Colony hybridization to identify mammalian cells containing amplified, transfected, or expressed sequences

The identification of variant cell clones has played an important role in the elucidation of various biochemical pathways. Such clones are typically selected by altering the medium or the growth conditions to give a selective advantage to the desired variant. The availability of cloned DNA probes has made it possible to identify bacterial colonies or viral plaques containing desired sequences, even in the absence of selection. We describe here a new method for the identification and isolation of mammalian cells containing any sequence for which a probe exists. Mammalian cell clones are first replicated onto nylon cloth. The original clones and the replicas are grown for a few days to enlarge the clones. All the clones on the original dish are transferred in situ to a filter and processed for hybridization. By altering the processing, either DNA or RNA sequences in the clones can be identified. When a clone of interest is located by hybridization, the cells can be isolated from the nylon replicas. We expect this method to be of value in the isolation of clones containing amplified, transfected, or mutated genes, as well as those exhibiting altered gene expression.