The Characterization of FYCO1 Expression and Function in Lens and Retinal Cells

Abstract

Purpose: : FYCO1 is an autophagy-associated protein whose mutation causes autosomal recessive congenital cataract (Chen et al., AJHG, 2011). To date, the function of FYCO1 in the lens and other ocular tissues has not been established. Here we explored the expression and function of FYCO1 in lens and retinal cells.

Methods: : FYCO1 expression was evaluated in embryonic mouse lens and retina by western analysis and immunohistochemistry. FYCO1 was localized in lens HLEB3 and retinal pigmented epithelium (RPE) ARPE19 cell organelles by confocal imaging and co-localized to specific autophagy markers including LC3 and Rab7. Autophagy was monitored in HLEB3 lens and ARP19 retinal cells by cadaverin fluorescence and fluorescently-tagged LC3 accumulation following autophagy induction with or without chloroquine inhibition. Stable FYCO1-knockout lens HLEB3 and ARPE 19 RPE cell lines were established by shRNA-viral insertion and the effect of FYCO1 deletion on viability and autophagy evaluated.

Results: : FYCO1 is highly expressed throughout the lens and retina and in both lens HLEB3 and RPE ARPE19 cells. FYCO1 was expressed at high levels in the lens epithelium, bow region and embryonic fibers. FYCO1 was detected at high levels in throughout the retina with the highest expression in the RPE and photoreceptor layers. FYCO1 also was localized to autophagosomes, lysosomes and endosomes in lens cells. Decreased expression of FYCO1 was associated with decreased growth rates of retinal cells.

Conclusions: : Our results demonstrate that FYCO1 is highly expressed in lens and retinal cells. Its association with the autophagy machinery suggests that it plays an important role in mediating autophagy in these tissues that is likely important for their ocular functions.

Keywords: cataract • mutations • retina