Fig. 6

Six MiniPromoters (MiniPs) showed cell type-specific expression in the retina. a The icre reporter led to identification of three retina positive MiniPs. Ple266-icre (S100B RRs) showed rare Müller glia expression as expected for the endogenous gene in one of two mice tested [69]. The astrocytic layer also demonstrated some staining. Ple302-icre (DCX RRs) intensely stained the ganglion cell layer (GCL), similar to previous DCX-based MiniPs [22]. For Ple303-icre (NOV RRs) we observed modest enrichment of staining in the outer side of the inner nuclear layer indicative of horizontal cells. Blue, β-gal positive; red, neutral red. b Constructs utilizing the EmGFP reporter identified an additional three MiniPs with retinal expression. In both cases tested, the presence of the WPRE enhanced the number and intensity of cells showing expression. Ple67-EmGFP ± WPRE (FEV RRs) demonstrated expression primarily in the GCL and inner nuclear layer in putative ganglion and amacrine cells. Rarely, additional cells were also positive with the WPRE-containing virus. Ple155-EmGFP ± WPRE (PCP2 RRs) restricted expression to bipolar ON cells. Ple264-EmGFP (NR2E1 RRs) showed strong staining of Müller glial cells. EmGFP, emerald green fluorescent protein; GCL, retinal ganglion cell layer; icre, improved cre recombinase; RRs, regulatory regions. [Scale bars = 100 μm]