September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Thyroid hormone receptor β and gdf6a may interact to specify cone photoreceptor identity
Author Affiliations & Notes
  • Michele G DuVal
    University of Alberta, Edmonton, Alberta, Canada
  • Ramona Rosca
    University of Alberta, Edmonton, Alberta, Canada
  • Quinton Schmidt
    University of Alberta, Edmonton, Alberta, Canada
  • Elizabeth Hodges
    University of Alberta, Edmonton, Alberta, Canada
  • W Ted Allison
    University of Alberta, Edmonton, Alberta, Canada
  • Footnotes
    Commercial Relationships   Michele DuVal, None; Ramona Rosca, None; Quinton Schmidt, None; Elizabeth Hodges, None; W Ted Allison, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 555. doi:
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      Michele G DuVal, Ramona Rosca, Quinton Schmidt, Elizabeth Hodges, W Ted Allison; Thyroid hormone receptor β and gdf6a may interact to specify cone photoreceptor identity. Invest. Ophthalmol. Vis. Sci. 2016;57(12):555.

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

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Abstract

Purpose : The cone photoreceptors of the retina mediate colour detection and visual acuity, thus are essential for functional vision. We aim to enhance stem cell therapy by determining mechanisms of photoreceptor specification in zebrafish, a powerful vision model with a dense population of four cone spectral subtypes and with impressive regenerative capacity. We investigated three factors (gdf6a, tbx2b, thrβ) regulating transcription during cone subtype specification. Considering that each factor differentially affects blue and UV cone subtype fate, we hypothesize that they are part of a shared gene regulatory network.

Methods : We created a transgenic zebrafish model of conditional thyroid hormone receptor β (thrβ) disruption via expression of a dominant negative thrβ (dnthrβ) under a heat shock promoter. To test for genetic interactions during cone development, we bred the transgenic line to gdf6a+/s327 and tbx2b+/fby compound mutants. Progeny of incrosses of these triple carriers possessed various combinations of each mutation and presence or absence of the transgene; these larvae were heat shocked, then fixed at 4dpf. UV, blue and red cones were labeled and quantified. Larvae were subsequently genotyped for gdf6a and tbx2b via RFLP analysis, and for dnthrβ via associated GFP fluorescence engineered into our construct.

Results : Preliminary results show that disrupting thrβ in a gdf6as327/s327 background exacerbates the gdf6a mutant cone phenotype by further reducing the number of blue cones compared to our previous findings (DuVal et al. 2014 PMID 24681822). The relative abundance of blue cones is reduced in gdf6as327/s327 mutants (by ~37%), but increased during thrβ disruption (by ~25%) compared to wild type. Reduction in blue cone abundance approximately doubles in magnitude (to ~73%) when thrβ and gdf6a are disrupted together.

Conclusions : Our goals are to determine critical genetic pathways for cone photoreceptor development, which will direct the selection and maturation of retinal progenitor cells for effective restoration of daytime vision. We have uncovered a preliminary novel link between gdf6a and thrβ, two gene expression regulatory factors that previously were understood to have disparate roles in photoreceptor development. This discovery, within a cone-rich model similar to the human macula, has the potential to fill long-standing gaps in our knowledge of cone photoreceptor subtype specification.

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

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