01 Dec 1998

(From Nature Biotechnology Press Release.) Current estimates predict that genome sequencing efforts may reveal between 3,000 and 10,000 new targets for drugs. In the December issue of Nature Biotechnology, Paul Negulescu and colleagues describe a rapid and sensitive assay for identifying such gene targets in live human cells. In their approach, a reporter gene encoding β-lactamase was introduced into human T lymphocytes in an attempt to tag virtually every gene in the genome. When these cells were exposed to phorbol ester—a chemical that primes T lymphocytes for action against foreign agents—gene sequencing revealed 10 tagged genes that had previously never been linked with lymphocyte activation. By rapidly selecting and enriching cells containing these genes using a method called flow cytometry, it should be possible to develop screens for rapidly assessing drug candidates.

Negulescu's team were able to assess the T lymphocyte genes that responded to phorbol ester by measuring expression responses after incubation with a membrane-permeant fluorogenic substrate CCF, which flouresces blue in cells expressing the reporter β-lactamase. Fourteen tagged genes modulated by phorbol ester were identified, 10 of which were shown to be novel on DNA sequencing. The β-lactamase tagging system thus represents a powerful method for imaging gene expression in individual live mammalian cells and may prove of great sensitivity compared with gene chips. The method may also be suitable for high-throughput screening of drug candidates, once cloned cell lines have been isolated and enriched by flow cytometry.—June Kinoshita