Abstract
BACKGROUND: Chordoid glioma (ChG) is a characteristic, slow growing and well-circumscribed diencephalic tumor, whose mutational landscape is unknown. METHODS: We analyzed primary chordoid glioma samples by whole exome sequencing, RNAseq, Sanger sequencing, RT-PCR and immunohistochemistry. We determined subcellular localization, kinase activity and effects on proliferation of wild-type and mutant PRKCA. RESULTS: We found that 14/15 ChG harbor the same PRKCAD463H mutation. PRKCA encodes the Protein kinase C (PKC) isozyme alpha (PKCα) and is mutated in a wide range of human cancers. However the hot spot ChG PRKCAD463H mutation is novel. Here we show that ChGs express the PRKCAD463H mutant at higher levels than the wild-type PRKCA gene. Pathway analysis of the expression data shows that PRKCAD463H is strongly associated with the activation of protein translation initiation (EIF2) pathway. Compared to wild type PKCα, the PKCα D463H mutant protein is depleted from the cell membrane in vitro and from adherens junctions in vivo and shows diffuse cytoplasmic localization. The PKCα D463H mutant exhibits increased kinase activity towards the PKCα substrate MARCKS (Myristoylated Alanine-Rich C Kinase Substrate) and enhances proliferation of human astrocytes. CONCLUSION: PRKCAD463H is the hallmark mutation of ChG and provides new targeting opportunities in ChG patients. Our results support a more complex change than a simple gain of function, and suggest that the mutation results in a neomorphic enzyme with very specific properties.