Chuvash polycythemia is an autosomal recessive form of erythrocytosis associated with a homozygous p.Arg200Trp mutation in the von Hippel-Lindau (VHL) gene. Since this discovery, additional VHL ...mutations have been identified in patients with congenital erythrocytosis, in a homozygous or compound-heterozygous state. VHL 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 VHL 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 VHL coding sequences) and in 1 large family with typical VHL disease but without any alteration in the other VHL exons. In this study, we show that the mutations induced a dysregulation of VHL 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 VHL 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 VHL alterations and reveals a novel complex splicing regulation of the VHL gene. These findings open new avenues for diagnosis and research regarding the VHL-related hypoxia-signaling pathway.
•Mutations in a VHL cryptic exon may be found in patients with familial erythrocytosis or VHL disease.•Synonymous mutations in VHL exon 2 may induce exon skipping and cause familial erythrocytosis or VHL disease.
Display omitted
Gain-of-function mutations in the EPAS1/HIF2A gene have been identified in patients with hereditary erythrocytosis that can be associated with the development of paraganglioma, pheochromocytoma and ...somatostatinoma. In the present study, we describe a unique European collection of 41 patients and 28 relatives diagnosed with an erythrocytosis associated with a germline genetic variant in EPAS1. In addition we identified two infants with severe erythrocytosis associated with a mosaic mutation present in less than 2% of the blood, one of whom later developed a paraganglioma. The aim of this study was to determine the causal role of these genetic variants, to establish pathogenicity, and to identify potential candidates eligible for the new hypoxia-inducible factor-2 α (HIF-2α) inhibitor treatment. Pathogenicity was predicted with in silico tools and the impact of 13 HIF-2b variants has been studied by using canonical and real-time reporter luciferase assays. These functional assays consisted of a novel edited vector containing an expanded region of the erythropoietin promoter combined with distal regulatory elements which substantially enhanced the HIF-2α-dependent induction. Altogether, our studies allowed the classification of 11 mutations as pathogenic in 17 patients and 23 relatives. We described four new mutations (D525G, L526F, G527K, A530S) close to the key proline P531, which broadens the spectrum of mutations involved in erythrocytosis. Notably, we identified patients with only erythrocytosis associated with germline mutations A530S and Y532C previously identified at somatic state in tumors, thereby raising the complexity of the genotype/phenotype correlations. Altogether, this study allows accurate clinical follow-up of patients and opens the possibility of benefiting from HIF-2α inhibitor treatment, so far the only targeted treatment in hypoxia-related erythrocytosis disease.
The discovery in 2005 of the
V617F gain-of-function mutation in myeloproliferative neoplasms and more particularly in polycythemia vera has deeply changed the diagnostic and therapeutic approaches to ...polycythemia. More recently, the use of NGS in routine practice has revealed a large number of variants, although it is not always possible to classify them as pathogenic. This is notably the case for the
E846D variant for which for which questions remain unanswered. In a large French national cohort of 650 patients with well-characterized erythrocytosis, an isolated germline heterozygous
E846D substitution was observed in only two cases. For one of the patients, a family study could be performed, without segregation of the variant with the erythrocytosis phenotype. On the other hand, based on the large UK Biobank resource cohort including more than half a million UK participants, the
E846D variant was found in 760 individuals, associated with a moderate increase in hemoglobin and hematocrit values, but with no significant difference to the mean values of the rest of the studied population. Altogether, our data as well as UK Biobank cohort analyses suggest that the occurrence of an absolute polycythemia cannot be attributed to the sole demonstration of an isolated
E846D variant. However, it must be accompanied by other stimuli or favoring factors in order to generate absolute erythrocytosis.
Purpose: MEM is an NGS algorithm that uses Expectation-Maximisation to detect the presence of unstable alleles from the NGS sequences of five microsatellites (BAT-25, BAT-26, NR-21, NR-24 and NR-27). ...The purpose of this study was to compare the MEM algorithm with a reference PCR method (MSI-PCR) and MisMatch Repair protein immunohistochemistry (MMR-IHC). Methods: FFPE colorectal cancer samples from 146 patients were analysed in parallel by MSI-PCR and NGS using the MEM algorithm. MMR-IHC results were available for 133 samples. Serial dilutions of an MSI positive control were performed to estimate the limit of detection. Results: the MEM algorithm was able to detect unstable alleles of each microsatellite with up to a 5% allelic fraction. Of the 146 samples, 28 (19.2%) were MSI in MSI-PCR. MEM algorithm results were in perfect agreement with those of MSI-PCR, at both MSI status and individual microsatellite level (Cohen’s kappa = 1). A high level of agreement was noted between MSI-PCR/MEM algorithm results and MMR-IHC results (Cohen’s kappa = 0.931). Conclusion: the MEM algorithm can determine the MSI status of colorectal cancer samples on a small NGS panel, using only five microsatellites approved by international guidelines, and can be combined with screening for targetable mutations.
A JAK2V617F‐negative polycythemia associated with low serum epo needs to be tested for an exon 12 JAK2 mutation. When negative, due to potential serious complications in PV, a next generation ...sequencing is necessary to rule out false negative results.
A JAK2V617F‐negative polycythemia associated with low serum epo needs to be tested for an exon 12 JAK2 mutation. When negative, due to potential serious complications in PV, a next generation sequencing is necessary to rule out false negative results.
AIM:To evaluate the risk associated with variants of the UNC5C gene recently suspected to predispose to familial colorectal cancer(CRC).METHODS:We screened patients with familial CRC forms as well as ...patients with sporadic CRCs.In a first time,we analyzed exon 11 of the UNC5C gene in 120unrelated patients with suspected hereditary CRC,58patients with suspected Lynch-associated cancer or polyposis,and 132 index cases of Lynch syndrome families with a characterized mutation in a DNA mismatch repair(MMR).Next,1023 patients with sporadic CRC and1121 healthy individuals were screened for the variants identified in patients with familial cancer.RESULTS:Of 120 patients with familial CRC of unknown etiology,one carried the previously reported mis-sense mutation p.Arg603Cys(R603C)and another exhibited the unreported variant of unknown significance p.Thr617Ile(T617I).The p.Ala628Lys(A628K)mutation previously described as the main UNC5C risk variant for familial CRC was not detected in any cases of familial CRC of unknown etiology,but was present in a patient with familial gastric cancer and in two Lynch syndrome patients in co-occurrence with MMR mutations.A statistically non-significant increase in cancer risk was identified in familial CRC and/or other Lynchassociated cancers(1/178 patients vs 2/1121 healthy controls,OR=3.2,95%CI:0.29-35.05,P=0.348)and in sporadic CRCs(4/1023 patients vs 2/1121 healthy controls,OR=2.2,95%CI:0.40-12.02,P=0.364).CONCLUSION:We confirm that UNC5C mutations are very rare in familial and sporadic CRCs,but further investigations are needed to justify routine UNC5C testing for diagnostic purposes.
We describe a patient with a Homo sapiens mutL homolog 1 （MLH1）-associated Lynch syndrome with previous diagnoses of two distinct primary cancers： a sigmoid colon cancer at the age of 39 years, and a ...right colon cancer at the age of 50 years. The muta- tion identified in his blood and buccal cells, c.1771delG, p.Asp591Ilefs＊25, appears to be a de novo event, as it was not transmitted by either of his parents. This type of de novo event is rare in MLH1 as only three cases have been reported in the literature so far. Further- more, the discordant results observed between repli- cation error phenotyping and immunohistochemistry highlight the importance of the systematic use of both pre-screening tests in the molecular diagnosis of Lynch syndrome.
SCN5A Mutation and ST Segment Elevation in Inferior Leads. Mutations in the SCN5A gene can lead to the Brugada syndrome, a genetically inherited form of idiopathic ventricular fibrillation that has a ...characteristic ECG phenotype usually restricted to precordial leads V1–V3. We identified a novel G752R SCN5A missense mutation leading to various degrees of the Brugada ECG phenotype in members of a French family. In the proband, the G752R mutation produced ST segment elevation and prominent J wave in leads II, III, and aVF. In four other relatives, ST segment elevation in the right precordial but not in the inferior leads was observed either spontaneously or under flecainide challenge. Recombinant G752R mutant exhibited a markedly reduced Na+ current amplitude and a voltage shift in both activation and inactivation curves. The mutant was found in all affected but not in nonaffected family members. One additional gene‐carrier had an almost normal ECG (silent gene‐carrier). We provide genetic demonstration that Brugada ECG anomalies related to a unique SCN5A mutation can be observed either in the inferior or the right precordial leads. (J Cardiovasc Electrophysiol, Vol. 14, pp. 200‐203, February 2003)
PDF
