August 2016
Volume 16, Issue 12
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2016
Factor analysis of individual differences in the spectral sensitivities of transgenic and wild-type mice: expression of wild-type (M) and human (L) cone photopigments
Author Affiliations
  • David Peterzell
    John F. Kennedy University
  • Michael Crognale
    University of Nevada, Reno
Journal of Vision September 2016, Vol.16, 1154. doi:10.1167/16.12.1154
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      David Peterzell, Michael Crognale; Factor analysis of individual differences in the spectral sensitivities of transgenic and wild-type mice: expression of wild-type (M) and human (L) cone photopigments. Journal of Vision 2016;16(12):1154. doi: 10.1167/16.12.1154.

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      © 2017 Association for Research in Vision and Ophthalmology.

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Abstract

Shabaan et al. (1998) were the first to examine how a newly added human cone photopigment could affect vision in genetically modified mice. They established that the human transgene for human long wavelength sensitive (L) photopigment was expressed in mouse cones, and that the pigment was efficient at transducing light. Following earlier modeling approaches (Webster & MacLeod, 1988; Peterzell, 1991), we factor-analyzed individual differences in the spectral sensitivity data of Shabaan et al. to (1) measure independent expression of M and L photopigments, and (2) extract estimates of their absorption spectra. Flicker-electroretinogram (ERG) responses from five wild-type controls and five transgenic mice were recorded at 15 and 19 wavelengths (460 to 640 nm). Visual inspection of spectral sensitivity functions revealed one factor for wild-type mice, and two for transgenic mice. Pearson correlations (r) revealed the same. Principal component analyses of covariance matrices confirmed that one- (wild-type) and two-factor (transgenic mice) solutions accounted for >97% of individual variability. Varimax-rotated ("simple structure") factor loadings for transgenic mice were bipolar, consistent with underlying absorption spectra for M and L photopigments with zero-crossings at deuteranopic and tritanopic confusion points (equal M or L responses in test and standard). Two transgenic mice showing maximum contribution from the L factor descended from a founder that had two copies of the human L-pigment gene. The other three descended from second founder with only a single copy. Individual differences in the L factor were therefore consistent with relative expression of the transgene into mRNA and transgene copy number in retinas of two founder lines. While Shabaan et al. demonstrated functional separability of L and M photopigments using chromatic adaptation, our analysis confirmed and directly estimated spectra. More generally, we demonstrated that flicker-ERG data contain little error variance, so small samples of high-quality data can yield unequivocal factor-analytic results.

Meeting abstract presented at VSS 2016

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