Mutational analysis of INI1 in sporadic human brain tumors

The INI1/SMARCB1/hSNF5 gene on chromosome 22 is frequently mutated in rhabdoid tumors. An association of INI1 mutations with allelic losses on chromosome 22 supports a classical tumor suppressor mechanism. Several brain tumor entities including astrocytomas, glioblastomas and ependymomas are characterized by allelic losses on chromosome 22. In the present study we examined a series of 200 brain tumors by Single-strand conformation polymorphism analysis and direct sequencing for point mutations in INI1. In addition, all tumors were analyzed for homozygous deletions spanning both exons 3 and 8 of INI1. No mutations or homozygous deletions were detected in astrocytomas, glioblastomas, oligodendroglial tumors, neurinomas or medulloblastomas. However, a point mutation could be identified in the single case of plexus carcinoma. Our data suggest that INI1 mutations are involved in the pathogenesis of plexus carcinoma; however, INI1 alterations are not a frequent event in the majority of brain tumor entities.