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Adam P Faranda, Samuel G Novo, Mahbubul H Shihan, Yan Wang, Melinda K Duncan; The molecular basis of aniridic cataract. Invest. Ophthalmol. Vis. Sci. 2020;61(7):5134.
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© ARVO (1962-2015); The Authors (2016-present)
Pax6 is a transcription factor that directs many aspects of eye development. Heterozygous Pax6 mutations are responsible for Aniridia; a rare genetic disorder which impairs vision at birth due to foveal hypoplasia and iris malformations. Later in life, humans with aniridia develop juvenile onset “wagon wheel” and/or anterior subcapsular cataracts (ASC) although their molecular etiology is unknown. Mice heterozygous for Pax6 mutations (“small eye” / Sey) mimic the progression of human Aniridia, including early cataract onset. While the role of Pax6 in early lens development is well studied, there is a knowledge gap surrounding its functions in the adult lens that this study seeks to fill.
Lenses were harvested from 5 month old Pax6+/tm1Pgr (Sey) mice and their wildtype littermates, and separated into epithelia (LEC) and fibers (LFC). Total RNA was purified from these isolates (N=3), sequencing libraries created with the TaKaRa Smarter Stranded PICO v2 kit and sequenced on the Illumina Novaseq platform. The Tuxedo suite was used to estimate transcript abundance and calculate differential expression statistics. Ipathway guide and custom scripts were used to identify the potential biological significance of differentially expressed genes (DEGs).
Pax6 expression was 50% lower in Sey lens cells compared to control. There were 1128 DEGs in Sey LECs, and 464 DEGs in Sey LFCs. Of these, 121 LEC DEGs and 65 LFC DEGs were previously experimentally verified as Pax6 targets in the lens by Chip-seq (PMID: 23342162). Glucagon was upregulated in Sey LFC and LEC, consistent with the known role of Pax6 in glucagon repression. In both cell types, DEGs were significantly enriched for genes involved in WNT and Tgfβ signaling as well as ion homeostasis. In Sey LECs, the upregulated DEGs included several pro-inflammatory genes and known fibrotic markers. Sey LFC downregulated 41 genes encoding ribosomal proteins, while markers of oxidative stress were upregulated. The KEGG “Glucagon Signaling” pathway was significantly enriched in Sey LFC DEGs.
Sey lens cells have molecular changes consistent with several well established, cataractogenic mechanisms including inflammation, pro-fibrotic changes, and alterations in ion homeostasis. This suggests that the correct Pax6 dosage is critical for adult lens homeostasis.
This is a 2020 ARVO Annual Meeting abstract.
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