Spectrum of novel mutations in the human PKLR gene in pyruvate kinase-deficient Indian patients with heterogeneous clinical phenotypes

Eighteen unrelated pyruvate kinase (PK)-deficient Indian patients were identified in the past 4 years with varied clinical phenotypes ranging from a mild chronic haemolytic anaemia to a severe transfusion-dependent disorder. We identified 17 different mutations in the PKLR gene among the 36 mutated alleles. Ten novel mutations were identified: 427G>A, 499C>A, 1072G>A, 1180G>T, 1216G>A, 1220A>G, 644delG, IVS5 (+20) C>A, IVS9 (+44) C>T, and IVS9 (+93) A>C. A severe syndrome was commonly associated with some mutations, 992A>G, 1436G>A, 1220A>G, 644delG and IVS9 (+93) A>C, in the PKLR gene. Molecular graphics analysis of human red blood cell PK (RPK), based on the crystal structure of human PK, shows that mutations located near the substrate or fructose 1,6-diphosphate binding site may change the conformation of the active site, resulting in very low PK activity and severe clinical symptoms. The mutations target distinct regions of RPK structure, including domain interfaces and catalytic and allosteric sites. In particular, the 1216G>A and 1219G>A mutations significantly affect the interdomain interaction because they are located near the catalytic site in the A/B interface domains. The most frequent mutations in the Indian population appear to be 1436G>A (19.44%), followed by 1456C>T (16.66%) and 992A>G (16.66%). This is the first study to correlate the clinical profile with the molecular defects causing PK deficiency from India where 10 novel mutations that produce non-spherocytic haemolytic anaemia were identified.