Enhancer models for tissue-specific expression of Luzp2 and Chrna7. (A) Deletion of a putative neuronal enhancer 3' of Luzp2 lowers expression levels of the gene. Symbols are: white boxes, exons; grey vertical box, 3'-untranslated region (UTR); arrow, transcriptional orientation; zig-zag line, transgene insertion-deletion breakpoint; grey horizontal box, enhancer; dashed arrow, neuronal enhancer contributing ~33% to the Luzp2 allelic promoter activity; X, block to enhancer function. Only the first and last exons of Luzp2 are shown. (B) Activation in TgPWS and TgAS mice of the Chrna7 promoter in cis by the immunoglobulin (Ig) enhancer from the LMP2A transgene active in B lymphocytes. Symbols are as for Fig. 6A, except: grey vertical box, 5'-untranslated region (UTR); dashed arrow, Ig enhancer upregulation of Chrna7 transcription. (C) Activation of the Chrna7 promoter in WT mice by a putative neuronal enhancer. The location of the enhancer is drawn arbitrarily but must map 3' to the TgPWS/TgAS deletion breakpoint in intron 4. Symbols are as for Fig. 6B, except: dashed arrow, neuronal enhancer for upregulation (~80%) of normal Chrna7 transcription. (D) Deletion of a neuronal enhancer in TgPWS and TgAS mice virtually silences Chrna7 expression in cis. Symbols are as for Fig. 6A and 6C.