Variants in doublecortin- and calmodulin kinase like 1, a gene up-regulated by BDNF, are associated with memory and general cognitive abilities

Hsc70 phosphorylation patterns and calmodulin regulate AP2 Clathrin-Coated-Vesicle life span for cell adhesion protein transport

AP2 forms AP2 CCV with clathrin and over 60 additional coat proteins. Due to this complexity, we have a limited understanding of CCV life cycle regulation. Synapses contain canonical AP2 CCV, canCCV, and more stable, thereby longer lived, AP2 CCV. The more stable AP2 CCV can be distinguished from canCCV due to the stable binding of Hsc70 to clathrin. The AP1/σ1B complex knockout leads to impaired synaptic vesicle recycling and altered endosomal protein sorting. This causes as a secondary phenotype the twofold upregulation of endocytosis by canCCV and by more stable AP2 CCV. These stable CCV are more stabilized than their wt counterpart, hence stCCV. They have less of the uncoating proteins synaptojanin1 and Hsc70, and more of the coat stabilizing AAK1. Hsc70 clathrin dissociation activity is regulated by complex phosphorylation patterns. Two major groups of hyper- and of hypo-phosphorylated Hsc70 proteins are formed. The latter are enriched in wt stable CCV and stabilized stCCV. Hsc70 T265 phosphorylation regulates binding of CaM/Ca2+. CaM/Ca2+ binding to the T265 domain blocks Hsc70 homodimerization and its concentration in stCCV required for clathrin disassembly. Kinases DYRK1A and CaMK-IIδ can phosphorylate T265 preventing CaM/Ca2+ binding. Their and the levels of STK38L and STK39/Cab39, which are able to phosphorylate additional Hsc70 residues are reduced in stCCV. The stCCV pathway sorts specifically the cell adhesion proteins CHL1 and Neurocan, supporting our model of that the stCCV pathway fulfills specific functions in synaptic plasticity.

DCLK1 and its oncogenic functions: A promising therapeutic target for cancers

Doublecortin-like kinase 1 (DCLK1), a significant constituent of the protein kinase superfamily and the doublecortin family, has been recognized as a prooncogenic factor that exhibits a strong association with the malignant progression and clinical prognosis of various cancers. DCLK1 serves as a stem cell marker that governs tumorigenesis, tumor cell reprogramming, and epithelial-mesenchymal transition. Multiple studies have indicated the capable of DCLK1 in regulating the DNA damage response and facilitating DNA damage repair. Additionally, DCLK1 is involved in the regulation of the immune microenvironment and the promotion of tumor immune evasion. Recently, DCLK1 has emerged as a promising therapeutic target for a multitude of cancers. Several small-molecule inhibitors of DCLK1 have been identified. Nevertheless, the biological roles of DCLK1 are mainly ambiguous, particularly with the disparities between its α- and β-form transcripts in the malignant progression of cancers, which impedes the development of more precisely targeted drugs. This article focuses on tumor stem cells, tumor epithelial-mesenchymal transition, the DNA damage response, and the tumor microenvironment to provide a comprehensive overview of the association between DCLK1 and tumor malignant progression, address unsolved questions and current challenges, and project future directions for targeting DCLK1 for the diagnosis and treatment of cancers.

Pleiotropic effects of DCLK1 in cancer and cancer stem cells

Doublecortin-like kinase 1 (DCLK1), a protein molecule, has been identified as a tumor stem cell marker in the cancer cells of gastrointestinal, pancreas, and human colon. DCLK1 expression in cancers, such as breast carcinoma, lung carcinoma, hepatic cell carcinoma, tuft cells, and human cholangiocarcinoma, has shown a way to target the DCLK1 gene and downregulate its expression. Several studies have discussed the inhibition of tumor cell proliferation along with neoplastic cell arrest when the DCLK1 gene, which is expressed in both cancer and normal cells, was targeted successfully. In addition, previous studies have shown that DCLK1 plays a vital role in various cancer metastases. The correlation of DCLK1 with numerous stem cell receptors, signaling pathways, and genes suggests its direct or an indirect role in promoting tumorigenesis. Moreover, the impact of DCLK1 was found to be related to the functioning of an oncogene. The downregulation of DCLK1 expression by using targeted strategies, such as embracing the use of siRNA, miRNA, CRISPR/Cas9 technology, nanomolecules, specific monoclonal antibodies, and silencing the pathways regulated by DCLK1, has shown promising results in both in vitro and in vivo studies on gastrointestinal (GI) cancers. In this review, we will discuss about the present understanding of DCLK1 and its role in the progression of GI cancer and metastasis.

OLA-1, an Obg-like ATPase, integrates hunger with temperature information in sensory neurons in C. elegans

Animals detect changes in both their environment and their internal state and modify their behavior accordingly. Yet, it remains largely to be clarified how information of environment and internal state is integrated and how such integrated information modifies behavior. Well-fed C. elegans migrates to past cultivation temperature on a thermal gradient, which is disrupted when animals are starved. We recently reported that the neuronal activities synchronize between a thermosensory neuron AFD and an interneuron AIY, which is directly downstream of AFD, in well-fed animals, while this synchrony is disrupted in starved animals. However, it remained to be determined whether the disruption of the synchrony is derived from modulation of the transmitter release from AFD or from the modification of reception or signal transduction in AIY. By performing forward genetics on a transition of thermotaxis behavior along starvation, we revealed that OLA-1, an Obg-like ATPase, functions in AFD to promote disruption of AFD-AIY synchrony and behavioral transition. Our results suggest that the information of hunger is delivered to the AFD thermosensory neuron and gates transmitter release from AFD to disrupt thermotaxis, thereby shedding light onto a mechanism for the integration of environmental and internal state to modulate behavior.

A comprehensive atlas of fetal splicing patterns in the brain of adult myotonic dystrophy type 1 patients

In patients with myotonic dystrophy type 1 (DM1), dysregulation of RNA-binding proteins like MBNL and CELF1 leads to alternative splicing of exons and is thought to induce a return to fetal splicing patterns in adult tissues, including the central nervous system (CNS). To comprehensively evaluate this, we created an atlas of developmentally regulated splicing patterns in the frontal cortex of healthy individuals and DM1 patients, by combining RNA-seq data from BrainSpan, GTEx and DM1 patients. Thirty-four splice events displayed an inclusion pattern in DM1 patients that is typical for the fetal situation in healthy individuals. The regulation of DM1-relevant splicing patterns could partly be explained by changes in mRNA expression of the splice regulators MBNL1, MBNL2 and CELF1. On the contrary, interindividual differences in splicing patterns between healthy adults could not be explained by differential expression of these splice regulators. Our findings lend transcriptome-wide evidence to the previously noted shift to fetal splicing patterns in the adult DM1 brain as a consequence of an imbalance in antagonistic MBNL and CELF1 activities. Our atlas serves as a solid foundation for further study and understanding of the cognitive phenotype in patients.

Research Progress of DCLK1 Inhibitors as Cancer Therapeutics

Doublecortin-like kinase 1 (DCLK1) has emerged over the last decade as a unique stem cell marker within gastrointestinal tissues. Evidence from mouse models shows that high Dclk1 expression denotes a population of cells that promote tissue regeneration and serve as potential cancer stem cells. Moreover, since specific DCLK1 isoforms are overexpressed in many cancers and not normal cells, targeting the expression or kinase activity of DCLK1 can inhibit cancer cell growth. Here we review the evidence for DCLK1 as a prospective cancer target, including its isoform-specific expression and mutational status in human cancers. We further discuss the challenges and current progress in the development of small-molecule inhibitors of DCLK1.

Daily oscillation of cognitive factors is modified in the temporal cortex of an amyloid β(1-42)-induced rat model of Alzheimer's disease

Alzheimer's disease (AD) is a devastating disease characterized by loss of synapses and neurons in the elderly. Accumulation of the β-amyloid peptide (Aβ) in the brain is thought to be central to the pathogenesis of AD. ApoE plays a key role in normal and physiological clearance of Aß, since it facilitates the peptide intra- and extracellular proteolytic degradation. Besides the cognitive deficit, AD patients also show alterations in their circadian rhythms. The objective of this study was to investigate the effects of an i.c.v. injection of Aβ (1-42) peptide on the 24 h rhythms of Apo E, BMAL1, RORα, Bdnf and trkB mRNA and Aβ levels in the rat temporal cortex. We found that an i.c.v. injection of Aβ aggregates phase shifts daily Bdnf expression as well as Apo E, BMAL1, RORα, Aβ and decreased the mesor of TrkB rhythms. Thus, elevated Aβ peptide levels might modify the temporal patterns of cognition-related factors, probably; by affecting the clock factors rhythms as well as in the 24 h rhythms of Apo E.

Examination and Comparison of Cognitive and Executive Functions in Clinically Stable Schizophrenia Disorder, Bipolar Disorder, and Major Depressive Disorder

BACKGROUND

Schizophrenia (SC), bipolar disorder (BD), and major depressive disorder (MDD) are associated with various cognitive and executive dysfunctions. The aim of the present study was to evaluate and compare cognitive and executive dysfunctions in schizophrenia, bipolar disorder, and major depressive disorder.

MATERIALS AND METHODS

Sixty-four schizophrenia patients, 68 bipolar patients, 62 patients with major depressive disorder, and 75 healthy individuals participated in the present study. All participants were assessed with the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I), Young Mania Rating Scale (YMRS), Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI-II), Trial Making Test (TMT), Four-Choice Reaction Time Task, Ruler Drop Method (RDM), Tower of London (TOL) task, and the Wisconsin Card Sorting Task (WCST). Data were analyzed by chi-square, Kolmogorov-Smirnov, and independent t-tests; ANOVA; and MANOVA.

RESULTS

In the cognitive function, the scores of SC, BD, and MDD patients were lower than those of healthy individuals. Also, the scores of MDD patients were lower than those of other patients, and the scores of BD patients were lower than those of SC patients. In the executive function, the scores of SC, BD, and MDD patients were lower than those of healthy individuals. Moreover, the scores of the MDD group were higher than those of the BD and SC groups, and the scores of the SC group were higher than those of the BD group.

CONCLUSION

Patients with SC, BD, and MDD have poorer cognitive and executive functions than healthy individuals, even when these patients are in a stable state. Assessment of cognitive and executive functions in SC, BD, and MDD patients can help in understanding the pathology of these disorders.

Neuronal activity regulates alternative exon usage

Neuronal activity-regulated gene transcription underlies plasticity-dependent changes in the molecular composition and structure of neurons. A large number of genes regulated by different neuronal plasticity inducing pathways have been identified, but altered gene expression levels represent only part of the complexity of the activity-regulated transcriptional program. Alternative splicing, the differential inclusion and exclusion of exonic sequence in mRNA, is an additional mechanism that is thought to define the activity-dependent transcriptome. Here, we present a genome wide microarray-based survey to identify exons with increased expression levels at 1, 4 or 8 h following neuronal activity in the murine hippocampus provoked by generalized seizures. We used two different bioinformatics approaches to identify alternative activity-induced exon usage and to predict alternative splicing, ANOSVA (ANalysis Of Splicing VAriation) which we here adjusted to accommodate data from different time points and FIRMA (Finding Isoforms using Robust Multichip Analysis). RNA sequencing, in situ hybridization and reverse transcription PCR validate selected activity-dependent splicing events of previously described and so far undescribed activity-regulated transcripts, including Homer1a, Homer1d, Ania3, Errfi1, Inhba, Dclk1, Rcan1, Cda, Tpm1 and Krt75. Taken together, our survey significantly adds to the comprehensive understanding of the complex activity-dependent neuronal transcriptomic signature. In addition, we provide data sets that will serve as rich resources for future comparative expression analyses.

[A new look at the genetics of neurocognitive deficits in schizophrenia]

The article presents current literature data on genetic studies of neurocognitive deficit in schizophrenia, including the genes of neurotransmitter systems (dopaminergic, glutamatergic, and serotonergic); genes analyzed in genome-wide association studies (GWAS), as well as other genetic factors related to the pathophysiological mechanisms underlying schizophrenia and neurocognitive disorders.

DCLK-1 LEVEL IN MULTIPLE SCLEROSIS PATIENTS AND ITS CORRELATION WITH CLINIC

INTRODUCTION AND OBJECTIVE

There are studies supporting the disruption of axonal transport in multiple sclerosis, a neurodegenerative disease. The aim of our study was to determine Doublecortin-like kinase 1 (DCLK1) levels in multiple sclerosis patients, which play a part in axonal transport, and to investigate its correlation with the disease.

MATERIALS AND METHODS

The study included 30 patients above 18 years of age with the diagnosis of multiple sclerosis and 30 healthy volunteers. The disease duration, number of annual attacks, Expanded Disability Status Scale (EDSS) scores and medications of the patients who had no history of attack within the last month were recorded. DCLK1 levels were studied in the venous blood samples taken from the patients and healthy volunteers using the ELISA method.

RESULTS

DCLK1 levels were significantly lower in the MS patient group than in the healthy control group. There was no significant correlation between disease duration, annual number of attacks, EDSS score and DCLK1 level.

CONCLUSION

Low levels of DCLK1 in multiple sclerosis patients support the disruption of axonal transport. The use of agents that provide DCLK1 expression may be a treatment option to prevent neurodegeneration in multiple sclerosis patients by eliminating the disruption in axonal transport, thereby improving the clinical course of the disease and cognition.

Doublecotin-Like Kinase 1 Increases Chemoresistance of Colorectal Cancer Cells through the Anti-Apoptosis Pathway

Background

Colorectal Cancer (CRC) is the third most common cancer diagnosed and the second leading cause of cancer-related deaths in the United States. Cancer Stem Cells (CSCs) are believed to be the primary reason for the recurrence of CRC. Specific stem cell marker, doublecortin-like kinase 1 (DCLK1) plays critical roles in the tumorigenesis and progression of CRC. Up-regulation of DCLK1 is correlated with poor prognosis. Whether DCLK1 is correlated with enhanced chemoresistance of CRC cells is unclear. We aim to reveal the association of DCLK1 with chemoresistance of CRC cells and the underlying molecular mechanisms.

Methods

Stable DCLK1 over-expression cells (DCLK1+) were established using the HCT116 cells (WT). DCLK1+ and WT cells were treated with 5-Fluorouracil (5-Fu) at different doses for 24 or 48 hours. MTT assay was used to evaluate cell viability and IC50 of 5-Fu was determined. Quantitative real-time PCR was applied to determine the gene expression of caspase-3 (casp-3), casp-4, and casp-10. Cleaved casp-3 expression was investigated using Western blot and immunofluorescence.

Results

Our results demonstrated that IC50 of 5-Fu for the DCLK1+ cells was significantly higher than that of the WT cells for both 24 and 48-hour treatment (p=0.002 and 0.048 respectively), indicating increased chemoresistance of the DCLK1+ cells. Gene expression of casp-3, casp-4, and casp-10 were significantly inhibited in the DCLK1+ cells after 5-Fu treatment compared to the WT cells (p=7.616e-08, 1.575e-05 and 5.307e-08, respectively). Cleaved casp-3 amount and casp-3 positive cells were significantly decreased in the DCLK1+ cells after 5-Fu treatment compared to the WT cells (p=0.015).

Conclusions

In conclusion, our results demonstrated that DCLK1 overexpression enhanced the chemoresistance of CRC cells to 5-Fu treatment by suppressing gene expression of key caspases in the apoptosis pathway and activation of the apoptosis pathway. DCLK1 can be an intriguing therapeutic target for the effective treatment of CRC patients.

DCLK1 phosphorylates the microtubule-associated protein MAP7D1 to promote axon elongation in cortical neurons

Doublecortin-like kinase 1 (DCLK1) is a member of the neuronal microtubule-associated doublecortin (DCX) family and functions in multiple stages of neural development including radial migration and axon growth of cortical neurons. DCLK1 is suggested to play the roles in part through its protein kinase activity, yet the kinase substrates of DCLK1 remain largely unknown. Here we have identified MAP7D1 (microtubule-associated protein 7 domain containing 1) as a novel substrate of DCLK1 by using proteomic analysis. MAP7D1 is expressed in developing cortical neurons, and knockdown of MAP7D1 in layer 2/3 cortical neurons results in a significant impairment of callosal axon elongation, but not of radial migration, in corticogenesis. We have further defined the serine 315 (Ser 315) of MAP7D1 as a DCLK1-induced phosphorylation site and shown that overexpression of a phosphomimetic MAP7D1 mutant in which Ser 315 is substituted with glutamic acid (MAP7D1 S315E), but not wild-type MAP7D1, fully rescues the axon elongation defects in Dclk1 knockdown neurons. These data demonstrate that DCLK1 phosphorylates MAP7D1 on Ser 315 to facilitate axon elongation of cortical neurons. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 419-437, 2017.

Neurocognitive function in clinically stable individuals with long-term bipolar I disorder: Comparisons with schizophrenia patients and controls

This study compared the levels of the five domains of neurocognitive function-executive function, attention, memory, verbal comprehension, and perceptual organization-among clinically stable individuals with long-term bipolar I disorder, individuals with long-term schizophrenia, and a group of controls. We recruited a total of 93 clinically stable individuals with bipolar I disorder, 94 individuals with schizophrenia, and 106 controls in this study. Their neurocognitive function was measured using a series of neurocognitive function tests: the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III), Line Cancellation Test, Visual Form Discrimination, Controlled Oral Word Association Test, Wisconsin Card Sorting Test, Continuous Performance Task, and Wechsler Memory Scale-Third Edition. Neurocognitive function was compared among the three groups through a multivariate analysis of variance. The results indicated that when the effect of age was controlled, clinically stable individuals with bipolar I disorder and those with schizophrenia demonstrated poor neurocognitive function on all tests except for the WAIS-III Similarity and Information and the Line Cancellation Test. The individuals with bipolar I disorder had similar levels of neurocognitive function compared with the schizophrenia group, but higher levels of neurocognitive function on the WAIS-III Comprehension, Controlled Oral Word Association Test, and Wechsler Memory Scale-Third Edition Auditory Immediate and Delayed Index and Visual Immediate and Delayed Index. The conclusions of this study suggest that compared with controls, individuals with long-term bipolar I disorder and those with long-term schizophrenia have poorer neurocognitive function, even when clinically stable. Individuals with long-term bipolar I disorder and those with long-term schizophrenia have similar levels of deficits in several domains of neurocognitive function.

Essential oils from two Allium species exert effects on cell proliferation and neuroblast differentiation in the mouse dentate gyrus by modulating brain-derived neurotrophic factor and acetylcholinesterase

Background

In the present study, we investigated the effects of oil products from two Allium species: Allium sativum (garlic) and Allium hookeri (Chinese chives) on cell proliferation and neuroblast differentiation in the mouse dentate gyrus.

Methods

Using corn oil as a vehicle, the essential oil from garlic (10 ml/kg), or Chinese chives (10 ml/kg) was administered orally to 9-week-old mice once a day for 3 weeks. One hour following the last treatment, a novel object recognition test was conducted and the animals were killed 2 h after the test.

Results

In comparison to the vehicle-treated group, garlic essential oil (GO) treatment resulted in significantly increased exploration time and discrimination index during the novel object recognition test, while Chinese chives essential oil (CO) reduced the exploration time and discrimination index in the same test. In addition, the number of Ki67-immunoreactive proliferating cells and doublecortin-immunoreactive neuroblasts significantly increased in the dentate gyrus of GO-treated animals. However, administration of CO significantly decreased cell proliferation and neuroblast differentiation. Administration of GO significantly increased brain-derived neurotrophic factor (BDNF) levels and decreased acetylcholinesterase (AChE) activity in the hippocampal homogenates. In contrast, administration of CO decreased BDNF protein levels and had no significant effect on AChE activity, compared to that in the vehicle-treated group.

Conclusions

These results suggest that GO significantly improves novel object recognition as well as increases cell proliferation and neuroblast differentiation, by modulating hippocampal BDNF protein levels and AChE activity, while CO impairs novel object recognition and decreases cell proliferation and neuroblast differentiation, by reducing BDNF protein levels in the hippocampus.

Epigenetic regulation of human DCLK-1 gene during colon-carcinogenesis: clinical and mechanistic implications

Colorectal carcinogenesis is a multi-step process. While ~25% of colorectal cancers (CRCs) arise in patients with a family history (genetic predisposition), ~75% of CRCs are due to age-associated accumulation of epigenetic alterations which can result in the suppression of key tumor suppressor genes leading to mutations and activation of oncogenic pathways. Sporadic colon-carcinogenesis is facilitated by many molecular pathways of genomic instability which include chromosomal instability (CIN), micro-satellite instability (MSI) and CpG island methylator phenotype (CIMP), leading towards loss of homeostasis and onset of neoplastic transformation. The unopposed activation of Wnt/β-catenin pathways, either due to loss of APC function or up-regulation of related stimulatory pathways, results in unopposed hyperproliferation of colonic crypts, considered the single most important risk factor for colon carcinogenesis. Hypermethylation of CpG islands within the promoters of specific genes can potentially inactivate DNA repair genes and/or critical tumor suppressor genes. Recently, CpG methylation of the 5' promoter of human (h) DCLK1 gene was reported in many human epithelial cancers, including colorectal cancers (CRCs), resulting in the loss of expression of the canonical long isoform of DCLK1 (DCLK1-L) in hCRCs. Instead, a shorter isoform of DCLK1 (DCLK1-S) was discovered to be expressed in hCRCs, from an alternate β promoter of DCLKL1-gene; the clinical and biological implications of these novel findings, in relation to recent publications is discussed.

Novel microRNA revealed by systematic analysis of the microRNA transcriptome in dentate gyrus granule cells

Post-transcriptional control of gene expression by microRNAs provides an important regulatory system within neurons, allowing co-ordinate and fine-tuned expression of plasticity-related proteins. Indeed, specific microRNAs have been shown to be regulated by synaptic activity in the dentate gyrus, and contribute to the regulated gene expression that underlies the persistence of long-term potentiation (LTP), a model of memory. To fully explore the contribution of microRNAs in synaptic plasticity, it is important to characterize the complete microRNA transcriptome in regions such as the dentate gyrus. Accordingly we used deep sequencing and miRDeep* analysis to search for novel microRNAs expressed in the dentate gyrus granule cell layer. Drawing on combined sequencing and bioinformatics analyses, including hairpin stability and patterns of precursor microRNA processing, we identified nine putative novel microRNAs. We did not find evidence of differential expression of any of these putative microRNAs following LTP at perforant path-granule cell synapses in awake rats (5 h post-tetanus; p > 0.05). Focusing on novel_miR-1, the most abundant novel miRNA, we showed that this sequence could be amplified from RNA extracted from dentate gyrus granule cells by reverse transcription-quantitative polymerase chain reaction. Further, by computationally predicting mRNA targets of this microRNA, we found that this novel microRNA likely contributes to the regulation of proteins that function at synapses.

Epigenetic changes and alternate promoter usage by human colon cancers for expressing DCLK1-isoforms: Clinical Implications

DCLK1 specifically marks colon/pancreatic cancers in mice, and is expressed by human colon adenocarcinomas (hCRCs). Down-regulation of DCLK1 results in loss of cancer-stem-cells (CSCs), and inhibits spheroidal/xenograft growths from hCRC-cells. The 5'-promoter of DCLK1-gene is reportedly hypermethylated in hCRCs, resulting in loss of expression of DCLK1-transcripts, originating from 5'(α)-promoter (termed DCLK1-L, in here). However, in mouse colon-tumors, 5'-promoter of DCLK1-gene remains unchanged, and DCLK1-L, originating from 5'(α)-promoter, is expressed. We hypothesized that elevated levels of DCLK1-protein in hCRC-cells, may be transcribed/translated from an alternate-promoter. Several in silico and molecular biology approaches were used to test our hypothesis. We report for the first time that majority of hCRCs express short-transcripts of DCLK1 (termed DCLK1-S, in here) from an alternate β-promoter in IntronV of the gene, while normal-colons mainly express DCLK1-L from 5'(α)-promoter. We additionally report an important role of β-catenin and TCF4/LEF binding-sites for activating (α)-promoter, while activated NF-κBp65 (bound to NF-κB-cis-element), activates (β)-promoter in cancer-cells. DCLK1-S expression was examined in a cohort of 92 CRC patients; high-expressors had significantly worse overall-survival compared to low-expressors. Our novel findings' regarding usage of alternate (β)-promoter by hCRCs, suggests that DCLK1-S may represent an important target for preventing/inhibiting colon-cancers, and for eliminating colon-CSCs.

Common variants in the ARC gene are not associated with cognitive abilities

INTRODUCTION

The Activity-Regulated Cytoskeleton-associated (ARC) gene encodes a protein that is critical for the consolidation of synaptic plasticity and long-term memory formation. Given ARC's key role in synaptic plasticity, we hypothesized that genetic variations in ARC may contribute to interindividual variability in human cognitive abilities or to attention-deficit hyperactivity disorder (ADHD) susceptibility, where cognitive impairment often accompanies the disorder.

METHODS

We tested whether ARC variants are associated with six measures of cognitive functioning in 670 healthy subjects in the Norwegian Cognitive NeuroGenetics (NCNG) by extracting data from its Genome-Wide Association Study (GWAS). In addition, the Swedish Betula sample of 1800 healthy subjects who underwent similar cognitive testing was also tested for association with 19 tag SNPs.

RESULTS

No ARC variants show association at the study-wide level, but several markers show a trend toward association with human cognitive functions. We also tested for association between ARC SNPs and ADHD in a Norwegian sample of cases and controls, but found no significant associations.

CONCLUSION

This study suggests that common genetic variants located in ARC do not account for variance in human cognitive abilities, though small effects cannot be ruled out.

Differential reprogramming of isogenic colorectal cancer cells by distinct activating KRAS mutations

Oncogenic mutations of Ras at codons 12, 13, or 61, that render the protein constitutively active, are found in ∼16% of all cancer cases. Among the three major Ras isoforms, KRAS is the most frequently mutated isoform in cancer. Each Ras isoform and tumor type displays a distinct pattern of codon-specific mutations. In colon cancer, KRAS is typically mutated at codon 12, but a significant fraction of patients have mutations at codon 13. Clinical data suggest different outcomes and responsiveness to treatment between these two groups. To investigate the differential effects upon cell status associated with KRAS mutations we performed a quantitative analysis of the proteome and phosphoproteome of isogenic SW48 colon cancer cell lines in which one allele of the endogenous gene has been edited to harbor specific KRAS mutations (G12V, G12D, or G13D). Each mutation generates a distinct signature, with the most variability seen between G13D and the codon 12 KRAS mutants. One notable example of specific up-regulation in KRAS codon 12 mutant SW48 cells is provided by the short form of the colon cancer stem cell marker doublecortin-like Kinase 1 (DCLK1) that can be reversed by suppression of KRAS.

Neuropsychological impairments in schizophrenia and psychotic bipolar disorder: findings from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) study

OBJECTIVE

Familial neuropsychological deficits are well established in schizophrenia but remain less well characterized in other psychotic disorders. This study from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) consortium 1) compares cognitive impairment in schizophrenia and bipolar disorder with psychosis, 2) tests a continuum model of cognitive dysfunction in psychotic disorders, 3) reports familiality of cognitive impairments across psychotic disorders, and 4) evaluates cognitive impairment among nonpsychotic relatives with and without cluster A personality traits.

METHOD

Participants included probands with schizophrenia (N=293), psychotic bipolar disorder (N=227), schizoaffective disorder (manic, N=110; depressed, N=55), their first-degree relatives (N=316, N=259, N=133, and N=64, respectively), and healthy comparison subjects (N=295). All participants completed the Brief Assessment of Cognition in Schizophrenia (BACS) neuropsychological battery.

RESULTS

Cognitive impairments among psychotic probands, compared to healthy comparison subjects, were progressively greater from bipolar disorder (z=-0.77) to schizoaffective disorder (manic z=-1.08; depressed z=-1.25) to schizophrenia (z=-1.42). Profiles across subtests of the BACS were similar across disorders. Familiality of deficits was significant and comparable in schizophrenia and bipolar disorder. Of particular interest were similar levels of neuropsychological deficits in relatives with elevated cluster A personality traits across proband diagnoses. Nonpsychotic relatives of schizophrenia probands without these personality traits exhibited significant cognitive impairments, while relatives of bipolar probands did not.

CONCLUSIONS

Robust cognitive deficits are present and familial in schizophrenia and psychotic bipolar disorder. Severity of cognitive impairments across psychotic disorders was consistent with a continuum model, in which more prominent affective features and less enduring psychosis were associated with less cognitive impairment. Cognitive dysfunction in first-degree relatives is more closely related to psychosis-spectrum personality disorder traits in psychotic bipolar disorder than in schizophrenia.

A Genome-Wide Association Study Suggests Novel Loci Associated with a Schizophrenia-Related Brain-Based Phenotype

Patients with schizophrenia and their siblings typically show subtle changes of brain structures, such as a reduction of hippocampal volume. Hippocampal volume is heritable, may explain a variety of cognitive symptoms of schizophrenia and is thus considered an intermediate phenotype for this mental illness. The aim of our analyses was to identify single-nucleotide polymorphisms (SNP) related to hippocampal volume without making prior assumptions about possible candidate genes. In this study, we combined genetics, imaging and neuropsychological data obtained from the Mind Clinical Imaging Consortium study of schizophrenia (n = 328). A total of 743,591 SNPs were tested for association with hippocampal volume in a genome-wide association study. Gene expression profiles of human hippocampal tissue were investigated for gene regions of significantly associated SNPs. None of the genetic markers reached genome-wide significance. However, six highly correlated SNPs (rs4808611, rs35686037, rs12982178, rs1042178, rs10406920, rs8170) on chromosome 19p13.11, located within or in close proximity to the genes NR2F6, USHBP1, and BABAM1, as well as four SNPs in three other genomic regions (chromosome 1, 2 and 10) had p-values between 6.75×10(-6) and 8.3×10(-7). Using existing data of a very recently published GWAS of hippocampal volume and additional data of a multicentre study in a large cohort of adolescents of European ancestry, we found supporting evidence for our results. Furthermore, allelic differences in rs4808611 and rs8170 were highly associated with differential mRNA expression in the cis-acting region. Associations with memory functioning indicate a possible functional importance of the identified risk variants. Our findings provide new insights into the genetic architecture of a brain structure closely linked to schizophrenia. In silico replication, mRNA expression and cognitive data provide additional support for the relevance of our findings. Identification of causal variants and their functional effects may unveil yet unknown players in the neurodevelopment and the pathogenesis of neuropsychiatric disorders.

Doublecortin-like kinase 1 exhibits cancer stem cell-like characteristics in a human colon cancer cell line

OBJECTIVE

Colon cancer stem cells (CSCs) are implicated in colorectal cancer carcinogenesis, metastasis, and therapeutic resistance. The identification of these cells could help to develop novel therapeutic strategies. Doublecortin-like kinase 1 (DCLK1) has been viewed as a marker for gastrointestinal stem cells that fuel the self-renewal process, however others view them as a marker of Tuft cells or as an enteroendocrine subtype. The purpose of this study was to use a colon cancer cell line to identify and characterize the stem-like characteristics of the DCLK1+ cell population.

METHODS

To enrich stem-like cells, HCT116 cells (derived from colon adenocarcinomas) were cultured using serum-free media to form spheres under both normal oxygen and hypoxia condition. DCLK1 transcript expression in the adherent parental cells and spheroids was quantified using quantitative real time reverse transcription- polymerase chain reaction [(q)RT-PCR]. DCLK1 protein expression was determined using flow cytometry. Self-renewal capability from adherent parental cells and spheroids was determined using extreme limiting dilution analysis (ELDA).

RESULTS

Under both normal oxygen and hypoxia condition, the adherent parental cells were composed of cells that express low levels of DCLK1. However, spheroids exhibited an increased frequency of cells expressing DCLK1 on both mRNA and protein levels. Cells derived from spheroids also possess stronger self-renewal capability.

CONCLUSIONS

The higher fraction of DCLK1+ cells exhibited by spheroids and hypoxia reflects the stem-like characteristics of these cells. DCLK1 may represent an ideal marker to study and develop effective strategies to overcome chemo-resistance and relapse of colon cancer.

Use of RNA interference by in utero electroporation to study cortical development: the example of the doublecortin superfamily

The way we study cortical development has undergone a revolution in the last few years following the ability to use shRNA in the developing brain of the rodent embryo. The first gene to be knocked-down in the developing brain was doublecortin (Dcx). Here we will review knockdown experiments in the developing brain and compare them with knockout experiments, thus highlighting the advantages and disadvantages using the different systems. Our review will focus on experiments relating to the doublecortin superfamily of proteins.

The role of brain-derived neurotrophic factor in the regulation of cell growth and gene expression in melanotrope cells of Xenopus laevis

Brain-derived neurotrophic factor (BDNF) is, despite its name, also found outside the central nervous system (CNS), but the functional significance of this observation is largely unknown. This review concerns the expression of BDNF in the pituitary gland. While the presence of the neurotrophin in the mammalian pituitary gland is well documented its functional significance remains obscure. Studies on the pars intermedia of the pituitary of the amphibian Xenopus laevis have shown that BDNF is produced by the neuroendocrine melanotrope cells, its expression is physiologically regulated, and the melanotrope cells themselves express receptors for the neurotrophin. The neurotrophin has been shown to act as an autocrine factor on the melanotrope to promote cell growth and regulate gene expression. In doing so BDNF supports the physiological function of the cell to produce and release α-melanophore-stimulating hormone for the purpose of adjusting the animal's skin color to that of its background.

Imaging and Cognitive Genetics: The Norwegian Cognitive NeuroGenetics Sample

Data collection for the Norwegian Cognitive NeuroGenetics sample (NCNG) was initiated in 2003 with a research grant (to Ivar Reinvang) to study cognitive aging, brain function, and genetic risk factors. The original focus was on the effects of aging (from middle age and up) and candidate genes (e.g., APOE, CHRNA4) in cross-sectional and longitudinal designs, with the cognitive and MRI-based data primarily being used for this purpose. However, as the main topic of the project broadened from cognitive aging to imaging and cognitive genetics more generally, the sample size, age range of the participants, and scope of available phenotypes and genotypes, have developed beyond the initial project. In 2009, a genome-wide association (GWA) study was undertaken, and the NCNG proper was established to study the genetics of cognitive and brain function more comprehensively. The NCNG is now controlled by the NCNG Study Group, which consists of the present authors. Prominent features of the NCNG are the adult life-span coverage of healthy participants with high-dimensional imaging, and cognitive data from a genetically homogenous sample. Another unique property is the large-scale (sample size 300–700) use of experimental cognitive tasks focusing on attention and working memory. The NCNG data is now used in numerous ongoing GWA-based studies and has contributed to several international consortia on imaging and cognitive genetics. The objective of the following presentation is to give other researchers the information necessary to evaluate possible contributions from the NCNG to various multi-sample data analyses.

The Imaging and Cognition Genetics Conference 2011, ICG 2011: A Meeting of Minds

In June 2011, 70 researchers from the disciplines of cognitive science, genetics, psychology, psychiatry, neurobiology, and computer science gathered in Os, Norway, for the first Imaging and Cognition Genetics meeting. The aim of the conference was to discuss progress, enhance collaboration, and maximize the sharing of resources within this new field. In this Perspective, we summarize the major themes that emerged from ICG 2011. The first is the importance of defining cognitive and imaging phenotypes and endophenotypes suitable for genetic analysis. These can come from differential psychology, cognitive science, structural MRI, tractography, and functional imaging. The second theme is the emergence of new methods for the analysis of complex traits. These include advanced computational and statistical techniques for analyzing complex datasets, and new ways of interpreting data from genome-wide association studies, such as jointly evaluating the contribution of SNPs in specific genes and pathways rather than considering single SNPs in isolation. The final theme is the importance of establishing functional correlates of newly identified genetic variants.

Differential BDNF signaling in dentate gyrus and perirhinal cortex during consolidation of recognition memory in the rat

Consolidation of long-term memory is dependent on synthesis of new proteins in the hippocampus and associated cortical regions. The neurotrophin brain-derived neurotrophic factor (BDNF) is tightly regulated by activity-dependent cellular processes and is strongly linked with mechanisms underlying learning and memory. BDNF activation of tyrosine receptor kinase (TrkB) stimulates intracellular signaling cascades implicated in plasticity, including the extracellular-signal related kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway and the phosphatidylinositide-3-kinase (PI3K)/Akt pathway. Here, we investigate the role of BDNF, ERK/MAPK, and PI3K/AKT signaling cascade in recognition memory in the rat. We report that recognition memory was associated with increased release of BDNF in the dentate gyrus and perirhinal cortex. This was associated with significant increases in p44ERK activation and c-fos expression in the dentate gyrus and PI3K activation and c-fos expression in the perirhinal cortex. Furthermore, both recognition memory and the associated cell signaling events in dentate gyrus and perirhinal cortex were blocked by intraperitoneal injection of the Trk receptor inhibitor tyrphostin AG879. These data are consistent with the hypothesis that BDNF-stimulated intracellular signaling plays a role in consolidation of recognition memory in the rat.

DCLK1 variants are associated across schizophrenia and attention deficit/hyperactivity disorder

Doublecortin and calmodulin like kinase 1 (DCLK1) is implicated in synaptic plasticity and neurodevelopment. Genetic variants in DCLK1 are associated with cognitive traits, specifically verbal memory and general cognition. We investigated the role of DCLK1 variants in three psychiatric disorders that have neuro-cognitive dysfunctions: schizophrenia (SCZ), bipolar affective disorder (BP) and attention deficit/hyperactivity disorder (ADHD). We mined six genome wide association studies (GWASs) that were available publically or through collaboration; three for BP, two for SCZ and one for ADHD. We also genotyped the DCLK1 region in additional samples of cases with SCZ, BP or ADHD and controls that had not been whole-genome typed. In total, 9895 subjects were analysed, including 5308 normal controls and 4,587 patients (1,125 with SCZ, 2,496 with BP and 966 with ADHD). Several DCLK1 variants were associated with disease phenotypes in the different samples. The main effect was observed for rs7989807 in intron 3, which was strongly associated with SCZ alone and even more so when cases with SCZ and ADHD were combined (P-value = 4×10⁻⁵ and 4×10⁻⁶, respectively). Associations were also observed with additional markers in intron 3 (combination of SCZ, ADHD and BP), intron 19 (SCZ+BP) and the 3′UTR (SCZ+BP). Our results suggest that genetic variants in DCLK1 are associated with SCZ and, to a lesser extent, with ADHD and BP. Interestingly the association is strongest when SCZ and ADHD are considered together, suggesting common genetic susceptibility. Given that DCLK1 variants were previously found to be associated with cognitive traits, these results are consistent with the role of DCLK1 in neurodevelopment and synaptic plasticity.

Gene-based analysis of regionally enriched cortical genes in GWAS data sets of cognitive traits and psychiatric disorders

BACKGROUND

Despite its estimated high heritability, the genetic architecture leading to differences in cognitive performance remains poorly understood. Different cortical regions play important roles in normal cognitive functioning and impairment. Recently, we reported on sets of regionally enriched genes in three different cortical areas (frontomedial, temporal and occipital cortices) of the adult rat brain. It has been suggested that genes preferentially, or specifically, expressed in one region or organ reflect functional specialisation. Employing a gene-based approach to the analysis, we used the regionally enriched cortical genes to mine a genome-wide association study (GWAS) of the Norwegian Cognitive NeuroGenetics (NCNG) sample of healthy adults for association to nine psychometric tests measures. In addition, we explored GWAS data sets for the serious psychiatric disorders schizophrenia (SCZ) (n = 3 samples) and bipolar affective disorder (BP) (n = 3 samples), to which cognitive impairment is linked.

PRINCIPAL FINDINGS

At the single gene level, the temporal cortex enriched gene RAR-related orphan receptor B (RORB) showed the strongest overall association, namely to a test of verbal intelligence (Vocabulary, P = 7.7E-04). We also applied gene set enrichment analysis (GSEA) to test the candidate genes, as gene sets, for enrichment of association signal in the NCNG GWAS and in GWASs of BP and of SCZ. We found that genes differentially expressed in the temporal cortex showed a significant enrichment of association signal in a test measure of non-verbal intelligence (Reasoning) in the NCNG sample.

CONCLUSION

Our gene-based approach suggests that RORB could be involved in verbal intelligence differences, while the genes enriched in the temporal cortex might be important to intellectual functions as measured by a test of reasoning in the healthy population. These findings warrant further replication in independent samples on cognitive traits.

Cohort profile: the Lothian Birth Cohorts of 1921 and 1936

This cohort profile describes the origins, tracing, recruitment, testing and follow-up of the University of Edinburgh-based Lothian Birth Cohorts of 1921 (LBC1921; N = 550) and 1936 (LBC1936; N = 1091). The participants undertook a general intelligence test at age 11 years and were recruited for these cohorts at mean ages of 79 (LBC1921) and 70 (LBC1936). The LBC1921 have been examined at mean ages of 79, 83, 87 and 90 years. The LBC1936 have been examined at mean ages of 70 and 73 years, and are being seen at 76 years. Both samples have an emphasis on the ageing of cognitive functions as outcomes. As they have childhood intelligence test scores, the cohorts' data have been used to search for determinants of lifetime cognitive changes, and also cognitive change within old age. The cohorts' outcomes also include a range of physical and psycho-social aspects of well-being in old age. Both cohorts have a wide range of variables: genome-wide genotyping, demographics, psycho-social and lifestyle factors, cognitive functions, medical history and examination, and biomarkers (from blood and urine). The LBC1936 participants also have a detailed structural magnetic resonance imaging (MRI) brain scan. A range of scientific findings is described, to illustrate the possible uses of the cohorts.

ERK-regulated double cortin-like kinase (DCLK)-short phosphorylation and nuclear translocation stimulate POMC gene expression in endocrine melanotrope cells

We tested whether double cortin-like kinase-short (DCLK-short), a microtubule-associated Ser/Thr kinase predominantly expressed in the brain, is downstream of the ERK signaling pathway and is involved in proopiomelanocortin gene (POMC) expression in endocrine pituitary melanotrope cells of Xenopus laevis. Melanotropes form a well-established model to study physiological aspects of neuroendocrine plasticity. The amphibian X. laevis adapts its skin color to the background light intensity by the release of α-MSH from the melanotrope cell. In frogs on a white background, melanotropes are inactive but they are activated during adaptation to a black background. Our results show that melanotrope activation is associated with an increase in DCLK-short mRNA and with phosphorylation of DCLK-short at serine at position 30 (Ser-30). Upon cell activation phosphorylated Ser-30-DCLK-short was translocated from the cytoplasm into the nucleus, and the ERK blocker U0126 inhibited this process. The mutation of Ser-30 to alanine also inhibited the translocation and reduced POMC expression, whereas overexpression stimulated POMC expression. This is the first demonstration of DCLK-short in a native endocrine cell. We conclude that DCLK-short is physiologically regulated at both the level of its gene expression and protein phosphorylation and that the kinase is effectively regulating POMC gene expression upon its ERK-mediated phosphorylation.

Neurogenetic effects on cognition in aging brains: a window of opportunity for intervention?

Knowledge of genetic influences on cognitive aging can constrain and guide interventions aimed at limiting age-related cognitive decline in older adults. Progress in understanding the neural basis of cognitive aging also requires a better understanding of the neurogenetics of cognition. This selective review article describes studies aimed at deriving specific neurogenetic information from three parallel and interrelated phenotype-based approaches: psychometric constructs, cognitive neuroscience-based processing measures, and brain imaging morphometric data. Developments in newer genetic analysis tools, including genome wide association, are also described. In particular, we focus on models for establishing genotype-phenotype associations within an explanatory framework linking molecular, brain, and cognitive levels of analysis. Such multiple-phenotype approaches indicate that individual variation in genes central to maintaining synaptic integrity, neurotransmitter function, and synaptic plasticity are important in affecting age-related changes in brain structure and cognition. Investigating phenotypes at multiple levels is recommended as a means to advance understanding of the neural impact of genetic variants relevant to cognitive aging. Further knowledge regarding the mechanisms of interaction between genetic and preventative procedures will in turn help in understanding the ameliorative effect of various experiential and lifestyle factors on age-related cognitive decline.

Epistasis between APOE and nicotinic receptor gene CHRNA4 in age related cognitive function and decline

Healthy participants (n = 237) aged 45-79 were tested neuropsychologically with tests of memory, speed, and cognitive control and followed up for 3-5 years (mean, 3.4 years). The sample was genotyped for apolipoprotein E (APOE) and CHolinergic Receptor for Nicotine Alpha 4 (CHRNA4), and genetic effects on cognitive function at initial testing and on cognitive decline was studied. We predicted relatively stronger effects of APOE on memory, and of CHRNA4 on speeded tasks. The predictions were partially confirmed, but we found interactive effects of APOE and CHRNA4 in several cognitive domains. Being an APOE epsilon4/CHRNA4 TT carrier was associated with slower and less efficient performance, and with steeper decline in speed tasks and in delayed recall. Age dependent genetic effects were found for both APOE and CHRNA4, where old participants (60-79 years) showed a negative influence of TT carrier status on initial memory performance, but a tendency for steeper memory decline in epsilon4 carriers. Inconsistent and small effects of APOE reported in previous studies of healthy groups may be caused by failure to consider epistasis of APOE with nicotinic receptor and other genes.