June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Inhibition of the Nxnl1 gene’s splicing result in its gain of function by production RdCVF or precede that event, a case of molecular exaptation?
Author Affiliations & Notes
  • Najate Maamri Maamri
    Genetic, Institut de la Vision, Paris, France
  • Frédéric Blond
    Genetic, Institut de la Vision, Paris, France
  • François Delalande
    Laboratoire de Spectrométrie de Masse Bio-Organique, Strasbourg, France
  • Alain VAN DORSSELAER
    Laboratoire de Spectrométrie de Masse Bio-Organique, Strasbourg, France
  • Thierry D Leveillard
    Genetic, Institut de la Vision, Paris, France
  • Footnotes
    Commercial Relationships   Najate Maamri, None; Frédéric Blond, None; François Delalande, None; Alain VAN DORSSELAER, None; Thierry Leveillard, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 597. doi:
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      Najate Maamri Maamri, Frédéric Blond, François Delalande, Alain VAN DORSSELAER, Thierry D Leveillard; Inhibition of the Nxnl1 gene’s splicing result in its gain of function by production RdCVF or precede that event, a case of molecular exaptation?. Invest. Ophthalmol. Vis. Sci. 2017;58(8):597.

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

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Abstract

Purpose : The first ancestors of photoreceptors were cones. Agnathans such as lampreys are among the oldest living chordate relatives of the vertebrates and are the first animals to possess photoreceptors resembling rods. Hydra (Hydra vulgaris) belongs to the cnidarians family with feature of not having a visual eye, while being sensitive to light. The bifunctional gene NXNL1 encodes two proteins by alternative splicing, a trophic factor RdCVF that is secreted by rods and protects cones and the enzyme RdCVFL that protects photoreceptors against oxidative stress. Cones express only RdCVFL and not RdCVF. The alternative spliced product with intron retention occurs only in the rods. Our goal is to understand if this alternative splicing occurred in the ancestral gene or appeared with rods during evolution. On the other hand, the RdCVF receptor basigin1 (BSG1) is an alternative splicing product of the Bsg gene specific to photoreceptors with a third additional extracellular domain, necessary for RdCVF binding. What splicing event came first is a key to understand the emergence of RdCVF metabolic signaling.

Methods : mRNA is extracted and quality controlled by lamprey retina and hydra tissues. An RT-PCR was performed by using specifics primers and an in situ hybridization (ISH) to discriminate the expression of the long and the short form of the Nxnl gene. The proteins were identified by mass spectrometry (MS/MS).

Results : The short and the long form of Nxnl1 gene in the lamprey retina were detected by RT-PCR. In hydra, the Nxnl ancestor gene expression profile by ISH matches that of a thioredoxin but a short isoform with intron 4 retention was detected. Hydra genome does not contain a basigin gene with the third extracellular domain as lamprey does as shown by RT-PCR and proteomics.

Conclusions :
We demonstrated that inhibition of splicing of the ancestral gene Nxnl1 occurs before the emergence of the agnathans. The investigation of Nxnl in hydra shows that the intron retention occurs prior to the emergence of RdCVF metabolic signaling, a possible case of exaptation.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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