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Researchers have revealed minuscule features on the leaves of a common desert plant that allow it to collect water from moist air. © 2 0 1 6 M a c m i l l a n P u b l i s h e r s L i m i t e d. A l l r i g h t s r e s e r v e d .

The radial migration of newborn neurons is critical for the lamination of the cerebral cortex. Proper neuronal migration requires precise and rapid reorganization of the actin and microtubule cytoskeleton. However, the underlying signaling mechanisms controlling cytoskeletal reorganization are not well understood. Here, we show that Mst3, a serine/threonine kinase highly expressed in the developing mouse brain, is essential for radial neuronal migration and final neuronal positioning in the developing mouse neocortex. Mst3 silencing by in utero electroporation perturbed the multipolar-to-bipolar transition of migrating neurons and significantly retards radial migration. Although the kinase activity of Mst3 is essential for its functions in neuronal morphogenesis and migration, it is regulated via its phosphorylation at Ser79 by a serine/threonine kinase, cyclin-dependent kinase 5 (Cdk5). Our results show that Mst3 regulates neuronal migration through modulating the activity of RhoA, a Rho-GTPase critical for actin cytoskeletal reorganization. Mst3 phosphorylates RhoA at Ser26, thereby negatively regulating the GTPase activity of RhoA. Importantly, RhoA knockdown successfully rescues neuronal migration defect in Mst3-knockdown cortices. Our findings collectively suggest that Cdk5-Mst3 signaling regulates neuronal migration via RhoA-dependent actin dynamics.

A long-standing hypothesis posits that a G protein-coupled signaling pathway mediates β-adrenergic nervous system functions, including learning and memory. Here we report that memory retrieval (reactivation) induces the activation of β1-adrenergic β-arrestin signaling in the brain, which stimulates ERK signaling and protein synthesis, leading to postreactivation memory restabilization. β-Arrestin2-deficient mice exhibit impaired memory reconsolidation in object recognition, Morris water maze, and cocaine-conditioned place preference paradigms. Postreactivation blockade of both brain β-adrenergic Gs protein- and β-arrestin–dependent pathways disrupts memory reconsolidation. Unexpectedly, selective blockade of the Gs/cAMP/PKA signaling but not the β-arrestin/ERK signaling by the biased β-adrenergic ligands does not inhibit reconsolidation. Moreover, the expression of β-arrestin2 in the entorhinal cortex of β-arrestin 2–deficient mice rescues β1-adrenergic ERK signaling and reconsolidation in a G protein pathway-independent manner. We demonstrate that β-arrestin–biased signaling regulates memory reconsolidation and reveal the potential for β-arrestin–biased ligands in the treatment of memory-related disorders.

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During cerebral cortex development, pyramidal neurons migrate through the intermediate zone and integrate into the cortical plate. These neurons undergo the multipolar-bipolar transition to initiate radial migration. While perturbation of this polarity acquisition leads to cortical malformations, how this process is initiated and regulated is largely unknown. Here we report that the specific upregulation of the Rap1 guanine nucleotide exchange factor, RapGEF2, in migrating neurons corresponds to the timing of this polarity transition. In utero electroporation and live-imaging studies reveal that RapGEF2 acts on the multipolar-bipolar transition during neuronal migration via a Rap1/N-cadherin pathway. Importantly, activation of RapGEF2 is controlled via phosphorylation by a serine/threonine kinase Cdk5, whose activity is largely restricted to the radial migration zone. Thus, the specific expression and Cdk5-dependent phosphorylation of RapGEF2 during multipolar-bipolar transition within the intermediate zone are essential for proper neuronal migration and wiring of the cerebral cortex.

X-ray absorption fine structure spectroscopy (XAFS), a powerful tool for the study of the local environment of a particular element, especially the luminescent center, was introduced to investigate the correlation between luminescent properties and local structure around Eu3+ ions in YBO3:Eu nanocrystals, which was prepared by a more facile sol−gel pyrolysis process in our previous work and which exhibited size-dependent chromaticity, that is, a relatively better chromaticity could be obtained in the smaller-sized samples. The YBO3:Eu phosphors were studied at the Eu LIII edge (6977 eV), and XAFS results showed that the higher levels of disorder in the nanocrystals were responsible for the relatively better chromaticity. By analyzing recent studies on the nanosized materials, we considered that the high levels of disorder in the YBO3:Eu nanocrystals resulted from the low levels of crystallization.