May 2006
Volume 47, Issue 13
ARVO Annual Meeting Abstract  |   May 2006
Circadian Oscillators in the Mouse Retina
Author Affiliations & Notes
  • G.–X. Ruan
    Biological Sciences, Vanderbilt, Nashville, TN
  • D.–Q. Zhang
    Biological Sciences, Vanderbilt, Nashville, TN
  • D.G. McMahon
    Biological Sciences, Vanderbilt, Nashville, TN
  • Footnotes
    Commercial Relationships  G. Ruan, None; D. Zhang, None; D.G. McMahon, None.
  • Footnotes
    Support  NIH Grant EY015815
Investigative Ophthalmology & Visual Science May 2006, Vol.47, 5525. doi:
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      G.–X. Ruan, D.–Q. Zhang, D.G. McMahon; Circadian Oscillators in the Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5525.

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

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Purpose: : Circadian clocks in a variety of mammalian tissues generate daily rhythms via an autoregulatory clock–gene network. In order to localize potential clock neurons within the mammalian retina, we have examined the cell–type specific expression of 6 core circadian clock genes in individual identified mouse retinal neurons, as well as characterized the clock gene expression rhythms in normal and photoreceptor degenerate rd mouse retinas.

Methods: : 2–4 month old mice were euthanized by cervical dislocation at Zeitgeber Time (ZT) 6. Individual photoreceptors, horizontal, bipolar, dopaminergic amacrine (DA), catecholaminergic amacrine (CA), and ganglion neurons were identified either by morphology, or by a tyrosine hydroxylase (TH) promoter–driven RFP fluorescent reporter. Cells were individually collected and their transcriptomes were subjected to single–cell real–time RT–PCR for the core clock genes Period (Per) 1 and 2, Cryptochrome (Cry) 1 and 2, Clock and Bmal1. For whole retina quantitative real–time PCR, sixty 8–10 week old male B6C3F1 mice and sixty 10–14 week old male C3H rd mice were either maintained in a 12::12 light/dark (LD) cycle or, before being used, transferred into constant darkness (DD) and kept there for 36–48 hr. Five animals were sampled for each time point examined at ZT and at Circadian Times (CT) 2, 6, 10, 14, 18 and 22. Total RNA was isolated from whole retinal homogenates and then subjected to TaqMan real–time RT–PCR for the 6 core clock genes.

Results: : Individual retinal neurons, but not photoreceptors, were found to express all 6 core clock genes, with the lowest proportion of putative clock cells in photoreceptors (0%) and the highest proportion in DA neurons (30%). In addition, clock gene rhythmicity was found to persist in rd mouse retinas in which photoreceptors had degenerated.

Conclusions: : Our results indicate that multiple types of retinal neurons are putative circadian clock neurons that express key elements of the circadian autoregulatory gene network and that the inner nuclear and ganglion cell layers are loci of mammalian retinal clock function.

Keywords: circadian rhythms • retina • gene/expression 

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