A BMAL1 mutant with arginine 91 substituted with alanine acts as a dominant negative inhibitor

Rewiring of lactate-IL-1β auto-regulatory loop with Clock-Bmal1: A feed-forward circuit in glioma

De-synchronized circadian rhythm in tumors is coincident with aberrant inflammation and dysregulated metabolism. As their inter-relationship in cancer etiology is largely unknown, we investigated the link between the three in glioma. Tumor metabolite lactate- mediated increase in pro-inflammatory cytokine IL-1β was concomitant with elevated levels of core circadian regulators Clock and Bmal1. siRNA mediated knockdown of Bmal1 and Clock decreased (i) LDHA and IL-1β levels and (ii) release of lactate and pro-inflammatory cytokines. Lactate mediated deacetylation of Bmal1 and its interaction with Clock, regulate IL-1β levels and vice versa. Site-directed mutagenesis and luciferase reporter assay indicated the functionality of E-box sites on LDHA and IL-1β promoters. ChIP-re-ChIP revealed that lactate-IL-1β crosstalk positively affects co-recruitment of Clock-Bmal1 to these E-box sites. Clock-Bmal1 enrichment was accompanied by decreased H3K9me3, and increased H3K9ac and RNA pol II occupancy. Lactate-IL-1β-Clock (LIC) loop positively regulated expression of genes associated with cell cycle, DNA damage and cytoskeletal organization involved in glioma progression. TCGA data analysis suggested the presence of lactate- IL-1β-crosstalk in other cancers. The responsiveness of stomach and cervical cancer cells to lactate inhibition followed the same trend exhibited by glioma cells. In addition, components of LIC loop were found to be correlated with (i) patient survival, (ii) clinically actionable genes, and (iii) anti-cancer drug sensitivity. Our findings provide evidence for a potential cancer-specific axis wiring of IL-1β and LDHA through Clock -Bmal1, the outcome of which is to fuel an IL-1β-lactate autocrine loop that drives pro-inflammatory and oncogenic signals.

Circadian clock mechanism driving mammalian photoperiodism

The annual photoperiod cycle provides the critical environmental cue synchronizing rhythms of life in seasonal habitats. In 1936, Bünning proposed a circadian-based coincidence timer for photoperiodic synchronization in plants. Formal studies support the universality of this so-called coincidence timer, but we lack understanding of the mechanisms involved. Here we show in mammals that long photoperiods induce the circadian transcription factor BMAL2, in the pars tuberalis of the pituitary, and triggers summer biology through the eyes absent/thyrotrophin (EYA3/TSH) pathway. Conversely, long-duration melatonin signals on short photoperiods induce circadian repressors including DEC1, suppressing BMAL2 and the EYA3/TSH pathway, triggering winter biology. These actions are associated with progressive genome-wide changes in chromatin state, elaborating the effect of the circadian coincidence timer. Hence, circadian clock-pituitary epigenetic pathway interactions form the basis of the mammalian coincidence timer mechanism. Our results constitute a blueprint for circadian-based seasonal timekeeping in vertebrates.

Hippocampal clock regulates memory retrieval via Dopamine and PKA-induced GluA1 phosphorylation

Cognitive performance in people varies according to time-of-day, with memory retrieval declining in the late afternoon-early evening. However, functional roles of local brain circadian clocks in memory performance remains unclear. Here, we show that hippocampal clock controlled by the circadian-dependent transcription factor BMAL1 regulates time-of-day retrieval profile. Inducible transgenic dominant negative BMAL1 (dnBMAL1) expression in mouse forebrain or hippocampus disrupted retrieval of hippocampal memories at Zeitgeber Time 8-12, independently of retention delay, encoding time and Zeitgeber entrainment cue. This altered retrieval profile was associated with downregulation of hippocampal Dopamine-cAMP signaling in dnBMAL1 mice. These changes included decreases in Dopamine Receptors (D1-R and D5-R) and GluA1-S845 phosphorylation by PKA. Consistently, pharmacological activation of cAMP-signals or D1/5Rs rescued impaired retrieval in dnBMAL1 mice. Importantly, GluA1 S845A knock-in mice showed similar retrieval deficits with dnBMAL1 mice. Our findings suggest mechanisms underlying regulation of retrieval by hippocampal clock through D1/5R-cAMP-PKA-mediated GluA1 phosphorylation.

MYOD1 functions as a clock amplifier as well as a critical co-factor for downstream circadian gene expression in muscle

In the present study we show that the master myogenic regulatory factor, MYOD1, is a positive modulator of molecular clock amplitude and functions with the core clock factors for expression of clock-controlled genes in skeletal muscle. We demonstrate that MYOD1 directly regulates the expression and circadian amplitude of the positive core clock factor Bmal1. We identify a non-canonical E-box element in Bmal1 and demonstrate that is required for full MYOD1-responsiveness. Bimolecular fluorescence complementation assays demonstrate that MYOD1 colocalizes with both BMAL1 and CLOCK throughout myonuclei. We demonstrate that MYOD1 and BMAL1:CLOCK work in a synergistic fashion through a tandem E-box to regulate the expression and amplitude of the muscle specific clock-controlled gene, Titin-cap (Tcap). In conclusion, these findings reveal mechanistic roles for the muscle specific transcription factor MYOD1 in the regulation of molecular clock amplitude as well as synergistic regulation of clock-controlled genes in skeletal muscle.

A case of Pitt-hopkins Syndrome with de novo mutation in TCF4: Clinical features and treatment for epilepsy

Pitt-Hopkins syndrome (PTHS), belonging to the group of 18q-syndromes, is a rare genetic disorder caused by mutations in TCF4. PTHS is characterized by distinctive facial appearance, intermittent hyperventilation, intellectual disability and developmental delay. Although patients with PTHS generally have various systemic symptoms, most of them with a TCF4 mutation manifest the central nervous system (CNS) disorders. We described the first Chinese case with Pitt-Hopkins syndrome based on clinical presentations and genetic findings. In addition to the typical features of PTHS, the girl also had paroxysms of tachypnea followed by cyanosis and recurrent seizures. Comprehensive medical examinations were performed including metabolic screening, hepatic and renal function evaluation, abdominal and cardiac ultrasounds. The presence of epileptic discharges in electroencephalography and abnormal brain magnetic resonance imaging were found. High-throughput sequencing was used to detect genetic mutations associated with CNS disorders. Sanger sequencing was used to confirm the mutations in the patient. The c.2182C＞T (p.Arg728Ter) mutation was a de novo nonsense mutation at exon 18 in the TCF4 gene of the patient. In conclusion, we have identified a de novo nonsense mutation of TCF4 carried by a Chinese girl with PTHS. The patient underwent anti-epileptic therapy (sodium valproate, levetiracetam, clonazepam), resulting in a reduction of the seizures.

PI3K regulates BMAL1/CLOCK-mediated circadian transcription from the Dbp promoter

The circadian rhythm generated by circadian clock underlies a molecular mechanism of rhythmic transcriptional regulation by transcription factor BMAL1/CLOCK. Importantly, the circadian clock is coordinated by exogenous cues to accommodate to changes in the external environment. However, the molecular mechanisms by which intracellular-signaling pathways mediate the adjustments of the circadian transcriptional rhythms remain unclear. In this study, we found that pharmacological inhibition or shRNA-mediated knockdown of phosphatidylinositol 3-kinase (PI3K) blocked upregulation of Dbp mRNA induced by serum shock in NIH 3T3 cells. Moreover, the inhibition of PI3K significantly reduced the promoter activity of the Dbp gene, as well as decreased the recruitment of BMAL1/CLOCK to the E-box in the Dbp promoter. Interestingly, the inhibition of PI3K blocked heterodimerization of BMAL1 and CLOCK. Our findings suggest that PI3K signaling plays a modulatory role in the regulation of the transcriptional rhythm of the Dbp gene by targeting BMAL1 and CLOCK.

Enhancement of fear memory by retrieval through reconsolidation

Memory retrieval is considered to have roles in memory enhancement. Recently, memory reconsolidation was suggested to reinforce or integrate new information into reactivated memory. Here, we show that reactivated inhibitory avoidance (IA) memory is enhanced through reconsolidation under conditions in which memory extinction is not induced. This memory enhancement is mediated by neurons in the amygdala, hippocampus, and medial prefrontal cortex (mPFC) through the simultaneous activation of calcineurin-induced proteasome-dependent protein degradation and cAMP responsive element binding protein-mediated gene expression. Interestingly, the amygdala is required for memory reconsolidation and enhancement, whereas the hippocampus and mPFC are required for only memory enhancement. Furthermore, memory enhancement triggered by retrieval utilizes distinct mechanisms to strengthen IA memory by additional learning that depends only on the amygdala. Our findings indicate that reconsolidation functions to strengthen the original memory and show the dynamic nature of reactivated memory through protein degradation and gene expression in multiple brain regions.

DOI:http://dx.doi.org/10.7554/eLife.02736.001

Video cameras allow us to record events as they happen. When we look back at a video clip, what we see is an exact replica of what was originally recorded. We tend to assume that our memories work in a similar manner. However, recent research suggests that our memories may be more malleable than we realize. Once a memory has been reactivated, it goes through a process known as reconsolidation that can make it stronger or weaker, or that can change its content.

Now, Fukushima et al. have carried out a series of experiments which shed light on the process of memory reconsolidation. Mice were trained to remember a negative event, and later tested on their memory of this event. Some of the mice were also given a ‘reactivation’ session, during which they were reminded of the original memory. These mice were more fearful of the event during the memory test than those who had not been reminded of it. This suggests that the process of reconsolidating the memory after it had been retrieved had the effect of making the memory stronger.

Fukushima et al. then demonstrated that this enhancement depended on the synthesis of proteins in particular regions of the brain. When the mice were given an injection to block protein synthesis immediately after reactivation of the memory, their memory of the negative event was weakened. Crucially, this effect only happened when the injection was given immediately after reactivation of the memory; if the memory had not been reactivated, the injection did not change its strength.

Fukushima et al. went on to show that three regions of the brain—the amygdala, the hippocampus, and the medial prefrontal cortex—are involved in memory enhancement. However, only one of them, the amygdala, is involved in the other aspects of reconsolidation. This research could support clinical work by elucidating the potential role of reconsolidation in conditions such as post-traumatic stress disorder.

DOI:http://dx.doi.org/10.7554/eLife.02736.002

Evidence for an internal and functional circadian clock in rat pituitary cells

In primary cultures of rat pituitary cells and in a pituitary sommatolactotroph cell line (GH4C1), endogenous core-clock- as well as hormone-genes such as prolactin displayed a rhythmic expression pattern, fitted by a sinusoidal equation in which the period value was close to the circadian one. This is consistent with the presence of a functional circadian oscillator in pituitary cells whose importance was ascertained in GH4C1 cell lines stably expressing a dominant negative mutant of BMAL1. In these cells, both endogenous core-clock- and prolactin-genes no more displayed a circadian pattern. Some genes we recently identified as mouse pituitary BMAL1-regulated genes in a DNA-microarray study, lost their circadian pattern in these cells, suggesting that BMAL1 controlled these genes locally in the pituitary. The intra-pituitary circadian oscillator could then play a role in the physiology of the gland that would not be seen anymore as a structure only driven by hypothalamic rhythmic control.

Interactions between αCaMKII and calmodulin in living cells: conformational changes arising from CaM-dependent and -independent relationships

BACKGROUND

αCaMKII plays central and essential roles in long-term potentiation (LTP), learning and memory. αCaMKII is activated via binding with Ca²⁺/CaM in response to elevated Ca²⁺ concentration. Furthermore, prolonged increase in Ca²⁺ concentration leads to the auto-phosphorylation of αCaMKII at T286, maintaining the activation of αCaMKII even after Ca²⁺/CaM dissociation. Importantly, the active form of αCaMKII is thought to exhibit conformational change. In order to elucidate the relationships between the interaction of αCaMKII with CaM and the conformational change of αCaMKII, we generated molecular probes (YFP-αCaMKII with CFP-CaM and YFP-αCaMKII-CFP) and performed time-lapse imaging of the interaction with CaM and the conformational change, respectively, in living cells using FRET.

RESULTS

The interaction of YFP-αCaMKII with CFP-CaM and the conformational change of YFP-αCaMKII-CFP were induced simultaneously in response to increased concentrations of Ca²⁺. Consistent with previous predictions, high levels of Ca²⁺ signaling maintained the conformational change of YFP-αCaMKII-CFP at the time when CFP-CaM was released from YFP-αCaMKII. These observations indicated the transfer of αCaMKII conformational change from CaM-dependence to CaM-independence. Furthermore, analyses using αCaMKII mutants showed that phosphorylation at T286 and T305/306 played positive and negative roles, respectively, during in vivo interaction with CaM and further suggested that CaM-dependent and CaM-independent conformational changed forms displays similar but distinct structures.

CONCLUSIONS

Importantly, these structual differences between CaM-dependent and -independent forms of αCaMKII may exhibit differential functions for αCaMKII, such as interactions with other molecules required for LTP and memory. Our molecular probes could thus be used to identify therapeutic targets for cognitive disorders that are associated with the misregulation of αCaMKII.

Pitt-Hopkins syndrome-associated mutations in TCF4 lead to variable impairment of the transcription factor function ranging from hypomorphic to dominant-negative effects

Transcription factor TCF4 (alias ITF2, SEF2 or E2-2) is a broadly expressed basic helix-loop-helix (bHLH) protein that functions as a homo- or heterodimer. Missense, nonsense, frame-shift and splice-site mutations as well as translocations and large deletions encompassing TCF4 gene cause Pitt-Hopkins syndrome (PTHS), a rare developmental disorder characterized by severe motor and mental retardation, typical facial features and breathing anomalies. Irrespective of the mutation, TCF4 haploinsufficiency has been proposed as an underlying mechanism for PTHS. We have recently demonstrated that human TCF4 gene is transcribed using numerous 5' exons. Here, we re-evaluated the impact of all the published PTHS-associated mutations, taking into account the diversity of TCF4 isoforms, and assessed how the reading frame elongating and missense mutations affect TCF4 functions. Our analysis revealed that not all deletions and truncating mutations in TCF4 result in complete loss-of-function and the impact of reading frame elongating and missense mutations ranges from subtle deficiencies to dominant-negative effects. We show that (i) missense mutations in TCF4 bHLH domain and the reading frame elongating mutation damage DNA-binding and transactivation ability in a manner dependent on dimer context (homodimer versus heterodimer with ASCL1 or NEUROD2); (ii) the elongating mutation and the missense mutation at the dimer interface of the HLH domain destabilize the protein; and (iii) missense mutations outside of the bHLH domain cause no major functional deficiencies. We conclude that different PTHS-associated mutations impair the functions of TCF4 by diverse mechanisms and to a varying extent, possibly contributing to the phenotypic variability of PTHS patients.

Dysfunction of the RAR/RXR signaling pathway in the forebrain impairs hippocampal memory and synaptic plasticity

Background

Retinoid signaling pathways mediated by retinoic acid receptor (RAR)/retinoid × receptor (RXR)-mediated transcription play critical roles in hippocampal synaptic plasticity. Furthermore, recent studies have shown that treatment with retinoic acid alleviates age-related deficits in hippocampal long-term potentiation (LTP) and memory performance and, furthermore, memory deficits in a transgenic mouse model of Alzheimer's disease. However, the roles of the RAR/RXR signaling pathway in learning and memory at the behavioral level have still not been well characterized in the adult brain. We here show essential roles for RAR/RXR in hippocampus-dependent learning and memory. In the current study, we generated transgenic mice in which the expression of dominant-negative RAR (dnRAR) could be induced in the mature brain using a tetracycline-dependent transcription factor and examined the effects of RAR/RXR loss.

Results

The expression of dnRAR in the forebrain down-regulated the expression of RARβ, a target gene of RAR/RXR, indicating that dnRAR mice exhibit dysfunction of the RAR/RXR signaling pathway. Similar with previous findings, dnRAR mice displayed impaired LTP and AMPA-mediated synaptic transmission in the hippocampus. More importantly, these mutant mice displayed impaired hippocampus-dependent social recognition and spatial memory. However, these deficits of LTP and memory performance were rescued by stronger conditioning stimulation and spaced training, respectively. Finally, we found that pharmacological blockade of RARα in the hippocampus impairs social recognition memory.

Conclusions

From these observations, we concluded that the RAR/RXR signaling pathway greatly contributes to learning and memory, and LTP in the hippocampus in the adult brain.

Upregulation of CREB-mediated transcription enhances both short- and long-term memory

Unraveling the mechanisms by which the molecular manipulation of genes of interest enhances cognitive function is important to establish genetic therapies for cognitive disorders. Although CREB is thought to positively regulate formation of long-term memory (LTM), gain-of-function effects of CREB remain poorly understood, especially at the behavioral level. To address this, we generated four lines of transgenic mice expressing dominant active CREB mutants (CREB-Y134F or CREB-DIEDML) in the forebrain that exhibited moderate upregulation of CREB activity. These transgenic lines improved not only LTM but also long-lasting long-term potentiation in the CA1 area in the hippocampus. However, we also observed enhanced short-term memory (STM) in contextual fear-conditioning and social recognition tasks. Enhanced LTM and STM could be dissociated behaviorally in these four lines of transgenic mice, suggesting that the underlying mechanism for enhanced STM and LTM are distinct. LTM enhancement seems to be attributable to the improvement of memory consolidation by the upregulation of CREB transcriptional activity, whereas higher basal levels of BDNF, a CREB target gene, predicted enhanced shorter-term memory. The importance of BDNF in STM was verified by microinfusing BDNF or BDNF inhibitors into the hippocampus of wild-type or transgenic mice. Additionally, increasing BDNF further enhanced LTM in one of the lines of transgenic mice that displayed a normal BDNF level but enhanced LTM, suggesting that upregulation of BDNF and CREB activity cooperatively enhances LTM formation. Our findings suggest that CREB positively regulates memory consolidation and affects memory performance by regulating BDNF expression.

PLCgamma2 Activates CREB-dependent Transcription in PC12 Cells Through Phosphorylation of CREB at Serine 133

The cAMP and Ca(2+) signaling pathways activate the transcription factor CREB through its phosphorylation at Serine 133. Activation of CREB is involved in the regulation of various biological phenomena. To understand further the mechanisms of the regulation of CREB activity in response to activation of the cAMP and Ca(2+) signaling pathways, we examined the roles of PLCgammas in CREB activation in PC12 cells. siRNA-mediated reduction of the expression of PLCgamma2, but not PLCgamma1, inhibited both the phosphorylation of CREB at S133 and the activation of CREB-dependent transcription following treatment of cells with forskolin or ionomycin, which increases the intracellular concentrations of cAMP or Ca(2+), respectively. Importantly, the siRNA targeting PLCgamma2 completely abolished CREB activation by Ca(2+) signaling but not by cAMP signaling. These results suggest that PLCgamma2 functions as an essential signal transducer leading to CREB activation in response to activation of the Ca(2+) signaling pathway and that the cAMP signaling pathway might activate CREB through phosphorylation of CREB by PKA and another signaling pathway mediated by PLCgamma2.

Development of a tightly-regulated tetracycline-dependent transcriptional activator and repressor co-expression system for the strong induction of transgene expression

The teteracycline (Tc)-dependent and -inducible transcriptional activator (rtTA) system has been used to express regulated transgene expression in vitro and in vivo. However, previous reports have demonstrated that, even in the absence of Tc, the rtTA binds weakly to the tetracycline response element (TRE), leading to a low level of background activity. In order to reduce the leaky gene expression induced by rtTA, we previously established a tightly regulated system (A-IRES-R system) that makes use of both the rtTA (A) and a Tc-dependent repressor (TetR-Kruppel-associated box; KRAB) (R). In addition, others have described a transactivator rtTA2-M2 (M2) that displays higher sensitivity to Dox than rtTA. In this study, to further develop the A-IRES-R system, we generated a derivative Tc system (M2-IRES-R system) that co-expresses both rtTA-M2 and TetR-KRAB from a single vector. We show that compared to the A-IRES-R system, the M2-IRES-R system leads to a greater level of induced TRE-mediated transcription in the presence of doxycycline (Dox) and yet displays a similar level of basal TRE-mediated transcription in the absence of Dox. Furthermore, the M2-IRES-R system also displays less leaky gene expression in the absence of Dox compared to rtTA-M2 and rtTA systems. Taken together, our results suggest that the M2-IRES-R system enables to tightly regulate and highly induce the expression of transgene compared to other systems.

Genotype-phenotype analysis of TCF4 mutations causing Pitt-Hopkins syndrome shows increased seizure activity with missense mutations

PURPOSE

Pitt-Hopkins syndrome is characterized by severe mental retardation, characteristic dysmorphic features, and susceptibility to childhood-onset seizures and intermittent episodes of hyperventilation. This syndrome is caused by haploinsufficiency of TCF4, which encodes a basic helix-loop-helix transcription factor. Missense, nonsense, splice-site mutations, and gene deletions have been found in individuals with Pitt-Hopkins syndrome. Previous reports have suggested that the Pitt-Hopkins syndrome phenotype is independent of mutation or deletion type.

METHODS

We screened 13,186 individuals with microarray-based comparative genomic hybridization. We also conducted a review of the literature and statistical analysis of the phenotypic features for all individuals with confirmed mutations or deletions of TCF4.

RESULTS

We identified seven individuals with TCF4 deletions. All patients have features consistent with Pitt-Hopkins syndrome, although only three have breathing anomalies, and none has seizures. Our review of previously reported cases with TCF4 mutations and deletions showed that all patients with Pitt-Hopkins syndrome reported to date have severe psychomotor retardation, the onsets of seizures and hyperventilation episodes are limited to the first decade in most reported patients with Pitt-Hopkins syndrome, hyperventilation episodes are more common than seizures and are seen in the oldest patients, and individuals with missense TCF4 mutations are more likely to develop seizures.

CONCLUSIONS

On the basis of an analysis of published cases, we propose a genotype-phenotype correlation of increased seizure activity with missense TCF4 mutations.

CBP/p300 is a cell type-specific modulator of CLOCK/BMAL1-mediated transcription

BACKGROUND

Previous studies have demonstrated tissue-specific regulation of the rhythm of circadian transcription, suggesting that transcription factor complex CLOCK/BMAL1, essential for maintaining circadian rhythm, regulates transcription in a tissue-specific manner. To further elucidate the mechanism of the cell type-specific regulation of transcription by CLOCK/BMAL1 at the molecular level, we investigated roles of CBP/p300 and tissue-specific cofactors in CLOCK/BMAL1-mediated transcription.

RESULTS

As shown previously, CBP/p300 stimulates CLOCK/BMAL1-mediated transcription in COS-1 cells. However, CBP/p300 repressed CLOCK/BMAL1-mediated transcription in NIH3T3 cells and knockdown of CBP or p300 expression by siRNA enhanced this transcription. Studies using GAL4-fusion proteins suggested that CBP represses CLOCK/BMAL1-mediated transcription by targeting CLOCK. We further investigated mechanisms of this cell type-specific modulation of CLOCK/BMAL1-mediated transcription by CBP by examining roles of co-repressor HDAC3 and co-activator pCAF, which are highly expressed in NIH3T3 and COS cells, respectively. CBP repressed CLOCK/BMAL1-mediated transcription in COS-1 cells when HDAC3 was overexpressed, but activated it in NIH3T3 cells when pCAF was overexpressed. CBP forms a complex with CLOCK by interacting with HDAC3 or pCAF; however, direct interaction of CBP with CLOCK was not observed.

CONCLUSION

Our findings indicate possible mechanisms by which CBP/p300 tissue-specifically acts cooperatively with pCAF and HDAC3 either as a co-activator or co-repressor, respectively, for CLOCK/BMAL1.

Transgenic up-regulation of alpha-CaMKII in forebrain leads to increased anxiety-like behaviors and aggression

Background

Previous studies have demonstrated essential roles for alpha-calcium/calmodulin-dependent protein kinase II (alpha-CaMKII) in learning, memory and long-term potentiation (LTP). However, previous studies have also shown that alpha-CaMKII (+/-) heterozygous knockout mice display a dramatic decrease in anxiety-like and fearful behaviors, and an increase in defensive aggression. These findings indicated that alpha-CaMKII is important not only for learning and memory but also for emotional behaviors. In this study, to understand the roles of alpha-CaMKII in emotional behavior, we generated transgenic mice overexpressing alpha-CaMKII in the forebrain and analyzed their behavioral phenotypes.

Results

We generated transgenic mice overexpressing alpha-CaMKII in the forebrain under the control of the alpha-CaMKII promoter. In contrast to alpha-CaMKII (+/-) heterozygous knockout mice, alpha-CaMKII overexpressing mice display an increase in anxiety-like behaviors in open field, elevated zero maze, light-dark transition and social interaction tests, and a decrease in locomotor activity in their home cages and novel environments; these phenotypes were the opposite to those observed in alpha-CaMKII (+/-) heterozygous knockout mice. In addition, similarly with alpha-CaMKII (+/-) heterozygous knockout mice, alpha-CaMKII overexpressing mice display an increase in aggression. However, in contrast to the increase in defensive aggression observed in alpha-CaMKII (+/-) heterozygous knockout mice, alpha-CaMKII overexpressing mice display an increase in offensive aggression.

Conclusion

Up-regulation of alpha-CaMKII expression in the forebrain leads to an increase in anxiety-like behaviors and offensive aggression. From the comparisons with previous findings, we suggest that the expression levels of alpha-CaMKII are associated with the state of emotion; the expression level of alpha-CaMKII positively correlates with the anxiety state and strongly affects aggressive behavior.

Upregulation of calcium/calmodulin-dependent protein kinase IV improves memory formation and rescues memory loss with aging

Previous studies have suggested that calcium/calmodulin-dependent protein kinase IV (CaMKIV) functions as a positive regulator for memory formation and that age-related memory deficits are the result of dysfunctional signaling pathways mediated by cAMP response element-binding protein (CREB), the downstream transcription factor of CaMKIV. Little is known, however, about the effects of increased CaMKIV levels on the ability to form memory in adult and aged stages. We generated a transgenic mouse overexpressing CaMKIV in the forebrain and showed that the upregulation of CaMKIV led to an increase in learning-induced CREB activity, increased learning-related hippocampal potentiation, and enhanced consolidation of contextual fear and social memories. Importantly, we also observed reduced hippocampal CaMKIV expression with aging and a correlation between CaMKIV expression level and memory performance in aged mice. Genetic overexpression of CaMKIV was able to rescue associated memory deficits in aged mice. Our findings suggest that the level of CaMKIV expression correlates positively with the ability to form long-term memory and implicate the decline of CaMKIV signaling mechanisms in age-related memory deficits.

Genetic enhancement of trace fear memory and cingulate potentiation in mice overexpressing Ca2+/calmodulin-dependent protein kinase IV

Long-term potentiation (LTP) is a key cellular model for studying mechanisms for learning and memory. Previous studies reported that the Ca(2+)/calmodulin-dependent protein kinase IV (CaMKIV) is critical for gene regulation, and behavioral learning and memory. Less is known about the roles of CaMKIV in cortical plasticity and trace fear memory. Here we have found that LTP was significantly enhanced in the anterior cingulate cortex (ACC) of the mice overexpressing CaMKIV. By contrast, neither alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated basal excitatory synaptic transmission nor N-methyl-d-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents were affected. Furthermore, paired-pulse ratio in the transgenic mice is normal. In behavioral tests, we found that the CaMKIV transgenic mice exhibited significant enhancement in trace fear memory, while the acute sensory thresholds were not affected. Our results provide strong evidence that forebrain CaMKIV contributes to trace fear memory by enhancing synaptic potentiation in the ACC.

Mutations in TCF4, encoding a class I basic helix-loop-helix transcription factor, are responsible for Pitt-Hopkins syndrome, a severe epileptic encephalopathy associated with autonomic dysfunction

Pitt-Hopkins syndrome (PHS) is a rare syndromic encephalopathy characterized by daily bouts of hyperventilation and a facial gestalt. We report a 1.8-Mb de novo microdeletion on chromosome 18q21.1, identified by array-comparative genomic hybridization in one patient with PHS. We subsequently identified two de novo heterozygous missense mutations of a conserved amino acid in the basic region of the TCF4 gene in three additional subjects with PHS. These findings demonstrate that TCF4 anomalies are responsible for PHS and provide the first evidence of a human disorder related to class I basic helix-loop-helix transcription-factor defects (also known as "E proteins"). Moreover, our data may shed new light on the normal processes underlying autonomic nervous system development and maintenance of an appropriate ventilatory neuronal circuitry.

Characterization of the promoter of the mouse preproorexin gene

The neuropeptide Orexin is involved in the regulation of the sleep-awake cycle and feeding behavior. We isolated a 22-kb genomic clone containing the 5' flanking region of the mouse Orexin promoter. We determined that the transcription start site (+1) is located 96 nucleotides upstream of the initiation codon. The start site region contained consensus sequences corresponding to the transcription initiator and TATA box. Analysis of promoter activity using PC12 cells showed that regions between -13 and +112 and between -1,868 and -780 contained nerve growth factor (NGF)-responsive positive regulatory element and a negative regulatory element respectively.

Tight regulation of transgene expression by tetracycline-dependent activator and repressor in brain

Methods to temporally and spatially regulate gene mutations will provide a powerful strategy to investigate gene function in the brain. To develop these methods, we have established a tightly regulated system for transgene expression in the forebrain using both a tetracycline (Tc)-dependent transcription activator (rtTA) and a repressor (TetR-Kruppel-associated box). In this system, the repressor binds to the Tc-responsive element (TRE) in the absence of doxycycline (Dox), leading to the repression of leaky activation of TRE-mediated transcription caused by weak binding of rtTA to TRE. Upon Dox administration, only the activator binds to TRE and activates transcription. We tested this system in cultured cells by bicistronically expressing both the regulators using an internal ribosome entry site (IRES). In COS-1, HeLa and SHSY5Y cells, leaky transcription activation led by rtTA in the absence of Dox was repressed without decreasing the level of activated transcription in the presence of Dox. Using this system, transgenic mice were produced that express both the regulators using IRES in the forebrain under the control of the alphaCaMKII promoter and were bred with transgenic mice carrying the TRE-dependent reporter transgene. In reverse transcription-polymerase chain reaction and in situ hybridization analyses of the forebrain in adult double transgenic mice, the treatment of Dox induces reporter mRNA expression, which was not detected before the treatment and after the withdraw of Dox following the treatment. These results indicate that this system allows the tight regulation of transgene expression in a Dox-dependent fashion in the forebrain and will be useful in investigating gene function in the brain.

Suggestive evidence for association of the circadian genes PERIOD3 and ARNTL with bipolar disorder

Bipolar affective disorder (BPAD) is suspected to arise in part from malfunctions of the circadian system, a system that enables adaptation to a daily and seasonally cycling environment. Genetic variations altering functions of genes involved with the input to the circadian clock, in the molecular feedback loops constituting the circadian oscillatory mechanism itself, or in the regulatory output systems could influence BPAD as a result. Several human circadian system genes have been identified and localized recently, and a comparison with linkage hotspots for BPAD has revealed some correspondences. We have assessed evidence for linkage and association involving polymorphisms in 10 circadian clock genes (ARNTL, CLOCK, CRY2, CSNK1epsilon, DBP, GSK3beta, NPAS2, PER1, PER2, and PER3) to BPAD. Linkage analysis in 52 affected families showed suggestive evidence for linkage to CSNK1epsilon. This finding was not substantiated in the association study. Fifty-two SNPs in 10 clock genes were genotyped in 185 parent proband triads. Single SNP TDT analyses showed no evidence for association to BPAD. However, more powerful haplotype analyses suggest two candidates deserving further studies. Haplotypes in ARNTL and PER3 were found to be significantly associated with BPAD via single-gene permutation tests (PG = 0.025 and 0.008, respectively). The most suggestive haplotypes in PER3 showed a Bonferroni-corrected P-value of PGC = 0.07. These two genes have previously been implicated in circadian rhythm sleep disorders and affective disorders. With correction for the number of genes considered and tests conducted, these data do not provide statistically significant evidence for association. However, the trends for ARNTL and PER3 are suggestive of their involvement in bipolar disorder and warrant further study in a larger sample.