|Title||Selective ablation of dehydrodolichyl diphosphate synthase (Dhdds) expression in RPE causes morphologic changes similar to dry AMD|
|Author, Co-Author||Steven Pittler, Stephanie Davis, Marci DeRamus, Bruce Pfeffer, Sriganesh Rao, Delores Davis, Steven Fliesler|
|Topic||Treatment and Management of Posterior Sgmt Disease|
|Abstract|| Purpose: Mutations in the human gene encoding dehydrodolichyl diphosphate synthase (DHDDS), which is required for N-linked protein glycosylation, cause retinitis pigmentosa (RP). We generated a conditional Dhdds knockout (KO) mouse model to study the effects of cell type-specific ocular Dhdds deficiency.
Methods: A Dhdds construct was introduced into murine ES cells and confirmed by PCR. Established mouse lines were bred to homozygosity and these mice were crossed to RPE-Cre mice (Yun Le, OUHSC). The resulting RPE-Dhdds-/- and control mice were assessed by OCT, ERG, histology, immunofluorescence, and TEM at 1, 2, and 3 mo postnatal.
Results: Cre-dependent GFP reporter expression indicated that >90% of RPE cells expressed Cre by 3 mo of age. OCT analysis of RPE-Dhdds-/- mice showed a significant reduction (vs. WT) in retinal thickness at all ages analyzed. No OCT changes were observed in RPE-Dhdds+/- mice. In RPE-Dhdds-/- mice, histologic analysis showed panretinal degeneration affecting the RPE and photoreceptor layers, that was similar to geographic atrophy seen in dry AMD. Additionally, TEM of 3 mo old homozygous mice revealed ectopic RPE migration into the retinal space, and displacement of the ELM. In 1 mo old RPE-Dhdds+/- mice, no differences from WT were observed in the scotopic ERG. However, RPE-Dhdds-/- mice exhibited significant reduction (42%, p < 0.01) in b-wave amplitudes compared to WT, with normal a-wave amplitudes. By 2 mo of age, hets (RPE-Dhdds+/-) showed a significant reduction in both the a-wave (17%, p < 0.05) and b-wave (44%, p < 0.001). These deficits were more pronounced in RPE-Dhdds-/- mice (a-wave, 42%, p < 0.01; b-wave, 52%, p < 0.001).
Conclusion: Homozygous Dhdds conditional KO mice exhibit progressive RPE and retinal degeneration with structural deficits similar to several features observed in dry AMD, suggesting a possible nexus of disease pathobiology between congenital disorders of N-glycosylation and AMD.
|Affiliation of Co-Authors||University of Alabama at Birmingham, University of Alabama at Birmingham, SUNY-Buffalo/VA Med Ctr-Buffalo, SUNY-Buffalo/VA Med Ctr-Buffalo, University of Alabama at Birmingham, SUNY-Buffalo/VA Med Ctr-Buffalo|