Genes and behaviour

Parallel FoxP1 and FoxP2 expression in songbird and human brain predicts functional interaction. Teramitsu, I. et al. J. Neurosci. 24, 3152–3163 (2004)

FoxP2 expression in avian vocal learners and non-learners. Haesler, S. et al. J. Neurosci. 24, 3164–3175 (2004)

FOXP2 is a forkhead gene that was identified as the gene that is mutated in a family with an autosomal-dominant speech and language disorder. These two papers provide evidence that it might also be involved in learned vocalisation in birds. Teramitsu et al. show that FoxP2 and the forkhead family member FoxP1 are expressed in an overlapping pattern in the songbird, in a corticostriatal pattern that reflects that structural abnormalities seen in the human patients and that is similar to the localization of FOXP1 and FOXP2 in the human fetal brain. Haesler et al. find that FoxP2 expression in songbirds varies seasonally, being stronger at times when vocal learning occurs in brain structures that are associated with song learning.

Neural development

A role for ligand-gated ion channels in rod photoreceptor development. Young, T. L. & Cepko, C. L. Neuron 41, 867–879 (2004)

Taurine is present in the developing vertebrate CNS and has been shown to potentiate the development of rod photoreceptors. Young and Cepko now show that this effect is probably mediated by glycine α2 and GABAA (γ-aminobutyric acid, subtype A) receptors. Strychnine (a glycine receptor antagonist) and bicuculline (a GABA receptor antagonist) inhibited the ability of taurine to induce the production of rod photoreceptors, and a gain-of-function study showed that signalling through glycine α2 receptors caused cells to leave mitosis and increased the number of rods. Consistent with this, a targeted knockdown of glycine α2 receptors led to a decrease in the number of rods but an increase in other retinal cells.

Synaptic physiology

The structural organization of the readily releasable pool of synaptic vesicles. Rizzoli, S. O. & Betz, W. J. Science 303, 2037–2039 (2004)

The authors labelled the readily releasable pool (RRP) — those vesicles that are recruited first during neuronal activity — with a fluorescent dye, FM1-43, that is taken up by recycling vesicles. Although it might be expected that the RRP would consist of those vesicles closest to the presynaptic membrane, Rizzoli and Betz found that the labelled vesicles were scattered throughout the nerve terminal, except for the centre of the cluster of vesicles. So, it seems that vesicle recruitment does not depend on proximity to the release sites, but instead involves a different mechanism of mobilization.