Molecular detection of deletions involving band q14 of chromosome 13 in retinoblastomas.

DNA fragments from a locus spanning 29 kilobases within chromosome band 13q14 detected deletions in 3 retinoblastomas out of 37 such tumors examined. Somatically occurring, homozygous deletions spanning at least 25 kilobases were detected in retinoblastomas from two unrelated patients. These deletions are bounded by the esterase D locus proximally. In a third patient, both tumor cells and leukocytes have a deletion of one chromosome 13 homolog, with one end of the deletion localized to a 1.55-kilobase fragment within the cloned region. It is likely that the cloned locus is within a few hundred kilobases of the retinoblastoma gene (i.e., the locus governing predisposition to such tumors) and that the deletions detected also involve the retinoblastoma gene. Further, it may be possible to base a successful approach to the isolation of the retinoblastoma gene on this assumed physical proximity of the two loci.