June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Abnormalities in the electroretinogram of a rat genetic model of Fragile X syndrome
Author Affiliations & Notes
  • Jeffrey Adam Jamison
    Experimentica Ltd, Kuopio, Finland
  • Marianna Bacellar-Galdino
    Experimentica Ltd, Kuopio, Finland
  • Olivier perche
    Kaerus Bioscience Ltd., London, England, United Kingdom
  • robert ring
    Kaerus Bioscience Ltd., London, England, United Kingdom
  • Footnotes
    Commercial Relationships   Jeffrey Jamison Experimentica, LTD, Code E (Employment); Marianna Bacellar-Galdino Experimentica, LTD, Code E (Employment); Olivier perche Kaerus Bioscience Ltd, Code E (Employment); robert ring Kaerus Bioscience Ltd, Code E (Employment)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 5219. doi:
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      Jeffrey Adam Jamison, Marianna Bacellar-Galdino, Olivier perche, robert ring; Abnormalities in the electroretinogram of a rat genetic model of Fragile X syndrome. Invest. Ophthalmol. Vis. Sci. 2023;64(8):5219.

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

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Abstract

Purpose : Fragile X syndrome (FXS) is the most common inherited causes of intellectual disability and autism globally. FXS is caused by epigenetic suppression of FMR1 gene expression and a subsequent reduction in the FMRP protein. FMRP is expressed in ganglion cell, inner nucleus and outer plexiform layers of the retina, with specific labeling observed in bipolar, horizontal, Müller and amacrine cells. Deficits in the b-wave (but not a-wave) and flicker amplitude of the electroretinogram (ERG) have been reported in both the genetic mouse models of FXS (Fmr1-/y) and human FXS subjects. The purpose of this study was to further investigate ERG abnormalities in a knockout rat model of FXS (Fmr1 KO).

Methods : Ten male Fmr1 KO (Fmr1-/null (em1Sage)) and 10 male age/weight matched Sprague Dawley wild type controls were acquired from Envigo, and allowed to acclimate to facility lighting conditions for 4 weeks. Animals were dark adapted overnight for at least 12 hours and recordings were made using ISCEV standard methods at 1000 Hz sampling frequency with ketamine and xylazine anesthesia. Dark adapted (DA) ERGs were collected over 10 intensities between 2.5*10E-5 to 5000 cd and light adapted (LA) ERGs from 5 to 5000 cd in log steps using a 25.5 cd white background. LA Flicker ERGs were collected from 0.5 to 30 Hz using a 50 cd xenon flash. The Photopic Negative Response (PhNr) was measured using a 10-100 cd green flash on a 10 cd blue background. ERG traces were imported into MATLAB and oscillator potentials (OP) were isolated using a 6th order, 10-40 Hz bandpass filter. Total peak (TP) latency was calculated using the timing of the first 3 OP peaks.

Results : Although differences in scotopic or photopic a-wave were not observed between groups, an average reduction in b-wave amplitude of 10% was observed in KO rats (P=0.093). Flicker amplitude was also reduced 25% in the KO at frequencies below 10 Hz (P=0.007). Absolute amplitude, and amplitude difference between groups, was also decreased as flicker frequency increased. Individual OP latencies were slightly delayed in the KO, but only the TP was statistically significant (P<0.001). Significant differences in the PhNr were not observed between groups at intensities tested.

Conclusions : Fmr1 KO rats exhibit small, but significant decreases in several components of the ERG response. These data expand the translational validity of ERG abnormalities as a biomarker of FXS.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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