Two Pairs of ON and OFF Retinal Ganglion Cells Are Defined by Intersectional Patterns of Transcription Factor Expression

• Foxp2 expression marks F-RGCs, two mini and two midi types comprising two pairs
• Intersectional expression of Foxp and Brn3 genes uniquely identifies each F-RGC type
• The two F-mini RGC types are unusually small, abundant, and direction selective
• Combinatorial expression of Foxp and Brn3 genes also marks RGC types in macaque retina

SummaryVisual information is conveyed to the brain by axons of >30 retinal ganglion cell (RGC) types. Characterization of these types is a prerequisite to understanding visual perception. Here, we identify a family of RGCs that we call F-RGCs on the basis of expression of the transcription factor Foxp2. Intersectional expression of Foxp1 and Brn3 transcription factors divides F-RGCs into four types, comprising two pairs, each composed of closely related cells. One pair, F-miniON and F-miniOFF, shows robust direction selectivity. They are among the smallest RGCs in the mouse retina. The other pair, F-midiON and F-midiOFF, is larger and not direction selective. Together, F-RGCs comprise >20% of RGCs in the mouse retina, halving the number that remain to be classified and doubling the number of known direction-selective cells. Co-expression of Foxp and Brn3 genes also marks subsets of RGCs in macaques that could be primate homologs of F-RGCs.

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