Truncated NF2 proteins are not detected in meningiomas and schwannomas

Neurofibromatosis type 2 is caused by mutations in the NF2 tumor suppressor gene. The NF2 gene encodes a 595-aminoacid protein, presumably functioning as a membrane-organizing element. Theoretically, the majority of mutations found in the NF2 gene should lead to a truncated protein product. Using immunoprecipitation with an antibody raised to N-terminal sequences of the NF2 protein, the authors sought to demonstrate the presence of truncated NF2 proteins in tumors. From 17 of 19 tumors (14 meningiomas and five schwannomas), 12 of which have previously been shown to harbor truncating NF2 mutations, wild-type NF2 protein was immunoprecipitated. From two tumors no protein was precipitated. Truncated NF2 proteins were not observed. The authors conclude that mutant NF2 proteins are unstable and undergo accelerated degradation.