SoxC transcription factors in retinal development and regeneration

Glaucoma and other optic neuropathies result in optic nerve degeneration and the loss of retinal ganglion cells (RGCs) through complex signaling pathways. Although the mechanisms that regulate RGC development remain unclear, uncovering novel developmental pathways may support new strategies to regenerate the optic nerve or replace RGCs. Here we review recent studies that provide strong evidence that the Sry-related high-mobility-group C (SoxC) subfamily of transcription factors (TFs) are necessary and sufficient for axon guidance and RGC fate specification. These findings also uncover novel SoxC-dependent mechanisms that serve as master regulators during important steps of RGC development. For example, we review work showing that SoxC TFs regulate RGC axon guidance and direction through the optic chiasm towards their appropriate targets in the brain. We also review work demonstrating that Sox11 subcellular localization is, in part, controlled through small ubiquitin-like post-translational modifier (SUMO) and suggest compensatory cross-talk between Sox4 and Sox11. Furthermore, Sox4 overexpression is shown to positively drive RGC differentiation in human induced pluripotent stem cells (hiPSCs). Finally, we discuss how these findings may contribute to the advancement of regenerative and cell-based therapies to treat glaucoma and other optic nerve neuropathies.