July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Tpm3.1 prevents the acquisition of the myofibroblast phenotype by lens cells, suppressing cataract development
Author Affiliations & Notes
  • Justin Parreno
    Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States
  • Michael Amadeo
    Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States
  • Velia M Fowler
    Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States
  • Footnotes
    Commercial Relationships   Justin Parreno, None; Michael Amadeo, None; Velia Fowler, None
  • Footnotes
    Support  NIH Grant R01-EY017724
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4792. doi:
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      Justin Parreno, Michael Amadeo, Velia M Fowler; Tpm3.1 prevents the acquisition of the myofibroblast phenotype by lens cells, suppressing cataract development. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4792.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Cataracts are opaque regions in the eye lens resulting in blurred vision. They are the most common cause of vision loss and eventual blindness after the age of 40 worldwide. The transition of anterior lens epithelial cells into myofibroblasts (EMyT) plays a major role in the development of cataracts. One central event in EMyT is the reorganization of actin into stress fibers. To explore whether actin stress fibers can be targeted to impede EMyT, in this study, we investigate the regulation of actin stress fibers by tropomyosins (Tpms). Tpms bind along actin filaments (F-actin) to stabilize them and coordinate their interactions with other molecules. There are 40 different Tpm isoforms, each with unique binding properties; six of these isoforms are known to associate with actin in stress fibers. We hypothesize that repression of stress fiber–associated Tpms may prevent lens EMyT.

Methods : We induced EMyT in immortalized mouse lens cells and whole mouse lenses using TGFβ2. Tpm isoform gene and protein levels were determined using RT-PCR and Wes immunoassay, respectively. The distribution of Tpm within the cells was assessed via confocal microscopy. To examine the function of the Tpm3.1 isoform, we used a pharmacological inhibitor (TR100) as well as Tpm3.1 knockout mouse lenses.

Results : We determined that immortalized mouse lens epithelial cells express eight Tpm isoforms, four of which (Tpms 1.7, 2.1, 3.1, and 4.2) are upregulated by treatment with TGFβ2 to induce EMyT. Out of these four isoforms, Tpm3.1 is the most substantially upregulated, and we confirmed by immunocytochemistry that it associates with actin in stress fibers. For these reasons, we explored whether targeting Tpm3.1 could prevent stress fiber formation and EMyT. Our treatment of the cultured lens cells with TR100 prevented the TGFβ2-induced development of stress fibers as well as the upregulation of αSMA. We also determined that Tpm3.1 promotes the incorporation of αSMA into F-actin within stress fibers. To verify the role of Tpm3.1 in EMyT, we examined whole lenses from Tpm3.1 knockout mice and confirmed the suppression of both TGFβ2-induced stress fiber formation and αSMA upregulation.

Conclusions : Our findings demonstrate that repression of stress fiber–associated Tpm3.1 reduces lens EMyT. Therefore, targeting Tpm3.1 may present a therapeutic opportunity to prevent cataracts in vivo.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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