Changes in tau phosphorylation levels in the hippocampus and frontal cortex following chronic stress.

Studies have indicated that early-life or early-onset depression is associated with a 2- to 4-fold increased risk of developing Alzheimer's disease (AD). In AD, aggregation of an abnormally phosphorylated form of the tau protein may be a key pathological event. Tau is known to play a major role in promoting microtubule assembly and stabilization, and in maintaining the normal morphology of neurons. Several studies have reported that stress may induce tau phosphorylation. The main aim of the present study was to investigate possible alterations in the tau protein in the hippocampus and frontal cortex of 32 male Sprague-Dawley rats exposed to chronic unpredictable mild stress (CUMS) and then re-exposed to CUMS to mimic depression and the recurrence of depression, respectively, in humans. We evaluated the effects of CUMS, fluoxetine, and CUMS re-exposure on tau and phospho-tau. Our results showed that a single exposure to CUMS caused a significant reduction in sucrose preference, indicating a state of anhedonia. The change in behavior was accompanied by specific alterations in phospho-tau protein levels, but fluoxetine treatment reversed the CUMS-induced impairments. Moreover, changes in sucrose preference and phospho-tau were more pronounced in rats re-exposed to CUMS than in those subjected to a single exposure. Our results suggest that changes in tau phosphorylation may contribute to the link between depression and AD.

Changes in tau phosphorylation levels in the hippocampus and frontal cortex following chronic stress

Studies have indicated that early-life or early-onset depression is associated with a 2- to 4-fold increased risk of developing Alzheimers disease (AD). In AD, aggregation of an abnormally phosphorylated form of the tau protein may be a key pathological event. Tau is known to play a major role in promoting microtubule assembly and stabilization, and in maintaining the normal morphology of neurons. Several studies have reported that stress may induce tau phosphorylation. The main aim of the present study was to investigate possible alterations in the tau protein in the hippocampus and frontal cortex of 32 male Sprague-Dawley rats exposed to chronic unpredictable mild stress (CUMS) and then re-exposed to CUMS to mimic depression and the recurrence of depression, respectively, in humans. We evaluated the effects of CUMS, fluoxetine, and CUMS re-exposure on tau and phospho-tau. Our results showed that a single exposure to CUMS caused a significant reduction in sucrose preference, indicating a state of anhedonia. The change in behavior was accompanied by specific alterations in phospho-tau protein levels, but fluoxetine treatment reversed the CUMS-induced impairments. Moreover, changes in sucrose preference and phospho-tau were more pronounced in rats re-exposed to CUMS than in those subjected to a single exposure. Our results suggest that changes in tau phosphorylation may contribute to the link between depression and AD.

Isolation of novel microsatellite markers from Paralichthys lethostigma (Paralichthyidae) and their cross-species application in Pleuronectiformes.

We investigated the genetic diversity of the southern flounder Paralichthys lethostigma. Microsatellite-enriched libraries were constructed and novel microsatellite markers were developed and applied for genetic detection of wild populations. Cross-species amplification was also conducted in five pleuronectiforme species. Of 45 randomly selected and sequenced clones, 43 contained a CA or GA repeat motif. Fourteen pairs of primers were designed to investigate the polymorphism and genetic structure of a wild population collected from North Carolina State coastal waters. Two loci were monomorphic and 12 loci were polymorphic. The number of alleles per polymorphic locus ranged from 2 to 16, with an average of 7.3, and the expected heterozygosity per locus ranged from 0.10 to 0.92, with an average of 0.58. Cross-species amplification showed that most of the markers could successfully amplify Paralichthys olivaceus DNAs, few markers amplified in Verasper variegatus and Verasper moseri, and none of them could amplify Scophthatmus maximus and Cynoglossus semilaevis DNAs. The isolated polymorphic markers would be useful for the genetic breeding and assessment of genetic variation within the genus Paralichthys.