The construction of the a7 protein and gene (Chrna7) reporter mouse lines; Chrna7-HA-IRES-tauGFP (a7 GFP ) and Chrna7-HA-IRES-Cre (a7 Cre ) have been described in detail . Briefly, as diagramed in Fig. 1A , the methods of homologous recombination were used to introduce an epitope hemagglutinin (HA) and stop codon extension to the a7 C-terminus and a bicistronic IRES-tauGFP reporter cassette ). This generated the a7 GFP mouse (Fig. 1A) , which expresses the tauGFP protein as a marker of Chrna7 transcription. The Speed Congenic Program of the Jackson Laboratory was used to achieve 98% C57BL/6 background congenicity . For conditional cell ablation of the cells expressing Cre as in the a7 Cre mouse, we crossed this mouse with the LoxP conditional diphtheria toxin (DTA) mouse lines as described previously .