TY - JOUR T1 - Unspecific expression in limited excitatory cell populations in interneuron-targeting Cre-driver lines can have large functional effects JF - bioRxiv DO - 10.1101/848655 SP - 848655 AU - Daniel Müller-Komorowska AU - Thoralf Opitz AU - Shehabeldin Elzoheiry AU - Michaela Schweizer AU - Heinz Beck Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/11/20/848655.abstract N2 - Transgenic Cre-recombinase expressing mouse lines are widely used to express fluorescent proteins and opto-/chemogenetic actuators, making them a cornerstone of modern neuroscience. Particularly, the investigation of interneurons has benefitted from the ability to target genetic constructs to defined cell types. However, the cell type specificity of some mouse lines has been called into questions. Here we show for the first time the functional consequences of unspecific expression in a somatostatin-Cre (SST-Cre) mouse line. We find large optogenetically evoked excitatory currents originating from unspecifically targeted CA3 pyramidal cells. We also used public Allen Brain Institute data to estimate expression specificity in other Cre lines. Another SST-Cre mouse lines shows comparable unspecificity, whereas a Parvalbumin-Cre mouse line shows much less unspecific expression. Finally, we make suggestions to ensure that the results from in-vivo use of Cre mouse lines are interpretable. ER -