Cognitive deficits in mice lacking Nsun5, a cytosine-5 RNA methyltransferase, with impairment of oligodendrocyte precursor cells.

Williams-Beuren syndrome (WBS) is a microdeletion disorder with cognitive phenotype. NSUN5 gene, which encodes a cytosine-5 RNA methyltransferase, is located in WBS deletion locus. To investigate the influence of NSUN5 deletion on cognitive behaviors, we produced single-gene Nsun5 knockout (Nsun5-KO) mice. Here, we report that adult Nsun5-KO mice showed spatial cognitive deficits. Size of the brain and hippocampal structures and the number of CA1 or CA3 pyramidal cells in Nsun5-KO mice did not differ from WT mice. Basal properties of Schaffer collateral-CA1 synaptic transmission in Nsun5-KO mice were unchanged, but NMDA receptor (NMDAr)-dependent long-term potentiation (LTP) was not induced. The NMDA-evoked current in CA1 pyramidal cells was reduced in Nsun5-KO mice without the changes in expression and phosphorylation of NMDAr subunits NR2A and NR2B. Although the protein level of AMPA receptor subunit GluR2 was attenuated in Nsun5-KO mice, the AMPA-evoked current was not altered. Hippocampal immuno-staining showed the selective expression of Nsun5 in NG2 or PDGFRα labeled oligodendrocyte precursor cells (OPCs), but not in pyramidal cells or astrocytes. Analysis of RT-PCR determined the Nsun5 expression in purified populations of OPCs rather than neurons or astrocytes. The Nsun5 deficiency led to decreases in the number and neurite outgrowth of OPCs in the hippocampal CA1 and DG, with the decline in NG2 expression and OPCs proliferation. These findings indicate that the Nsun5 deletion suppresses NMDAr activity in neuronal cells probably through the disrupted development and function of OPCs, leading to deficits in NMDAr-dependent LTP and spatial cognitive abilities.

The Low-Threshold Calcium Channel Cav3.2 Mediates Burst Firing of Mature Dentate Granule Cells.

Mature granule cells are poorly excitable neurons that were recently shown to fire action potentials, preferentially in bursts. It is believed that the particularly pronounced short-term facilitation of mossy fiber synapses makes granule cell bursting a very effective means of properly transferring information to CA3. However, the mechanism underlying the unique bursting behavior of mature granule cells is currently unknown. Here, we show that Cav3.2 T-type channels at the axon initial segment are responsible for burst firing of mature granule cells in rats and mice. Accordingly, Cav3.2 knockout mice fire tonic spikes and exhibit impaired bursting, synaptic plasticity and dentate-to-CA3 communication. The data show that Cav3.2 channels are strong modulators of bursting and can be considered a critical molecular switch that enables effective information transfer from mature granule cells to the CA3 pyramids.

Autism Related Neuroligin-4 Knockout Impairs Intracortical Processing but not Sensory Inputs in Mouse Barrel Cortex.

Neuroligin-4 (Nlgn4) is a cell adhesion protein that regulates synapse organization and function. Mutations in human NLGN4 are among the causes of autism spectrum disorders. In mouse, Nlgn4 knockout (KO) perturbs GABAergic synaptic transmission and oscillatory activity in hippocampus, and causes social interaction deficits. The complex profile of cellular and circuit changes that are caused by Nlgn4-KO is still only partly understood. Using Nlgn4-KO mice, we found that Nlgn4-KO increases the power in the alpha frequency band of spontaneous network activity in the barrel cortex under urethane anesthesia in vivo. Nlgn4-KO did not affect single-whisker-induced local field potentials, but suppressed the late evoked multiunit activity in vivo. Although Nlgn4-KO did not affect evoked EPSCs in layer 4 (L4) spiny stellate cells in acute thalamocortical slices elicited by electrical stimulation of thalamocortical inputs, it caused a lower frequency of both miniature (m) IPSCs and mEPSCs, and a decrease in the number of readily releasable vesicles at GABAergic and glutamatergic connections, weakening both excitatory and inhibitory transmission. However, Nlgn4 deficit strongly suppresses glutamatergic activity, shifting the excitation-inhibition balance to inhibition. We conclude that Nlgn4-KO does not influence the incoming whisker-mediated sensory information to the barrel cortex, but modifies intracortical information processing.

The Relation Between Long-Term Synaptic Plasticity at Glutamatergic Synapses in the Amygdala and Fear Learning in Adult Heterozygous BDNF-Knockout Mice.

Brain-derived neurotrophic factor (BDNF) heterozygous knockout mice (BDNF+/- mice) show fear learning deficits from 3 months of age onwards. Here, we addressed the question how this learning deficit correlates with altered long-term potentiation (LTP) in the cortical synaptic input to the lateral amygdala (LA) and at downstream intra-amygdala synapses in BDNF+/- mice. Our results reveal that the fear learning deficit in BDNF+/- mice was not paralleled by a loss of LTP, neither at cortical inputs to the LA nor at downstream intra-amygdala glutamatergic synapses. As we did observe early fear memory (30 min after training) in BDNF+/- mice while long-term memory (24 h post-training) was absent, the stable LTP in cortico-LA and downstream synapses is in line with the intact acquisition of fear memories. Ex vivo recordings in acute slices of fear-conditioned wildtype (WT) mice revealed that fear learning induces long-lasting changes at cortico-LA synapses that occluded generation of LTP 4 and 24 h after training. Overall, our data show that the intact LTP in the tested amygdala circuits is consistent with intact acquisition of fear memories in both WT and BDNF+/- mice. In addition, the lack of learning-induced long-term changes at cortico-LA synapses in BDNF+/- mice parallels the observed deficit in fear memory consolidation.

Electrical and Network Neuronal Properties Are Preferentially Disrupted in Dorsal, But Not Ventral, Medial Entorhinal Cortex in a Mouse Model of Tauopathy.

The entorhinal cortex (EC) is one of the first areas to be disrupted in neurodegenerative diseases such as Alzheimer's disease and frontotemporal dementia. The responsiveness of individual neurons to electrical and environmental stimuli varies along the dorsal-ventral axis of the medial EC (mEC) in a manner that suggests this topographical organization plays a key role in neural encoding of geometric space. We examined the cellular properties of layer II mEC stellate neurons (mEC-SCs) in rTg4510 mice, a rodent model of neurodegeneration. Dorsoventral gradients in certain intrinsic membrane properties, such as membrane capacitance and afterhyperpolarizations, were flattened in rTg4510 mEC-SCs, while other cellular gradients [e.g., input resistance (Ri), action potential properties] remained intact. Specifically, the intrinsic properties of rTg4510 mEC-SCs in dorsal aspects of the mEC were preferentially affected, such that action potential firing patterns in dorsal mEC-SCs were altered, while those in ventral mEC-SCs were unaffected. We also found that neuronal oscillations in the gamma frequency band (30-80 Hz) were preferentially disrupted in the dorsal mEC of rTg4510 slices, while those in ventral regions were comparatively preserved. These alterations corresponded to a flattened dorsoventral gradient in theta-gamma cross-frequency coupling of local field potentials recorded from the mEC of freely moving rTg4510 mice. These differences were not paralleled by changes to the dorsoventral gradient in parvalbumin staining or neurodegeneration. We propose that the selective disruption to dorsal mECs, and the resultant flattening of certain dorsoventral gradients, may contribute to disturbances in spatial information processing observed in this model of dementia. SIGNIFICANCE STATEMENT: The medial entorhinal cortex (mEC) plays a key role in spatial memory and is one of the first areas to express the pathological features of dementia. Neurons of the mEC are anatomically arranged to express functional dorsoventral gradients in a variety of neuronal properties, including grid cell firing field spacing, which is thought to encode geometric scale. We have investigated the effects of tau pathology on functional dorsoventral gradients in the mEC. Using electrophysiological approaches, we have shown that, in a transgenic mouse model of dementia, the functional properties of the dorsal mEC are preferentially disrupted, resulting in a flattening of some dorsoventral gradients. Our data suggest that neural signals arising in the mEC will have a reduced spatial content in dementia.

Combined Pharmacological and Genetic Manipulations Unlock Unprecedented Temporal Elasticity and Reveal Phase-Specific Modulation of the Molecular Circadian Clock of the Mouse Suprachiasmatic Nucleus.

UNLABELLED: The suprachiasmatic nucleus (SCN) is the master circadian oscillator encoding time-of-day information. SCN timekeeping is sustained by a cell-autonomous transcriptional-translational feedback loop, whereby expression of the Period and Cryptochrome genes is negatively regulated by their protein products. This loop in turn drives circadian oscillations in gene expression that direct SCN electrical activity and thence behavior. The robustness of SCN timekeeping is further enhanced by interneuronal, circuit-level coupling. The aim of this study was to combine pharmacological and genetic manipulations to push the SCN clockwork toward its limits and, by doing so, probe cell-autonomous and emergent, circuit-level properties. Circadian oscillation of mouse SCN organotypic slice cultures was monitored as PER2::LUC bioluminescence. SCN of three genetic backgrounds-wild-type, short-period CK1ε(Tau/Tau) mutant, and long-period Fbxl3(Afh/Afh) mutant-all responded reversibly to pharmacological manipulation with period-altering compounds: picrotoxin, PF-670462 (4-[1-Cyclohexyl-4-(4-fluorophenyl)-1H-imidazol-5-yl]-2-pyrimidinamine dihydrochloride), and KNK437 (N-Formyl-3,4-methylenedioxy-benzylidine-gamma-butyrolactam). This revealed a remarkably wide operating range of sustained periods extending across 25 h, from ≤17 h to >42 h. Moreover, this range was maintained at network and single-cell levels. Development of a new technique for formal analysis of circadian waveform, first derivative analysis (FDA), revealed internal phase patterning to the circadian oscillation at these extreme periods and differential phase sensitivity of the SCN to genetic and pharmacological manipulations. For example, FDA of the CK1ε(Tau/Tau) mutant SCN treated with the CK1ε-specific inhibitor PF-4800567 (3-[(3-Chlorophenoxy)methyl]-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine hydrochloride) revealed that period acceleration in the mutant is due to inappropriately phased activity of the CK1ε isoform. In conclusion, extreme period manipulation reveals unprecedented elasticity and temporal structure of the SCN circadian oscillation. SIGNIFICANCE STATEMENT: The master circadian clock of the suprachiasmatic nucleus (SCN) encodes time-of-day information that allows mammals to predict and thereby adapt to daily environmental cycles. Using combined genetic and pharmacological interventions, we assessed the temporal elasticity of the SCN network. Despite having evolved to generate a 24 h circadian period, we show that the molecular clock is surprisingly elastic, able to reversibly sustain coherent periods between ≤17 and >42 h at the levels of individual cells and the overall circuit. Using quantitative techniques to analyze these extreme periodicities, we reveal that the oscillator progresses as a sequence of distinct stages. These findings reveal new properties of how the SCN functions as a network and should inform biological and mathematical analyses of circadian timekeeping.

Altered Intrinsic Pyramidal Neuron Properties and Pathway-Specific Synaptic Dysfunction Underlie Aberrant Hippocampal Network Function in a Mouse Model of Tauopathy.

The formation and deposition of tau protein aggregates is proposed to contribute to cognitive impairments in dementia by disrupting neuronal function in brain regions, including the hippocampus. We used a battery of in vivo and in vitro electrophysiological recordings in the rTg4510 transgenic mouse model, which overexpresses a mutant form of human tau protein, to investigate the effects of tau pathology on hippocampal neuronal function in area CA1 of 7- to 8-month-old mice, an age point at which rTg4510 animals exhibit advanced tau pathology and progressive neurodegeneration. In vitro recordings revealed shifted theta-frequency resonance properties of CA1 pyramidal neurons, deficits in synaptic transmission at Schaffer collateral synapses, and blunted plasticity and imbalanced inhibition at temporoammonic synapses. These changes were associated with aberrant CA1 network oscillations, pyramidal neuron bursting, and spatial information coding in vivo. Our findings relate tauopathy-associated changes in cellular neurophysiology to altered behavior-dependent network function. SIGNIFICANCE STATEMENT: Dementia is characterized by the loss of learning and memory ability. The deposition of tau protein aggregates in the brain is a pathological hallmark of dementia; and the hippocampus, a brain structure known to be critical in processing learning and memory, is one of the first and most heavily affected regions. Our results show that, in area CA1 of hippocampus, a region involved in spatial learning and memory, tau pathology is associated with specific disturbances in synaptic, cellular, and network-level function, culminating in the aberrant encoding of spatial information and spatial memory impairment. These studies identify several novel ways in which hippocampal information processing may be disrupted in dementia, which may provide targets for future therapeutic intervention.

Tolcapone-Enhanced Neurocognition in Healthy Adults: Neural Basis and Predictors.

Background: Failure of procognitive drug trials in schizophrenia may reflect the clinical heterogeneity of schizophrenia, underscoring the need to identify biomarkers of treatment sensitivity. We used an experimental medicine design to test the procognitive effects of a putative procognitive agent, tolcapone, using an electroencephalogram-based cognitive control task in healthy subjects. Methods: Healthy men and women (n=27; ages 18-35 years), homozygous for either the Met/Met or Val/Val rs4680 genotype, received placebo and tolcapone 200 mg orally across 2 test days separated by 1 week in a double-blind, randomized, counterbalanced, within-subject design. On each test day, neurocognitive performance was assessed using the MATRICS Consensus Cognitive Battery and an electroencephalogram-based 5 Choice-Continuous Performance Test. Results: Tolcapone enhanced visual learning in low-baseline MATRICS Consensus Cognitive Battery performers (d=0.35) and had an opposite effect in high performers (d=0.5), and enhanced verbal fluency across all subjects (P=.03) but had no effect on overall MATRICS Consensus Cognitive Battery performance. Tolcapone reduced false alarm rate (d=0.8) and enhanced frontal P200 amplitude during correctly identified nontarget trials (d=0.6) in low-baseline 5 Choice-Continuous Performance Test performers and had opposite effects in high performers (d=0.5 and d=0.25, respectively). Tolcapone's effect on frontal P200 amplitude and false alarm rate was correlated (rs=-0.4, P=.05). All neurocognitive effects of tolcapone were independent of rs4680 genotype. Conclusion: Tolcapone enhanced neurocognition and engaged electroencephalogram measures relevant to cognitive processes in specific subgroups of healthy individuals. These findings support an experimental medicine model for identifying procognitive treatments and provide a strong basis for future biomarker-informed procognitive studies in schizophrenia patients.

From Shortage to Surge: A Developmental Switch in Hippocampal-Prefrontal Coupling in a Gene-Environment Model of Neuropsychiatric Disorders.

Cognitive deficits represent a major burden of neuropsychiatric disorders and result in part from abnormal communication within hippocampal-prefrontal circuits. While it has been hypothesized that this network dysfunction arises during development, long before the first clinical symptoms, experimental evidence is still missing. Here, we show that pre-juvenile mice mimicking genetic and environmental risk factors of disease (dual-hit GE mice) have poorer recognition memory that correlates with augmented coupling by synchrony and stronger directed interactions between prefrontal cortex and hippocampus. The network dysfunction emerges already during neonatal development, yet it initially consists in a diminished hippocampal theta drive and consequently, a weaker and disorganized entrainment of local prefrontal circuits in discontinuous oscillatory activity in dual-hit GE mice when compared with controls. Thus, impaired maturation of functional communication within hippocampal-prefrontal networks switching from hypo- to hyper-coupling may represent a mechanism underlying the pathophysiology of cognitive deficits in neuropsychiatric disorders.

Is Aspartate an Excitatory Neurotransmitter?

Recent evidence has resurrected the idea that the amino acid aspartate, a selective NMDA receptor agonist, is a neurotransmitter. Using a mouse that lacks the glutamate-selective vesicular transporter VGLUT1, we find that glutamate alone fully accounts for the activation of NMDA receptors at excitatory synapses in the hippocampus. This excludes a role for aspartate and, by extension, a recently proposed role for the sialic acid transporter sialin in excitatory transmission. SIGNIFICANCE STATEMENT: It has been proposed that the amino acid aspartate serves as a neurotransmitter. Although aspartate is a selective agonist for NMDA receptors, we find that glutamate alone fully accounts for neurotransmission at excitatory synapses in the hippocampus, excluding a role for aspartate.

α7-nAChR agonist enhances neural plasticity in the hippocampus via a GABAergic circuit.

Agonists of the α7-nicotinic acetylcholine receptor (α7-nAChR) have entered clinical trials as procognitive agents for treating schizophrenia and Alzheimer's disease. The most advanced compounds are orthosteric agonists, which occupy the ligand binding site. At the molecular level, agonist activation of α7-nAChR is reasonably well understood. However, the consequences of activating α7-nAChRs on neural circuits underlying cognition remain elusive. Here we report that an α7-nAChR agonist (FRM-17848) enhances long-term potentiation (LTP) in rat septo-hippocampal slices far below the cellular EC50 but at a concentration that coincides with multiple functional outcome measures as we reported in Stoiljkovic M, Leventhal L, Chen A, Chen T, Driscoll R, Flood D, Hodgdon H, Hurst R, Nagy D, Piser T, Tang C, Townsend M, Tu Z, Bertrand D, Koenig G, Hajós M. Biochem Pharmacol 97: 576-589, 2015. In this same concentration range, we observed a significant increase in spontaneous γ-aminobutyric acid (GABA) inhibitory postsynaptic currents and a moderate suppression of excitability in whole cell recordings from rat CA1 pyramidal neurons. This modulation of GABAergic activity is necessary for the LTP-enhancing effects of FRM-17848, since inhibiting GABAA α5-subunit-containing receptors fully reversed the effects of the α7-nAChR agonist. These data suggest that α7-nAChR agonists may increase synaptic plasticity in hippocampal slices, at least in part, through a circuit-level enhancement of a specific subtype of GABAergic receptor.

Disrupted hippocampal network physiology following PTEN deletion from newborn dentate granule cells.

Abnormal hippocampal granule cells are present in patients with temporal lobe epilepsy, and are a prominent feature of most animal models of the disease. These abnormal cells are hypothesized to contribute to epileptogenesis. Isolating the specific effects of abnormal granule cells on hippocampal physiology, however, has been difficult in traditional temporal lobe epilepsy models. While epilepsy induction in these models consistently produces abnormal granule cells, the causative insults also induce widespread cell death among hippocampal, cortical and subcortical structures. Recently, we demonstrated that introducing morphologically abnormal granule cells into an otherwise normal mouse brain - by selectively deleting the mTOR pathway inhibitor PTEN from postnatally-generated granule cells - produced hippocampal and cortical seizures. Here, we conducted acute slice field potential recordings to assess the impact of these cells on hippocampal function. PTEN deletion from a subset of granule cells reproduced aberrant responses present in traditional epilepsy models, including enhanced excitatory post-synaptic potentials (fEPSPs) and multiple, rather than single, population spikes in response to perforant path stimulation. These findings provide new evidence that abnormal granule cells initiate a process of epileptogenesis - in the absence of widespread cell death - which culminates in an abnormal dentate network similar to other models of temporal lobe epilepsy. Findings are consistent with the hypothesis that accumulation of abnormal granule cells is a common mechanism of temporal lobe epileptogenesis.

The aetiological association between the dynamics of cortisol productivity and ADHD.

Attention-deficit/hyperactivity disorder (ADHD) has been linked to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, indexed by salivary cortisol. The phenotypic and aetiological association of cortisol productivity with ADHD was investigated. A selected twin design using 68 male twin-pairs aged 12-15, concordant or discordant for high ADHD symptom scores, or control twin-pairs with low ADHD symptoms, based on developmentally stable parental ADHD ratings. A genetic growth curve model was applied to cortisol samples obtained across three points during a cognitive-electroencephalography assessment, to examine the aetiological overlap of ADHD affection status (high versus low ADHD symptom scores) with latent intercept and slope factors. A significant phenotypic correlation emerged between ADHD and the slope factor, with cortisol levels dropping faster for the group with high ADHD symptom scores. The analyses further suggested this overlap was mostly driven by correlated genetic effects. We identified change in cortisol activity over time as significantly associated with ADHD affection status, primarily explained by shared genetic effects, suggesting that blunted cortisol productivity can be a marker of genetic risk in ADHD.

The ANK3 gene and facial affect processing: An ERP study.

ANK3 is one of the most promising candidate genes for bipolar disorder (BD). A polymorphism (rs10994336) within the ANK3 gene has been associated with BD in at least three genome-wide association studies of BD [McGuffin et al., 2003; Kieseppä, 2004; Edvardsen et al., 2008]. Because facial affect processing is disrupted in patients with BD, the current study aimed to explore whether the BD risk alleles are associated with the N170, an early event-related potential (ERP) component related to facial affect processing. We collected data from two independent samples of healthy individuals (Ns = 83 and 82, respectively) to test the association between rs10994336 and an early event-related potential (ERP) component (N170) that is sensitive to facial affect processing. Repeated-measures analysis of covariance in both samples consistently revealed significant main effects of rs10994336 genotype (Sample I: F (1, 72) = 7.24, P = 0.009; Sample II: F (1, 69) = 11.81, P = 0.001), but no significant interaction of genotype × electrodes (Ps > 0.05) or genotype × emotional conditions (Ps > 0.05). These results suggested that rs10994336 was linked to early ERP component reflecting facial structural encoding during facial affect processing. These results shed new light on the brain mechanism of this risk SNP and associated disorders such as BD. © 2016 Wiley Periodicals, Inc.

Spinal muscular atrophy associated with progressive myoclonic epilepsy: A rare condition caused by mutations in ASAH1.

OBJECTIVE: To present the clinical features and the results of laboratory investigations in three patients with spinal muscular atrophy associated with progressive myoclonic epilepsy (SMA-PME), a rare condition caused by mutations in the N-acylsphingosine amidohydrosilase 1 (ASAH1) gene. METHODS: The patients were submitted to clinical evaluation, neurophysiologic investigations (that included wakefulness and sleep electroencephalography [EEG], video-polygraphic recording with jerk-locked back-averaging, multimodal evoked potentials, and electromyography), brain magnetic resonance imaging (MRI), biochemical screening, muscle and skin biopsies, and molecular genetic analysis. RESULTS: The main clinical features were onset in childhood with proximal muscular weakness, generalized epilepsy with absences and myoclonic seizures, cognitive impairment of variable degree; the course was progressive with muscle wasting and uncontrolled epileptic seizures. In one patient, earlier onset before the age of 2 years was associated with a more complex clinical picture, with abnormal eye movements, progressive cognitive impairment, and a more rapid and severe course. EEG/polygraphic data were consistent with PME, demonstrating generalized spike-and-wave discharges, evidence of positive and negative myoclonia, and prominent photosensitivity. In one patient, transcranial magnetic stimulation showed a hyperexcitable motor cortex, whereas somatosensory evoked potentials were unaffected. Possible involvement of the central acoustic and visual pathways was suggested by abnormal auditory and visual evoked potentials. Muscle biopsies showed typical signs of neurogenic damage. Molecular genetic analysis showed mutations of the ASAH1 gene. SIGNIFICANCE: Our data indicate that SMA-PME associated with ASAH1 mutations is a genetically distinct condition with specific clinical and neurophysiologic features. Further studies are warranted to explore the role of the ASAH1 gene in muscle and brain function.

Presymptomatic and symptomatic ALS SOD1(G93A) mice differ in adenosine A1 and A2A receptor-mediated tonic modulation of neuromuscular transmission.

Amyotrophic lateral sclerosis (ALS) is a disease leading to neuromuscular transmission impairment. A2A adenosine receptor (A2AR) function changes with disease stage, but the role of the A(1) receptors (A1Rs) is unknown and may have a functional cross-talk with A2AR. The role of A1R in the SOD1(G93A) mouse model of ALS in presymptomatic (4-6 weeks old) and symptomatic (12-14 weeks old) phases was investigated by recording endplate potentials (EPPs), miniature endplate potentials (MEPPs), and quantal content (q.c.) of EPPs, from Mg(2+) paralyzed hemidiaphragm preparations. In presymptomatic mice, the A1R agonist, N (6)-cyclopentyladenosine (CPA) (50 nM), decreased mean EPP amplitude, MEPP frequency, and q.c. of EPPs, an effect quantitatively similar to that in age-matched wild-type (WT) mice. However, coactivation of A2AR with CGS 21680 (5 nM) prevented the effects of CPA in WT mice but not in presymptomatic SOD1(G93A) mice, suggestive of A1R/A2AR cross-talk disruption in this phase of ALS. DPCPX (50 nM) impaired CGS 21680 facilitatory action on neuromuscular transmission in WT but not in presymptomatic mice. In symptomatic animals, CPA only inhibited transmission if added in the presence of adenosine deaminase (ADA, 1 U/mL). ADA and DPCPX enhanced more transmission in symptomatic mice than in age-matched WT mice, suggestive of increase in extracellular adenosine during the symptomatic phase of ALS. The data documents that at the neuromuscular junction of presymptomatic SOD1(G93A) mice, there is a loss of A1R-A2AR functional cross-talk, while in symptomatic mice there is increased A1R tonic activation, and that with disease progression, changes in A1R-mediated adenosine modulation may act as aggravating factors during the symptomatic phase of ALS.

The ultra-slow NAT2*6A haplotype is associated with reduced higher cognitive functions in an elderly study group.

N-Acetyltransferase 2 (NAT2) genotype is associated with age-related declines in basic sensory hearing functions. However, the possible modulatory role of NAT2 for higher cognitive functions has not yet been studied. We tested auditory goal-directed behavior and attentional control in 120 NAT2 genotyped subjects (63-88 years), using an auditory distraction paradigm in which participants responded to the duration of long and short tone stimuli. We studied involuntary shifts in attention to task-irrelevant deviant stimuli and applied event-related potentials (ERPs) to examine which cognitive subprocesses are affected by NAT2 status on a neurophysiological level. Relative to the standard stimuli, deviant stimuli decreased performance in the recently described ultra-slow acetylators (NAT2*6A and *7B): The increase in error-corrected reaction times (a combined measure of response speed and accuracy) in ultra-slow acetylators (254 ms increase) was more than twice as high as in the rapid acetylator reference group (111 ms increase; p < 0.01). The increase was still higher than in the other slow acetylators (149 ms increase, p < 0.05). In addition, clear differences were found in the ERP results: Ultra-slow acetylators showed deficits specifically in the automatic detection of changes in the acoustic environment as evidenced by reduced mismatch negativity (MMN, p < 0.005 compared to rapid acetylators). Refocussing of attention after a distracting event was also impaired in the ultra-slow acetylators as evidenced by a reduced re-orienting negativity (RON, p < 0.01 compared to rapid acetylators). In conclusion, the ultra-slow acetylation status was associated with reduced higher cognitive functions.

Heterotrimeric G protein subunit Gγ13 is critical to olfaction.

The activation of G-protein-coupled olfactory receptors on the olfactory sensory neurons (OSNs) triggers a signaling cascade, which is mediated by a heterotrimeric G-protein consisting of α, ß, and γ subunits. Although its α subunit, Gαolf, has been identified and well characterized, the identities of its ß and γ subunits and their function in olfactory signal transduction, however, have not been well established yet. We, and others, have found the expression of Gγ13 in the olfactory epithelium, particularly in the cilia of the OSNs. In this study, we generated a conditional gene knock-out mouse line to specifically nullify Gγ13 expression in the olfactory marker protein-expressing OSNs. Immunohistochemical and Western blot results showed that Gγ13 subunit was indeed eliminated in the mutant mice's olfactory epithelium. Intriguingly, Gαolf, ß1 subunits, Ric-8B and CEP290 proteins, were also absent in the epithelium whereas the presence of the effector enzyme adenylyl cyclase III remained largely unaltered. Electro-olfactogram studies showed that the mutant animals had greatly reduced responses to a battery of odorants including three presumable pheromones. Behavioral tests indicated that the mutant mice had a remarkably reduced ability to perform an odor-guided search task although their motivation and agility seemed normal. Our results indicate that Gαolf exclusively forms a functional heterotrimeric G-protein with Gß1 and Gγ13 in OSNs, mediating olfactory signal transduction. The identification of the olfactory G-protein's ßγ moiety has provided a novel approach to understanding the feedback regulation of olfactory signal transduction pathways as well as the control of subcellular structures of OSNs.

A dynamic deep sleep stage in Drosophila.

How might one determine whether simple animals such as flies sleep in stages? Sleep in mammals is a dynamic process involving different stages of sleep intensity, and these are typically associated with measurable changes in brain activity (Blake and Gerard, 1937; Rechtschaffen and Kales, 1968; Webb and Agnew, 1971). Evidence for different sleep stages in invertebrates remains elusive, even though it has been well established that many invertebrate species require sleep (Campbell and Tobler, 1984; Hendricks et al., 2000; Shaw et al., 2000; Sauer et al., 2003). Here we used electrophysiology and arousal-testing paradigms to show that the fruit fly, Drosophila melanogaster, transitions between deeper and lighter sleep within extended bouts of inactivity, with deeper sleep intensities after ∼15 and ∼30 min of inactivity. As in mammals, the timing and intensity of these dynamic sleep processes in flies is homeostatically regulated and modulated by behavioral experience. Two molecules linked to synaptic plasticity regulate the intensity of the first deep sleep stage. Optogenetic upregulation of cyclic adenosine monophosphate during the day increases sleep intensity at night, whereas loss of function of a molecule involved in synaptic pruning, the fragile-X mental retardation protein, increases sleep intensity during the day. Our results show that sleep is not homogenous in insects, and suggest that waking behavior and the associated synaptic plasticity mechanisms determine the timing and intensity of deep sleep stages in Drosophila.

Goofy coordinates the acuity of olfactory signaling.

The basic scheme of odor perception and signaling from olfactory cilia to the brain is well understood. However, factors that affect olfactory acuity of an animal, the threshold sensitivity to odorants, are less well studied. Using signal sequence trap screening of a mouse olfactory epithelium cDNA library, we identified a novel molecule, Goofy, that is essential for olfactory acuity in mice. Goofy encodes an integral membrane protein with specific expression in the olfactory and vomeronasal sensory neurons and predominant localization to the Golgi compartment. Goofy-deficient mice display aberrant olfactory phenotypes, including the impaired trafficking of adenylyl cyclase III, stunted olfactory cilia, and a higher threshold for physiological and behavioral responses to odorants. In addition, the expression of dominant-negative form of cAMP-dependent protein kinase results in shortening of olfactory cilia, implying a possible mechanistic link between cAMP and ciliogenesis in the olfactory sensory neurons. These results demonstrate that Goofy plays an important role in establishing the acuity of olfactory sensory signaling.