Purchase this article with an account.
Muhammad Ali, Shahid Yar Khan, Firoz Kabir, Sheikh Riazuddin, J. Fielding Hejtmancik, S Amer Riazuddin; Investigating the role of pexophagy in the development of the ocular lens and cataractogenesis. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2042.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine the genetic basis of congenital cataracts in an inbred familal case and investigate the role of pexophagy in the development of the ocular lens and cataractogenesis.
We recruited a large family with multiple members having congenital cataracts. All participating members underwent clinical and ophthalmic examinations. Genomic DNAs of three individuals with cataracts were selected for whole-exome sequencing. The exome data analysis was performed using Lasergene Genomics Suite. A tandem fluorochrome pexophagy assay was performed to quantitate the mRFP/EGPF-SKL ratio using a flow cytometer in a human lens epithelial cell line (HLE). The localization patterns of PXMP2 (a peroxisome marker), wild-type and mutant PEX5, and substrate harboring peroxisome target sequence (PTS1) were examined.
The ophthalmological examinations of affected members indicated congenital cataracts. We identified 2,201 homozygous variants shared among the three affected individuals. Of these, only a variant in PEX5 (c.653T>C; p.F218S) showed segregation with the disease phenotype in the family, and was absent in ethnically matched control chromosomes. Furthermore, F218 is completely conserved in orthologs of PEX5, and in silico analysis predicted that the mutant allele would be disruptive to the native protein structure. PEX5 is a receptor protein that is indispensable for pexophagy, the selective degradation of peroxisomes. Importantly, it is expressed in the developing murine lens transcriptome and proteome. To understand the physiological significance of PEX5 in the development of the ocular lens and the role of the causative mutation in cataractogenesis, we performed a flow cytometry-based tandem fluorochrome pexophagy assay in an HLE cell line. This analysis revealed H2O2-induced pexophagy in the wild-type HLE cells. Immunofluorescence tracking showed a peroxisomal localization pattern for both the wild-type and mutant PEX5 proteins. However, the mutant protein did not transport the substrate harboring PTS1 to the peroxisome. These results suggest that the mutation compromises the ability of PEX5 to transport cargo bearing the PTS1 signal.
Here, we report a novel missense mutation in PEX5 responsible for cataractogenesis. To the best of our knowledge, this is the first report implicating pexophagy in cataractogenesis.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only