Clostridium tetani tetanus toxin (tetX) light chain expression is driven by a tetracycline operator ((tetO; also called tetracycline-responsive element (TRE)) in this transgenic line. Although GFP is fused to tetX (TetO-GFPTeTX), fluorescence may not be detectable. Several lines were generated including lines 5696 and 2. (J:131852)