Tctp in Neuronal Circuitry Assembly.

Although tctp expression in many areas of the human brain was reported more than 15 years ago, little was known about how it functions in neurons. The early notion that Tctp is primarily expressed in mitotic cells, together with reports suggesting a relative low abundance in the brain, has perhaps potentiated this almost complete disregard for the study of Tctp in the context of neuron biology. However, recent evidence has challenged this view, as a number of independent genome-wide profiling studies identified tctp mRNA among the most enriched in the axonal compartment across diverse neuronal populations, including embryonic retinal ganglion cells. Considering the emerging parallels between axon guidance and cancer cell invasion, the axonal expression of cancer-associated tctp was suggestive of it holding an unexplored role in the wiring of neuronal circuits. Our study revealed that Tctp is necessary for the accurate and timely development of axon projections during the formation of vertebrate retinal circuits via its association with the survival machinery of the axon. Globally, the findings indicate that compromised pro-survival signaling in Tctp-deficient axons results in mitochondrial dysfunction and a subsequent decrease in axonal mitochondrial density. These effects likely translate into a metabolic state inadequate to support the normal guidance and extension processes of a developing axon.