Meilei Jin

SNAP-25 in hippocampal CA1 region is involved in memory consolidation

As a synaptosomal protein, SNAP‐25 plays a role in a number of neuronal functions including axonal growth, dendrite formation, fusion of synaptic vesicles with membrane and the expression of long‐term potentiation (LTP) in the hippocampus. Using a learning/memory behavior screening, we identified SNAP‐25 as one of the differentially expressed genes in the hippocampus upon behavioral training. The inhibition of SNAP‐25 with intracerebroventricular antisense oligonucleotide caused a deficit in long‐ but not short‐term memory for step‐down inhibitory avoidance. Intra‐CA1 infusion of the SNAP‐25 antisense oligonucleotide impaired long‐term contextual fear memory and spatial memory and interfered with the LTP of synaptic transmission in the CA1 region. The inhibitory effect on LTP was not mediated by a pre‐synaptic mechanism because paired pulse facilitation of synaptic transmission was not affected after administration of the antisense oligonucleotide. Together, the results suggest that SNAP‐25 in the CA1 region is involved in memory consolidation.

The negative cell cycle regulator, Tob (transducer of ErbB-2), is a multifunctional protein involved in hippocampus-dependent learning and memory

Tob (transducer of ErbB2) is a negative cell cycle regulator with anti-proliferative activity in the periphery. Using a behavioral screening paradigm to look for novel gene functions in the brain, we identified Tob as a brain-expressed protein involved in learning and memory. Behavioral training of fear-conditioning triggered a transient elevation of Tob protein, which preceded the formation of long-term memory. Functional perturbation of Tob by intra-CA1 infusion of antisense oligonucleotides in rats impaired spatial learning and memory in the Morris water maze and long-term memory for contextual fear conditioning, two behavioral paradigms that require the hippocampus. Furthermore, long-term potentiation was suppressed by Tob antisense infusion into the CA1 region. Together, these results indicate that the negative cell cycle regulator Tob is a multifunctional protein involved in hippocampus-dependent learning and memory.

Low dose MK-801 reduces social investigation in mice.

To characterize MK-801s effect on social behavior in mice, we examined adult male ICR mice for interaction with companion mice (juvenile male). Test mice were injected with either saline or MK-801 (0.1 mg/kg), and were tested 30 min later for their social behavior during a 5-min session. A second encounter took place 30 min later, with either a familiar companion mouse (the same as in the initial encounter) or a novel mouse. In saline controls, second encounter with a familiar companion mouse showed reduced social investigative behaviors (anogenital sniffing and staying together), indicating habituation toward a familiar mouse. Second encounter with a novel companion mouse did not show habituation in social investigative behaviors. Pretreatment with MK-801 reduced anogenital sniffing during the first encounter. At the second encounter, these mice displayed non-discriminative habituation of social investigative behaviors, with reduced anogenital sniffing and staying together, regardless of whether the companion mouse was a familiar or a novel one. These results indicate that MK-801 affected exploratory activities of mice, resulting in both reduced social investigative behaviors during first encounter with a companion mouse, and diminished discriminative capacities for a familiar vs. a novel companion mouse during subsequent encounter.

rSac3, a novel Sac domain phosphoinositide phosphatase, promotes neurite outgrowth in PC12 cells

Sac domain-containing proteins belong to a newly identified family of phosphoinositide phosphatases (the PIPPase family). Despite well-characterized enzymatic activity, the biological functions of this mammalian Sac domain PIPPase family remain largely unknown. We identified a novel Sac domain-containing protein, rat Sac3 (rSac3), which is widely expressed in various tissues and localized to the endoplasmic reticulum, Golgi complex and recycling endosomes. rSac3 displays PIPPase activity with PI(3)P, PI(4)P and PI(3,5)P2 as substrates in vitro, and a mutation in the catalytic core of the Sac domain abolishes its enzymatic activity. The expression of rSac3 is upregulated during nerve growth factor (NGF)-stimulated PC12 cell neuronal differentiation, and overexpression of this protein promotes neurite outgrowth in PC12 cells. Conversely, inhibition of rSac3 expression by antisense oligonucleotides reduces neurite outgrowth of NGF-stimulated PC12 cells, and the active site mutation of rSac3 eliminates its neurite-outgrowth-promoting activity. These results indicate that rSac3 promotes neurite outgrowth in differentiating neurons through its PIPPase activity, suggesting that Sac domain PIPPase proteins may participate in forward membrane trafficking from the endoplasmic reticulum and Golgi complex to the plasma membrane, and may function as regulators of this crucial process of neuronal cell growth and differentiation.

Chronic alcohol consumption from adolescence-to-adulthood in mice—Effect on growth and social behavior

Experimentation with alcohol is common during adolescence. However the long-term consequences from moderate alcohol use during adolescence development are not clear. Using a two-bottle free-choice paradigm in the home-cage setting, we studied adolescent mice (4 weeks old) across a 6-week time span of the adolescence-to-adulthood development period. Adolescent mice readily reached a steady level of alcohol consumption and maintained this level throughout the 6-week period. Chronic alcohol consumption resulted in reduced growth in adolescent mice, as well as accelerated acclimation to a novel environment. During a social interaction test, similar levels of initial social investigation and subsequent habituation were observed in both the chronic alcohol and the water-only control groups. However, chronic alcohol self-administration resulted in impaired social recognition and decreased social play/fight behavior. Taken together, these results indicated that chronic alcohol consumption across adolescence development negatively impacted both physical growth and social behavior in mice, highlighting the detrimental consequences from prolonged alcohol drinking in adolescence.

Effect of GNTI, a kappa opioid receptor antagonist, on MK-801-induced hyperlocomotion and stereotypy in mice

AbstractAim:To examine the effect of GNTI [5′-guanidinyl-17-(cyclopropylmethyl)-6,7-dehydro-4,5α-epoxy-3,14-dihydroxy-6,7-2′,3′-indolomorphinan], a selective antagonist for the kappa opioid receptor, in the MK-801 (dizocilpine maleate)-induced behavioral model of psychosis in schizophrenia as a way to explore the involvement of the kappa opioid receptor in modulating psychotic symptoms of schizophrenia.Methods:Two doses of MK-801 (0.3 mg/kg and 0.6 mg/kg) were administered by systemic injection in mice to induce psychosis-like behavior as a rodent schizophrenia model, preceded by an injection of different doses of GNTI. Both locomotion and stereotypy were measured as the behavioral endpoints for quantitative analysis.Results:GNTI inhibited MK-801-induced hyperlocomotion and stereotypy. In particular, GNTI showed differential modulation of stereotypy induced by 0.3 mg/kg vs 0.6 mg/kg MK-801.Conclusion:Antagonism of kappa opioid receptors attenuates MK-801-induced behavior, suggesting a potential involvement of the kappa opioid receptor in psychosis-like symptoms of schizophrenia. GNTI appears to be a useful pharmacological tool to explore the kappa opioid receptor function in vivo.

A novel method for analyzing genetic association with longitudinal phenotypes.

Abstract Knowledge of genes influencing longitudinal patterns may offer information about predicting disease progression. We developed a systematic procedure for testing association between SNP genotypes and longitudinal phenotypes. We evaluated false positive rates and statistical power to localize genes for disease progression. We used genome-wide SNP data from the Framingham Heart Study. With longitudinal data from two real studies unrelated to Framingham, we estimated three trajectory curves from each study. We performed simulations by randomly selecting 500 individuals. In each simulation replicate, we assigned each individual to one of the three trajectory groups based on the underlying hypothesis (null or alternative), and generated corresponding longitudinal data. Individual Bayesian posterior probabilities (BPPs) for belonging to a specific trajectory curve were estimated. These BPPs were treated as a quantitative trait and tested (using the Wald test) for genome-wide association. Empirical false positive rates and power were calculated. Our method maintained the expected false positive rate for all simulation models. Also, our method achieved high empirical power for most simulations. Our work presents a method for disease progression gene mapping. This method is potentially clinically significant as it may allow doctors to predict disease progression based on genotype and determine treatment accordingly.

Vitamin A depletion alters sensitivity of motor behavior to MK-801 in C57BL/6J mice

BackgroundVitamin A and its derivatives (retinoids) are crucial for the development, maintenance and morphogenesis of the central nervous system (CNS). Although motor impairment has been reported in postnatal vitamin A depletion rodents, the effect of vitamin A depletion on homeostasis maintaining capability in response to external interference is not clear.MethodsIn the current study, we measured the effect of vitamin A depletion on motor ability and pain sensitivity under two different conditions: 1. prior to any injection and 2. after the injection of an N-methyl-D-aspartate (NMDA) receptor antagonist (MK-801).ResultsVitamin A depletion mice showed decreased body weight, enhanced locomotor activity, increased rearing and less tail flick latency. Vitamin A depletion also induced hypersensitivity of stereotypy, ataxia, rearing, and tail flick latency to MK-801, but hyposensitivity of locomotion to MK-801.ConclusionsThese findings suggest that vitamin A depletion affect broad basal behavior and disrupt homeostasis maintaining capability in response to glutamate perturbation. We provide a useful animal model for assessing the role of vitamin A depletion in regulating animal behavior, and for detecting how neurotransmitter pathways might be involved in vitamin A depletion related behavioral abnormalities.

Sciatic Nerve Neuropathy in Cynomolgus Monkey Macaca Fascicularis: AlteredLeg Usage and Peripheral Nerve Firing

Sciatic nerve is susceptible to trauma and injuries. Animal models for sciatic nerve trauma are mostly in rodents, with limited information about injury-induced neuropathy in non-human primates. We constructed a model of sciatic nerve neuropathy (SNN) in the cynomolgus macaque monkey, Macaca fascicularis, with mild injury to, but without transection of, the sciatic nerve. Monkeys’ behavioral and physiological properties were characterized. SNN led to reduced leg usage as well as muscle atrophy. Sciatic nerve retained the ability of nerve signal transduction, and showed a flat-line type of firing rate profile, consistent with the hypothesis of injury-resulted hyper-sensitization. These data suggest that mild injury to sciatic nerve result in long-lasting malfunction and neuropathy in monkeys. This model may serve as a non-human primate model to study functional changes, as well as underlying pathological mechanisms, of traumatic injury to the sciatic nerve.

Chronic alcohol consumption from adolescence-to-adulthood in mice - hypothalamic gene expression changes in the dilated cardiomyopathy signaling pathway

BackgroundAdolescence is a developmental stage vulnerable to alcohol drinking-related problems and the onset of alcoholism. Hypothalamus is a key brain region for food and water intake regulation, and is one of the alcohol-sensitive brain regions. However, it is not known what would be the alcohol effect on hypothalamus following adolescent alcohol intake, chronically over the adolescent development, at moderate levels.ResultsWe employed a paradigm of chronic moderate alcohol intake from adolescence-to-adulthood in mice, and analyzed the alcohol effect on both behavioral and hypothalamic gene expression changes. A total of 751 genes were found and subjected to pathway analysis. The dilated cardiomyopathy (DCM) pathway was identified. The changes of ten genes under this pathway were further verified using RT-PCR. Chronic alcohol consumption during adolescence, even at moderate levels, led to a decrease of motor activity in mice, and also a concerted down regulation of signaling pathway initiating factor (SPIF) genes in the DCM signaling pathway, including β1-adrenergic receptor (Adrb1), Gs protein (Gnas), adenylyl cyclase 1 (Adcy1), and dihydropyridine receptor/L-type calcium channel (Cacna1d).ConclusionsThese findings suggest that adolescent alcohol intake may trigger gene expression changes in the CNS that parallel those found in the dilated cardiomyopathy signaling pathway. If such effects also take place in humans, our findings would serve as a warning against alcohol intake in youth, such as by teens and/or college students.