LOSS OF ALLELES IN VESTIBULAR SCHWANNOMAS - USE OF MICROSATELLITE MARKERS ON CHROMOSOME-22

Objective: Using highly informative microsatellite markers flanking th e neurofibromatosis type 2 gene, we determined the frequency of chromo some 22 allele loss in vestibular schwannomas. Design: Peripheral lymp hocyte/vestibular schwannoma DNA pairs were analyzed with five differe nt microsatellite markers on chromosome 22. Patients: Samples were tak en from 32 patients (17 females and 15 males). Twenty-seven tumors occ urred sporadically, and five were from patients with neurofibromatosis type 2. Results: Using the microsatellite markers D22S351, CRYB2, D22 S268, D22S304, and interleukin type 2R beta, we found loss of heterozy gosity for at least two markers in 12 tumors. Ten tumors showed loss o f heterozygosity for markers flanking the neurofibromatosis type 2 gen e. Although microsatellite markers for and are highly informative, all ele may be to interpret in some cases. Conclusions: Loss of heterozygo sity of chromosome 22 alleles was a frequent event in vestibular schwa nnomas. In 10 tumors, heterozygosity was lost for centromeric and telo meric markers indicating likely monosomy 22. However, 63% of tumors di d not reveal a detectable chromosomal loss. Unless a second vestibular schwannoma locus exists, these tumors likely harbor point mutations i n the neurofibromatosis type 2 gene or deletions below the level of re solution of the markers used in this study.