c.598C>T
The authors identify a new VHL cryptic exon (termed E1') deep in intron 1 that is naturally expressed in many tissues. Mutations in E1' are identified in 7 families with erythrocytosis and in 1 large family with typical VHL disease but without any alteration in the other VHL exons. Whole blood was isolated from patients and sequenced using sanger sequencing and whole-genome sequencing performed at the clinically accredited Molecular Diagnostics Laboratory at the John Radcliffe Hospital using the Hi-Sequation 4000 platform (Illumina Inc., San Diego, CA) in high-throughput mode. As well, paired-end sequencing was carried out in a single lane on the HiSeq 2500 system (Illumina).In this study, the authors show that the mutations in E1' induced dysregulation of VHL splicing with excessive retention of E1' and were associated with a downregulation of VHL protein expression. Three patients were found with both the c.598C>T germline VHL mutation and the c.340+770T>C mutation resulting in p.Ser179Pro mutation on potential X1 protein encoded by E1' exon. In family 2, II.1 was the only person who had both of these mutations. In family 3, brothers II.1 and II.2 had these two mutations. Biological material from the parents of these three children were not available but chuvash core haplotype analysis demonstrated that all patients were compound heterozygous with one mutation being inherited from each parent. All three cases described above had erythrocytosis.