Four alpha ganglion cell types in mouse retina: Function, structure, and molecular signatures

Abstract

The retina communicates with the brain using ≥30 parallel channels, each carried by axons of distinct types of retinal ganglion cells. In every mammalian retina one finds so-called "alpha" ganglion cells (αRGCs), identified by their large cell bodies, stout axons, wide and mono-stratified dendritic fields, and high levels of neurofilament protein. In the mouse, three αRGC types have been described based on responses to light steps: On-sustained, Off-sustained, and Off-transient. Here we employed a transgenic mouse line that labels αRGCs in the live retina, allowing systematic targeted recordings. We characterize the three known types and identify a fourth, with On-transient responses. All four αRGC types share basic aspects of visual signaling, including a large receptive field center, a weak antagonistic surround, and absence of any direction selectivity. They also share a distinctive waveform of the action potential, faster than that of other RGC types. Morphologically, they differ in the level of dendritic stratification within the IPL, which accounts for their response properties. Molecularly, each type has a distinct signature. A comparison across mammals suggests a common theme, in which four large-bodied ganglion cell types split the visual signal into four channels arranged symmetrically with respect to polarity and kinetics.

Digital Museum of Retinal Ganglion Cells with Dense Anatomy and Physiology

“…The four alpha types are a counterexample to this idea, because they exhibit sustained-transient differences (Fig. 7D) consistent with those that have been observed using electrophysiology (Pang et al, 2012; Krieger et al, 2017). …”

“…4A (see Methods for detailed justifications). Our 1wt, 4ow, and 8w correspond to the classical alpha types (Pang et al, 2012), and our 6sw corresponds to the nonclassical transient On alpha type (Krieger et al, 2017). Our 37c, 37d, 37r, and 37v correspond to the On-Off DS types, and 7ir, 7id, and 7iv correspond to the classical On DS types.…”

“…It has a smaller soma than 4ow, but its arbor is very similar when viewed along the light axis. 6sw corresponds to a fourth alpha type that has recently been genetically identified (Krieger et al, 2017), and to “ON transient, large” G 19 of Baden et al (2016). 6sw was presumably not regarded as an alpha cell by Pang et al (2003) because its soma and primary dendrites, though large, are not as large as those of the classical alpha types.…”

Diverse inhibitory and excitatory mechanisms shape temporal tuning in transient OFF α ganglion cells in the rabbit retina

“…; Krieger et al . ), and anatomically with the G11 cells identified by Rockhill et al . () in the rabbit.…”

“…In both rabbit and mouse retinas, four types of α ganglion cells can be distinguished: ON and OFF types come in both sustained and transient varieties (Caldwell & Daw, ; Famiglietti, ; Krieger et al . ). α cells can be targeted for electrical recordings since they have the largest somas in the ganglion cell layer.…”