Novel Mutations in the <i>EPO-R, VHL</i> Genes and a Reported Mutation in <i>EPAS1</i> Gene in the Congenital Erythrocytosis Patients in a Southern State of India

Abstract

Background: Congenital erythrocytosis (CE) can be classified as primary and secondary and 82 consecutive patients of erythrocytosis who were JAK-2 mutation negative, were further investigated. Methods: The genomic DNA was extracted from all the patients and the EPO-R, VHL, EGLN1 and EPAS1 genes were PCR amplified and sequenced. Findings: The sequence analysis showed 34.14% patients had mutations. Among them, 67.86% patients had mutations in exon 8 of EPO-R gene, out of which 7 patients showed novel missense mutations, p.(Gly418Ala), p.(Gly390Ala), p.(Ala411Thr), p.(Gly475Val), p.(Glu490Asp), p.(Glu362Gln) and three (3 out of 19) patients showed novel frameshift mutations, p.(Glu336*), p.(Pro327Hisfs*68), p.(Gly479Alafs*37), the rest being the reported ones, resulting in truncated protein formation. All these EPO-R patients were heterozygotes and were forming Endogenous Erythrocyte Colonies (EEC). Some patients (28.57%) had mutations in VHL gene, out of which 3 novel homozygous missense mutations in exon 1 of VHL gene, p.Gly80Asp, p.Gln107Glu and p.Gln113Glu, were identified. In addition, 3.5% patients had reported heterozygous missense mutation in exon 12 of EPAS1 gene p.Gly537Arg. Further, in silico analysis indicated most of the mutations, probably, were damaging the protein structures, causing the CE in these patients. Interpretation: Of the JAK-2-negative erythrocytosis patients in the southern state of India, 34.14% were seen to have CE, EPO-R alleles (67.86%) being the most frequently seen, followed by, VHL (28.57%) and EPAS1 (HIF-2α) (3.5%). Certain novel and reported mutations were identified. Nearly, one third of all CE patients presented with vascular thrombosis and CE could be an important etiological factor. Funding Statement: None. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The study was cleared by the Institutional Ethics Committee (IEC.NO: 966). A written consent was obtained from all the individuals studied.