Axon-dendrite polarity is a cardinal feature of neuronal morphology essential for information flow. Here we report a differential distribution of GSK-3beta activity in the axon versus the dendrites. A constitutively active GSK-3beta mutant inhibited axon formation, whereas multiple axons formed from a single neuron when GSK-3beta activity was reduced by pharmacological inhibitors, a peptide inhibitor, or siRNAs. An active mechanism for maintaining neuronal polarity was revealed by the conversion of preexisting dendrites into axons upon GSK-3 inhibition. Biochemical and functional data show that the Akt kinase and the PTEN phosphatase are upstream of GSK-3beta in determining neuronal polarity. Our results demonstrate that there are active mechanisms for maintaining as well as establishing neuronal polarity, indicate that GSK-3beta relays signaling from Akt and PTEN to play critical roles in neuronal polarity, and suggest that application of GSK-3beta inhibitors can be a novel approach to promote generation of new axons after neural injuries.

Water‐mass transports in the vast and seemingly quiescent abyssal ocean, basically along topographically‐guided pathways, play a pivotal role in the Earth's climate. The pulse of abyssal circulations can be taken with observations at topographic choke points. The Yap‐Mariana Junction (YMJ) is the exclusive choke point through which the Lower Circumpolar Deep Water (LCDW) enters the Philippine Sea. Here, we quantify the LCDW transport and its variability based on mooring observations at the YMJ and the Mariana Trench (MT). The LCDW flows northward toward the Philippine Sea as an intensified current on the western side of the YMJ, with maximum mean velocity reaching 7.6 cm/s. The mean LCDW transports through the MT and the YMJ are 2.2 ± 1.0 Sv and 2.1 ± 0.4 Sv, respectively. Reversal flow at autumn in both the YMJ and MT is captured, indicating seasonal variability of the abyssal flow.