September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Anisotropic geometry of lens placode cells is mediated by planar polarized inhibition of junctional contraction during invagination.
Author Affiliations & Notes
  • Timothy F. Plageman
    College of Optometry, The Ohio State University, Columbus, Ohio, United States
  • Footnotes
    Commercial Relationships   Timothy Plageman, None
  • Footnotes
    Support  March of Dimes: Basil O'Connor Starter Scholar Research Award
Investigative Ophthalmology & Visual Science September 2016, Vol.57, No Pagination Specified. doi:
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      Timothy F. Plageman; Anisotropic geometry of lens placode cells is mediated by planar polarized inhibition of junctional contraction during invagination.. Invest. Ophthalmol. Vis. Sci. 201657(12):.

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

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Abstract

Purpose : Lens placode invagination is an early step during embryonic development of the lens and dictates the size of both the lens and the whole eye. The principal forces that drive the inward bending of the placodal epithelia have yet to be elucidated. Because it was recently found that lens placode cells are geometrically anisotropic and move toward the placode center during invagination, the mechanisms governing placode cell shape and behavior were investigated.

Methods : Live confocal imaging of transgenic embryos (E-cadherin-CFP) and imaging of fixed embryos in combination with cell culture experiments were utilized to test the role of specific proteins during placode invagination and the contraction of epithelial cell junctions. Differences in the dimensions of cells and junctions were quantified and two-tailed Student’s t-test was used to analyze statistical differences.

Results : The shape of peripheral lens placode cells changed at the onset of invagination converting from isotropic to anisotropic through the elongation of junctions orientated parallel to the placode perimeter (circumferential) and the contraction of perpendicularly orientated junctions (radial). We determined that contractile proteins and Shroom3 are preferentially localized to the shorter, radially orientated junctions and are required for anisotropic geometry. To test the hypothesis that junctional contraction inhibition leads to the elongation of junctions we used a candidate gene approach to identify proteins that can inhibit Shroom3 function. We determined that Cdc42 and members of the Par-complex inhibit Shroom3-induced contractility and promote anisotropic placode cell geometry through inhibition of contractility in circumferential junctions. We also found that Cdc42 facilitates anistropic geometry by promoting radial junction contractility by inhibiting the accumulation of the Par-complex protein aPKC to radial junctions.

Conclusions : The results presented here suggest an interplay between proteins promoting and antagonizing junctional contractility and are consistent with the hypothesis that junction elongation is primarily due to the inhibition of junctional contraction. We conclude that invagination of the lens placode requires careful orchestration of these opposing processes and is mediated by the planar polarization of junctional proteins.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

En face view of a lens placode.

En face view of a lens placode.

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