Hippocampus-specific knockdown of Shati/Nat8l impairs cognitive function and electrophysiological response in mice.

Shati/Nat8l was identified as an upregulated molecule in the nucleus accumbens (NAc) of mice following repeated methamphetamine administration. Region-specific roles of this molecule are associated with psychiatric disorders. In the present study, we examined the importance of Shati/Nat8l in the hippocampus because of its high expression in this region. Mice with a hippocampus-specific knockdown of Shati/Nat8l (hippocampal Shati-cKD) were prepared by the microinjection of adeno-associated virus (AAV) vectors carrying Cre into the hippocampus of Shati/Nat8lflox/flox mice, and their phenotypes were investigated. Drastic reduction in the expression and function of Shati/Nat8l in the hippocampus was observed in Shati-cKD mice. These mice exhibited cognitive dysfunction in behavioral experiments and impaired the electrophysiological response to the stimuli, which elicits long-term potentiation. Shati/Nat8l in the hippocampus is suggested to possibly play an important role in synaptic plasticity to maintain cognitive function. This molecule could be a therapeutic target for hippocampus-related disorders such as dementia.

The Role of GABA in the Dorsal Striatum-Raphe Nucleus Circuit Regulating Stress Vulnerability in Male Mice with High Levels of Shati/Nat8l.

Depression is a frequent and serious illness, and stress is considered the main risk factor for its onset. First-line antidepressants increase serotonin (5-hydroxytryptamine; 5-HT) levels in the brain. We previously reported that an N-acetyltransferase, Shati/Nat8l, is upregulated in the dorsal striatum (dSTR) of stress-susceptible mice exposed to repeated social defeat stress (RSDS) and that dSTR Shati/Nat8l overexpression in mice (dSTR-Shati OE) induces stress vulnerability and local reduction in 5-HT content. Male mice were used in this study, and we found that dSTR 5-HT content decreased in stress-susceptible but not in resilient mice. Moreover, vulnerability to stress in dSTR-Shati OE mice was suppressed by the activation of serotonergic neurons projecting from the dorsal raphe nucleus (dRN) to the dSTR, followed by upregulation of 5-HT content in the dSTR using designer receptors exclusively activated by designer drugs (DREADD). We evaluated the role of GABA in modulating the serotonergic system in the dRN. Stress-susceptible after RSDS and dSTR-Shati OE mice exhibited an increase in dRN GABA content. Furthermore, dRN GABA content was correlated with stress sensitivity. We found that the blockade of GABA signaling in the dRN suppressed stress susceptibility in dSTR-Shati OE mice. In conclusion, we propose that dSTR 5-HT and dRN GABA, controlled by striatal Shati/Nat8l via the dSTR-dRN neuronal circuitry, critically regulate stress sensitivity. Our study provides insights into the neural processes that underlie stress and suggests that dSTR Shati/Nat8l could be a novel therapeutic target for drugs against depression, allowing direct control of the dRN serotonergic system.

DNA methylation status of SHATI/NAT8L promoter in the blood of cigarette smokers.

AIMS: Cigarette smoking is a preventable risk factor for various diseases such as cancer, ischemic stroke, cardiac stroke, and chronic obstructive pulmonary disease. Smoking cessation is of great importance not only for individual smokers but also for social health. Regarding current cessation therapies, the effectiveness of nicotine replacement is limited, and the cost of varenicline medication is considerable. Thus, a method for screening smokers who are responsive to cessation therapy based on the therapeutic effectiveness is required. Peripheral biomarkers reflecting smoking dependence status are necessary to establish a method for achieving effective cessation therapy. METHODS: Methylation status of smokers' blood DNA was evaluated focusing on SHATI/NAT8L, an addiction-related gene. Eight CpG sites in SHATI/NAT8L were quantified by pyrosequencing. RESULTS: There was no difference in the methylation status of this gene between smokers (n = 129) and non-smokers (n = 129) at all CpG sites. No correlations between the methylation status of SHATI/NAT8L and indicators of smoking dependence were found. CONCLUSIONS: Although the present study found no significance in the DNA methylation of SHATI/NAT8L among smokers, the exploration of predictable peripheral biomarkers for the effectiveness of smoking cessation therapy is required.

Shati/Nat8l Overexpression Improves Cognitive Decline by Upregulating Neuronal Trophic Factor in Alzheimer's Disease Model Mice.

Alzheimer's disease (AD) is a type of dementia characterized by the deposition of amyloid ß, a causative protein of AD, in the brain. Shati/Nat8l, identified as a psychiatric disease related molecule, is a responsive enzyme of N-acetylaspartate (NAA) synthesis. In the hippocampi of AD patients and model mice, the NAA content and Shati/Nat8l expression were reported to be reduced. Having recently clarified the involvement of Shati/Nat8l in cognitive function, we examined the recovery effect of the hippocampal overexpression of Shati/Nat8l in AD model mice (5XFAD). Shati/Nat8l overexpression suppressed cognitive dysfunction without affecting the Aß burden or number of NeuN-positive neurons. In addition, brain-derived neurotrophic factor mRNA was upregulated by Shati/Nat8l overexpression in 5XFAD mice. These results suggest that Shati/Nat8l overexpression prevents cognitive dysfunction in 5XFAD mice, indicating that Shati/Nat8l could be a therapeutic target for AD.

N-Acetyl Transferase, Shati/Nat8l, in the Dorsal Hippocampus Suppresses Aging-induced Impairment of Cognitive Function in Mice.

As the elderly population rapidly increases worldwide, the onset of cognitive dysfunction is expected to increase. Although neuronal plasticity, neurogenesis, and mitochondrial dysfunction have been reported to be involved in cognitive function, the detailed mechanism of cognitive impairment accompanied by aging is poorly understood as there are many confounding factors associated with aging. Therefore, effective treatments for aging have not yet been developed, and the establishment of therapeutic strategies has not progressed accordingly. We have previously found a decline of cognitive function in the developmental stage in mice who lack the expression of Shati/Nat8l, an N-acetyl transferase However, the contribution of Shati/Nat8l to cognitive impairment in aged mice has not yet been investigated. In this study, we aimed to investigate the role of Shati/Nat8l in cognitive function during aging. We observed a reduction in Shati/Nat8l mRNA expression in the dorsal hippocampus of mice as a result of their aging. Moreover, the cognitive dysfunction observed in aged mice was reversed by Shati/Nat8l overexpression in the dorsal hippocampus. Shati/Nat8l overexpression in the dorsal hippocampus of mice did not alter the expression of neurotrophic factors or mitochondrial function-related genes, including Bdnf or Pgc-1α, which are suggested to be downstream genes of Shati/Nat8l. Decreased N-acetyl aspartate (NAA) in aged mice was upregulated by Shati/Nat8l overexpression, suggesting that the Shati/Nat8l-NAA pathway determines cognitive function with aging. Taken together, Shati/Nat8l and NAA in the dorsal hippocampus may be novel targets for the treatment of cognitive impairment.

A Role of BDNF in the Depression Pathogenesis and a Potential Target as Antidepressant: The Modulator of Stress Sensitivity "Shati/Nat8l-BDNF System" in the Dorsal Striatum.

Depression is one of the most common mental diseases, with increasing numbers of patients globally each year. In addition, approximately 30% of patients with depression are resistant to any treatment and do not show an expected response to first-line antidepressant drugs. Therefore, novel antidepressant agents and strategies are required. Although depression is triggered by post-birth stress, while some individuals show the pathology of depression, others remain resilient. The molecular mechanisms underlying stress sensitivity remain unknown. Brain-derived neurotrophic factor (BDNF) has both pro- and anti-depressant effects, dependent on brain region. Considering the strong region-specific contribution of BDNF to depression pathogenesis, the regulation of BDNF in the whole brain is not a beneficial strategy for the treatment of depression. We reviewed a novel finding of BDNF function in the dorsal striatum, which induces vulnerability to social stress, in addition to recent research progress regarding the brain regional functions of BDNF, including the prefrontal cortex, hippocampus, and nucleus accumbens. Striatal BDNF is regulated by Shati/Nat8l, an N-acetyltransferase through epigenetic regulation. Targeting of Shati/Nat8l would allow BDNF to be striatum-specifically regulated, and the striatal Shati/Nat8l-BDNF pathway could be a promising novel therapeutic agent for the treatment of depression by modulating sensitivity to stress.

Shati/Nat8l deficiency disrupts adult neurogenesis and causes attentional impairment through dopaminergic neuronal dysfunction in the dentate gyrus.

Successful completion of daily activities relies on the ability to select the relevant features of the environment for memory and recall. Disruption to these processes can lead to various disorders, such as attention-deficit hyperactivity disorder (ADHD). Dopamine is a neurotransmitter implicated in the regulation of several processes, including attention. In addition to the higher-order brain function, dopamine is implicated in the regulation of adult neurogenesis. Previously, we generated mice lacking Shati, an N-acetyltransferase-8-like protein on a C57BL/6J genetic background (Shati/Nat8l-/- ). These mice showed a series of changes in the dopamine system and ADHD-like behavioral phenotypes. Therefore, we hypothesized that deficiency of Shati/Nat8l would affect neurogenesis and attentional behavior in mice. We found aberrant morphology of neurons and impaired neurogenesis in the dentate gyrus of Shati/Nat8l-/- mice. Additionally, research has suggested that impaired neurogenesis might be because of the reduction of dopamine in the hippocampus. Galantamine (GAL) attenuated the attentional impairment observed in the object-based attention test via increasing the dopamine release in the hippocampus of Shati/Nat8l-/- mice. The α7 nicotinic acetylcholine receptor antagonist, methyllycaconitine, and dopamine D1 receptor antagonist, SCH23390, blocked the ameliorating effect of GAL on attentional impairment in Shati/Nat8l-/- mice. These results suggest that the ameliorating effect of GAL on Shati/Nat8l-/- attentional impairment is associated with activation of D1 receptors following increased dopamine release in the hippocampus via α7 nicotinic acetylcholine receptor. In summary, Shati/Nat8l is important in both morphogenesis and neurogenesis in the dentate gyrus and attention, possible via modulation of dopaminergic transmission. Cover Image for this issue: https://doi.org/10.1111/jnc.15061.

Impairment of cognitive function induced by Shati/Nat8l overexpression in the prefrontal cortex of mice.

A novel N-acetyltransferase, Shati/Nat8l, was identified in the brains of mice exposed to methamphetamine. Shati/Nat8l overexpression in the medial prefrontal cortex (mPFC) was found to attenuate methamphetamine-induced dependence. The mPFC is a brain region that plays an important role in cognitive function. However, the effect of Shati/Nat8l on cognition and memory has not yet been clarified. To understand the role of Shati/Nat8l in memory, we generated C57BL/6J mice with overexpressed Shati/Nat8l in the mPFC and performed memory-related experiments, including novel object-location and object-in-context tests. Furthermore, we used quantitative immunohistochemistry to assess the presynaptic and postsynaptic proteins, synaptophysin and postsynaptic density protein (PSD)-95, respectively. Shati/Nat8l overexpression in the mPFC impaired both novel object-location and object-in-context memory. Moreover, Shati/Nat8l overexpression in the mPFC reduced PSD-95 levels, but not synaptophysin levels in the mPFC. These results demonstrated that Shati/Nat8l overexpression in the mPFC is involved in location and contextual memory, and can affect the excitatory postsynaptic protein, PSD-95.

Investigating DNA Methylation of SHATI/NAT8L Promoter Sites in Blood of Unmedicated Patients with Major Depressive Disorder.

Major depressive disorder (MDD) is one of the most common psychiatric diseases. However, early detection and diagnosis of MDD is difficult, largely because there is no known biomarker or objective diagnostic examination, and its diagnosis is instead based on a clinical interview. The aim of this study was to develop a novel diagnostic tool using DNA methylation as a blood biomarker. We sought to determine whether unmedicated patients with MDD showed significant differences in DNA methylation in the promoter region of the SHATI/N-acetyltransferase 8 like (SHATI/NAT8L) gene compared to healthy controls. Sixty participants with MDD were recruited from all over Japan. They were diagnosed and assessed by at least two trained psychiatrists according to DSM-5 criteria. DNA was extracted from peripheral blood. We then assessed DNA methylation of the SHATI/NAT8L promoter regions in patients with MDD by pyrosequencing. Methylation levels of the SHATI/NAT8L promoter region at CpG sites in peripheral blood from unmedicated patients were significantly higher than in healthy controls. In contrast, medicated patients with MDD showed significantly lower methylation levels in the same region compared to healthy controls. Since previous studies of DNA methylation in MDD only assessed medicated patients, the methylation status of the SHATI/NAT8L promoter region in unmedicated patients presented herein may prove useful for the diagnosis of MDD. To our knowledge, this is the first attempt to measure methylation of the SHATI/NAT8L gene in drug-naïve patients with psychiatric diseases. Based on our findings, methylation of SHATI/NAT8L DNA might be a diagnostic biomarker of MDD.

A Single Medical Marker for Diagnosis of Methamphetamine Addiction - DNA Methylation of SHATI/NAT8L Promoter Sites from Patient Blood.

BACKGROUND: Methamphetamine (METH) is one of the most widely distributed psychostimulants worldwide. Despite active counter measures taken by different countries, neither overall usage of METH nor the frequency of repeat users has reduced over the past decade. METH induces abuse and dependence as it acts on the central nervous system and temporarily stimulates the brain. The recidivism rate for abuse of stimulants in Japan is very high and therefore prevention of repeated usage is paramount. However, we lack information about the relationship between METH users and genomic changes in humans in Japan, which would provide important information to aid such efforts. OBJECTIVE: Shati/Nat8l is a METH-inducible molecule and its overexpression has protective effects on the brain upon METH usage. Here we investigated the effect of METH usage on DNA methylation rates at the promoter site of SHATI/NAT8L. We used DNA samples from human METH users, who are usually difficult to recruit in Japan. METHODS: We measured DNA methylation at SHATI/NAT8L promoter sites by pyrosequencing method using 193 samples of METH users and 60 samples of healthy subjects. In this method, DNA methylation is measured by utilizing the property that only non-methylated cytosine changes to urasil after bisulfite conversion. RESULTS: We found that the rate of DNA methylation at six CpG islands of SHATI/NAT8L promoter sites is significantly higher in METH users when compared to healthy subjects. CONCLUSION: These results suggest that the DNA methylation rate of SHATI/NAT8L promotor regions offers a new diagnostic method for METH usage.

Inhibitory effects of Shati/Nat8l overexpression in the medial prefrontal cortex on methamphetamine-induced conditioned place preference in mice.

Shati/Nat8l is a novel N-acetyltransferase identified in the brain of mice treated with methamphetamine (METH). Shati/Nat8l mRNA is expressed in various brain areas, including the prefrontal cortex (PFC), where the expression level is higher than that in other brain regions. Shati/Nat8l overexpression in the nucleus accumbens (NAc) attenuates the pharmacological response to METH via mGluR3. Meanwhile, dopamine (DA) and glutamate dysregulations have been reported in the medial prefrontal cortex (mPFC) and NAc after METH self-administration and during reinstatement. However, the mechanism, the reward system, and function of Shati/Nat8l in the mPFC is unclear. Here, we injected an adeno-associated virus (AAV) vector containing Shati/Nat8l into the mPFC of mice, to overexpress Shati/Nat8l in the mPFC (mPFC-Shati/Nat8l). Interestingly, the METH-induced conditioned place preference (CPP) was attenuated in the mPFC-Shati/Nat8l mice, but locomotor activity was not. Additionally, immunohistochemical results from mice that were injected with AAV-GFP showed fluorescence in the mPFC and other brain regions, mainly the NAc, indicating an mPFC-NAc top-down connection. Finally, in vivo microdialysis experiments revealed that Shati/Nat8l overexpression in the mPFC reduced extracellular DA levels and suppressed the METH-induced DA increase in the NAc. Moreover, decreased extracellular glutamate levels were observed in the NAc. These results indicate that Shati/Nat8l overexpression in the mPFC attenuates METH-induced CPP by decreasing extracellular DA in the NAc. In contrast, Shati/Nat8l-mPFC overexpression did not alter METH-induced hyperlocomotion. This study demonstrates that Shati/Nat8l in the mPFC attenuates METH reward-seeking behaviour but not the psychomotor activity of METH.

Vulnerability to depressive behavior induced by overexpression of striatal Shati/Nat8l via the serotonergic neuronal pathway in mice.

The number of patients with depressive disorders is increasing. However, the mechanism of depression onsets has not been completely revealed. We previously identified Shati/Nat8l, an N-acetyltransferase, in the brain using an animal model of psychosis. In this study, we revealed the involvement of Shati/Nat8l in the vulnerability to major depression. Shati/Nat8l mRNA was increased only in the striatum of mice, which were exposed to chronic social defeat stress. Shati/Nat8l-overexpressed mice showed impairment in social interaction and sucrose preference after the subthreshold social defeat (microdefeat) stress. These depression-like behaviors were restored by fluvoxamine and LY341495 injection prior to these tests. Furthermore, the intracerebral administration of only fluvoxamine, but not of LY341495, to the dorsal striatum and direct infusion of LY341495 to the dorsal raphe also rescued. Taken together, Shati/Nat8l in the striatum has an important role in the vulnerability to depression onsets by regulating the origin of serotonergic neuronal system via GABAergic projection neuron in the dorsal raphe from the dorsal striatum.

Regulatory system of mGluR group II in the nucleus accumbens for methamphetamine-induced dopamine increase by the medial prefrontal cortex.

AIM: We previously reported that methamphetamine (METH)-induced conditioned place preference was attenuated by Shati/Nat8l overexpression in the medial prefrontal cortex (mPFC). Shati/Nat8l overexpression in the mPFC expressed lower levels of both glutamate and dopamine (DA) in the nucleus accumbens (NAc) and attenuated METH-induced DA elevation. We suggested a mechanism in which a decline of glutamate levels in the NAc decreases extracellular DA levels. However, the hypothesis has not confirmed. METHODS: We conducted a recovery experiments by pre-microinjection of an mGluR group II antagonist, LY341495, into the NAc shell of mPFC-Shati/Nat8l-overexpressed mice followed by METH injection and DA levels measurement by in vivo microdialysis. RESULTS: Pretreatment with LY341495 was able to restore METH-induced DA increase. Furthermore, mice injected with an adeno-associated virus vector containing GFP (AAV-GFP vector) in the mPFC expressed a colocalization of GFP with DARPP-32 a medium spiny neuron (MSN) marker. Next, co-immunostaining of DARPP-32 and neuronal nitric oxide synthase (nNOS: expressed in a subtype of gamma-Aminobutyric acid (GABA interneurons) in ventral tegmental area (VTA) showed a colocalization of nNOS and DARPP-32. CONCLUSION: These results provided a proof that Shati/Nat8l attenuation of METH-induced DA increase is mediated by mGluR group II in the NAc. Moreover, immunohistochemical study showed a direct connection of mPFC projection neurons with NAc MSN and a connection of MSN projection neurons with a subtype of GABA interneurons in VTA.

Shati/Nat8l knockout mice show behavioral deficits ameliorated by atomoxetine and methylphenidate.

We previously identified a novel molecule, SHATI/NAT8L, as having an inhibitory effect on methamphetamine dependence. We generated Shati/Nat8l knockout (KO) mice and found that they showed neurochemical changes and behavioral abnormalities related to attention deficit/hyperactivity disorder (AD/HD). In this study, we assessed validities of the Shati/Nat8l KO mice as a new animal model for AD/HD through a behavioral pharmacology approach. We conducted a locomotor activity test in a novel environment, a cliff avoidance test, and an object-based attention assay using Shati/Nat8l KO mice at the ages of 4 and 8 weeks. We found that at the ages of both 4 and 8 weeks, Shati/Nat8l KO mice showed hyperactivity in locomotor activity test, shortened jumping latency in cliff avoidance test, and lower recognition index in object-based recognition test. Moreover, we evaluated the effects of atomoxetine (ATX) and methylphenidate (MPH) on the behavioral deficits in Shati/Nat8l KO mice. As the result, almost all behavioral deficits were improved by the treatment of both ATX and MPH. Our findings suggest that Shati/Nat8l KO mice have an impaired neural system similar to AD/HD pathophysiology. Shati/Nat8l KO mice might serve as a novel and a useful animal model for the pathophysiology of AD/HD.

Striatal N-Acetylaspartate Synthetase Shati/Nat8l Regulates Depression-Like Behaviors via mGluR3-Mediated Serotonergic Suppression in Mice.

Background: Several clinical studies have suggested that N-acetylaspartate and N-acetylaspartylglutamate levels in the human brain are associated with various psychiatric disorders, including major depressive disorder. We have previously identified Shati/Nat8l, an N-acetyltransferase, in the brain using an animal model of psychosis. Shati/Nat8l synthesizes N-acetylaspartate from L-aspartate and acetyl-coenzyme A. Further, N-acetylaspartate is converted into N-acetylaspartylglutamate, a neurotransmitter for metabotropic glutamate receptor 3. Methods: Because Shati/Nat8l mRNA levels were increased in the dorsal striatum of mice following the exposure to forced swimming stress, Shati/Nat8l was overexpressed in mice by the microinjection of adeno-associated virus vectors containing Shati/Nat8l gene into the dorsal striatum (dS-Shati/Nat8l mice). The dS-Shati/Nat8l mice were further assessed using behavioral and neurochemical tests. Results: The dS-Shati/Nat8l mice exhibited behavioral despair in the forced swimming and tail suspension tests and social withdrawal in the 3-chamber social interaction test. These depression-like behaviors were attenuated by the administration of a metabotropic glutamate receptor 2/3 antagonist and a selective serotonin reuptake inhibitor. Furthermore, the metabolism of N-acetylaspartate to N-acetylaspartylglutamate was decreased in the dorsal striatum of the dS-Shati/Nat8l mice. This finding corresponded with the increased expression of glutamate carboxypeptidase II, an enzyme that metabolizes N-acetylaspartylglutamate present in the extracellular space. Extracellular serotonin levels were lower in the dorsal striatum of the dS-Shati/Nat8l and normal mice that were repeatedly administered a selective glutamate carboxypeptidase II inhibitor. Conclusions: Our findings indicate that the striatal expression of N-acetylaspartate synthetase Shati/Nat8l plays a role in major depressive disorder via the metabotropic glutamate receptor 3-mediated functional control of the serotonergic neuronal system.

Deletion of SHATI/NAT8L decreases the N-acetylaspartate content in the brain and induces behavioral deficits, which can be ameliorated by administering N-acetylaspartate.

We previously identified a novel molecule "SHATI/NAT8L" that exerts an inhibitory effect on methamphetamine (METH)-induced behavioral deficits. Recently, it has been reported that SHATI might function as an aspartate N-acetyltransferase, which synthesizes N-acetylaspartate (NAA) in vitro. However, whether SHATI actually synthesizes NAA in vivo in the brain is still unclear. In this study, we found that both Shati-deleted mice showed significantly lower NAA levels in all brain areas than wild-type (Shati(+/+)) mice using HPLC and fluorescence detection, suggesting that SHATI regulates NAA content in the brain. Next, we measured the levels of monoamines and their metabolites in the adult mouse brain and found that the activities of monoaminergic systems were altered in Shati(-/-) mice. In particular, dopaminergic turnover increased in the nucleus accumbens (NAc) in Shati(-/-) mice, suggesting activation of the dopaminergic system. In fact, basal level of extracellular dopamine, and METH-induced dopamine release in the NAc of Shati(-/-) mice was significantly higher than that of Shati(+/+) and Shati(+/-) mice, which is consistent with findings that Shati(-/-) mice showed enhanced hyperlocomotion induced by METH. Moreover, in the forced swimming test, Shati-deleted mice showed a shortened immobility time, which was improved by intracerebroventricular (i.c.v.) administration of NAA prior to the test in Shati(+/-) but not in Shati(-/-) mice. The i.c.v. preinjection of NAA inhibited dopamine release after high K(+) stimulation in the NAc of Shati(+/+) and Shati(+/-) mice, but not Shati(-/-) mice. These results suggested that the behavioral deficits in Shati-deleted mice were caused by dopaminergic abnormality via deprivation of NAA.

SHATI/NAT8L regulates neurite outgrowth via microtubule stabilization.

We previously identified a new molecule, "SHATI/NAT8L," which has an inhibitory effect on methamphetamine (METH)-induced hyperlocomotion, sensitization, and conditioned place preference. Nevertheless, the extent of SHATI localization and its functions are only partially understood. In this study, we used the FLAG-tag method to investigate SHATI localization. We found that SHATI was localized to microtubules when expressed in COS7 cells and cortical primary neurons. This distribution of SHATI was less apparent after cells were treated with colchicine, a tubulin polymerization inhibitor that disrupts the microtubule structure. This finding suggests that SHATI is associated with microtubule structure. Interestingly, overexpression of SHATI in COS7 cells could attenuate the colchicine-induced decrease in acetylated microtubules, indicating that SHATI plays a role in stabilizing microtubules. Furthermore, we showed that Shati deletion impaired neurite elongation. In cortical primary neurons, neurite length and complexity in Shati-knockout (KO) mice were significantly decreased. In pyramidal neurons in the prefrontal cortex, dendrite length and complexity were also significantly decreased in Shati-KO mice compared with wild-type mice. These results suggest a novel function for SHATI, which may be a new member of the microtubule-associated protein family.

Roles of a novel molecule 'shati' in the development of methamphetamine-induced dependence.

The ability of drugs of abuse to cause dependence can be viewed as a form of neural plasticity. Recently, we have demonstrated that tumor necrosis factor-α (TNF-α) increases dopamine uptake and inhibits methamphetamine-induced dependence. Moreover, we have identified a novel molecule 'shati' in the nucleus accumbens of mice treated with methamphetamine using the PCR-select cDNA subtraction method and clarified that it is involved in the development of methamphetamine dependence: Treatment with the shati antisense oligonucleotide (shati-AS), which inhibits the expression of shati mRNA, enhanced the methamphetamine-induced hyperlocomotion, sensitization, and conditioned place preference. Further, blockage of shati mRNA by shati-AS potentiated the methamphetamine-induced increase of dopamine overflow and the methamphetamine-induced decrease in dopamine uptake in the nucleus accumbens. Interestingly, treatment with shati-AS also inhibited expression of TNF-α. Transfection of the vector containing shati cDNA into PC12 cells, dramatically induced the expression of shati and TNF-α mRNA, accelerated dopamine uptake, and inhibited the methamphetamine-induced decrease in dopamine uptake. These effects were blocked by neutralizing TNF-α. These results suggest that the functional roles of shati in methamphetamine-induced behavioral changes are mediated through the induction of TNF-α expression which inhibits the methamphetamine-induced increase of dopamine overflow and decrease in dopamine uptake.