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Ellen Piccillo, Emma M Lessieur, Gabrielle C Nivar, Brian D Perkins; Visual performance evaluation of zebrafish with mutations in cilia transition zone proteins. Invest. Ophthalmol. Vis. Sci. 2017;58(8):362.
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© ARVO (1962-2015); The Authors (2016-present)
Joubert syndrome (JBTS) is an autosomal recessive ciliopathy with genotypic and phenotypic variability. The genes cep290, ahi1, and arl13b encode ciliary transition zone proteins and mutations in these genes have been associated with JBTS. It is well known that mutations in second-site modifier genes can modulate phenotypic severity, but detailed analyses of how this affects visual performance are limited. This study investigates whether heterozygous and homozygous mutations of ahi1 and arl13b exacerbate the visual acuity defects observed in zebrafish cep290-/- mutants.
Progeny from pairwise crosses cep290+/-;ahi1+/-, and cep290+/-;arl13b+/- adults were tested by optokinetic response (OKR) behaviors for contrast sensitivity and spatial frequency. To test visual function, the VisioTracker system was used to calculate the OKR gain in order to assess contrast sensitivity and spatial frequency in zebrafish larvae at 5 days post fertilization (dpf).
Plotting the OKR gain as a function of either stimulus contrast or spatial frequency, it was shown that cep290-/- and arl13b-/- mutants had reduced visual performance compared to wild-type animals. Furthermore, cep290-/-;arl13b-/- mutants exhibited decreased visual performance compared to cep290-/-;arl13b+/- mutants and the cep290-/- and arl13b-/- single mutants. It was also shown that visual acuity in ahi1-/- single mutants was comparable to wild-type zebrafish. The cep290-/-;ahi1-/- mutants exhibited decreased visual performance compared to cep290-/-;ahi1+/- and cep290-/- and ahi1-/- single mutants.
Based on the results, it was determined that cep290-/- mutants and arl13b-/- mutants showed reduced visual function at 5dpf. The cep290-/-;arl13b+/- mutants had worse visual acuity compared to cep290-/- mutants and wild-type zebrafish. Visual acuity of cep290-/-;arl13b-/- mutants was further compromised compared to the cep290-/-;arl13b+/- mutants, suggesting that arl13b acts as a modifier to cep290 in a dose-dependent fashion. Similarly, the cep290-/-;ahi1+/- mutants exhibited decreased visual acuity compared to cep290-/- mutants and the cep290-/-;ahi1-/- mutants were further compromised, indicating that loss of ahi1 also exacerbates the visual deficit of cep290-/- mutants in a dose-dependent fashion.
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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