The role of FYCO1-dependent autophagy in lens fiber cell differentiation

FYCO1 (FYVE and coiled-coil domain containing 1) is an adaptor protein, expressed ubiquitously and required for microtubule-dependent, plus-end-directed transport of macroautophagic/autophagic vesicles. We have previously shown that loss-of-function mutations in <i>FYCO1</i> cause cataracts with no other ocular and/or extra-ocular phenotype. Here, we show <i>fyco1</i> homozygous knockout (<i>fyco1^−/−</i>) mice recapitulate the cataract phenotype consistent with a critical role of FYCO1 and autophagy in lens morphogenesis. Transcriptome coupled with proteome and metabolome profiling identified many autophagy-associated genes, proteins, and lipids respectively perturbed in <i>fyco1^−/−</i> mice lenses. Flow cytometry of <i>FYCO1</i> (c.2206C&gt;T) knock-in (KI) human lens epithelial cells revealed a decrease in autophagic flux and autophagic vesicles resulting from the loss of FYCO1. Transmission electron microscopy showed cellular organelles accumulated in <i>FYCO1</i> (c.2206C&gt;T) KI lens-like organoid structures and in <i>fyco1^−/−</i> mice lenses. In summary, our data confirm the loss of FYCO1 function results in a diminished autophagic flux, impaired organelle removal, and cataractogenesis. <b>Abbreviations:</b> CC: congenital cataracts; DE: differentially expressed; ER: endoplasmic reticulum; FYCO1: FYVE and coiled-coil domain containing 1; hESC: human embryonic stem cell; KI: knock-in; OFZ: organelle-free zone; qRT-PCR: quantitative real-time PCR; PE: phosphatidylethanolamine; RNA-Seq: RNA sequencing; SD: standard deviation; sgRNA: single guide RNA; shRNA: shorthairpin RNA; TEM: transmission electron microscopy; WT: wild type