Delta-catenin/NPRAP: A new member of the glycogen synthase kinase-3beta signaling complex that promotes beta-catenin turnover in neurons

Inhibition of δ-catenin palmitoylation slows the progression of prostate cancer

Prostate cancer (PCa) is the second leading cause of death in males. It has been reported that δ-catenin expression is upregulated during the late stage of prostate cancer. Palmitoylation promotes protein transport to the cytomembrane and regulates protein localization and function. However, the effect of δ-catenin palmitoylation on the regulation of cancer remains unknown. In this study, we utilized prostate cancer cells overexpressing mutant δ-catenin (J6A cells) to induce a depalmitoylation phenotype and investigate its effect on prostate cancer. Our results indicated that depalmitoylation of δ-catenin not only reduced its membrane expression but also promoted its degradation in the cytoplasm, resulting in a decrease in the effect of EGFR and E-cadherin signaling. Consequently, depalmitoylation of δ-catenin reduced the proliferation and metastasis of prostate cancer cells. Our findings provide novel insights into potential therapeutic strategies for controlling the progression of prostate cancer through palmitoylation-based targeting of δ-catenin.

Loss of ctnnd2b affects neuronal differentiation and behavior in zebrafish

Delta-catenin (CTNND2) is an adhesive junction associated protein belonging to the family of p120 catenins. The human gene is located on the short arm of chromosome 5, the region deleted in Cri-du-chat syndrome (OMIM #123450). Heterozygous loss of CTNND2 has been linked to a wide spectrum of neurodevelopmental disorders such as autism, schizophrenia, and intellectual disability. Here we studied how heterozygous loss of ctnnd2b affects zebrafish embryonic development, and larvae and adult behavior. First, we observed a disorganization of neuronal subtypes in the developing forebrain, namely the presence of ectopic isl1-expressing cells and a local reduction of GABA-positive neurons in the optic recess region. Next, using time-lapse analysis, we found that the disorganized distribution of is1l-expressing forebrain neurons resulted from an increased specification of Isl1:GFP neurons. Finally, we studied the swimming patterns of both larval and adult heterozygous zebrafish and observed an increased activity compared to wildtype animals. Overall, this data suggests a role for ctnnd2b in the differentiation cascade of neuronal subtypes in specific regions of the vertebrate brain, with repercussions in the animal's behavior.

The autism-associated loss of δ-catenin functions disrupts social behavior

δ-catenin is expressed in excitatory synapses and functions as an anchor for the glutamatergic AMPA receptor (AMPAR) GluA2 subunit in the postsynaptic density. The glycine 34 to serine (G34S) mutation in the δ-catenin gene has been found in autism spectrum disorder (ASD) patients and results in loss of δ-catenin functions at excitatory synapses, which is presumed to underlie ASD pathogenesis in humans. However, how the G34S mutation causes loss of δ-catenin functions to induce ASD remains unclear. Here, using neuroblastoma cells, we identify that the G34S mutation increases glycogen synthase kinase 3β (GSK3β)-dependent δ-catenin degradation to reduce δ-catenin levels, which likely contributes to the loss of δ-catenin functions. Synaptic δ-catenin and GluA2 levels in the cortex are significantly decreased in mice harboring the δ-catenin G34S mutation. The G34S mutation increases glutamatergic activity in cortical excitatory neurons while it is decreased in inhibitory interneurons, indicating changes in cellular excitation and inhibition. δ-catenin G34S mutant mice also exhibit social dysfunction, a common feature of ASD. Most importantly, pharmacological inhibition of GSK3β activity reverses the G34S-induced loss of δ-catenin function effects in cells and mice. Finally, using δ-catenin knockout mice, we confirm that δ-catenin is required for GSK3β inhibition-induced restoration of normal social behavior in δ-catenin G34S mutant animals. Taken together, we reveal that the loss of δ-catenin functions arising from the ASD-associated G34S mutation induces social dysfunction via alterations in glutamatergic activity and that GSK3β inhibition can reverse δ-catenin G34S-induced synaptic and behavioral deficits.

The autism-associated loss of δ-catenin functions disrupts social behaviors

δ-catenin is expressed in excitatory synapses and functions as an anchor for the glutamatergic AMPA receptor (AMPAR) GluA2 subunit in the postsynaptic density. The glycine 34 to serine (G34S) mutation in the δ-catenin gene is found in autism spectrum disorder (ASD) patients and induces loss of δ-catenin functions at excitatory synapses, which is presumed to underlie ASD pathogenesis in humans. However, how the G34S mutation causes loss of δ-catenin functions to induce ASD remains unclear. Here, using neuroblastoma cells, we discover that the G34S mutation generates an additional phosphorylation site for glycogen synthase kinase 3β (GSK3β). This promotes δ-catenin degradation and causes the reduction of δ-catenin levels, which likely contributes to the loss of δ-catenin functions. Synaptic δ-catenin and GluA2 levels in the cortex are significantly decreased in mice harboring the δ-catenin G34S mutation. The G34S mutation increases glutamatergic activity in cortical excitatory neurons while it is decreased in inhibitory interneurons, indicating changes in cellular excitation and inhibition. δ-catenin G34S mutant mice also exhibit social dysfunction, a common feature of ASD. Most importantly, inhibition of GSK3β activity reverses the G34S-induced loss of δ-catenin function effects in cells and mice. Finally, using δ-catenin knockout mice, we confirm that δ-catenin is required for GSK3β inhibition-induced restoration of normal social behaviors in δ-catenin G34S mutant animals. Taken together, we reveal that the loss of δ-catenin functions arising from the ASD-associated G34S mutation induces social dysfunction via alterations in glutamatergic activity and that GSK3β inhibition can reverse δ-catenin G34S-induced synaptic and behavioral deficits.

Significance Statement

δ-catenin is important for the localization and function of glutamatergic AMPA receptors at synapses in many brain regions. The glycine 34 to serine (G34S) mutation in the δ-catenin gene is found in autism patients and results in the loss of δ-catenin functions. δ-catenin expression is also closely linked to other autism-risk genes involved in synaptic structure and function, further implying that it is important for the autism pathophysiology. Importantly, social dysfunction is a key characteristic of autism. Nonetheless, the links between δ-catenin functions and social behaviors are largely unknown. The significance of the current research is thus predicated on filling this gap by discovering the molecular, cellular, and synaptic underpinnings of the role of δ-catenin in social behaviors.

Faecal Proteomics and Functional Analysis of Equine Melanocytic Neoplasm in Grey Horses

Equine melanocytic neoplasm (EMN) is a common disease in older grey horses. The purpose of this study was to examine the potential proteins throughout EMN stages from faecal proteomic outlining using functional analysis. Faecal samples were collected from the rectum of 25 grey horses divided into three groups; normal group without EMN (n = 10), mild EMN (n = 6) and severe EMN (n = 9). Based on the results, 5910 annotated proteins out of 8509 total proteins were assessed from proteomic profiling. We observed differentially expressed proteins (DEPs) between the normal group and the EMN group, and 109 significant proteins were obtained, of which 28 and 81 were involved in metabolic and non-metabolic functions, respectively. We found 10 proteins that play a key role in lipid metabolism, affecting the tumour microenvironment and, consequently, melanoma progression. Interestingly, FOSL1 (FOS like 1, AP-1 transcription factor subunit) was considered as a potential highly expressed protein in a mild EMN group involved in melanocytes cell and related melanoma. Diacylglycerol kinase (DGKB), TGc domain-containing protein (Tgm2), structural maintenance of chromosomes 4 (SMC4) and mastermind-like transcriptional coactivator 2 (MAML2) were related to lipid metabolism, facilitating melanoma development in the severe-EMN group. In conclusion, these potential proteins can be used as candidate biomarkers for the monitoring of early EMN, the development of EMN, further prevention and treatment.

Repurposing cancer drugs identifies kenpaullone which ameliorates pathologic pain in preclinical models via normalization of inhibitory neurotransmission

Inhibitory GABA-ergic neurotransmission is fundamental for the adult vertebrate central nervous system and requires low chloride concentration in neurons, maintained by KCC2, a neuroprotective ion transporter that extrudes intracellular neuronal chloride. To identify Kcc2 gene expression‑enhancing compounds, we screened 1057 cell growth-regulating compounds in cultured primary cortical neurons. We identified kenpaullone (KP), which enhanced Kcc2/KCC2 expression and function in cultured rodent and human neurons by inhibiting GSK3ß. KP effectively reduced pathologic pain-like behavior in mouse models of nerve injury and bone cancer. In a nerve-injury pain model, KP restored Kcc2 expression and GABA-evoked chloride reversal potential in the spinal cord dorsal horn. Delta-catenin, a phosphorylation-target of GSK3ß in neurons, activated the Kcc2 promoter via KAISO transcription factor. Transient spinal over-expression of delta-catenin mimicked KP analgesia. Our findings of a newly repurposed compound and a novel, genetically-encoded mechanism that each enhance Kcc2 gene expression enable us to re-normalize disrupted inhibitory neurotransmission through genetic re-programming.

A Mouse Brain-based Multi-omics Integrative Approach Reveals Potential Blood Biomarkers for Ischemic Stroke

Stroke remains a leading cause of death and disability worldwide. Despite continuous advances, the identification of key molecular signatures in the hyper-acute phase of ischemic stroke is still a primary interest for translational research on stroke diagnosis, prognosis, and treatment. Data integration from high-throughput -omics techniques has become crucial to unraveling key interactions among different molecular elements in complex biological contexts, such as ischemic stroke. Thus, we used advanced data integration methods for a multi-level joint analysis of transcriptomics and proteomics data sets obtained from mouse brains at 2 h after cerebral ischemia. By modeling net-like correlation structures, we identified an integrated network of genes and proteins that are differentially expressed at a very early stage after stroke. We validated 10 of these deregulated elements in acute stroke, and changes in their expression pattern over time after cerebral ischemia were described. Of these, CLDN20, GADD45G, RGS2, BAG5, and CTNND2 were next evaluated as blood biomarkers of cerebral ischemia in mice and human blood samples, which were obtained from stroke patients and patients presenting stroke-mimicking conditions. Our findings indicate that CTNND2 levels in blood might potentially be useful for distinguishing ischemic strokes from stroke-mimicking conditions in the hyper-acute phase of the disease. Furthermore, circulating GADD45G content within the first 6 h after stroke could also play a key role in predicting poor outcomes in stroke patients. For the first time, we have used an integrative biostatistical approach to elucidate key molecules in the initial stages of stroke pathophysiology and highlight new notable molecules that might be further considered as blood biomarkers of ischemic stroke.

Intra-axonal Synthesis of SNAP25 Is Required for the Formation of Presynaptic Terminals

Localized protein synthesis is a mechanism for developing axons to react acutely and in a spatially restricted manner to extracellular signals. As such, it is important for many aspects of axonal development, but its role in the formation of presynapses remains poorly understood. We found that the induced assembly of presynaptic terminals required local protein synthesis. Newly synthesized proteins were detectable at nascent presynapses within 15 min of inducing synapse formation in isolated axons. The transcript for the t-SNARE protein SNAP25, which is required for the fusion of synaptic vesicles with the plasma membrane, was recruited to presynaptic sites and locally translated. Inhibition of intra-axonal SNAP25 synthesis affected the clustering of SNAP25 and other presynaptic proteins and interfered with the release of synaptic vesicles from presynaptic sites. This study reveals a critical role for the axonal synthesis of SNAP25 in the assembly of presynaptic terminals.

Frequently rearranged and overexpressed δ-catenin is responsible for low sensitivity of prostate cancer cells to androgen receptor and β-catenin antagonists

The mechanism of prostate cancer (PCa) progression towards the hormone refractory state remains poorly understood. Treatment options for such patients are limited and present a major clinical challenge. Previously, δ-catenin was reported to promote PCa cell growth in vitro and its increased level is associated with PCa progression in vivo. In this study we show that re-arrangements at Catenin Delta 2 (CTNND2) locus, including gene duplications, are very common in clinically significant PCa and may underlie δ-catenin overexpression. We find that δ-catenin in PCa cells exists in a complex with E-cadherin, p120, and α- and β-catenin. Increased expression of δ-catenin leads to its further stabilization as well as upregulation and stabilization of its binding partners. Resistant to degradation and overexpressed δ-catenin isoform activates Wnt signaling pathway by increasing the level of nuclear β-catenin and subsequent stimulation of Tcf/Lef transcription targets. Evaluation of responses to treatments, with androgen receptor (AR) antagonist and β-catenin inhibitors revealed that cells with high levels of δ-catenin are more resistant to killing with single agent treatment than matched control cells. We show that combination treatment targeting both AR and β-catenin networks is more effective in suppressing tumor growth than targeting a single network. In conclusion, targeting clinically significant PCa with high levels of δ–catenin with anti-androgen and anti β-catenin combination therapy may prevent progression of the disease to a castration-resistant state and, thus, represents a promising therapeutic strategy.

δ-Catenin (CTNND2) missense mutation in familial cortical myoclonic tremor and epilepsy

OBJECTIVE

To identify the causative gene in a large Dutch family with familial cortical myoclonic tremor and epilepsy (FCMTE).

METHODS

We performed exome sequencing for 3 patients of our FCMTE family. Next, we performed knock-down (shRNA) and rescue experiments by overexpressing wild-type and mutant human δ-catenin (CTNND2) proteins in cortical mouse neurons and compared the results with morphologic abnormalities in the postmortem FCMTE brain.

RESULTS

We identified a missense mutation, p.Glu1044Lys, in the CTNND2 gene that cosegregated with the FCMTE phenotype. The knock-down of Ctnnd2 in cultured cortical mouse neurons revealed increased neurite outgrowth that was rescued by overexpression of wild-type, but not mutant, CTNND2 and was reminiscent of the morphologic abnormalities observed in cerebellar Purkinje cells from patients with FCMTE.

CONCLUSIONS

We propose CTNND2 as the causal gene in FCMTE3. Functional testing of the mutant protein revealed abnormal neuronal sprouting, consistent with the abnormal cerebellar Purkinje cell morphology in patients with FCMTE.

Lithium increases synaptic GluA2 in hippocampal neurons by elevating the δ-catenin protein

Lithium (Li⁺) is a drug widely employed for treating bipolar disorder, however the mechanism of action is not known. Here we study the effects of Li⁺ in cultured hippocampal neurons on a synaptic complex consisting of δ-catenin, a protein associated with cadherins whose mutation is linked to autism, and GRIP, an AMPA receptor (AMPAR) scaffolding protein, and the AMPAR subunit, GluA2. We show that Li⁺ elevates the level of δ-catenin in cultured neurons. δ-catenin binds to the ABP and GRIP proteins, which are synaptic scaffolds for GluA2. We show that Li⁺ increases the levels of GRIP and GluA2, consistent with Li⁺-induced elevation of δ-catenin. Using GluA2 mutants, we show that the increase in surface level of GluA2 requires GluA2 interaction with GRIP. The amplitude but not the frequency of mEPSCs was also increased by Li⁺ in cultured hippocampal neurons, confirming a functional effect and consistent with AMPAR stabilization at synapses. Furthermore, animals fed with Li⁺ show elevated synaptic levels of δ-catenin, GRIP, and GluA2 in the hippocampus, also consistent with the findings in cultured neurons. This work supports a model in which Li⁺ stabilizes δ-catenin, thus elevating a complex consisting of δ-catenin, GRIP and AMPARs in synapses of hippocampal neurons. Thus, the work suggests a mechanism by which Li⁺ can alter brain synaptic function that may be relevant to its pharmacologic action in treatment of neurological disease.

Genetic alterations of δ-catenin/NPRAP/Neurojungin (CTNND2): functional implications in complex human diseases

Some genes involved in complex human diseases are particularly vulnerable to genetic variations such as single nucleotide polymorphism, copy number variations, and mutations. For example, Ras mutations account for over 30 % of all human cancers. Additionally, there are some genes that can display different variations with functional impact in different diseases that are unrelated. One such gene stands out: δ-catenin/NPRAP/Neurojungin with gene designation as CTNND2 on chromosome 5p15.2. Recent advances in genome wide association as well as molecular biology approaches have uncovered striking involvement of δ-catenin gene variations linked to complex human disorders. These disorders include cancer, bipolar disorder, schizophrenia, autism, Cri-du-chat syndrome, myopia, cortical cataract-linked Alzheimer's disease, and infectious diseases. This list has rapidly grown longer in recent years, underscoring the pivotal roles of δ-catenin in critical human diseases. δ-Catenin is an adhesive junction-associated protein in the delta subfamily of the β-catenin superfamily. δ-Catenin functions in Wnt signaling to regulate gene expression and modulate Rho GTPases of the Ras superfamily in cytoskeletal reorganization. δ-Catenin likely lies where Wnt signaling meets Rho GTPases and is a unique and vulnerable common target for mutagenesis in different human diseases.

PI3K mediated activation of GSK-3β reduces at-level primary afferent growth responses associated with excitotoxic spinal cord injury dysesthesias

Background

Neuropathic pain and sensory abnormalities are a debilitating secondary consequence of spinal cord injury (SCI). Maladaptive structural plasticity is gaining recognition for its role in contributing to the development of post SCI pain syndromes. We previously demonstrated that excitotoxic induced SCI dysesthesias are associated with enhanced dorsal root ganglia (DRG) neuronal outgrowth. Although glycogen synthase kinase-3β (GSK-3β) is a known intracellular regulator neuronal growth, the potential contribution to primary afferent growth responses following SCI are undefined. We hypothesized that SCI triggers inhibition of GSK-3β signaling resulting in enhanced DRG growth responses, and that PI3K mediated activation of GSK-3β can prevent this growth and the development of at-level pain syndromes.

Results

Excitotoxic SCI using intraspinal quisqualic acid (QUIS) resulted in inhibition of GSK-3β in the superficial spinal cord dorsal horn and adjacent DRG. Double immunofluorescent staining showed that GSK-3β^P was expressed in DRG neurons, especially small nociceptive, CGRP and IB4-positive neurons. Intrathecal administration of a potent PI3-kinase inhibitor (LY294002), a known GSK-3β activator, significantly decreased GSK-3β^P expression levels in the dorsal horn. QUIS injection resulted in early (3 days) and sustained (14 days) DRG neurite outgrowth of small and subsequently large fibers that was reduced with short term (3 days) administration of LY294002. Furthermore, LY294002 treatment initiated on the date of injury, prevented the development of overgrooming, a spontaneous at-level pain related dysesthesia.

Conclusions

QUIS induced SCI resulted in inhibition of GSK-3β in primary afferents and enhanced at-level DRG intrinsic growth (neurite elongation and initiation). Early PI3K mediated activation of GSK-3β attenuated QUIS-induced DRG neurite outgrowth and prevented the development of at-level dysesthesias.

Loss of δ-catenin function in severe autism

Autism is a multifactorial neurodevelopmental disorder affecting more males than females; consequently, under a multifactorial genetic hypothesis, females are affected only when they cross a higher biological threshold. We hypothesize that deleterious variants at conserved residues are enriched in severely affected patients arising from FEMFs (female-enriched multiplex families) with severe disease, enhancing the detection of key autism genes in modest numbers of cases. We show the utility of this strategy by identifying missense and dosage sequence variants in the gene encoding the adhesive junction-associated delta catenin protein (CTNND2) in FEMFs and demonstrating their loss-of-function effect by functional analyses in zebrafish embryos and cultured hippocampal neurons from wildtype and Ctnnd2 null mouse embryos. Finally, through gene expression and network analyses, we highlight a critical role for CTNND2 in neuronal development and an intimate connection to chromatin biology. Our data contribute to the understanding of the genetic architecture of autism and suggest that genetic analyses of phenotypic extremes, such as FEMFs, are of innate value in multifactorial disorders.

δ-Catenin, a Wnt/β-catenin modulator, reveals inducible mutagenesis promoting cancer cell survival adaptation and metabolic reprogramming

Mutations of Wnt/β-catenin signaling pathway has essential roles in development and cancer. Although β-catenin and adenomatous polyposis coli (APC) gene mutations are well established and are known to drive tumorigenesis, discoveries of mutations in other components of the pathway lagged, which hinders the understanding of cancer mechanisms. Here we report that δ-catenin (gene designation: CTNND2), a primarily neural member of the β-catenin superfamily that promotes canonical Wnt/β-catenin/LEF-1-mediated transcription, displays exonic mutations in human prostate cancer and promotes cancer cell survival adaptation and metabolic reprogramming. When overexpressed in cells derived from prostate tumor xenografts, δ-catenin gene invariably gives rise to mutations, leading to sequence disruptions predicting functional alterations. Ectopic δ-catenin gene integrating into host chromosomes is locus nonselective. δ-Catenin mutations promote tumor development in mouse prostate with probasin promoter (ARR2PB)-driven, prostate-specific expression of Myc oncogene, whereas mutant cells empower survival advantage upon overgrowth and glucose deprivation. Reprogramming energy utilization accompanies the downregulation of glucose transporter-1 and poly (ADP-ribose) polymerase cleavage while preserving tumor type 2 pyruvate kinase expression. δ-Catenin mutations increase β-catenin translocation to the nucleus and hypoxia-inducible factor 1α (HIF-1α) expression. Therefore, introducing δ-catenin mutations is an important milestone in prostate cancer metabolic adaptation by modulating β-catenin and HIF-1α signaling under glucose shortage to amplify its tumor-promoting potential.

14-3-3ε and ζ regulate neurogenesis and differentiation of neuronal progenitor cells in the developing brain

During brain development, neural progenitor cells proliferate and differentiate into neural precursors. These neural precursors migrate along the radial glial processes and localize at their final destination in the cortex. Numerous reports have revealed that 14-3-3 proteins are involved in many neuronal activities, although their functions in neurogenesis remain unclear. Here, using 14-3-3ε/ζ double knock-out mice, we found that 14-3-3 proteins are important for proliferation and differentiation of neural progenitor cells in the cortex, resulting in neuronal migration defects and seizures. 14-3-3 deficiency resulted in the increase of δ-catenin and the decrease of β-catenin and αN-catenin. 14-3-3 proteins regulated neuronal differentiation into neurons via direct interactions with phosphorylated δ-catenin to promote F-actin formation through a catenin/Rho GTPase/Limk1/cofilin signaling pathway. Conversely, neuronal migration defects seen in the double knock-out mice were restored by phosphomimic Ndel1 mutants, but not δ-catenin. Our findings provide new evidence that 14-3-3 proteins play important roles in neurogenesis and neuronal migration via the regulation of distinct signaling cascades.

The cross-talk between canonical and non-canonical Wnt-dependent pathways regulates P-glycoprotein expression in human blood-brain barrier cells

In this work, we investigate if and how transducers of the 'canonical' Wnt pathway, i.e., Wnt/glycogen synthase kinase 3 (GSK3)/β-catenin, and transducers of the 'non-canonical' Wnt pathway, i.e., Wnt/RhoA/RhoA kinase (RhoAK), cooperate to control the expression of P-glycoprotein (Pgp) in blood-brain barrier (BBB) cells. By analyzing human primary brain microvascular endothelial cells constitutively activated for RhoA, silenced for RhoA or treated with the RhoAK inhibitor Y27632, we found that RhoAK phosphorylated and activated the protein tyrosine phosphatase 1B (PTP1B), which dephosphorylated tyrosine 216 of GSK3, decreasing the GSK3-mediated inhibition of β-catenin. By contrast, the inhibition of RhoA/RhoAK axis prevented the activation of PTP1B, enhanced the GSK3-induced phosphorylation and ubiquitination of β-catenin, and reduced the β-catenin-driven transcription of Pgp. The RhoAK inhibition increased the delivery of Pgp substrates like doxorubicin across the BBB and improved the doxorubicin efficacy against glioblastoma cells co-cultured under a BBB monolayer. Our data demonstrate that in human BBB cells the expression of Pgp is controlled by a cross-talk between canonical and non-canonical Wnt pathways. The disruption of this cross-talk, e.g., by inhibiting RhoAK, downregulates Pgp and increases the delivery of Pgp substrates across the BBB.

Crebinostat: a novel cognitive enhancer that inhibits histone deacetylase activity and modulates chromatin-mediated neuroplasticity

Long-term memory formation is known to be critically dependent upon de novo gene expression in the brain. As a consequence, pharmacological enhancement of the transcriptional processes mediating long-term memory formation provides a potential therapeutic strategy for cognitive disorders involving aberrant neuroplasticity. Here we focus on the identification and characterization of small molecule inhibitors of histone deacetylases (HDACs) as enhancers of CREB (cAMP response element-binding protein)-regulated transcription and modulators of chromatin-mediated neuroplasticity. Using a CREB reporter gene cell line, we screened a library of small molecules structurally related to known HDAC inhibitors leading to the identification of a probe we termed crebinostat that produced robust activation of CREB-mediated transcription. Further characterization of crebinostat revealed its potent inhibition of the deacetylase activity of recombinant class I HDACs 1, 2, 3, and class IIb HDAC6, with weaker inhibition of the class I HDAC8 and no significant inhibition of the class IIa HDACs 4, 5, 7, and 9. In cultured mouse primary neurons, crebinostat potently induced acetylation of both histone H3 and histone H4 as well as enhanced the expression of the CREB target gene Egr1 (early growth response 1). Using a hippocampus-dependent, contextual fear conditioning paradigm, mice systemically administered crebinostat for a ten day time period exhibited enhanced memory. To gain insight into the molecular mechanisms of memory enhancement by HDAC inhibitors, whole genome transcriptome profiling of cultured mouse primary neurons treated with crebinostat, combined with bioinformatic analyses of CREB-target genes, was performed revealing a highly connected protein-protein interaction network reflecting modules of genes important to synaptic structure and plasticity. Consistent with these findings, crebinostat treatment increased the density of synapsin-1 punctae along dendrites in cultured neurons. Finally, crebinostat treatment of cultured mouse primary neurons was found to upregulate Bdnf (brain-derived neurotrophic factor) and Grn (granulin) and downregulate Mapt (tau) gene expression-genes implicated in aging-related cognitive decline and cognitive disorders. Taken together, these results demonstrate that crebinostat provides a novel probe to modulate chromatin-mediated neuroplasticity and further suggests that pharmacological optimization of selective of HDAC inhibitors may provide an effective therapeutic approach for human cognitive disorders. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

A large scale multivariate parallel ICA method reveals novel imaging-genetic relationships for Alzheimer's disease in the ADNI cohort

The underlying genetic etiology of late onset Alzheimer's disease (LOAD) remains largely unknown, likely due to its polygenic architecture and a lack of sophisticated analytic methods to evaluate complex genotype-phenotype models. The aim of the current study was to overcome these limitations in a bi-multivariate fashion by linking intermediate magnetic resonance imaging (MRI) phenotypes with a genome-wide sample of common single nucleotide polymorphism (SNP) variants. We compared associations between 94 different brain regions of interest derived from structural MRI scans and 533,872 genome-wide SNPs using a novel multivariate statistical procedure, parallel-independent component analysis, in a large, national multi-center subject cohort. The study included 209 elderly healthy controls, 367 subjects with amnestic mild cognitive impairment and 181 with mild, early-stage LOAD, all of them Caucasian adults, from the Alzheimer's Disease Neuroimaging Initiative cohort. Imaging was performed on comparable 1.5 T scanners at over 50 sites in the USA/Canada. Four primary "genetic components" were associated significantly with a single structural network including all regions involved neuropathologically in LOAD. Pathway analysis suggested that each component included several genes already known to contribute to LOAD risk (e.g. APOE4) or involved in pathologic processes contributing to the disorder, including inflammation, diabetes, obesity and cardiovascular disease. In addition significant novel genes identified included ZNF673, VPS13, SLC9A7, ATP5G2 and SHROOM2. Unlike conventional analyses, this multivariate approach identified distinct groups of genes that are plausibly linked in physiologic pathways, perhaps epistatically. Further, the study exemplifies the value of this novel approach to explore large-scale data sets involving high-dimensional gene and endophenotype data.

Caspase-3 cleavage links delta-catenin to the novel nuclear protein ZIFCAT

δ-Catenin is an Armadillo protein of the p120-catenin subfamily capable of modulating cadherin stability, small GTPase activity, and nuclear transcription. From yeast two-hybrid screening of a human embryonic stem cell cDNA library, we identified δ-catenin as a potential interacting partner of the caspase-3 protease, which plays essential roles in apoptotic as well as non-apoptotic processes. Interaction of δ-catenin with caspase-3 was confirmed using cleavage assays conducted in vitro, in Xenopus apoptotic extracts, and in cell line chemically induced contexts. The cleavage site, a highly conserved caspase consensus motif (DELD) within Armadillo repeat 6 of δ-catenin, was identified through peptide sequencing. Cleavage thus generates an amino-terminal (residues 1-816) and carboxyl-terminal (residues 817-1314) fragment, each containing about half of the central Armadillo domain. We found that cleavage of δ-catenin both abolishes its association with cadherins and impairs its ability to modulate small GTPases. Interestingly, 817-1314 possesses a conserved putative nuclear localization signal that may facilitate the nuclear targeting of δ-catenin in defined contexts. To probe for novel nuclear roles of δ-catenin, we performed yeast two-hybrid screening of a mouse brain cDNA library, resolving and then validating interaction with an uncharacterized KRAB family zinc finger protein, ZIFCAT. Our results indicate that ZIFCAT is nuclear and suggest that it may associate with DNA as a transcriptional repressor. We further determined that other p120 subfamily catenins are similarly cleaved by caspase-3 and likewise bind ZIFCAT. Our findings potentially reveal a simple yet novel signaling pathway based upon caspase-3 cleavage of p120-catenin subfamily members, facilitating the coordinate modulation of cadherins, small GTPases, and nuclear functions.

Common SNPs in myelin transcription factor 1-like (MYT1L): association with major depressive disorder in the Chinese Han population

BACKGROUND

Myelin transcription factor 1-like (MYT1L) is a member of the myelin transcription factor 1 (MYT1) gene family, and the neural specific, zinc-finger-containing, DNA-binding protein that it encodes plays a role in the development of the nervous system. On the basis of a recent copy number variation (CNV) study showing that this gene is disrupted in mental disorder patients, we investigated whether MYT1L also plays a role in MDD.

METHODS

In this study, 8 SNPs were analyzed in 1139 MDD patients and 1140 controls of Chinese Han origin.

RESULTS

Statistically significant differences were noted between cases and controls for rs3748989 (allele: permutated p = 0.0079, corrected p = 0.0048, genotype: corrected p = 0.0204). A haplotype of rs1617213 and rs6759709 G-C was also significant (permutated p = 0.00007).

CONCLUSION

Our results indicate that MYT1L may be a potential risk gene for MDD in the Chinese Han population.

δ-Catenin dysregulation in cancer: interactions with E-cadherin and beyond

Stable E-cadherin-based adherens junctions are pivotal in maintaining epithelial tissue integrity and are the major barrier for epithelial cancer metastasis. Proteins of the p120(ctn) subfamily have emerged recently as critical players for supporting this stability. The identification of the unique juxtamembrane domain (JMD) in E-cadherin that binds directly to delta-catenin/NPRAP/neurojungin (CTNND2) and p120(ctn) (CTNND1) provides a common motif for their interactions. Recently, crystallographic resolution of the JMD of p120(ctn) further highlighted possibilities of intervening between interactions of p120(ctn) subfamily proteins and E-cadherin for designing anti-cancer therapeutics. For most epithelial cancers, studies have demonstrated a reduction of p120(ctn) expression or alteration of its subcellular distribution. On the other hand, delta-catenin, a primarily neural-enriched protein in the brain of healthy individuals, is up-regulated in all cancer types that have been studied to date. Two research articles in the September 2010 issue of The Journal of Pathology increase our understanding of the involvement of these proteins in lung cancer. One reports the identification of rare p120(ctn) (CTNND1) gene amplification in lung cancer. One mechanism by which delta-catenin and p120(ctn) may play a role in carcinogenesis is their competitive binding to E-cadherin through the JMD. The other presents the first vigorous characterization of delta-catenin overexpression in lung cancer. Unexpectedly, the authors observed that delta-catenin promotes malignant phenotypes of non-small cell lung cancer by non-competitive binding to E-cadherin with p120(ctn) in the cytoplasm. Looking towards the future, the understanding of delta-catenin and p120(ctn) with and beyond their localization at the cell-cell junction should provide further insight into their roles in cancer pathogenesis.