Best vitelliform macular dystrophy (BVMD) is an untreatable autosomal dominant disorder affecting the macula in the central retina. BVMD is caused by mutations in the Bestrophin-1 protein which is expressed in the retinal pigment epithelium (RPE). The RPE is a monolayer of pigmented cuboidal cells located between the retina and the choroid that functions to maintain photoreceptor integrity and ion homeostasis. Disruption to RPE function causes accumulation of debris within and beneath the RPE, resulting in RPE and photoreceptor degeneration and death that leads to blindness.
Little is known about the mechanism of BVMD, however, in vitro over-expression studies in non-RPE cell lines suggest that the Bestrophin-1 protein is a multifunctional ion channel. A novel human embryonic stem cell (hESC) line, GENEA069, contains the F305S Bestrophin-1 mutation and thus offers a novel system to study the molecular mechanisms of BVMD. Like normal hESCs, GENEA069 provide an indefinite source of undifferentiated cells in vitro while retaining the capacity to differentiate into any cell type in the body, including RPE. The hypothesis for this study is that electrophysiological characterisation of normal hESC-derived RPE will provide useful information regarding the intrinsic properties of these clinically-relevant cells, while at the same time providing a baseline for comparison with GENEA069-derived RPE.
Preliminary electrophysiological characterisation of voltage-gated ion channels was performed on normal hESC-derived RPE. These data indicate that normal hESC-derived RPE show similar features of voltage-gated ion channels to published data from both native human foetal and adult RPE (Wen, Lui et al. 1993). Based on this data, an electrophysiological analysis of GENEA069 hESC-derived RPE will be undertaken to provide insight into the molecular mechanisms of BVMD. These investigations have the potential to aid in the development of therapies to treat BVMD and related RPE-based blinding disorders such as macular degeneration.