The lead author on the study, Sammy Lee, was a postdoctoral researcher working in Reese's lab and supported by a C.J. Martin National Health & Medical Research Council fellowship from Australia during the course of the study. Lee labeled individual cone bipolar cells with a fluorescent dye through a new microinjection procedure developed by Patrick Keeley, a graduate student in the Reese lab.
"What Dr. Lee has shown is that cone bipolar cells modulate the size of their dendritic fields (branched extensions of the neuron) in association with the local density of like-type neurons," said Reese. "One line of mice has conspicuously fewer cone bipolar cells, each now with a larger dendritic territory, while the other line shows heightened densities and correspondingly smaller dendritic fields."
Other studies have suggested such homotypic (like-type) modulation of dendritic field size, but the current study directly shows this modulation following genetic manipulation of neuronal density, according to Reese.
Additionally, the researchers found that connectivity with the afferent population of cone photoreceptors is impacted directly, with the larger dendritic fields being innervated by more cones, and the smaller dendritic fields connecting with fewer cones. At any individual cone, the number of dendritic endings associating with that cone was not observed to change, so that the total number of connections made by a cone bipolar cell was remarkably plastic, defined solely by the number of cone contacts formed.
"This developmental plasticity in dendritic growth and synapse number may be well-suited to ensure uniform coverage and connectivity between two populations of neurons afferents and their targets when the number of cells in each population is specified independen
|Contact: Gail Gallessich|
University of California - Santa Barbara