Difference between revisions of "W3 Cell"
(Adds URL to ref) |
|||
| Line 1: | Line 1: | ||
[[Image:w3_connections.png|thumb|right|320px|A W3 cell in connection with a few different types of [[Amacrine Cell|amacrine cells]].]] | [[Image:w3_connections.png|thumb|right|320px|A W3 cell in connection with a few different types of [[Amacrine Cell|amacrine cells]].]] | ||
| − | |||
| − | + | Retinal ganglion cells (RGCs) are the cells which are responsible for transferring information from the eye to the brain. These cells come with distinct functional signature, size, and morphology, and their dendritic arbors have been shown to be confined to specific sublayers of the inner plexiform layer (IPL) of the retina. However, despite this heterogeneity in structure, connectivity and function, to this point, many studies on the development of the visual system and its pathways have regarded all RGC's as being part of a single group. Studies are now emerging that show that different subclasses of RGC's are maximally responsive to particular visual features, and that they arborize selectively within particular layers of the IPL. The number of RGC subtypes and the extent to which they differ from one another remains to be seen, but based upon studies on dendritic morphology, it is estimated that, in mammals, there are approximately 20 subtypes of RCG's. | |
| + | One example is the W3 retinal ganglion cell, which has been identified in the mouse retina. W3 is considered to be the equivalent to the object motion selective (OMS) ganglion cell in salamanders. Because relatively little work has been done specifically on W3 and a fair amount has been done regarding connections and properties of OMS, some of the information in the article will be about OMS. The W3 class is named after the transgenic line of mice that was used to mark it, and is referred to as such because there is not yet an accepted classification or scheme for the nomenclature of RGC subtypes. | ||
== Physiology == | == Physiology == | ||
| − | OMS and W3 both respond sensitively to differential motion between the receptive field center and surround, as produced by an object moving over the background, | + | OMS and W3 both respond sensitively to differential motion between the receptive field center and surround, as produced by an object moving over the background. However, both are strongly suppressed by global image motion, as produced by the observer’s head or eye movements. While it is clear that W3 is responsive to moving stimuli, there is no evidence of preference for motion in a particular direction. |
== Anatomy == | == Anatomy == | ||
| − | W3 cells have small cell body and small arbors that are densely branched. Typically, the diameter of their | + | |
| + | W3 cells have small cell body and small arbors that are densely branched. Typically, the diameter of their somatic field is about 120 microns (as compared with other RGC types such as W7, which has an average dendritic field diameter of nearly 300 microns). If the IPL is divided into 10 arbitrary and evenly-spaced strata, dendritic arbors of W3 occupy a thick swath in the middle of the IPL (from sublayer4 (SL4) through SL6)) with minor arborization in SL1. The region that is most populated with W3 dendritic arbors (SL4 to SL6)f lies sandwiched between 2 ChAT (choline acetyltransferase) positive bands. | ||
| + | |||
| + | The dendritic arbors of W3 have been shown to form in a step-wise manner at different times during the development of the mouse visual system. Initially, the arbors are completely restricted between sublayers 4 and 6. However, over the next few days in development, dendritic arbors expand to reach sublayers 1 and 2. Later still, the proximal processes between SL4 and SL6 expand, and the distal ones become isolated to SL1 and expand there as well. In adults, there is therefore a bistratified dendritic arbor distribution. | ||
=== Location === | === Location === | ||
Revision as of 19:43, 6 April 2012
Retinal ganglion cells (RGCs) are the cells which are responsible for transferring information from the eye to the brain. These cells come with distinct functional signature, size, and morphology, and their dendritic arbors have been shown to be confined to specific sublayers of the inner plexiform layer (IPL) of the retina. However, despite this heterogeneity in structure, connectivity and function, to this point, many studies on the development of the visual system and its pathways have regarded all RGC's as being part of a single group. Studies are now emerging that show that different subclasses of RGC's are maximally responsive to particular visual features, and that they arborize selectively within particular layers of the IPL. The number of RGC subtypes and the extent to which they differ from one another remains to be seen, but based upon studies on dendritic morphology, it is estimated that, in mammals, there are approximately 20 subtypes of RCG's.
One example is the W3 retinal ganglion cell, which has been identified in the mouse retina. W3 is considered to be the equivalent to the object motion selective (OMS) ganglion cell in salamanders. Because relatively little work has been done specifically on W3 and a fair amount has been done regarding connections and properties of OMS, some of the information in the article will be about OMS. The W3 class is named after the transgenic line of mice that was used to mark it, and is referred to as such because there is not yet an accepted classification or scheme for the nomenclature of RGC subtypes.
Contents
Physiology
OMS and W3 both respond sensitively to differential motion between the receptive field center and surround, as produced by an object moving over the background. However, both are strongly suppressed by global image motion, as produced by the observer’s head or eye movements. While it is clear that W3 is responsive to moving stimuli, there is no evidence of preference for motion in a particular direction.
Anatomy
W3 cells have small cell body and small arbors that are densely branched. Typically, the diameter of their somatic field is about 120 microns (as compared with other RGC types such as W7, which has an average dendritic field diameter of nearly 300 microns). If the IPL is divided into 10 arbitrary and evenly-spaced strata, dendritic arbors of W3 occupy a thick swath in the middle of the IPL (from sublayer4 (SL4) through SL6)) with minor arborization in SL1. The region that is most populated with W3 dendritic arbors (SL4 to SL6)f lies sandwiched between 2 ChAT (choline acetyltransferase) positive bands.
The dendritic arbors of W3 have been shown to form in a step-wise manner at different times during the development of the mouse visual system. Initially, the arbors are completely restricted between sublayers 4 and 6. However, over the next few days in development, dendritic arbors expand to reach sublayers 1 and 2. Later still, the proximal processes between SL4 and SL6 expand, and the distal ones become isolated to SL1 and expand there as well. In adults, there is therefore a bistratified dendritic arbor distribution.
Location
Shape
Connections
Molecules
Until recently, few if any molecular markers were available to identify these RGC subtypes, so most analyses depended on nonselective labeling methods. Likewise, many developmental studies have treated RGCs as a single population. This limitation severely compromises analysis of RGC projections and development. For example, it is difficult to learn whether subtypes develop in distinct ways if they can be identified only after they have matured.This problem is now being circumvented in mice by generation of genetically engineered lines in which RGC subsets are marked with reporter genes (Hattar et al., 2002; Kim et al., 2008[1]; Yonehara et al., 2008; Badea et al., 2009; Huberman et al., 2009; Siegert et al., 2009). Here, we characterize the structure and function of RGCs marked in four transgenic lines, then use them to address a set of open questions about patterning and development of axonal and dendritic arbors:
History
Open Questions and Relevance to the EyeWire Project
References
- ↑ Script error: No such module "Citation/CS1".
