Identification of a new VHL exon and complex splicing alterations in familial erythrocytosis or von Hippel-Lindau disease

Abstract

Chuvash polycythemia is an autosomal recessive form of erythrocytosis associated with a homozygous p.Arg200Trp mutation in the von Hippel-Lindau () gene. Since this discovery, additional mutations have been identified in patients with congenital erythrocytosis, in a homozygous or compound-heterozygous state. is a major tumor suppressor gene, mutations in which were first described in patients presenting with VHL disease, which is characterized by the development of highly vascularized tumors. Here, we identify a new cryptic exon (termed E1') deep in intron 1 that is naturally expressed in many tissues. More importantly, we identify mutations in E1' in 7 families with erythrocytosis (1 homozygous case and 6 compound-heterozygous cases with a mutation in E1' in addition to a mutation in coding sequences) and in 1 large family with typical VHL disease but without any alteration in the other exons. In this study, we show that the mutations induced a dysregulation of splicing with excessive retention of E1' and were associated with a downregulation of VHL protein expression. In addition, we demonstrate a pathogenic role for synonymous mutations in exon 2 that altered splicing through E2-skipping in 5 families with erythrocytosis or VHL disease. In all the studied cases, the mutations differentially affected splicing, correlating with phenotype severity. This study demonstrates that cryptic exon retention and exon skipping are new alterations and reveals a novel complex splicing regulation of the gene. These findings open new avenues for diagnosis and research regarding the VHL-related hypoxia-signaling pathway.

Case report: a synonymous VHL mutation (c.414A > G, p.Pro138Pro) causes pathogenic familial hemangioblastoma through dysregulated splicing

“…This mutation is a recurrent synonymous mutation in VHL disease. Based on this and two additional recent studies [17,18], the mutation has been reported in 29 individuals of 8 independent families (Supplementary Table S2). The overall association is with Type 2A (i.e.…”

“…diagnosis of PHEO and HGB but rarely RCC). Although this variant was shown to be associated with PHEO [17,18], the clinical information on its role in HGB was limited. In the clinic, HGB instead of RCC is the major contributor to the unfavorable overall survival of VHL patients [20], highlighting the importance of understanding the etiology of HGB.…”

“…The reduced but not completely abolished pVHL protein in a LOH genetic backdrop may underlie the etiology of VHL disease. Previous studies used lymphoblastoid cell lines established from VHL patients [17,21], which require transformation of B lymphocytes with Epstein-Barr virus and the immunosuppressant Cyclosporine A [22,23]. In contrast, the culture of primary fibroblasts is technically straightforward [19] and does not require transformation, a procedure that might complicate the interpretation of the biological functions of tumor suppressor genes to study [24].…”

“…E1E3 encodes a protein of 172 amino acids (pVHL 172 ) with generally low expression abundance and a possible lack of the tumor suppressor function due to the disruption of the HIF-binding domain [16]. Recent studies suggest that synonymous mutations of VHL can also lead to dysregulated splicing [17,18]. However, the clinical and molecular evidence to support the role of synonymous mutations in VHL disease is still very limited.…”

The structural basis for intermitochondrial communications is fundamentally different in cardiac and skeletal muscle

“…Levels of the von Hippel–Lindau protein are reduced in this condition, leading to a largely hypoxic phenotype at multiple levels and exposing the mitochondria to metabolic stress. These findings suggest that the development of intermitochondrial connecting ducts might be a common response, worth investigating in other circumstances where the functioning of the hypoxia‐inducible factor pathway is altered (Formenti et al., , ; Lenglet et al., ; Perrotta et al., ; Petousi et al., ; Thompson et al., ).…”