Genetic access to functionally distinct ganglion cell types in the Somatostatin-IRES-Cre mouse retina

Retinal ganglion cells (GCs) are a functionally diverse neuron population that encodes and transmits distinct representations of the visual image on the retina to target nuclei in the brain. Independent studies of visually-evoked responses, cell morphology, and gene expression each suggest that GCs in mouse may comprise as many as forty distinct cell types. To date, only a subset of these types have been characterized in detail, and for most genetic access is still lacking. Thus, the majority of identified GC types remains inaccessible for targeted electrophysiology and functional imaging, precluding efficient studies of their response properties, and the cell-intrinsic mechanisms and presynaptic circuits that generate these properties. Here we show that an existing mouse line that is commonly used for studies of cortical inhibitory circuits - Somatostatin-IRES-Cre (Sst-Cre), consistently labels an understudied subset of four GC types with distinct visual responses. We characterized these types both anatomically and functionally using Cre-dependent reporter mouse lines and confocal fluorescence imaging, calcium imaging, and whole-cell electrophysiology. We show that one of the labeled GC types is suppressed by luminance contrast, while another matches a recently described orientation-selective GC type. Our results give new information about these two identified GC types, and establish the utility of the Sst-Cre transgenic mouse line for studies of recently identified GC circuits in the mouse retina.