding. The change to Lys is predicted to significantly alter the target site recognition sequence, both by subverting normal recognition and by enabling interac- tion with novel sites. Consistent with this, we find high level ectopic expression of genes not normally present in the red cell. These altered prop- erties explain patients’ clinical and phenotypic features, and elucidate the dominant character of the mutation.
Introduction
Congenital dyserythropoietic anemias (CDA) encompass a set of rare, chronic anemias that are heterogeneous but commonly exhibit morphologically abnormal bone marrow erythropoiesis. There are four subtypes that are differentiated by their causative genetic mutations: type I in CDA1, type II in SEC23B, and type III in KIF23.1-3 The genetic cause for the rare CDA type IV (OMIM 613673) is unique in that it derives from a transcription factor mutation. A G-to-A transition in one allele of exon 3 of KLF1 (erythroid Krüppel-like factor; EKLF) results in the substi- tution of a glutamate 325 by a lysine (E325K). CDA type IV patients present with severe hemolytic anemia, splenomegaly, elevated fetal hemoglobin (HbF), iron overload, red cell osmotic fragility, and dyserythropoiesis in the bone marrow.4-13 These clinical properties do not fit into the typical categories for hereditary persist- ence of fetal hemoglobin, ß-thalassemia, or hereditary spherocytosis.5,12,13 The high levels of nucleated and bi-nucleated erythroid cells in the bone marrow and in the peripheral blood are quite striking.
The E325K mutation, within the second zinc finger of the KLF1 protein, is at a universally conserved residue/amino acid that is critical for proper DNA target site recognition. KLF114 is a zinc finger hematopoietic transcription factor that plays a global role in activation of genes critical for genetic control within the erythroid lin- eage.15-18 It performs this essential function by binding to its cognate DNA 5’CCM- CRCCCN3’ element, interacting with basal transcription factors, and recruiting
Lilian Varricchio,1 Antanas Planutis,2 Deepa Manwani,3 Julie Jaffray,4 W. Beau Mitchell,5 Anna Rita Migliaccio1,6,* and James J. Bieker1,2,7,8,*
Correspondence:
JAMES J. BIEKER
james.bieker@mssm.edu
Received: October 22, 2018. Accepted: March 12, 2019. Pre-published: March 14, 2019.
doi:10.3324/haematol.2018.209858
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