Ipsilateral and contralateral retinal ganglion cells express distinct genes during decussation at the optic chiasm

The retinal projection neurons, retinal ganglion cells (RGCs), can be categorized into distinct morphological and functional subtypes and by the laterality of their projections. Here, we used a new method for purifying the sparse population of ipsilaterally projecting RGCs in mouse retina from their contralaterally-projecting counterparts during embryonic development through rapid retrograde labeling followed by fluorescence-activated cell sorting (FACS). Through microarray analysis, we have uncovered the distinct molecular signatures that define and distinguish ipsilateral and contralateral RGCs during the critical period of axonal outgrowth and decussation, with over three hundred genes differentially experienced within these two cell populations. Amongst the genes upregulated in ipsilateral RGCs are many that are known to be expresed in progenitors cells and mark immaturity," including Math5 (Atoh7), Sox2, and cyclin D2. Many of these differentially regulated genes were subsequently validated via in vivo expression analysis. Thus, the molecular signatures of ipsilateral and contralateral RGCs and the mechanisms that regulate their differentiation are more diverse than previously expected.

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Wang Q, Marcucci F, Cerullo I, Mason C