Unravelling the genetic and phenotypic heterogeneity of SPTA1 gene variants in Hereditary Elliptocytosis and Hereditary Pyropoikilocytosis patients using next-generation sequencing

Abstract

Hereditary Elliptocytosis (HE) and Hereditary Pyropoikilocytosis (HPP) are clinically and genetically heterogeneous red cell membranopathies that result from the defects in the horizontal linkage between RBC (red blood cell) membrane and cytoskeletal proteins affecting its mechanical stability and deformability thereby reducing its lifespan. The principal defect in HE and HPP is due to dysfunction or deficiency of RBC cytoskeletal proteins namely, α-spectrin (SPTA1), β-spectrin (SPTB) and protein 4.1R (EPB41R). This study reports the genetic and phenotypic heterogeneity of 10 Indian patients (5 with HE and 5 with HPP)harboringSPTA1 gene variants. We used targeted next-generation sequencing (t-NGS) to characterize the causative genetic variants in 10 HE/HPP suspected patients and studied the correlation between the identified variants with their corresponding phenotypic features.t-NGS detected 12 SPTA1 variants, out of which 8 are novel. Nearly all of the detected variants have a damaging effect on the protein stability and function, as shown by the insilico analysis. The possible effect of the detected variants on the protein structure was studied using the HOPE software and DynaMut tools wherever possible. To the best of our knowledge, this is the first report on HE/HPP cases confirmed by a genetic study from India. To conclude, HE is caused by monoallelic mutations while HPP, the more severe form, is typically caused by biallelic (homozygous or compound heterozygous) mutations justifying the phenotypic heterogeneity associated with patients. Moreover, analysis at the molecular level by NGS permits diagnosis in these disorders with highly variable heterogeneity requiring regular transfusions and may facilitate prognostic contemplations.