Loss of Lebercilin causes dysregulation of RPE maturation and ciliary function in cellular and animal models

Abstract

Purpose : This work is aimed to understand the pathological changes occurring in the visual system in Leber Congenital Amaurosis 5 (LCA5), a disease caused by loss of expression of the Lebercilin-encoding LCA5 gene. Previous studies elucidated the detrimental effect of Lebercilin deficiency on the neuroretina, and specifically on photoreceptors. Our study aimed to further elucidate the pathogenic mechanisms leading to LCA5 by focusing on the contribution of normal LCA5 expression to the development and function of the retinal pigmented epithelium (RPE).

Methods : We implemented two independent experimental paradigms: One used generation of RPE cells from induced pluripotent stem cells (iPSCs) from both normal sighted individuals and those with LCA5. RPE cell morphology, pigmentation, cell-specific markers and characteristics of the primary cilia were measured. The second approach evaluated studies of the retinas of wildtype mice compared to those of a murine model for LCA5 deficiency (LCA5^gt/gt mice). The spacial-temporal differentiation patterns were characterized in order to delineate the degenerative vs developmental changes occurring in the visual system caused by lack of LCA5 protein.

Results : The results demonstrate that LCA5 deficiency in both human RPE cell models and in the RPE of living mice causes profound alterations in the development of those cells. Through gene expression analysis, we identified the dysregulation of key proteins responsible for ciliogenesis and intraflagellar transport, pigmentation, and developmental WNT signaling pathway. Immunostaining also identified differences in the epithelial barrier consistent with altered maturation due to loss of LCA5 protein function.

Conclusions : Our work reveals the detrimental effect of LCA5 suppression in RPE through alteration of processes such as pigmentation, potentially due to an inhibition of intracellular trafficking or indirectly by delaying the maturation progression of these cells. In this study, we introduce the potential primary role of RPE cells in retinal pathology traditionally attributed to photoreceptor malfunction. The results pave the way for future exploration of the primary effects of ciliopathies on RPE cells and to development of therapies that may ameliorate retinal degeneration due to mutations in LCA5 and other cilia-associated genes.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.