Abstract
Purpose :
We recently found that Campana cells share many structural and functional features with bipolar cells, such as transmitting visual signals from photoreceptors to retinal ganglion cells (RGCs). The purpose of this study is to determine whether Campana cells could relay visual signals to CNS through RGCs for visual perception.
Methods :
We use C57BL/6J (WT) and VSX2-SED/D mice, in which the VSX2 super-enhancer is mutated ledding to the absence of bipolar cells, in this study. We accessed the capability of Campana cells to transmit visual signals from photoreceptors to RGCs by recording light evoked response of RGCs. Accordingly, AAV2-syn-jRGECO1a viral vector was injected into the eyes of VSX2-SED/D mice and the retinas were stimulated with an LED array. The calcium transients of RGCs were imaged using a two-photon microscope, and afterward, the retinas were labeled by anti-melanopsin and anti-RBPMS antibodies.
We accessed the visual perception of WT and VSX2-SED/D mice by a fear conditioning test, in which mice learn to associate a conditional stimulus (CS) with an aversive unconditional stimulus (US; a mild electrical foot shock) and show a conditional response (CR/fear response). Accordingly, we use uniform light and checkboard as conditional stimuli (CS) to determine the light perception and pattern perception of these mice. If the mice can recognize the CS, they will exhibit reduced movement (freezing) when the CS is presented.
Results :
In the VSX2-SED/D mice retina, calcium activity was recorded from 202 RGCs (7 retinas), and 51 of them (25.25%) exhibited a light-evoked calcium transient. None of these light-responsive RGCs was labeled by anti-melanopsin antibody. The visually evoked fear conditioning tests showed that the freezing time is increased by 12.5 folds (0.69 ±0.59 sec in control and 8.69 ± 7.98 sec in CS, n=8) for light perception and 2.2 folds (1.03 ± 1.34 sec in control and 2.31 ± 2.42 sec in CS, n=8) for form perception in WT mice. In the VSX2-SED/D mice, the freezing time is increased by 8.2 folds (0.50 ± 0.60 sec in control and 4.08 ± 3.13 sec in CS, n=13) for light perception and 2.4 folds (1.13 ± 1.83 sec in control and 2.71 ± 2.90 sec in CS, 1n=3) for form perception.
Conclusions :
Campana cells were identified in the retina of VSX2-SED/D mice and 25.25% of RGCs received synaptic inputs from Campana cells. The Campana cells of VSX2-SED/D mice could relay visual signals to CNS through RGCs for visual perception without bipolar cells.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.