Novel CIC Point Mutations and an Exon-Spanning, Homozygous Deletion Identified in Oligodendroglial Tumors by a Comprehensive Genomic Approach Including Transcriptome Sequencing

Sophie Eisenreich, Khalil Abou-El-Ardat, Karol Szafranski, Jaime A. Campos Valenzuela, Andreas Rump, Janice M. Nigro, Rolf Bjerkvig, Eva Maria Gerlach, Karl Hackmann, Evelin Schröck, Dietmar Krex, Lars Kaderali, Gabriele Schackert, Matthias Platzer, Barbara Klink*

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

16 Citations (Scopus)

Abstract

Oligodendroglial tumors form a distinct subgroup of gliomas, characterized by a better response to treatment and prolonged overall survival. Most oligodendrogliomas and also some oligoastrocytomas are characterized by a unique and typical unbalanced translocation, der(1,19), resulting in a 1p/19q co-deletion. Candidate tumor suppressor genes targeted by these losses, CIC on 19q13.2 and FUBP1 on 1p31.1, were only recently discovered. We analyzed 17 oligodendrogliomas and oligoastrocytomas by applying a comprehensive approach consisting of RNA expression analysis, DNA sequencing of CIC, FUBP1, IDH1/2, and array CGH. We confirmed three different genetic subtypes in our samples: i) the "oligodendroglial" subtype with 1p/19q co-deletion in twelve out of 17 tumors; ii) the "astrocytic" subtype in three tumors; iii) the "other" subtype in two tumors. All twelve tumors with the 1p/19q co-deletion carried the most common IDH1 R132H mutation. In seven of these tumors, we found protein-disrupting point mutations in the remaining allele of CIC, four of which are novel. One of these tumors also had a deleterious mutation in FUBP1. Only by integrating RNA expression and array CGH data, were we able to discover an exon-spanning homozygous microdeletion within the remaining allele of CIC in an additional tumor with 1p/19q co-deletion. Therefore we propose that the mutation rate might be underestimated when looking at sequence variants alone. In conclusion, the high frequency and the spectrum of CIC mutations in our 1p/19q-codeleted tumor cohort support the hypothesis that CIC acts as a tumor suppressor in these tumors, whereas FUBP1 might play only a minor role.

Original languageEnglish
Article numbere76623
JournalPLoS ONE
Volume8
Issue number9
DOIs
Publication statusPublished - 27 Sep 2013
Externally publishedYes

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