[en] The genotypes were analyzed at 11 polymorphic DNA loci (restriction fragment length alleles) on chromosome 22 in tumor and normal tissues from 35 unrelated patients with meningiomas. Sixteen tumors retained the constitutional genotype along chromosome 22, while 14 tumors (40%) showed loss of one constitutional allele at all informative loci, consistent with monosomy 22 in the tumor DNA. The remaining 5 tumors (14%) showed loss of heterozygosity in the tumor DNA at one or more chromosome 22 loci and retained heterozygosity at other loci, consistent with variable terminal deletions of one chromosome 22 in the tumor DNA. The results suggest that a meningioma locus is located distal to the myoglobin locus, within 22q12.3-qter. Multiple loci on their chromosomes also were studied, and 12 of the 19 tumors with losses of chromosome 22 alleles showed additional losses of heterozygosity at loci on one to three other chromosomes. All tumors that retained the constitutional genotype on chromosome 22 also retained heterozygosity at all informative loci on other chromosomes analyzed, suggesting that the rearrangement of chromosome 22 is a primary event in the tumorigenesis of meningioma

[en] Allelic combinations at seven loci on human chromosome 17 defined by restriction fragment length polymorphisms were determined in tumor and normal tissues from 35 patients with gliomas. Loss of constitutional heterozygosity at one or more of these loci was observed in 8 of the 24 tumors displaying astrocytic differentiation and in the single primitive neuroectodermal tumor examined. The astrocytomas showing these losses included examples of each adult malignancy grade of the disease, including glioblastoma (malignancy grade IV), and seven of them demonstrated concurrent maintenance of heterozygosity for at least one chromosome 17 locus. Determination of allele dosage together with the genotypic data indicated that the tumor chromosomes 17 were derived by mitotic recombination in 7 of the 9 cases with shared homozygosity of the region 17p11.2-ptr in all cases. In contrast, tumors of oligodendrocytic, ependymal, or mixed cellular differentiation did not exhibit loss of alleles at any of the loci examined. These data suggest that the somatic attainment of homozygosity for loci on chromosome 17p is frequently associated with the oncogenesis of central nervous system tumors, particularly those showing solely astrocytic differentiation, and that mitotic recombination mapping is a useful approach towards the subregional localization of a locus whose rearrangement is involved in this disease

[en] Short communication