A visually guided swim assay for mouse models of human retinal disease recapitulates the multi-luminance mobility test in humans.

PURPOSE: The purpose of this study was to develop a visually guided swim assay (VGSA) for measuring vision in mouse retinal disease models comparable to the multi-luminance mobility test (MLMT) utilized in human clinical trials. METHODS: Three mouse retinal disease models were studied: Bardet-Biedl syndrome type 1 (Bbs1M390R/M390R), n = 5; Bardet-Biedl syndrome type 10 (Bbs10-/-), n = 11; and X linked retinoschisis (retinoschisin knockout; Rs1-KO), n = 5. Controls were normally-sighted mice, n = 10. Eyeless Pax6Sey-Dey mice, n = 4, were used to determine the performance of animals without vision in VGSA. RESULTS: Eyeless Pax6Sey-Dey mice had a VGSA time-to-platform (TTP) 7X longer than normally-sighted controls (P < 0.0001). Controls demonstrated no difference in their TTP in both lighting conditions; the same was true for Pax6Sey-Dey. At 4-6 M, Rs1-KO and Bbs10-/- had longer TTP in the dark than controls (P = 0.0156 and P = 1.23 × 10-8, respectively). At 9-11 M, both BBS models had longer TTP than controls in light and dark with times similar to Pax6Sey-Dey (P < 0.0001), demonstrating progressive vision loss in BBS models, but not in controls nor in Rs1-KO. At 1 M, Bbs10-/- ERG light-adapted (cone) amplitudes were nonrecordable, resulting in a floor effect. VGSA did not reach a floor until 9-11 M. ERG combined rod/cone b-wave amplitudes were nonrecordable in all three mutant groups at 9-11 M, but VGSA still showed differences in visual function. ERG values correlate non-linearly with VGSA, and VGSA measured the continual decline of vision. CONCLUSION: ERG is no longer a useful endpoint once the nonrecordable level is reached. VGSA differentiates between different levels of vision, different ages, and different disease models even after ERG is nonrecordable, similar to the MLMT in humans.

Subretinal gene therapy delays vision loss in a Bardet-Biedl Syndrome type 10 mouse model.

Blindness in Bardet-Biedl syndrome (BBS) is caused by dysfunction and loss of photoreceptor cells in the retina. BBS10, mutations of which account for approximately 21% of all BBS cases, encodes a chaperonin protein indispensable for the assembly of the BBSome, a cargo adaptor important for ciliary trafficking. The loss of BBSome function in the eye causes a reduced light sensitivity of photoreceptor cells, photoreceptor ciliary malformation, dysfunctional ciliary trafficking, and photoreceptor cell death. Cone photoreceptors lacking BBS10 have congenitally low electrical function in electroretinography. In this study, we performed gene augmentation therapy by injecting a viral construct subretinally to deliver the coding sequence of the mouse Bbs10 gene to treat retinal degeneration in a BBS10 mouse model. Long-term efficacy was assessed by measuring the electrical functions of the retina over time, imaging of the treated regions to visualize cell survival, conducting visually guided swim assays to measure functional vision, and performing retinal histology. We show that subretinal gene therapy slowed photoreceptor cell death and preserved retinal function in treated eyes. Notably, cone photoreceptors regained their electrical function after gene augmentation. Measurement of functional vision showed that subretinal gene therapy provided a significant benefit in delaying vision loss.

Progressive retinal degeneration of rods and cones in a Bardet-Biedl syndrome type 10 mouse model.

Bardet-Biedl syndrome (BBS) is a multi-organ autosomal-recessive disorder caused by mutations in at least 22 different genes. A constant feature is early-onset retinal degeneration leading to blindness. Among the most common forms is BBS type 10 (BBS10), which is caused by mutations in a gene encoding a chaperonin-like protein. To aid in developing treatments, we phenotyped a Bbs10 knockout (Bbs10-/-) mouse model. Analysis by optical coherence tomography (OCT), electroretinography (ERG) and a visually guided swim assay (VGSA) revealed a progressive degeneration (from P19 to 8 months of age) of the outer nuclear layer that is visible by OCT and histology. Cone ERG was absent from at least P30, at which time rod ERG was reduced to 74.4% of control levels; at 8 months, rod ERG was 2.3% of that of controls. VGSA demonstrated loss of functional vision at 9 months. These phenotypes progressed more rapidly than retinal degeneration in the Bbs1M390R/M390R knock-in mouse. This study defines endpoints for preclinical trials that can be utilized to detect a treatment effect in the Bbs10-/- mouse and extrapolated to human clinical trials.

Microarray comparative genomic hybridization profile of a murine model for epithelial ovarian cancer reveals genomic imbalances resembling human ovarian carcinomas.

Microarray comparative genomic hybridization (mCGH) is emerging as a high-resolution technology to detect gene dosage alterations in numerous pathologies, including cancer. We optimized cDNA microarrays to identify genome-wide imbalances in spontaneously transformed mouse ovarian surface epithelial cell lines, an in vitro murine model for ovarian cancer. Amplification of chromosome 19 and a more variable gain pattern of chromosomes 15 and 5 were detected and independently validated using conventional metaphase CGH. In addition, cryptic aberrations in segments of chromosomes 4, 7, 8, 9, 11, 17, and X, allowed identification of 2 related genomic variants among six cell lines studied. Mouse-human synteny revealed an overall early transformation stage with approximately 80% conservation relative to human ovarian malignancies of epithelial origin including low malignant potential tumors, serous carcinoma, and carcinoma cell lines. Importantly, three of the cells bear gained segments 13 and 41 Mbp length of chromosomes 5 and 15, respectively, which are syntenic to human 22q11-13, 8q24 and 12p11-q24, the two latter chromosomal regions thought to define one pathway of karyotypic changes in the development of human ovarian tumors. Our findings support the utility of mouse ovarian surface epithelial (MOSE) cells in studying initiation and progression of human ovarian cancer and as a suitable model to evaluate therapeutic approaches.