Campana cells relay visual signals from photoreceptors to retinal ganglion cells without bipolar cells

Abstract

Purpose : To determine whether Campana cells could transmit visual signals from photoreceptors to retinal ganglion cells (RGCs) without bipolar cells.

Methods : We use C57BL/6J (WT) and VSX2-SE^△/△ mice as working models in this study. In the VSX2-SE^△/△ mice, a specific segment within the VSX2 super-enhancer (SE) is deleted, which encompasses the VSX2 binding site and leads to the total absence of bipolar cells. To compare Campana cell density and dendritic area between WT mice (n = 3) and VSX2-SE^△/△ mice (n = 3), we examined the 2-month-old retinas of the two strains. The anti-GlyT1 antibody was used to label Campana cells. Retinas were imaged using a two-photon microscope. To record the light-evoked response of RGCs, the AAV2-syn-jRGECO1a viral vector was injected into the eyes of adult VSX2-SE^△/△ mice four weeks before recording. The retinas were stimulated with a custom-built LED array, and calcium transients were imaged using a two-photon microscope. After the recording, the retinas were labeled by anti-melanopsin antibody for ipRGCs and anti-RBPMS antibody for RGCs. Statistical analysis was performed using a two-tailed Student’s t-test and Kolmogorov-Smirnov Test.

Results : The density of Campana cells in WT mice (82.4 ± 6.0/mm²) was significantly lower than that of VSX2-SE^△/△ mice (305.7 ± 4.8/mm², p=0.0017). In WT mice, the min, max, and median Campana cell dendritic areas were 10.14 µm², 4236.79 µm², and 255.66 µm², respectively. Meanwhile, in VSX2-SE^△/△ mice, the min, max, and median Campana cell dendritic areas were 4.84 µm², 828.50 µm², and 67.81 µm² (p < 0.001). In the VSX2-SE^△/△ mice retina, calcium activity was recorded from 202 RGCs, and 51 of them (25.25%) exhibited a light-evoked calcium transient. The anti-melanopsin antibody staining revealed that the light-responsive RGCs were not ipRGCs.

Conclusions : Campana cells were identified in the retina of VSX2-SE^△/△ mice. The density of Campana cells increased, while the dendritic area decreased compared to WT mouse retinas. Approximately one-fourth of recorded RGCs exhibited a light response, suggesting that these RGCs likely received inputs from Campana cells. These findings underscore the role of Campana cells in the visual signaling pathway.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.