Preferential loss of paternal 19q, but not 1p, alleles in oligodendrogliomas.

Portions of chromosomes 1p and 19q, which are frequently deleted in oligodendrogliomas, are subject to genomic imprinting, suggesting that the putative tumor suppressor genes could be monoallelically expressed. The parental origins of 1p and 19q allele losses were determined in 6 cases of pure oligodendroglioma. An equilibrated parental loss (3 maternal and 3 paternal) was found for 1p deletions. In contrast, 19q deletions always occurred on the paternal copy (p = 0.015). In this setting, a cloning strategy based on a search for homozygous deletion or mutation of the remaining allele would be appropriate for identifying the tumor suppressor gene located on 1p but inappropriate for identifying the presumably monoallelically expressed tumor suppressor gene located on 19q.