Process Outgrowth

Filopodial calcium transients regulate growth cone motility and guidance through local activation of calpain. Robles, E. et al. Neuron 38, 597–609 (2003)

Calcium transients in filopodia affect growth cone motility, but their downstream effectors are unknown. Here, the authors show that calpain is one of these effectors; it promotes a decrease in tyrosine dephosphorylation, the net effect of which is filopodial stabilization, reduced outgrowth and repulsive turning.

Neurophysiology

Action potentials in basal and oblique dendrites of rat neocortical pyramidal neurons. Antic, S. D. J. Physiol. (Lond.) 9 May 2003 (doi:10.1113/jphysiol.2002.033746)

The apical dendrites of pyramidal cells markedly modulate backpropagating action potentials, owing to the existence of active conductances. By using voltage-sensitive dyes, the author found this not to be the case for basal and oblique dendrites, which behaved as an integral part of the axosomatic compartment.

Sensory Systems

NompC TRP channel required for vertebrate sensory hair cell mechanotransduction Sidi, S. et al. Science. 12 June 2003 (doi:10.1126/science.1084370)

The mechanosensitive channel that mediates the excitation of hair cells in the inner ear in response to sound is unknown. Here, the authors identify the zebrafish homologue of the Drosophila protein NompC as the missing channel. Reducing NompC expression in zebrafish embryos led to a reduction of electrical responses in hair cells, deafness and loss of balance.

Ion Channels

Agonist unbinding from receptor dictates the nature of deactivation kinetics of G protein-gated K+ channels. Benians, A. et al. Proc. Natl Acad. Sci. USA 100, 6239–6244 (2003)

G protein-gated K+ channels are activated as a result of agoinst binding to G-protein-coupled receptors (GPCRs), and their deactivation depends on the hydrolysis of GTP by Gα after agonist removal. Here, the authors identify a new deactivation mechanism; for some agonists, the rate of unbinding from the GPCR is the key step in the termination of channel activity.

Neurogenetics

Neurons but not glial cells show reciprocal imprinting of sense and antisense transcripts of Ube3a. Yamasaki, K. et al. Hum. Mol. Genet. 12, 837–847 (2003)

The authors report that the mouse Ube3a gene, which codes for a ubiquitin ligase, is transcribed from both alleles in glia, but only from the maternal allele in neurons. This is the first evidence that genomic imprinting is cell-type specific in the brain.