The E3-ubiquitin ligase TRIM2 regulates neuronal polarization.

The establishment of a polarized morphology with a single axon and multiple dendrites is an essential step during neuronal differentiation. This cellular polarization is largely depending on changes in the dynamics of the neuronal cytoskeleton. Here, we show that the tripartite motif (TRIM)-NHL protein TRIM2 is regulating axon specification in cultured mouse hippocampal neurons, where one of several initially indistinguishable neurites is selected to become the axon. Suppression of TRIM2 by RNA interference results in the loss of neuronal polarity while over-expression of TRIM2 induces the specification of multiple axons. TRIM2 conducts its function during neuronal polarization by ubiquitination of the neurofilament light chain. Together, our results imply an important function of TRIM2 for axon outgrowth during development.