AUTHOR=Kristan Aleša , Pajič Tadej , Maver Aleš , Režen Tadeja , Kunej Tanja , Količ Rok , Vuga Andrej , Fink Martina , Žula Špela , Podgornik Helena , Anžej Doma Saša , Preložnik Zupan Irena , Rozman Damjana , Debeljak Nataša 

TITLE=Identification of Variants Associated With Rare Hematological Disorder Erythrocytosis Using Targeted Next-Generation Sequencing Analysis

JOURNAL=Frontiers in Genetics

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2021.689868

DOI=10.3389/fgene.2021.689868

ISSN=1664-8021

ABSTRACT=<p>An erythrocytosis is present when the red blood cell mass is increased, demonstrated as elevated hemoglobin and hematocrit in the laboratory evaluation. Congenital predispositions for erythrocytosis are rare, with germline variants in several genes involved in oxygen sensing (<italic>VHL</italic>, <italic>EGLN1</italic>, and <italic>EPAS1</italic>), signaling for hematopoietic cell maturation (<italic>EPOR</italic> and <italic>EPO</italic>), and oxygen transfer (<italic>HBB</italic>, <italic>HBA1</italic>, <italic>HBA2</italic>, and <italic>BPGM</italic>) that were already associated with the eight congenital types (ECYT1–8). Screening for variants in known congenital erythrocytosis genes with classical sequencing approach gives a correct diagnosis for only up to one-third of the patients. The genetic background of erythrocytosis is more heterogeneous, and additional genes involved in erythropoiesis and iron metabolism could have a putative effect on the development of erythrocytosis. This study aimed to detect variants in patients with yet unexplained erythrocytosis using the next-generation sequencing (NGS) approach, targeting genes associated with erythrocytosis and increased iron uptake and implementing the diagnostics of congenital erythrocytosis in Slovenia. Selected 25 patients with high hemoglobin, high hematocrit, and no acquired causes were screened for variants in the 39 candidate genes. We identified one pathogenic variant in <italic>EPAS1</italic> gene and three novel variants with yet unknown significance in genes <italic>EPAS1</italic>, <italic>JAK2</italic>, and <italic>SH2B3.</italic> Interestingly, a high proportion of patients were heterozygous carriers for two variants in <italic>HFE</italic> gene, otherwise pathogenic for the condition of iron overload. The association between the <italic>HFE</italic> variants and the development of erythrocytosis is not clearly understood. With a targeted NGS approach, we determined an actual genetic cause for the erythrocytosis in one patient and contributed to better management of the disease for the patient and his family. The effect of variants of unknown significance on the enhanced production of red blood cells needs to be further explored with functional analysis. This study is of great significance for the improvement of diagnosis of Slovenian patients with unexplained erythrocytosis and future research on the etiology of this rare hematological disorder.</p>