Neuron-specific and inducible recombination by Cre recombinase in the mouse.

To investigate the neuronal function of genes in vivo, a neuron-specific and inducible gene targeting system is desirable. In this study, we generated a knockin mouse line that expresses a fusion protein consisting of the Cre recombinase and the progesterone receptor (CrePR) in neurons. The neuron-specific expression of CrePR was attained by inserting CrePR gene into the tau locus, because tau is expressed strongly in neurons but scarcely in glias and other tissues. By crossing this knockin mouse line (tau(CrePR)) with ROSA26 lacZ reporter mouse line (R26R), we observed that the antiprogesterone RU486 could induce recombinase activity of the CrePR specifically in neurons. Thus, tau (CrePR) knockin line is a useful tool for studying neuronal gene functions.