DRD4-RGC

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On-Off DSGC from DRD4-GFP mouse filled with biocytin. White arrow shows the axon, yellow arrows show "looping" arborizations characteristic of mouse DSGCs. Image adapted from Huberman et al., 2009

DRD4-DSGCs are On-Off direction selective ganglion cells that respond to global posterior motion (backward motion in relation to the world). These cells were discovered in transgenic mice that express GFP under the control of the dopamine receptor 4 promoter (DRD4-EGFP). Interestingly, the GFP positive RGCs in this mouse line all have properties of On-Off DSGCs, and exclusively prefer posterior motion. This selective labeling of On-Off DSGCs allowed for previously uncharacterized brain circuitry and axonal connection pattern of a specific subset of On-Off DSGC.

Anatomy

DRD4-DSGC cells exhibit canonical morphological characteristics of On-Off DSGCs. They are bistratified, costratifying with starburst amacrine cell (SAC) processes. Their dendritic fields are egg-shaped and dendritic arbors exhibit "looping" patterns. Although their dendritic arbors are mostly symmetric, their somas tend to shift slightly away from the center of their dendritic fields. The cells form a regular mosaic with a relatively high coverage factor (2.99 on average) (Rivlin-Etzion et al., 2011).

Physiology

Molecular Marker

Saggital section of Drd4 BAC transgenic mouse brain revealing high expression of Drd4 in the prefrontal cortex. Image adapted from Gong et al., 2003
GFP positive cells in DR4-GFP retina with no immunostaining. Scale= 200um, 100um respectively. Image adapted from Huberman et al., 2009)

These posterior motion-preferring On-Off DSGCs (pDSGCs) are characterized by their expression of Drd4 (dopamine receptor D4). Drd4-GFP BAC transgenic mice express Drd4 prominently in the prefrontal cortex, and also in the ganglion cell layer (GCL) of the retina (Gong et al., 2003, Huberman et al., 2009). Upon further inspection of the retina, dendrites of the GFP positive cells of the Drd4-GFP mouse were found to stratify in two distinct bands in the inner plexiform layer (IPL), suggesting bistratification (Huberman et al., 2009). The GFP positive dendrites appeared to be costratified with processes of startburst amacrine cells (SACs).

Central Projections

References

Gong S, Zheng C, Doughty ML, Losos K, Didkovsky N, Schambra UB, Nowak NJ, Joyner A, LIblanc G, Hatten ME, Heintz N (2003). A gene expression atlas of the central nervous system based on bacterial artificial chromosomes. Nature 425, 917-925.

Huberman AD, Wei W, Elstrott J, Stafford BK, Feller MB, Barres BA (2009). Genetic identification of an On-Off direction selective ganglion cell subtype reveals a layer-specific subcortical map of posterior motion. Neuron 62, 327-334.

Rivlin-Etzion M, Zhou K, Wei W, Elstrott J, Nguyen PL, Barres BA, Huberman AD, Feller MB (2011). Transgenic mice reveal unexpected diversity of ON-Off direction selective ganglion cell subtypes and brain structures involved in motion processing. J Neurosci. 31, 8760-8769.