Generation of L7-tTA knock-in mice.

We generated a versatile mouse line, L7-tTA knock-in mouse, in which tetracycline-responsive transcriptional activator (tTA) gene was introduced into exon 2 of L7 locus. Since L7 is specifically expressed in cerebellar Purkinje cells, we expected Purkinje cell-restricted expression of tTA gene in the knock-in mice. In situ hybridization analysis exhibited that tTA mRNAs in those mice were expressed only in Purkinje cells. Introduction of transgene consisting of tetracycline-responsive element that is a binding site for tTA and ideal cDNAs into L7-tTA knock-in mouse would result in specific expression of cDNA encoding proteins in Purkinje cells and its expression could be controlled by doxycycline administration. L7-tTA knock-in mice would provide us with opportunity to elucidate the role of specific genes in cerebellar Purkinje cells.