New pool of cortical interneuron precursors in the early postnatal dorsal white matter.

The migration of cortical γ-aminobutyric acidergic interneurons has been extensively studied in rodent embryos, whereas few studies have documented their postnatal migration. Combining in vivo analysis together with time-lapse imaging on cortical slices, we explored the origin and migration of cortical interneurons during the first weeks of postnatal life. Strikingly, we observed that a large pool of GAD65-GFP-positive cells accumulate in the dorsal white matter region during the first postnatal week. Part of these cells divides and expresses the transcription factor paired box 6 indicating the presence of local transient amplifying precursors. The vast majority of these cells are immature interneurons expressing the neuronal marker doublecortin and partly the calcium-binding protein calretinin. Time-lapse imaging reveals that GAD65-GFP-positive neurons migrate from the white matter pool into the overlying anterior cingulate cortex (aCC). Some interneurons in the postnatal aCC express the same immature neuronal markers suggesting ongoing migration of calretinin-positive interneurons. Finally, bromodeoxyuridine incorporation experiments confirm that a small fraction of interneurons located in the aCC are generated during the early postnatal period. These results altogether reveal that at postnatal ages, the dorsal white matter contains a pool of interneuron precursors that divide and migrate into the aCC.

The Munc13 proteins differentially regulate readily releasable pool dynamics and calcium-dependent recovery at a central synapse.

The Munc13 gene family encodes molecules located at the synaptic active zone that regulate the reliability of synapses to encode information over a wide range of frequencies in response to action potentials. In the CNS, proteins of the Munc13 family are critical in regulating neurotransmitter release and synaptic plasticity. Although Munc13-1 is essential for synaptic transmission, it is paradoxical that Munc13-2 and Munc13-3 are functionally dispensable at some synapses, although their loss in other synapses leads to increases in frequency-dependent facilitation. We addressed this issue at the calyx of Held synapse, a giant glutamatergic synapse that we found to express all these Munc13 isoforms. We studied their roles in the regulation of synaptic transmission and their impact on the reliability of information transfer. Through detailed electrophysiological analyses of Munc13-2, Munc13-3, and Munc13-2-3 knock-out and wild-type mice, we report that the combined loss of Munc13-2 and Munc13-3 led to an increase in the rate of calcium-dependent recovery and a change in kinetics of release of the readily releasable pool. Furthermore, viral-mediated overexpression of a dominant-negative form of Munc13-1 at the calyx demonstrated that these effects are Munc13-1 dependent. Quantitative immunohistochemistry using Munc13-fluorescent protein knock-in mice revealed that Munc13-1 is the most highly expressed Munc13 isoform at the calyx and the only one highly colocalized with Bassoon at the active zone. Based on these data, we conclude that Munc13-2 and Munc13-3 isoforms limit the ability of Munc13-1 to regulate calcium-dependent replenishment of readily releasable pool and slow pool to fast pool conversion in central synapses.

Anàlisi dels canvis dels usos i cobertes del sòl al massís dels Ports (Part Nord) a les comarques del Baix Ebre i Terra Alta

El treball pretén establir en quina mesura ha afectat l’abandó del mon rural en els canvis dels usos del sòl i en l’estructura del paisatge. Es presenta una breu descripció de la part nord del Parc Natural dels Ports així com de la història d’aquest en relació amb l’ésser humà. Es recullen els mètodes i materials utilitzats per a la preparació del material cartogràfic i l’execució d’eines d’informació geogràfica (SIG) així com la descripció dels estadístics socioeconòmics dels municipis estudiats. Els resultats, igual que els mètodes, s’agrupen en canvis de cobertes, estructura del paisatge, canvis en relació a paràmetres físics del terreny i evolució de les estadístiques socioeconòmiques.