The phenotypic changes of increased motility and invasiveness of cancer cells are reminiscent of the epithelial-mesenchymal transition (EMT) that occurs during embryonic development. Snail, a zinc-finger transcription factor, triggers this process by repressing E-cadherin expression; however, the mechanisms that regulate Snail remain elusive. Here we find that Snail is highly unstable, with a short half-life about 25 min. We show that GSK-3beta binds to and phosphorylates Snail at two consensus motifs to dually regulate the function of this protein. Phosphorylation of the first motif regulates its beta-Trcp-mediated ubiquitination, whereas phosphorylation of the second motif controls its subcellular localization. A variant of Snail (Snail-6SA), which abolishes these phosphorylations, is much more stable and resides exclusively in the nucleus to induce EMT. Furthermore, inhibition of GSK-3beta results in the upregulation of Snail and downregulation of E-cadherin in vivo. Thus, Snail and GSK-3beta together function as a molecular switch for many signalling pathways that lead to EMT.

The results are consistent with the effects of electrical stimulation involving a pathway of extracellular Ca(2+) influx via voltage-gated calcium channels rather than from intracellular Ca(2+) repositories; and with downstream roles for calmodulin, calcineurin and nuclear factor of activated T-cells (NF-AT) rather than for phospholipase C and IP(3).

Antibodies against human Rad51 protein were used to examine the distribution of Rad51 on meiotic chromatin in mouse spermatocytes and oocytes as well as chicken oocytes during sequential stages of meiosis. We observed the following dynamic changes in distribution of Rad51 during meiosis: (1) in early leptotene nuclei there are multiple, apparently randomly distributed, foci that by late leptonema become organized into tracks of foci. (2) These foci persist into zygonema, but most foci are now localized on Rad51-positive axes that correspond to lateral elements of the synaptonemal complex. As homologs synapse foci from homologous axes fuse. The distribution and involvement of Rad51 foci as contact points between homologs suggest that they may be components to early recombination nodules. (3) As pachynema progresses the number of foci drops dramatically; the temporal occurrence (mice) and physical and numerical distribution of foci on axes (chickens) suggest that they may be a component of late recombination nodules. (4) In early pachynema there are numerous Rad51 foci on the single axis of the X (mouse spermatocytes) or the Z (chicken oocytes) chromosomes that neither pair, nor recombine. (5) In late pachynema in mouse spermatocytes, but not oocytes, the Rad51 signal is preferentially enhanced at both ends of all the bivalents. As bivalents in spermatocytes, but not oocytes, begin to desynapse at diplonema they are often held together at these Rad51-positive termini. These observations parallel observations that recombination rates are exceptionally high near chromosome ends in male but not female eutherian mammals. (6) From diakinesis through metaphase I, Rad51 protein is detected as low-intensity fluorescent doublets that localize with CREST-specific antigens (kinetochores), suggesting that Rad51 participates, at least as a structural component of the materials involved, in sister kinetochore cohesiveness. Finally, the changes in Rad51 distribution during meiosis do not appear to be species specific, but intrinsic to the meiotic process.

Background and Purpose-In vitro and in vivo studies have demonstrated neuroprotective actions of lithium. The present study investigated the effect of a low dose of lithium on infarct volume and neurological outcome as well as on apoptotic and inflammatory processes in rats exposed to focal ischemia. Methods-Cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 90 minutes followed by reperfusion. Lithium (1 mmol/kg) was given subcutaneously daily for 14 days before the onset of MCAO and 2 days thereafter. Blood parameters and cerebral blood flow were assessed before, during, and after MCAO. Rats were examined for neurological deficits 24 and 48 hours after MCAO. Two days after MCAO, the brains were removed for immunohistochemical evaluation of caspase-3, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), activated microglia, and the expression of AP-1 proteins (c-Fos and c-Jun). Infarct volume was assessed by cresyl violet staining. Results-Pretreatment with lithium did not alter cerebral blood flow or blood parameters. Neurological deficits were significantly decreased in rats treated with lithium at 24 and 48 hours after ischemia. Infarct volume was reduced in rats treated with lithium at 48 hours after ischemia. Lithium significantly decreased the ischemia-induced caspase-3 immunoreactivity and TUNEL staining as well as the AP-1 protein expression in the penumbra of the ischemic cortex.No changes in activated microglia were observed. Conclusions-The

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