Goal-Directed Action Is Initially Impaired in a hAPP-J20 Mouse Model of Alzheimer's Disease.

Cognitive-behavioral testing in preclinical models of Alzheimer's disease has failed to capture deficits in goal-directed action control. Here, we provide the first comprehensive investigation of goal-directed action in a transgenic mouse model of Alzheimer's disease. Specifically, we tested outcome devaluation performance in male and female human amyloid precursor protein (hAPP)-J20 mice. Mice were first trained to press left and right levers for pellet and sucrose outcomes, respectively (counterbalanced), over 4 d. On test, mice were prefed one of the outcomes to satiety and given a choice between levers. Devaluation performance was intact for 36-week-old wild-types of both sexes, who responded more on the valued relative to the devalued lever (Valued > Devalued). By contrast, devaluation was impaired (Valued = Devalued) for J20 mice of both sexes, and for 52-week-old male mice regardless of genotype. After additional lever press training (i.e., 8-d lever pressing in total), devaluation was intact for all mice, demonstrating that the initial deficits were not a result of a nonspecific impairment in reward processing, depression, or locomotor activity in J20 or aging mice. Follow-up analyses revealed that microglial expression in the dorsal CA1 region of the hippocampus was associated with poorer outcome devaluation performance on initial, but not later tests. Together, these data demonstrate that goal-directed action is initially impaired in J20 mice of both sexes and in aging male mice regardless of genotype, and that this impairment is related to neuroinflammation in the dorsal CA1 hippocampal region.

Association Study of a Comprehensive Panel of Neuropeptide-Related Polymorphisms Suggest Potential Roles in Verbal Learning and Memory.

Neuropeptides are mostly expressed in regions of the brain responsible for learning and memory and are centrally involved in cognitive pathways. The majority of neuropeptide research has been performed in animal models; with acknowledged differences between species, more research into the role of neuropeptides in humans is necessary to understand their contribution to higher cognitive function. In this study, we investigated the influence of genetic polymorphisms in neuropeptide genes on verbal learning and memory. Variants in genes encoding neuropeptides and neuropeptide receptors were tested for association with learning and memory measures using the Hopkins Verbal Learning Test-Revised (HVLT-R) in a healthy cohort of individuals (n = 597). The HVLT-R is a widely used task for verbal learning and memory assessment and provides five sub-scores: recall, delay, learning, retention, and discrimination. To determine the effect of candidate variants on learning and memory performance, genetic association analyses were performed for each HVLT-R sub-score with over 1300 genetic variants from 124 neuropeptide and neuropeptide receptor genes, genotyped on Illumina OmniExpress BeadChip arrays. This targeted analysis revealed numerous suggestive associations between HVLT-R test scores and neuropeptide and neuropeptide receptor gene variants; candidates include the SCG5, IGFR1, GALR1, OXTR, CCK, and VIPR1 genes. Further characterization of these genes and their variants will improve our understanding of the genetic contribution to learning and memory and provide insight into the importance of the neuropeptide network in humans.

Quantification of AMPA receptor subunits and RNA editing-related proteins in the J20 mouse model of Alzheimer's disease by capillary western blotting.

Introduction: Accurate modelling of molecular changes in Alzheimer's disease (AD) dementia is crucial for understanding the mechanisms driving neuronal pathology and for developing treatments. Synaptic dysfunction has long been implicated as a mechanism underpinning memory dysfunction in AD and may result in part from changes in adenosine deaminase acting on RNA (ADAR) mediated RNA editing of the GluA2 subunit of AMPA receptors and changes in AMPA receptor function at the post synaptic cleft. However, few studies have investigated changes in proteins which influence RNA editing and notably, AD studies that focus on studying changes in protein expression, rather than changes in mRNA, often use traditional western blotting. Methods: Here, we demonstrate the value of automated capillary western blotting to investigate the protein expression of AMPA receptor subunits (GluA1-4), the ADAR RNA editing proteins (ADAR1-3), and proteins known to regulate RNA editing (PIN1, WWP2, FXR1P, and CREB1), in the J20 AD mouse model. We describe extensive optimisation and validation of the automated capillary western blotting method, demonstrating the use of total protein to normalise protein load, in addition to characterising the optimal protein/antibody concentrations to ensure accurate protein quantification. Following this, we assessed changes in proteins of interest in the hippocampus of 44-week-old J20 AD mice. Results: We observed an increase in the expression of ADAR1 p110 and GluA3 and a decrease in ADAR2 in the hippocampus of 44-week-old J20 mice. These changes signify a shift in the balance of proteins that play a critical role at the synapse. Regression analysis revealed unique J20-specific correlations between changes in AMPA receptor subunits, ADAR enzymes, and proteins that regulate ADAR stability in J20 mice, highlighting potential mechanisms mediating RNA-editing changes found in AD. Discussion: Our findings in J20 mice generally reflect changes seen in the human AD brain. This study underlines the importance of novel techniques, like automated capillary western blotting, to assess protein expression in AD. It also provides further evidence to support the hypothesis that a dysregulation in RNA editing-related proteins may play a role in the initiation and/or progression of AD.

HSPGs glypican-1 and glypican-4 are human neuronal proteins characteristic of different neural phenotypes.

Generating neurons from human stem cells has potential for brain damage therapy and neurogenesis modeling, but current efficacy is limited by culture heterogeneity and the lack of markers. We have previously reported the heparan sulfate proteoglycans (HSPGs) glypican-1 (GPC1) and -4 (GPC4) as the markers of lineage-specific human neural stem cells (hNSCs) and mediators of hNSC lineage potential. Here, we further examined phenotypical characteristics and GPC1 and GPC4 during neural differentiation of hNSCs in the presence of two neurogenic growth factors reported to bind to heparan sulfate: brain-derived neurotrophic factor (BDNF) and platelet-derived growth factor-B (PDGF-B). In hNSC neural cultures, GPC1 and GPC4 were expressed along neurites and cell bodies in long-term (40-60 days) neural differentiation cultures demonstrating the areas of differential localization-suggesting potentially different functions. Neural differentiation cultures in the presence of BDNF or PDGF-B generated phenotypically different neural cells with BDNF treatment associated with higher GPC4 versus GPC1 expression, increased heterogeneity, and differential neuron subtype marker expression to PDGF-B cultures. PDGF-B cultures exhibited higher levels of spontaneous activity and reduced heterogeneity over long-term culture associated with decreased GPC4. Untreated neural cultures were highly variable, supporting the use of neuroregulatory growth factors for guided differentiation. Targeted siRNA downregulation of GPC1/4 reduced neural differentiation markers and altered response to exogenous BDNF and PDGF-B. This work confirms GPC1 and GPC4 as regulators of human neural differentiation and supports their use as novel markers of neural cell characterization.

Multilayered control of exon acquisition permits the emergence of novel forms of regulatory control.

BACKGROUND: The long introns of mammals are pools of evolutionary potential due to the multiplicity of sequences that permit the acquisition of novel exons. However, the permissibility of genes to this type of acquisition and its influence on the evolution of cell regulation is poorly understood. RESULTS: Here, we observe that human genes are highly permissive to the inclusion of novel exonic regions permitting the emergence of novel regulatory features. Our analysis reveals the potential for novel exon acquisition to occur in over 30% of evaluated human genes. Regulatory processes including the rate of splicing efficiency and RNA polymerase II (RNAPII) elongation control this process by modulating the "window of opportunity" for spliceosomal recognition. DNA damage alters this window promoting the inclusion of repeat-derived novel exons that reduce the ribosomal engagement of cell cycle genes. Finally, we demonstrate that the inclusion of novel exons is suppressed in hematological cancer samples and can be reversed by drugs modulating the rate of RNAPII elongation. CONCLUSION: Our work demonstrates that the inclusion of repeat-associated novel intronic regions is a tightly controlled process capable of expanding the regulatory capacity of cells.

Investigation of the CADM2 polymorphism rs17518584 in memory and executive functions measures in a cohort of young healthy individuals.

The common polymorphism rs17518584, near the cell adhesion molecule 2 gene (CADM2), was previously identified as playing a role in information processing speed in a genome-wide association study of executive functions and processing speed performed in a cohort of non-demented older adults. In this study, we investigated this polymorphism in a younger population cohort (≤30 years old, median age 19 years), with no known memory or psychiatric disorders, for which we had phenotyped all participants for memory function (n = 514), and a subset of the participants for executive functions (n = 338), using a battery of tests measuring visuo-spatial memory, working memory, verbal memory, and frontal lobe functions (visual scanning, graphomotor speed, and cognitive flexibility). The polymorphism rs17518584 was genotyped by a restriction fragment length polymorphism assay and analysis indicated that the CADM2 polymorphism showed evidence of association with information processing speed as inferred from scores from the Stroop Word, Colour, and Colour-Word Tests (p = 0.005, p = 0.04, and p = 0.028, respectively, in a dominant inheritance model), as well as Trail Making Test Part A (p = 0.005 in an additive model). Significant associations of rs17518584 with scores from other tests of memory subtypes were not detected. The findings of this study provide further support for a role of CADM2 in aspects of cognitive function, in particular reading and information processing speed, and suggest that this role extends to younger individuals.

A CREB1 Gene Polymorphism (rs2253206) Is Associated with Prospective Memory in a Healthy Cohort.

Prospective memory (PM) is generally defined as remembering to perform intended actions in the future and is important for functioning in daily life. Cyclic adenosine monophosphate (cAMP) responsive element binding protein 1 (CREB1) plays an important role in cognitive functions. In this study, we hypothesized that genetic variation in the CREB1 gene is associated with PM. We genotyped a CREB1 promoter polymorphism rs2253206 and tested it for association with PM in 619 healthy subjects. PM performance was measured using the Prospective and Retrospective Memory Questionnaire (PRMQ), the Comprehensive Assessment of Prospective Memory (CAPM), and the Memory for Intentions Screening Test (MIST). Generalized linear model analysis was conducted for each PM test independently using different inheritance models to identify any associations (p < 0.05). After multiple testing adjustments, a significant association was found between the rs2253206 genotype and PM performance for CAPM instrumental activities of daily living measure (p = 0.016). These results suggest that the rs2253206 polymorphism in the CREB1 gene locus is associated with PM in healthy individuals and contributes to knowledge on the genetics of this particular type of memory.

BDNF Variants May Modulate Long-Term Visual Memory Performance in a Healthy Cohort.

Brain-derived neurotrophic factor (BDNF) is involved in numerous cognitive functions including learning and memory. BDNF plays an important role in synaptic plasticity in humans and rats with BDNF shown to be essential for the formation of long-term memories. We previously identified a significant association between the BDNF Val66Met polymorphism (rs6265) and long-term visual memory (p-value = 0.003) in a small cohort (n = 181) comprised of healthy individuals who had been phenotyped for various aspects of memory function. In this study, we have extended the cohort to 597 individuals and examined multiple genetic variants across both the BDNF and BDNF-AS genes for association with visual memory performance as assessed by the Wechsler Memory Scale-Fourth Edition subtests Visual Reproduction I and II (VR I and II). VR I assesses immediate visual memory, whereas VR II assesses long-term visual memory. Genetic association analyses were performed for 34 single nucleotide polymorphisms genotyped on Illumina OmniExpress BeadChip arrays with the immediate and long-term visual memory phenotypes. While none of the BDNF and BDNF-AS variants were shown to be significant for immediate visual memory, we found 10 variants (including the Val66Met polymorphism (p-value = 0.006)) that were nominally associated, and three variants (two variants in BDNF and one variant in the BDNF-AS locus) that were significantly associated with long-term visual memory. Our data therefore suggests a potential role for BDNF, and its anti-sense transcript BDNF-AS, in long-term visual memory performance.

The effect of 1 mg folic acid supplementation on clinical outcomes in female migraine with aura patients.

BACKGROUND: Migraine is a common neurovascular condition that may be linked to hyperhomocysteinemia. We have previously provided evidence that reduction of homocysteine with a vitamin supplementation can reduce the occurrence of migraine in women. The current study examined the occurrence of migraine in response to vitamin supplementation with a lower dose of folic acid. METHODS: This was a 6 month randomised, double blinded placebo controlled trial of daily vitamin supplementation containing 1 mg of folic acid, 25 mg of Vitamin B6 and Vitamin B12, on reduction of homocysteine and the occurrence of migraine in 300 female patients diagnosed with migraine with aura. RESULTS: Vitamin supplementation with 1 mg of folic acid, did not significantly decrease homocysteine levels (P = 0.2). The treatment group did not show a significant decrease in the percentage of participants with high migraine disability, severity or frequency at the end of the 6 month intervention (P > 0.1). CONCLUSION: 1 mg of folic acid in combination with vitamin B6 and B12 is less effective in reducing migraine associated symptoms compared to the previously tested dosage of 2 mg folic acid in combination with 25 mg of vitamin B6 and 400 µg of vitamin B12.