Abstract
Purpose :
In glaucoma, progressive and irreversible vision loss results from the death of retinal ganglion cells (RGCs). Restoring lost vision requires the replacement of these RGCs. Ankyrin G (AnkG), a scaffold protein organizing the axonal initial segment (AIS), plays a crucial role in regenerating axons. We propose to anatomically characterize the AIS in RGCs to gain insights into the restoration of functional RGCs with axons.
Methods :
The AIS of adult AnkG-GFP mice, wild-type mice, and rats, along with primary RGC cultures from adult retinas, were analyzed using immunohistochemistry. Antibodies against AnkG to label AIS, neurofilament and bIIItub to label axons and SPP1 to label αRGCs were used. Measurements of AIS length as well as distance from the soma and soma diameters were taken.
Results :
After using the AnkG-GFP mouse model, the detection of AnkG with antibodies in the RGCs AIS was confirmed both in vivo and in vitro. Our findings indicate that, in most cases, as soma size increases, so does the distance between the soma and AIS (in mouse 11.46±1.18µm in small (<15µm), 25.86±3.97 µm in medium (15 to 20µm) and 24.38±3.11µm in large (>20µm) RGCs and in rat 9.21±1.76µm, 15.05±1.5µm and 19.35±2.52µm, respectively). Notably, the distance between soma and AIS tends to be greater in peripheral RGCs. Furthermore, larger RGCs exhibit a trend toward longer AIS lengths (in mouse 18.65±1.02µm in small, 27.16±2.97 µm in medium and 32.17±1.72µm in large RGCs and in rat 23.97±2.22µm, 29.76+2.28µm and 29.58+2.86µm respectively). Characterization of rat αRGCs with larger soma diameter (30.48±1.18μm) also revealed an extended AIS length (38.79±2.95μm). Moreover, in RGCs cultures, the appearance of the AIS appears to be dispersed throughout the soma as well as in long extension of the longest neurite.
Conclusions :
These findings suggest a trend toward longer distance to AIS and AIS lengths in larger RGCs in mice and rats, implying a relationship between cellular morphology and the organization of this structure. Additionally, observing potential AIS organization in vitro RGC highlights the capacity of RGCs to develop AIS in absence of the neuronal target. Furthermore, efforts should be focused on organizing the RGCs AIS in vitro for therapeutic purposes.
Supported by ELKARTEK (KK-2019/00086), Gobierno Vasco (IT1510-22), MINECO-Retos (PID2019-111139RB-I00), PIBA (2020_1_0026), thanks to Bordeaux IdEx program to EV.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.