Introduction
In the developing brain, axons use different mechanisms in order to find their correct path and target. A critical element helping to guide axons through long distance is the presence of intermediate targets or guidepost cells which provide information all along the path. During development, cortico-cortical (callosal) projections traverse a complex environment and need to make several critical decisions before reaching their target. Glial cells localized around the corpus callosum are believed to be the principal actors involved in the guidance of callosal axons during the early developmental stages.
Current research
While the guidepost function of glial cells has been well documented, certain studies indicate that neurons may play a similar function in the developing mammalian brain as well. In a recent series of experiments, we have discovered that, during embryonic development, the corpus callosum, which was generally considered as a structure poor in neurons, is in fact populated by numerous glutamatergic and GABAergic neurons. With the use of various transgenic mice and transplant experiments, we demonstrated that the neurons of the corpus callosum are essential for the correct midline crossing of callosal axons. Thus, guidance cues secreted by glial and neuronal cells may be complementary mechanisms building up the organization of commissural axons. Based on these data, the aim of our project is to better characterize the respective roles of neurons and glia partners in guiding commissural axons and the associated mechanisms of axon guidance.
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