Novel Variant of the SLC4A1 Gene Associated with Hereditary Spherocytosis.

Hereditary spherocytosis (HS) refers to the group of the most frequently occurring non-immune hereditary hemolytic anemia in people of Caucasian central or northern European ancestry. HS is mainly associated with pathogenic variants of genes encoding defects in five membrane proteins, including anion exchanger 1 encoded by the SLC4A1 gene. In this study, in a family affected with HS, we identified a hitherto unreported AE1 defect, variant p.G720W. The result of it is most likely the HS phenotype. Molecular dynamics simulation study of the AE1 transmembrane domain may indicate reasonable changes in AE1 domain structure, i.e., significant displacement of the tryptophan residue towards the membrane surface connected with possible changes in AE1 function. The WES analysis verified by classical sequencing in conjunction with biochemical analysis and molecular simulation studies shed light on the molecular mechanism underlying this case of hereditary spherocytosis, for which the newly discovered AE1 variant p.G720W seems crucial.

A rare mutation (p.F149del) of the NT5C3A gene is associated with pyrimidine 5'-nucleotidase deficiency.

Pyrimidine 5'-nucleotidase deficiency is a rare erythrocyte enzymopathy. Here we report two cases of hemolytic anemia in brothers of Polish origin that are associated with a very rare mutation. Heterozygous deletion in the NT5C3A gene (c.444_446delGTT), inherited most likely from their asymptomatic mother, resulted in a single amino acid residue deletion (p.F149del) in cytosolic pyrimidine 5'-nucleotidase. However, only the mutated transcript was present in the reticulocyte transcriptome of both patients. Only residual activity of pyrimidine 5'-nucleotidase in the brothers' erythrocytes could be observed when compared with the controls, including their asymptomatic father and sister. Western blot showed no sign of the presence of 5'-nucleotidase protein in the erythrocytes of both studied patients. The 2.5-fold reduction of the purine/pyrimidine ratio observed only in the brothers' erythrocytes confirms the correlation of the results of molecular analysis, including whole-exome sequencing, with the phenotype of the pyrimidine 5'-nucleotidase deficiency. Altogether, our results may substantiate the hypothesis of the heterogeneity of the molecular basis of the defect involving both the mutation presented here and negative regulation of expression of the "normal" allele.

Identification of a Novel Mutation of ß-Spectrin in Hereditary Spherocytosis Using Whole Exome Sequencing.

Hereditary spherocytosis (HS), the most commonly inherited hemolytic anemia in northern Europeans, comprises a group of diseases whose heterogeneous genetic basis results in a variable clinical presentation. High-throughput genome sequencing methods have made a leading contribution to the recent progress in research on and diagnostics of inherited diseases and inspired us to apply whole exome sequencing (WES) to identify potential mutations in HS. The data presented here reveal a novel mutation probably responsible for HS in a single Polish family. Patients with clinical evidence of HS (clinical symptoms, hematological data, and EMA test) were enrolled in the study. The examination of the resulting WES data showed a number of polymorphisms in 71 genes associated with known erythrocyte pathologies (including membranopathies, enzymopathies, and hemoglobinopathies). Only a single SPTB gene variant indicated the possible molecular mechanism of the disease in the studied family. The new missense mutation p.C183Y was identified using WES in the SPTB gene, which is most likely the cause of clinical symptoms typical of hereditary spherocytosis (membranopathy) due to structural and functional impairments of human ß-spectrin. This mutation allows for a better understanding of the molecular mechanism(s) of one of the membranopathies, hereditary spherocytosis.

Efficient method for isolation of reticulocyte RNA from healthy individuals and hemolytic anaemia patients.

Despite enormous progress and development of high-throughput methods in genome-wide mRNA analyses, data on the erythroid transcriptome are still limited, even though they could be useful in medical diagnostics and personalized therapy as well as in research on normal and pathological erythroid maturation. Although obtaining normal and pathological reticulocyte transcriptome profiles should contribute greatly to our understanding of the molecular bases of terminal erythroid differentiation as well as the mechanisms of the hematological diseases, a basic limitation of these studies is the difficulty of efficient reticulocyte RNA isolation from human peripheral blood. The restricted number of possible parallel experiments primarily concern healthy individuals with the lowest number of reticulocytes in the peripheral blood and a low RNA content. In the present study, an efficient method for reticulocyte RNA isolation from healthy individuals and hemolytic anaemia patients is presented. The procedure includes leukofiltration, Ficoll-Paque gradient centrifugation, Percoll gradient centrifugation, and negative (CD45 and CD61) immunomagnetic separation. This relatively fast and simple four-stage method was successfully applied to obtain a reticulocyte-rich population from healthy subjects, which was used to efficiently isolate the high-quality RNA essential for successful NGS-based transcriptome analysis.