Abstract
Purpose: :
Amacrine cells are essential for visual function, modulating synapses between bipolar cells and retinal ganglion cells (RGCs). More than 30 types of amacrine cells in the mammalian retina can be classified by morphology, physiology, or expression of specific markers. In the developing retina, amacrine cells are born at the same time as RGCs, and many of them even migrate to the same layer of the retina as RGCs. Little is known about amacrine cell biology, however. For example, what is the molecular basis for their resistance to degeneration? Why do they fail to grow axons like their sibling RGCs?
Methods: :
Embryonic and postnatal amacrine cells were purified and cultured in serum-free media with or without trophic factors. We quantified survival at 1, 2 and 3DIV using live/dead assays, and performed Western Blot to study molecular pathways necessary for survival. Three to four biological replicates were independently processed for Genechip analysis using Affymetrix RAE 230 2.0 arrays. We classified the probes by Gene Ontology and compared the gene expression profiles of amacrines and RGCs.
Results: :
We found that amacrine cell survival in vitro is independent of cell density and the presence of BDNF and CNTF, but it requires Erk activation via MEK1/2. Analysis of the expression levels of "polarity genes" during development of amacrine cells and RGCs led to the identification of a subset of genes that are differentially expressed in these cell types.
Conclusions: :
We have developed a method to purify and culture amacrine cells in vitro. Comparing the gene expression profiles of amacrine cells and RGCs may reveal candidate genes that explain their fundamental differences in survival signaling, migration, and neurite growth and polarization.
Keywords: amacrine cells • ganglion cells • neuroprotection