Diacylglycerol kinase β knockout mice exhibit attention-deficit behavior and an abnormal response on methylphenidate-induced hyperactivity

An updated review on animal models to study attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a neuropsychiatric disorder affecting both children and adolescents. Individuals with ADHD experience heterogeneous problems, such as difficulty in attention, behavioral hyperactivity, and impulsivity. Recent studies have shown that complex genetic factors play a role in attention-deficit hyperactivity disorders. Animal models with clear hereditary traits are crucial for studying the molecular, biological, and brain circuit mechanisms underlying ADHD. Owing to their well-managed genetic origins and the relative simplicity with which the function of neuronal circuits is clearly established, models of mice can help learn the mechanisms involved in ADHD. Therefore, in this review, we highlighting the important genetic animal models that can be used to study ADHD.

Thrsp Gene and the ADHD Predominantly Inattentive Presentation

There are three presentations of attention-deficit/hyperactivity disorder (ADHD): the predominantly inattention (ADHD-PI), predominantly hyperactive-impulsive (ADHD-HI), and combined (ADHD-C) presentations of ADHD. These may represent distinct childhood-onset neurobehavioral disorders with separate etiologies. ADHD diagnoses are behaviorally based, so investigations into potential etiologies should be founded on behavior. Animal models of ADHD demonstrate face, predictive, and construct validity when they accurately reproduce elements of the symptoms, etiology, biochemistry, and disorder treatment. Spontaneously hypertensive rats (SHR/NCrl) fulfill many validation criteria and compare well with clinical cases of ADHD-C. Compounding the difficulty of selecting an ideal model to study specific presentations of ADHD is a simple fact that our knowledge regarding ADHD neurobiology is insufficient. Accordingly, the current review has explored a potential animal model for a specific presentation, ADHD-PI, with acceptable face, predictive, and construct validity. The Thrsp gene could be a biomarker for ADHD-PI presentation, and THRSP OE mice could represent an animal model for studying this distinct ADHD presentation.

Single cannabidiol administration affects anxiety-, obsessive compulsive-, object memory-, and attention-like behaviors in mice in a sex and concentration dependent manner

RATIONALE

The behavioral effects of cannabidiol (CBD) are understudied, but are important, given its therapeutic potential and widespread use as a natural supplement.

OBJECTIVE

The objective of this study was to test whether a single injection of CBD affected anxiety-like or attention-like behavior, or memory in wildtype mice or mice with reported trait anxiety due to a targeted gene-deletion in a voltage-dependent potassium channel, Kv1.3.

METHODS

Wildtype C57BL/6 J and Kv1.3-/- mice of both sexes were reared to adulthood and then administered an intraperitoneal injection of 10 or 20 mg/kg CBD. Mice were behaviorally-phenotyped using the marble-burying test, the light-dark box (LDB), short (1 h) and long-term (24 h) object memory test, the elevated-plus maze (EPM), and the object-based attention task in order to assess obsessive compulsive-, anxiety-, and attention-like behaviors, and memory.

RESULTS

We discovered that acute CBD treatment reduced marble burying in male, but not female mice. CBD was effective in lessening anxiety-like behaviors determined by the LDB test in both male and female wildtype mice, whereby the effective dose required to observe the effect in females was less. In Kv1.3-/- mice, CBD increased anxiety-like behaviors in the LDB in both sexes at the higher concentration of CBD and it similarly increased anxiety-like behavior in females in the EPM at the lower concentration of CBD. Long-term object memory was reduced in male wildtype mice at the lower concentration of CBD. Finally, ADHD- or attention-like behaviors were not altered by CBD in wildtype mice, but in Kv1.3-/- mice, females were observed to have a loss in attention while males demonstrated improved attention.

CONCLUSIONS

We conclude that administration of a single dose of CBD has immediate effects on mouse behavior that is dose, sex, and anxiety-state dependent - and that these behavioral outcomes are important to examine in parallel human trials.

RalA, PLD and mTORC1 Are Required for Kinase-Independent Pathways in DGKβ-Induced Neurite Outgrowth

Diacylglycerol kinase β (DGKβ) is an enzyme that converts diacylglycerol to phosphatidic acid and is mainly expressed in the cerebral cortex, hippocampus and striatum. We previously reported that DGKβ induces neurite outgrowth and spinogenesis, contributing to higher brain functions, including emotion and memory. To elucidate the mechanisms involved in neuronal development by DGKβ, we investigated the importance of DGKβ activity in the induction of neurite outgrowth using human neuroblastoma SH-SY5Y cells. Interestingly, both wild-type DGKβ and the kinase-negative (KN) mutant partially induced neurite outgrowth, and these functions shared a common pathway via the activation of mammalian target of rapamycin complex 1 (mTORC1). In addition, we found that DGKβ interacted with the small GTPase RalA and that siRNA against RalA and phospholipase D (PLD) inhibitor treatments abolished DGKβKN-induced neurite outgrowth. These results indicate that binding of RalA and activation of PLD and mTORC1 are involved in DGKβKN-induced neurite outgrowth. Taken together with our previous reports, mTORC1 is a key molecule in both kinase-dependent and kinase-independent pathways of DGKβ-mediated neurite outgrowth, which is important for higher brain functions.

Precise Regulation of the Basal PKCγ Activity by DGKγ Is Crucial for Motor Coordination

Diacylglycerol kinase γ (DGKγ) is a lipid kinase to convert diacylglycerol (DG) to phosphatidic acid (PA) and indirectly regulates protein kinase C γ (PKCγ) activity. We previously reported that the basal PKCγ upregulation impairs cerebellar long-term depression (LTD) in the conventional DGKγ knockout (KO) mice. However, the precise mechanism in impaired cerebellar LTD by upregulated PKCγ has not been clearly understood. Therefore, we first produced Purkinje cell-specific DGKγ KO (tm1d) mice to investigate the specific function of DGKγ in Purkinje cells and confirmed that tm1d mice showed cerebellar motor dysfunction in the rotarod and beam tests, and the basal PKCγ upregulation but not PKCα in the cerebellum of tm1d mice. Then, the LTD-induced chemical stimulation, K-glu (50 mM KCl + 100 µM, did not induce phosphorylation of PKCα and dissociation of GluR2 and glutamate receptor interacting protein (GRIP) in the acute cerebellar slices of tm1d mice. Furthermore, treatment with the PKCγ inhibitor, scutellarin, rescued cerebellar LTD, with the phosphorylation of PKCα and the dissociation of GluR2 and GRIP. In addition, nonselective transient receptor potential cation channel type 3 (TRPC3) was negatively regulated by upregulated PKCγ. These results demonstrated that DGKγ contributes to cerebellar LTD by regulation of the basal PKCγ activity.

mGlu5 in GABAergic neurons modulates spontaneous and psychostimulant-induced locomotor activity

RATIONALE

A role of group I metabotropic glutamate receptor 5 (mGlu5) in regulating spontaneous locomotion and psychostimulant-induced hyperactivity has been proposed.

OBJECTIVES

This study aims to determine if mGlu5 in GABAergic neurons regulates spontaneous or psychostimulant-induced locomotion.

METHODS

We generated mice specifically lacking mGlu5 in forebrain GABAergic neuron by crossing DLX-Cre mice with mGlu5^flox/flox mice to generate DLX-mGlu5 KO mice. The locomotion of adult mice was examined in the open-field assay (OFA) and home cage setting. The effects of the mGlu5 antagonist 6-methyl-2-(phenylethynyl)pyridine (MPEP), cocaine, and methylphenidate on acute motor behaviors in DLX-mGlu5 KO and littermate control mice were assessed in OFA. Striatal synaptic plasticity of these mice was examined with field potential electrophysiological recordings.

RESULTS

Deleting mGlu5 from forebrain GABAergic neurons results in failure to induce long-term depression (LTD) in the dorsal striatum and absence of habituated locomotion in both novel and familiar settings. In a familiar environment (home cage), DLX-mGlu5 KO mice were hyperactive. In the OFA, DLX-mGlu5 KO mice exhibited initial hypo-activity, and then gradually increased their locomotion with time, resulting in no habituation response. DLX-mGlu5 KO mice exhibited almost no locomotor response to MPEP (40 mg/kg), while the same dose elicited hyperlocomotion in control mice. The DLX-mGlu5 KO mice also showed reduced hyperactivity response to cocaine, while they retained normal hyperactivity response to methylphenidate, albeit with delayed onset.

CONCLUSION

mGlu5 in forebrain GABAergic neurons is critical to trigger habituation upon the initiation of locomotion as well as to mediate MPEP-induced hyperlocomotion and modulate psychostimulant-induced hyperactivity.

mTORC1 is involved in DGKβ-induced neurite outgrowth and spinogenesis

Diacylglycerol kinase β (DGKβ) is an enzyme converting DG to phosphatidic acid (PA) and is specifically expressed in neurons, especially those in the cerebral cortex, hippocampus and striatum. We previously reported that DGKβ induces neurite outgrowth and spinogenesis, contributing to higher brain function including emotion and memory, and plasma membrane localization of DGKβ via the C1 domain and a cluster of basic amino acids at the C-terminus is necessary for its function. To clarify the mechanisms involved in neuronal development by DGKβ, we investigated whether DGKβ activity induces neurite outgrowth using human neuroblastoma SH-SY5Y cells. DGKβ induced neurite outgrowth by activation of mammalian target of rapamycin complex 1 (mTORC1) through a kinase-dependent pathway. In addition, in primary cultured cortical and hippocampal neurons, inhibition of mTORC1 abolished DGKβ induced-neurite outgrowth, branching and spinogenesis. These results indicated that DGKβ induces neurite outgrowth and spinogenesis by activating mTORC1 in a kinase-dependent pathway.

Elevated Anxiety and Impaired Attention in Super-Smeller, Kv1.3 Knockout Mice

It has long been recognized that olfaction and emotion are linked. While chemosensory research using both human and rodent models have indicated a change in emotion can contribute to olfactory dysfunction, there are few studies addressing the contribution of olfaction to a modulation in emotion. In mice, olfactory deficits have been linked with heightened anxiety levels, suggesting that there could be an inverse relationship between olfaction and anxiety. Furthermore, increased anxiety is often co-morbid with psychiatric conditions such as attention disorders. Our study aimed to investigate the roles of olfaction in modulating anxiety. Voltage-gated potassium ion channel Kv1.3 knockout mice (Kv1.3−/−), which have heightened olfaction, and wild-type (WT) mice were examined for anxiety-like behaviors using marble burying (MB), light-dark box (LDB) and elevated-plus maze (EPM) tests. Because Kv1.3−/− mice have increased locomotor activity, inattentive and hyperactive behaviors were quantified for both genotypes. Kv1.3−/− mice showed increased anxiety levels compared to their WT counterparts and administration of methylphenidate (MPH) via oral gavage alleviated their increased anxiety. Object-based attention testing indicated young and older Kv1.3−/− mice had attention deficits and treatment with MPH also ameliorated this condition. Locomotor testing through use of a metabolic chamber indicated that Kv1.3−/− mice were not significantly hyperactive and MPH treatment failed to modify this activity. Our data suggest that heightened olfaction does not necessarily lead to decreased anxiety levels, and that Kv1.3−/− mice may have behaviors associated with inattentiveness.

Learning and memory are impaired in the object recognition task during metestrus/diestrus and after sleep deprivation

Females are an under-represented research model and the mechanisms through which sleep loss impairs cognition are not clear. Since levels of reproductive hormones and the estrous cycle are sensitive to sleep loss and necessary for learning and memory, we hypothesized that sleep deprivation impacts learning and memory in female mice by interfering with the estrous cycle. We used the object recognition task to assess learning and memory in female mice during separate phases of the estrous cycle and after sleep loss. Mice in metestrus/diestrus attended to sample objects less than mice in proestrus/estrus during object acquisition, the first phase of the object recognition task. Subsequently, during the recognition phase of the task, only mice in proestrus/estrus displayed a preference for the novel object. Sleep deprivation for 12h immediately before the object recognition task reduced time attending to sample objects and novel object preference for mice in proestrus/estrus, without changing length of the estrous cycle. These results show that sleep deprived mice in proestrus/estrus had learning deficits and memory impairments, like mice in metestrus/diestrus. Since sleep deprivation did not disrupt the estrous cycle, however, results did not support the hypothesis. Cognitive impairments due to acute sleep loss were not due to alterations to the estrous cycle.

Sensorimotor gating deficits and effects of antipsychotics on the hyperactivity in VGF-overexpressing mice

BACKGROUND

VGF nerve growth factor inducible (VGF) is a neuropeptide which is expressed in neuronal cells and endocrine cells. VGF is induced by several neurotrophic factors. The expression level of VGF in patients with schizophrenia is increased in cerebrospinal fluid (CSF) and prefrontal cortex. In our previous study, we generated mice in which the expression level of VGF in the brain was increased. VGF-overexpressing mice exhibited abnormal behaviors including hyperactivity. However, it remains unknown whether VGF-overexpressing mice exhibit the endophenotype of schizophrenia and whether abnormal behaviors in these mice can be improved by antipsychotics.

METHODS

In the present study, we investigated schizophrenia-like behaviors and the responsiveness to antipsychotics in transgenic mice.

RESULTS

VGF-overexpressing mice (1) exhibited prepulse inhibition (PPI) impairment, (2) showed normalized hyperactivity following antipsychotic drug treatment, and (3) showed abnormal responsiveness to haloperidol.

CONCLUSION

Upregulation of VGF may be implicated in the pathophysiology of schizophrenia and abnormalities of dopaminergic signaling.

Exploring the Validity of Proposed Transgenic Animal Models of Attention-Deficit Hyperactivity Disorder (ADHD)

Attention-deficit/hyperactivity disorder (ADHD) is a common, behavioral, and heterogeneous neurodevelopmental condition characterized by hyperactivity, impulsivity, and inattention. Symptoms of this disorder are managed by treatment with methylphenidate, amphetamine, and/or atomoxetine. The cause of ADHD is unknown, but substantial evidence indicates that this disorder has a significant genetic component. Transgenic animals have become an essential tool in uncovering the genetic factors underlying ADHD. Although they cannot accurately reflect the human condition, they can provide insights into the disorder that cannot be obtained from human studies due to various limitations. An ideal animal model of ADHD must have face (similarity in symptoms), predictive (similarity in response to treatment or medications), and construct (similarity in etiology or underlying pathophysiological mechanism) validity. As the exact etiology of ADHD remains unclear, the construct validity of animal models of ADHD would always be limited. The proposed transgenic animal models of ADHD have substantially increased and diversified over the years. In this paper, we compiled and explored the validity of proposed transgenic animal models of ADHD. Each of the reviewed transgenic animal models has strengths and limitations. Some fulfill most of the validity criteria of an animal model of ADHD and have been extensively used, while there are others that require further validation. Nevertheless, these transgenic animal models of ADHD have provided and will continue to provide valuable insights into the genetic underpinnings of this complex disorder.

Memantine, an NMDA receptor antagonist, improves working memory deficits in DGKβ knockout mice

Diacylglycerol kinase (DGK) β is a type 1 isozyme of the DGK family. We previously reported that DGKβ was deeply involved in neurite spine formation, and DGKβ knockout (KO) mice exhibited behavioral abnormalities concerning spine formation, such as cognitive, emotional, and attentional impairment. Moreover, some of these abnormalities were ameliorated by the administration of a mood stabilizer. However, there is no data about how memory-improving drugs used in the treatment of Alzheimer's disease affect DGKβ KO mice. In the present study, we evaluated the effect of an anti-Alzheimer's drug, memantine on the working memory deficit observed in DGKβ KO mice. In the Y-maze test, the administration of memantine significantly improved working memory of DGKβ KO mice. We also found that the expression levels of the NR2A and NR2B N-methyl-d-aspartate (NMDA) receptor subunits were increased in the prefrontal cortex, but decreased in the hippocampus of DGKβ KO mice. These altered expression levels of NR2 subunits might be related to the effect of an NMDA receptor antagonist, memantine. Taken together, these findings may support the hypothesis that DGKβ has a pivotal role in cognitive function.

Brinp1(-/-) mice exhibit autism-like behaviour, altered memory, hyperactivity and increased parvalbumin-positive cortical interneuron density

BACKGROUND

BMP/RA-inducible neural-specific protein 1 (Brinp1) is highly conserved in vertebrates, and continuously expressed in the neocortex, hippocampus, olfactory bulb and cerebellum from mid-embryonic development through to adulthood.

METHODS

Brinp1 knock-out (Brinp1(-/-)) mice were generated by Cre-recombinase-mediated removal of the third exon of Brinp1. Knock-out mice were characterised by behavioural phenotyping, immunohistochemistry and expression analysis of the developing and adult brain.

RESULTS

Absence of Brinp1 during development results in a behavioural phenotype resembling autism spectrum disorder (ASD), in which knock-out mice show reduced sociability and changes in vocalisation capacity. In addition, Brinp1(-/-) mice exhibit hyper-locomotor activity, have impaired short-term memory, and exhibit poor reproductive success. Brinp1(-/-) mice show increased density of parvalbumin-expressing interneurons in the adult mouse brain. Brinp1(-/-) mice do not show signs of altered neural precursor proliferation or increased apoptosis during late embryonic brain development. The expression of the related neuronal migration genes Astn1 and Astn2 is increased in the brains of Brinp1(-/-) mice, suggesting that they may ameliorate the effects of Brinp1 loss.

CONCLUSIONS

Brinp1 plays an important role in normal brain development and function by influencing neuronal distribution within the cortex. The increased cortical PV-positive interneuron density and altered behaviour of Brinp1(-/-) mice resemble features of a subset of human neurological disorders; namely autism spectrum disorder (ASD) and the hyperactivity aspect of attention deficit hyperactivity disorder (ADHD).

Molecular Pathways: Targeting Diacylglycerol Kinase Alpha in Cancer

Lipid kinases have largely been neglected as targets in cancer, and an increasing number of reports suggest diacylglycerol kinase alpha (DGKα) may be one with promising therapeutic potential. DGKα is one of 10 DGK family members that convert diacylglycerol (DAG) to phosphatidic acid (PA), and both DAG and PA are critical lipid second messengers in the plasma membrane. A host of important oncogenic proteins and pathways affect cancer cells in part through DGKα, including the c-Met and VEGF receptors. Others partially mediate the effects of DGKα inhibition in cancer, such as mTOR and HIF-1α. DGKα inhibition can directly impair cancer cell viability, inhibits angiogenesis, and notably may also boost T-cell activation and enhance cancer immunotherapies. Although two structurally similar inhibitors of DGKα were established decades ago, they have seen minimal in vivo usage, and it is unlikely that either of these older DGKα inhibitors will have utility for cancer. An abandoned compound that also inhibits serotonin receptors may have more translational potential as a DGKα inhibitor, but more potent and specific DGKα inhibitors are sorely needed. Other DGK family members may also provide therapeutic targets in cancer, but require further investigation.

mRNA expression of diacylglycerol kinase isoforms in insulin-sensitive tissues: effects of obesity and insulin resistance

Diacylglycerol kinase (DGK) isoforms regulate signal transduction and lipid metabolism. DGKδ deficiency leads to hyperglycemia, peripheral insulin resistance, and metabolic inflexibility. Thus, dysregulation of other DGK isoforms may play a role in metabolic dysfunction. We investigated DGK isoform mRNA expression in extensor digitorum longus (EDL) and soleus muscle, liver as well as subcutaneous and epididymal adipose tissue in C57BL/6J mice and obese and insulin-resistant ob/ob mice. All DGK isoforms, except for DGKκ, were detectable, although with varying mRNA expression. Liver DGK expression was generally lowest, with several isoforms undetectable. In soleus muscle, subcutaneous and epididymal adipose tissue, DGKδ was the most abundant isoform. In EDL muscle, DGKα and DGKζ were the most abundant isoforms. In liver, DGKζ was the most abundant isoform. Comparing obese insulin-resistant ob/ob mice to lean C57BL/6J mice, DGKβ, DGKι, and DGKθ were increased and DGKε expression was decreased in EDL muscle, while DGKβ, DGKη and DGKθ were decreased and DGKδ and DGKι were increased in soleus muscle. In liver, DGKδ and DGKζ expression was increased in ob/ob mice. DGKη was increased in subcutaneous fat, while DGKζ was increased and DGKβ, DGKδ, DGKη and DGKε were decreased in epididymal fat from ob/ob mice. In both adipose tissue depots, DGKα and DGKγ were decreased and DGKι was increased in ob/ob mice. In conclusion, DGK mRNA expression is altered in an isoform- and tissue-dependent manner in obese insulin-resistant ob/ob mice. DGK isoforms likely have divergent functional roles in distinct tissues, which may contribute to metabolic dysfunction.

Glucagon-like peptide-1 protects the murine hippocampus against stressors via Akt and ERK1/2 signaling

Alzheimer's disease (AD) is a common neurodegenerative disease characterized by cognitive dysfunction and neuronal cell death in the hippocampus and cerebral cortex. Glucagon-like peptide-1 (GLP-1) is an insulinotropic peptides. GLP-1-associated medicines are widely used as treatments for type 2 diabetes. In addition, they have been shown to ameliorate pathology in AD mouse models. Here, we investigated the effects of GLP-1 on different stressors in murine hippocampal HT22 cells. GLP-1 (7-36) prevented H2O2-, l-glutamate-, tunicamycin-, thapsigargin-, and amyloid β1-42-induced neuronal cell death in a concentration-dependent manner. GLP-1 (7-36) treatment for 1 h significantly increased phosphorylated Akt and extracellular signal-regulated kinase 1 and 2 (ERK1/2) when compared with vehicle-treatment. These results suggest that GLP-1 (7-36) is protective against these stressors via activation of survival signaling molecules, such as Akt and ERK1/2 in HT22 cells. In conclusion, GLP-1 and activators of the GLP-1 receptor might be useful targets for the treatment of AD.

Diacylglycerol, phosphatidic acid, and their metabolic enzymes in synaptic vesicle recycling

The synaptic vesicle (SV) cycle includes exocytosis of vesicles loaded with a neurotransmitter such as glutamate, coordinated recovery of SVs by endocytosis, refilling of vesicles, and subsequent release of the refilled vesicles from the presynaptic bouton. SV exocytosis is tightly linked with endocytosis, and variations in the number of vesicles, and/or defects in the refilling of SVs, will affect the amount of neurotransmitter available for release (Sudhof, 2004). There is increasing interest in the roles synaptic vesicle lipids and lipid metabolizing enzymes play in this recycling. Initial emphasis was placed on the role of polyphosphoinositides in SV cycling as outlined in a number of reviews (Lim and Wenk, 2009; Martin, 2012; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). Other lipids are now recognized to also play critical roles. For example, PLD1 (Humeau et al., 2001; Rohrbough and Broadie, 2005) and some DGKs (Miller et al., 1999; Nurrish et al., 1999) play roles in neurotransmission which is consistent with the critical roles for phosphatidic acid (PtdOH) and diacylglycerol (DAG) in the regulation of SV exo/endocytosis (Cremona et al., 1999; Exton, 1994; Huttner and Schmidt, 2000; Lim and Wenk, 2009; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). PLD generates phosphatidic acid by catalyzing the hydrolysis of phosphatidylcholine (PtdCho) and in some systems this PtdOH is de-phosphorylated to generate DAG. In contrast, DGK catalyzes the phosphorylation of DAG thereby converting it into PtdOH. While both enzymes are poised to regulate the levels of DAG and PtdOH, therefore, they both lead to the generation of PtdOH and could have opposite effects on DAG levels. This is particularly important for SV cycling as PtdOH and DAG are both needed for evoked exocytosis (Lim and Wenk, 2009; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). Two lipids and their involved metabolic enzymes, two sphingolipids have also been implicated in exocytosis: sphingosine (Camoletto et al., 2009; Chan et al., 2012; Chan and Sieburth, 2012; Darios et al., 2009; Kanno et al., 2010; Rohrbough et al., 2004) and sphingosine-1-phosphate (Chan, Hu, 2012; Chan and Sieburth, 2012; Kanno et al., 2010). Finally a number of reports have focused on the somewhat less well studies roles of sphingolipids and cholesterol in SV cycling. In this report, we review the recent understanding of the roles PLDs, DGKs, and DAG lipases, as well as sphingolipids and cholesterol play in synaptic vesicle cycling.

The strength of combined cytogenetic and mate-pair sequencing techniques illustrated by a germline chromothripsis rearrangement involving FOXP2

Next-generation mate-pair sequencing (MPS) has revealed that many constitutional complex chromosomal rearrangements (CCRs) are associated with local shattering of chromosomal regions (chromothripsis). Although MPS promises to identify the molecular basis of the abnormal phenotypes associated with many CCRs, none of the reported mate-pair sequenced complex rearrangements have been simultaneously studied with state-of-the art molecular cytogenetic techniques. Here, we studied chromothripsis-associated CCR involving chromosomes 2, 5 and 7, associated with global developmental and psychomotor delay and severe speech disorder. We identified three truncated genes: CDH12, DGKB and FOXP2, confirming the role of FOXP2 in severe speech disorder, and suggestive roles of CDH12 and/or DGKB for the global developmental and psychomotor delay. Our study confirmes the power of MPS for detecting breakpoints and truncated genes at near nucleotide resolution in chromothripsis. However, only by combining MPS data with conventional G-banding and extensive fluorescence in situ hybridizations could we delineate the precise structure of the derivative chromosomes.

Transgenic mouse models for ADHD

Attention-deficit hyperactivity disorder (ADHD) is a developmental disorder characterized by symptoms of inattention, impulsivity and hyperactivity that adversely affect many aspects of life. Whereas the etiology of ADHD remains unknown, growing evidence indicates a genetic involvement in the development of this disorder. The brain circuits associated with ADHD are rich in monoamines, which are involved in the mechanism of action of psychostimulants and other medications used to treat this disorder. Dopamine (DA) is believed to play a major role in ADHD but other neurotransmitters are certainly also involved. Genetically modified mice have become an indispensable tool used to analyze the contribution of genetic factors in the pathogenesis of human disorders. Although rodent models cannot fully recapitulate complex human psychiatric disorders such as ADHD, transgenic mice offer an opportunity to directly investigate in vivo the specific roles of novel candidate genes identified in ADHD patients. Several knock-out and transgenic mouse models have been proposed as ADHD models, mostly based on targeting genes involved in DA transmission, including the gene encoding the dopamine transporter (DAT1). These mutant models provided an opportunity to evaluate the contribution of dopamine-related processes to brain pathology, to dissect the neuronal circuitry and molecular mechanisms involved in the antihyperkinetic action of psychostimulants and to evaluate novel treatments for ADHD. New transgenic models mouse models targeting other genes have recently been proposed for ADHD. Here, we discuss the recent advances and pitfalls in modeling ADHD endophenotypes in genetically altered animals.

Methylphenidate enhances NMDA-receptor response in medial prefrontal cortex via sigma-1 receptor: a novel mechanism for methylphenidate action

Methylphenidate (MPH), commercially called Ritalin or Concerta, has been widely used as a drug for Attention Deficit Hyperactivity Disorder (ADHD). Noteworthily, growing numbers of young people using prescribed MPH improperly for pleasurable enhancement, take high risk of addiction. Thus, understanding the mechanism underlying high level of MPH action in the brain becomes an important goal nowadays. As a blocker of catecholamine transporters, its therapeutic effect is explained as being due to proper modulation of D1 and α2A receptor. Here we showed that higher dose of MPH facilitates NMDA-receptor mediated synaptic transmission via a catecholamine-independent mechanism, in layer V∼VI pyramidal cells of the rat medial prefrontal cortex (PFC). To indicate its postsynaptic action, we next found that MPH facilitates NMDA-induced current and such facilitation could be blocked by σ1 but not D1/5 and α2 receptor antagonists. And this MPH eliciting enhancement of NMDA-receptor activity involves PLC, PKC and IP3 receptor mediated intracellular Ca(2+) increase, but does not require PKA and extracellular Ca(2+) influx. Our additional pharmacological studies confirmed that higher dose of MPH increases locomotor activity via interacting with σ1 receptor. Together, the present study demonstrates for the first time that MPH facilitates NMDA-receptor mediated synaptic transmission via σ1 receptor, and such facilitation requires PLC/IP3/PKC signaling pathway. This novel mechanism possibly explains the underlying mechanism for MPH induced addictive potential and other psychiatric side effects.