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Blood, 1 September 2005, Vol. 106, No. 5, pp. 1851-1856. Prepublished online as a Blood First Edition Paper on May 3, 2005; DOI 10.1182/blood-2005-02-0555.
Submitted February 17, 2005
Department of Biochemistry and Molecular Biology IV, Universidad Complutense de Madrid, Madrid, Spain * Corresponding author; email: jmbau{at}vet.ucm.es.
Human erythrocyte R-type pyruvate kinase (RPK) deficiency is an autosomal recessive disorder produced by mutations in the PKLR gene causing chronic nonspherocytic haemolytic anaemia. Patient survival in severe RPK deficiency has been associated with the compensatory expression in the red blood cells of M2PK, an isoenzyme showing wide tissue distribution. We describe a novel homozygous null mutation of the PKLR gene found in a female patient diagnosed before birth as having a PK deficiency. The mutant PK gene revealed an 11-nt duplication at exon 8 causing frameshift of the PKLR transcript, predicting a truncated protein inferred to have no catalytic activity. Western blot analysis and qRT-PCR detected no M2PK expression in the peripheral blood red cell fraction. The expression of mutant RPK mRNA in the red blood cells was almost six times higher than that detected in a control patient with hereditary spherocytosis. This molecular phenotypic analysis of the null mutation in the PKLR gene provides evidence for a lack of M2PK in the mature red blood cells of this patient, and suggests that normal red cell functions and survival are achieved through a population of young erythroid cells released into the circulation in response to anaemia.
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