Bipolar Cell Type 2 (BC2) are one of five OFF bipolar cells in the retina. They stratify in the OFF sublamina in the inner plexiform layer (IPL). BC2s are in contact with at least one or two cone pedicles, and They can be distinguished from other bipolar cells with their expression of recoverin and a type II cadherin, cdh8 (Havercamp et al., 2003, Duan et al., 2014).
There are several markers and transgenes that can be used to label BC2s, although not all of them are selective.
GFP positive cells in whole mount CB2-GFP mouse retina. A. whole mount retina. Scale = 500um B. GFP positive cells. C. Alpha RGCs are immunpositive to SMI-32 cells. D. GFP positive cells are all SMI-32 positive. CB2-RGCs appear to be alpha type RGCs. scale = 125um. E. GFP positive cells in the GCL (CB2-RGCs) and INL (amacrine cells). Scale = 100um. Image adapted from Huberman et al., 2008
[[File:Cb2physio_huberman2008.PNG|thumb|500px|none|Physiological responses of CB2-RGCs to visual stimuli. A. Membrane potential response shows spike at offset of flash. B. Average subthreshold flash response of seven cells (gray), and average flash response of two example cells (blue, red). Image adapted from Huberman et al., 2
CB2-RGCs show a nonrandom, regularly spaced mosaic. F. Density profile of CB2-RGCs in relation to each of their distances from other CB2-RGCs. Their G. CB2-RGCs filled with DiI to elucidate dendritic morphology and overlap with each other. Scale = 75um. Image adapted from Huberman et al., 2008
Schematic showing circuitry of alpha RGCs in mouse retina. S-pigment dominated cones send inputs to M-cone-dominated hyperpolarizing bipolar cell, which in turn sends its signals to transient alpha RGC. This signal is mediated by amacrine cells with mixed rod-cone inputs. Image adapted from Pang et al., 2003
Axonal projections of CB2-RGCs to SC. A. Ctb-594 labeling (red) of all RGC axons. B. GFP positive CB2-RGCs (green). C. Merge of both Ctb and GFP. CB2-RGC projections are organized in a highly specific manner. They project exclusively to the lower SGS of the SC, and organize in columnar fashion. Scale = 250um. Image adapted from Huberman et al., 2008
Axonal projections of CB2-RGCs to dLGN. E. Ctb-594 labeling (red) of all RGC axons. F. GFP positive CB2-RGCs (green). Asterisks mark where axons project through the lateral third of the dLGN to terminate in inner dLGN. G. Merge of both Ctb and GFP positive cells. Scale = 250um. Image adapted from Huberman et al., 2008
Developmental differences of CB2-RGC projections to SC in P4 and P10 mice. B. CB2-RGC projections in P4 mouse show beginnings of laminar and columnar structure, but are relatively nonspecific. E. CB2-RGC projections in P10 mouse exhibit laminar and columnar structure similar to that of the adult mouse. Scale = 250um. Image adapted from Huberman et al., 2008