Glial TGFβ activity promotes axon survival in peripheral nerves

Axons can represent the majority of the volume of a neuron and are energetically very demanding. Specialized glia ensheathe axons and are believed to support axon function and maintenance throughout life, but molecular details of glia-neuron support mechanisms remain poorly defined. Here we identify a collection of secreted and transmembrane genes that are required in glia for long-term axon survival in vivo. We show that key components of the TGF{beta} superfamily are required cell-autonomously in glia for peripheral nerve maintenance, although their loss does not disrupt glial morphology. We observe age-dependent neurodegeneration in the absence of glial TGF{beta} signaling that can be rescued by genetic blockade of Wallerian degeneration. Our data argue that glial TGF{beta} signaling normally acts to promote axon survival and suppress neurodegeneration. Significance StatementAxon maintenance is critical to preserving the functional integrity of the nervous system across animal lifespan. Glia contribute to axon maintenance, but their precise roles remain to be fully characterized. We identify glial genes that regulate axon support and provide new molecular insight into the means by which glia promote axon survival, which may help explain why neurodegeneration occurs when glia are lost in disease. We show that TGF{beta} signaling in mature glia is essential for long-term maintenance of axons, and that loss of TGF{beta} signaling activates an axon death signaling pathway.