'Specific' oligonucleotides often recognize more than one gene: the limits of in situ hybridization applied to GABA receptors.

As exquisite probes for gene sequences, oligonucleotides are one of the most powerful tools of recombinant molecular biology. In studying the GABA receptor subunits in the neonatal hippocampus we have used oligonucleotide probes in in situ hybridization and cloning techniques. The oligonucleotides used and assumed to be specific for the target gene, actually recognized more than one gene, leading to surprising and contradictory results. In particular, we found that a GABA(A)-rho specific oligonucleotide recognized an abundant, previously unknown, transcription factor in both in situ and library screening, while oligos 'specific' for GABA(A) subunits were able to recognize 30 additional unrelated genes in library screening. This suggests that positive results obtained with oligonucleotides should be interpreted with caution unless confirmed by identical results with oligonucleotides from different parts of the same gene, or cDNA library screening excludes the presence of other hybridizing species.