Objectives: Glucose-6-phosphate isomerase (GPI) deficiency is an autosomal recessive genetic disorder causing hereditary non-spherocytic hemolytic anemia (HNSHA) coupled with a neurological disorder. The aim of this study was to identify GPI genetic defects in a cohort of Indian patients with HNSHA coupled with neurological dysfunction.
Methods: Thirty-five patients were screened for GPI deficiency in the HNSHA patient group; some were having neurological dysfunction. Enzyme activity was measured by spectrophotometric method. The genetic study was done by single-stranded conformation polymorphism (SSCP) analysis, restriction fragment length polymorphism (RFLP) analysis by the restriction enzyme AciI for p.Arg347His (p.R347H) and confirmation by Sanger's sequencing.
Results: Out of 35 patients, 15 showed 35% to 70% loss of GPI activity, leading to neurological problems with HNSHA. Genetic analysis of PCR products of exon 12 of the GPI gene showed altered mobility on SSCP gel. Sanger's sequencing revealed a homozygous c1040G > A mutation predicting a p.Arg347His replacement which abolishes AciI restriction site. The molecular modeling analysis suggests p.Arg347 is involved in dimerization of the enzyme. Also, this mutation generates a more labile enzyme which alters its three-dimensional structure and function.
Conclusions: This report describes the high prevalence of p.Arg347His pathogenic variant identified in Indian GPI deficient patients with hemolytic anemia and neuromuscular impairment. It suggests that neuromuscular impairment with hemolytic anemia cases could be investigated for p.Arg347His pathogenic variant causing GPI deficiency because of neuroleukin activity present in the GPI monomer which has neuroleukin action at the same active site and generates neuromuscular problems as well as hemolytic anemia.
Keywords: Glucose-6-phosphate isomerase (GPI) deficiency; Glycolysis; Hereditary non-spherocytic hemolytic anemia (HNSHA); India; Molecular modeling; Neurological dysfunction.