Depression, a severe psychiatric disorder, has been studied for decades, but the underlying mechanisms still remain largely unknown. Depression is closely associated with alterations in dendritic spine morphology and spine density. Therefore, understanding dendritic spines is vital for uncovering the mechanisms underlying depression. Several chronic stress models, including chronic restraint stress (CRS), chronic unpredictable mild stress (CUMS), and chronic social defeat stress (CSDS), have been used to recapitulate depression-like behaviors in rodents and study the underlying mechanisms. In comparison with CRS, CUMS overcomes the stress habituation and has been widely used to model depression-like behaviors. CSDS is one of the most frequently used models for depression, but it is limited to the study of male mice. Generally, chronic stress causes dendritic atrophy and spine loss in the neurons of the hippocampus and prefrontal cortex. Meanwhile, neurons of the amygdala and nucleus accumbens exhibit an increase in spine density. These alterations induced by chronic stress are often accompanied by depression-like behaviors. However, the underlying mechanisms are poorly understood. This review summarizes our current understanding of the chronic stress-induced remodeling of dendritic spines in the hippocampus, prefrontal cortex, orbitofrontal cortex, amygdala, and nucleus accumbens and also discusses the putative underlying mechanisms.

The 13q21 tumor suppressor locus, as defined by chromosomal deletion, harbors the KLF5 transcription factor which may have tumor suppressor function. To investigate whether KLF5 plays a role in breast cancer, we evaluated all genes and/or expressed sequence tags (ESTs) within a 3.3 Mb common region of deletion at 13q21. Of these, only KLF5 mRNA was expressed at high levels in non-neoplastic breast epithelial cells and in normal human mammary tissue, but at lower levels in various breast cancer cell lines. Using the real time TaqMan PCR assay, hemizygous deletion at KLF5 was detected in 13 out of 30, or 43% of breast cancer cell lines tested, and various degrees of loss of expression were detected in 21 out of 30, or 70% of these cell lines. Each of the cases with hemizygous deletion also exhibited loss of KLF5 expression, suggesting that loss of expression can result from chromosomal deletion, and that KLF5 may undergo haploinsufficiency during carcinogenesis. Only one of the 30 breast cancer cell lines tested exhibited a mutation in KLF5, and neither promoter methylation nor homozygous deletion was detected in any of the cell lines. In contrast, loss of heterozygosity (LOH) was frequently detected at KLF5. Re-expression of wild-type KLF5 in T-47D breast cancer cells significantly inhibited colony formation in these cells. Of the KLF5-transfected clones that did form colonies, none were found to express KLF5 mRNA. These findings suggest that loss of function by deletion and/or loss of expression frequently occurs at KLF5, and KLF5 suppresses tumor cell growth in breast cancer.

Noninvasive or minimally invasive prediction of tumor metastatic potential would facilitate individualized cancer management. Studies were performed on a panel of human melanoma xenografts that spanned the full range of metastatic potential measured by an in vivo lung colony assay and an in vitro membrane invasion culture system. Three imaging methods potentially transferable to the clinic [dynamic contrast-enhanced (DCE) MRI, T1-MRI, and low-temperature fluorescence imaging (measurable on biopsy specimens)] distinguished between relatively less metastatic and more metastatic human melanoma xenografts in nude mice. DCE-MRI, analyzed with the shutterspeed relaxometric algorithm and using an arterial input function simultaneously measured in the left ventricle of the mouse heart, yielded a blood transfer rate constant, Ktrans, that measures vascular perfusion/permeability. Ktrans was significantly higher in the core of the least metastatic melanoma (A375P) than in the core of the most metastatic melanoma (C8161). C8161 melanoma had more blood vascular structures but fewer functional blood vessels than A375P melanoma. The A375P melanoma exhibited mean T1 values that were significantly higher than those of C8161 melanoma. Measurements of T1 and T2 relaxation times did not differ significantly between these 2 melanomas. The mitochondrial redox ratio, Fp/(Fp ؉ NADH), where Fp and NADH are the fluorescences of oxidized flavoproteins and reduced pyridine nucleotides, respectively, varied linearly with the in vitro invasive potential of the 5 melanoma cell lines (A375P, A375M, A375P10, A375P5, and C8161). This study shows that a harsh microenvironment may promote melanoma metastasis and provides potential biomarkers of metastatic potential. dynamic contrast enhanced MRI ͉ mitochondrial redox state ͉ T1rho ͉ invasive potential ͉ human melanoma xenografts M elanoma is treated primarily by surgical excision, which is often curative if the tumor is detected in its early stages. However, if recurrence with metastasis occurs, the prognosis is very poor because effective methods for treating systemic disease are not available. Evaluation of the metastatic potential of a melanoma at the time of surgery could determine the aggressiveness of the surgical procedures to be undertaken and the frequency of postsurgical surveillance.Criteria currently available for staging human melanoma malignancies and predicting their metastatic potential include histopathological evaluation, height of the lesion, disease progression to sentinel lymph nodes, and genomic and proteomic approaches currently under development and evaluation (1-5). The objective of this study was to explore a variety of noninvasive and biopsy-based imaging methods that could be used to better distinguish between aggressive and indolent neoplasms and to identify biomarkers of tumor aggressiveness.We chose to study melanoma because of the availability of a panel of human melanoma cell lines and their corresponding xenografts in immunosuppressed mice that span the full rang...

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gene copy number variation and the resulting overexpression of the protein E6AP is directly linked to autism spectrum disorders (ASDs). However, the underlying cellular and molecular neurobiology remains less clear. Here we report the role of ASD-related increased dosage of Ube3A/E6AP in dendritic arborization during brain development. We show that increased E6AP expression in primary cultured neurons leads to a reduction in dendritic branch number and length. The E6AP-dependent remodeling of dendritic arborization results from retraction of dendrites by thinning and fragmentation at the tips of dendrite branches, leading to shortening or removal of dendrites. This remodeling effect is mediated by the ubiquitination and degradation of XIAP (X-linked inhibitors of aptosis protein) by E6AP, which leads to activation of caspase-3 and cleavage of microtubules. , male and female 2X ASD mice show decreased XIAP levels, increased caspase-3 activation, and elevated levels of tubulin cleavage. Consistently, dendritic branching and spine density are reduced in cortical neurons of 2X ASD mice. In revealing an important role for Ube3A/E6AP in ASD-related developmental alteration in dendritic arborization and synapse formation, our findings provide new insights into the pathogenesis of Ube3A/E6AP-dependent ASD. Copy number variation of the gene and aberrant overexpression of the gene product E6AP protein is a common cause of autism spectrum disorders (ASDs). During brain development, dendritic growth and remodeling play crucial roles in neuronal connectivity and information integration. We found that in primary neurons and in Ube3A transgenic autism mouse brain, overexpression of E6AP leads to significant loss of dendritic arborization. This effect is mediated by the ubiquitination of XIAP (X-linked inhibitor of aptosis protein) by E6AP, subsequent activation of caspases, and the eventual cleavage of microtubules, leading to local degeneration and retraction at the tips of dendritic branches. These findings demonstrate dysregulation in neuronal structural stability as a major cellular neuropathology in ASD.