Conditional ablation of neurones in transgenic mice

Conditional targeted ablation of specific cell populations in living transg enic animals is a very powerful strategy to determine cell functions in viv o. This approach would be of particular value to study the functions of dis tinct neuronal populations; however, the transgene of choice for conditiona l cell ablation studies in mice, the herpes simplex virus thymidine kinase gene, cannot be used to ablate neurones as its principal mode of action rel ies on cell proliferation. Here we report that expression of the E,coli nit roreductase gene (Ntr) and metabolism of the prodrug CB1954 (5-aziridin-1-y l-2-4-dinitrobenzamide) to its cytotoxic derivative can be used to conditio nally and acutely ablate specific neuronal populations in live. As proof of principal, we have ablated olfactory and vomeronasal receptor neurones by expressing Ntr under the control of the olfactory marker protein (OMP) gene promoter. We demonstrate that following CB1954 administration, olfactory a nd vomeronasal receptor neurones expressing the transgene were selectively eliminated from the olfactory epithelium (OE), and projections to the olfac tory bulb (OB) were lost. The functional efficacy of cell ablation was demo nstrated using a highly sensitive behavioural test to show that ablated mic e had lost the olfactory ability to discriminate distinct odors and were co nsequently rendered anosmic, Targeted expression of Ntr to specific neurona l populations using conventional transgenes, as described here, or by "knoc k-in" gene targeting using embryonic stem cells may be of significant value to address the functions of distinct neuronal populations in vivo. (C) 200 1 John Wiley & Sons, Inc.