Satb1 expression in retinal ganglion cells of marmosets, macaques and humans.

Recent advances in single-cell RNA sequencing have enabled the molecular distinction of ganglion cell populations in mammalian retinas. Here we used antibodies against the transcription factor Special AT-rich binding protein 1 (Satb1, a protein which is expressed by ON-OFF direction selective ganglion cells in mouse retina) to study Satb1 expression in the retina of marmosets (Callithrix jacchus), macaques (Macaca fascicularis) and humans. In all species, Satb1 was exclusively expressed in retinal ganglion cells. The Satb1 cells made up ∼2 % of the ganglion cell population in central retina of all species, rising to a maximum ∼7% in peripheral marmoset retina. Intracellular injections in marmoset and macaque retinas revealed that most Satb1 expressing ganglion cells are widefield ganglion cells. In marmoset, Satb1 cells have a densely branching dendritic tree and included broad and narrow thorny, recursive bistratified and parasol cells, all of which showed some co-stratification with the outer or inner cholinergic amacrine cells. The recursive bistratified cells showed the strongest co-stratification but did not show extensive co-fasciculation as reported for ON-OFF direction selective cells in rabbit and rodent retinas. In macaque, Satb1 was not expressed in recursive bistratified cells, but in large sparsely branching cells. Our findings further support the idea that the expression of transcription factors in retinal ganglion cells is not conserved across Old World (human and macaque) and New World (marmoset) primates and provides a further step to link a molecular marker with specific cell types. This article is protected by copyright. All rights reserved.