New Wistar Kyoto and spontaneously hypertensive rat transgenic models with ubiquitous expression of green fluorescent protein

Abstract

The Wistar Kyoto (WKY) rat and the spontaneously hypertensive (SHR) rat inbred strains are well-established models for human crescentic glomerulonephritis (CRGN) and metabolic syndrome, respectively. Novel transgenic (Tg) strains add research opportunities and increase scientific value to well-established rat models. We have created two novel Tg strains using Sleeping Beauty transposon germline transgenesis, ubiquitously expressing green fluorescent protein (GFP) under the rat elongation factor 1 alpha (EF1a) promoter on the WKY and SHR genetic backgrounds. The Sleeping Beauty system functioned with high transgenesis efficiency; 75% of new rats born after embryo microinjections were transgene positive. By ligation-mediated PCR, we located the genome integration sites, confirming no exonic disruption and defining a single or low copy number of the transgenes in the new WKY-GFP and SHR-GFP Tg lines. We report GFP-bright expression in embryos, tissues and organs in both lines and show preliminaryin vitroandin vivoimaging data that demonstrate the utility of the new GFP-expressing lines for adoptive transfer, transplantation and fate mapping studies of CRGN, metabolic syndrome and other traits for which these strains have been extensively studied over the past four decades.

Keywords: GFP; Rat; SHR; Transgenics; WKY.

Fig. 1.

GFP transgenic rat design. (A) Schematic plasmid representation. Rat elongation factor 1 alpha promoter (rEF1a) replaces CAG promoter (CAGGS). IR, inverted repeats; GFP, green fluorescent protein cDNA. (B) Photograph of WKY-GFP pups (left) and adult (right) rats under excitation light 489 nm, showing wild-type and GFP Tg animals. (C) Schematic genome locus showing TA integration sites location of transgene for SHR-GFP in chromosome 5, and WKY-GFP in chromosome 1 and 8. Genomic sequence (left junction) in capitals and transgene in lowercase, dotted horizontal line refers to intergenic, continuous black line to intronic, and vertical blocks to exonic sequences.

Fig. 2.

GFP expression in embryos. Female WKT-GFP rats were crossed with wild-type WKY male rats and one-cell embryos removed and imaged under confocal microscope. Representation of three experiments from one-cell embryos at E4.5 and E4.5 plus 12 h showing bright field (BF) images and expression of GFP. Scale bar: 15 μm (top panel); 40 μm (bottom panel).

Fig. 3.

GFP expression in organs and tissues. Wild type (from SHR strain), WKY-GFP and SHR-GFP rats were examined for gross GFP expression in dissected heart, brain, kidney, eyes, thymus, gut, liver, spleen and muscle tissues. Whole organ extracts were mounted for white light (left three panels) and stereo-fluorescence imaging (right three panels). Scale bar: 2 mm.

Fig. 4.

GFP expression in blood leukocyte populations. Anticoagulated blood from wild-type, WKY-GFP and SHR-GFP rats were examined for GFP expression with or without fluorescent-labelled antibodies using flow cytometry. (A) Histograms of GFP expression in SSC^hi and SSC^low populations. (B) Lower panels: dot plots of GFP expression versus granulocyte (Gran)-, MHC class II (MHC-II)- or CD68-positive populations, in cells gated by R1 (upper panel). Representative of at least n=4 rats.

Fig. 5.

GFP expression in BMDM and intravital microscopy. (A) Bone marrow-derived macrophages (BMDM) were harvested and cultured for 5 or 10 days and intensity of GFP examined in WKY-GFP and SHR-GFP rats. Scale bar: 75 μm. (B). WKY rats underwent irradiation and bone marrow transplant from a WKY-GFP donor. After successful chimerisation, kidney cortex was imaged after injection of 70 kDa fluorescent dextran under anaesthesia. Snapshot is shown of GFP-positive cells interacting with endothelial surfaces within the kidney (arrows). Representative of at least n=4 rats. Scale bar: 40 μm.