Adenylyl cyclase subtype 1 is essential for late-phase long term potentiation and spatial propagation of synaptic responses in the anterior cingulate cortex of adult mice

Long-term potentiation (LTP) is a key cellular mechanism for pathological pain in the central nervous system. LTP contains at least two different phases: early-phase LTP (E-LTP) and late-phase LTP (L-LTP). Among several major cortical areas, the anterior cingulate cortex (ACC) is a critical brain region for pain perception and its related emotional changes. Periphery tissue or nerve injuries cause LTP of excitatory synaptic transmission in the ACC. Our previous studies have demonstrated that genetic deletion of calcium-stimulated adenylyl cyclase 1 (AC1) or pharmacological application of a selective AC1 inhibitor NB001 blocked E-LTP in the ACC. However, the effect of AC1 on L-LTP, which requires new protein synthesis and is important for the process of chronic pain, has not been investigated. Here we tested the effects of NB001 on the ACC L-LTP and found that bath application of NB001 (0.1 μM) totally blocked the induction of L-LTP and recruitment of cortical circuitry without affecting basal excitatory transmission. In contrast, gabapentin, a widely used analgesic drug for neuropathic pain, did not block the induction of L-LTP and circuitry recruitment even at a high concentration (100 μM). Gabapentin non-selectively decreased basal synaptic transmission. Our results provide strong evidence that the selective AC1 inhibitor NB001 can be used to inhibit pain-related cortical L-LTP without affecting basal synaptic transmission. It also provides basic mechanisms for possible side effects of gabapentin in the central nervous system and its ineffectiveness in some patients with neuropathic pain.

Long-term temporal imprecision of information coding in the anterior cingulate cortex of mice with peripheral inflammation or nerve injury

Temporal properties of spike firing in the central nervous system (CNS) are critical for neuronal coding and the precision of information storage. Chronic pain has been reported to affect cognitive and emotional functions, in addition to trigger long-term plasticity in sensory synapses and behavioral sensitization. Less is known about the possible changes in temporal precision of cortical neurons in chronic pain conditions. In the present study, we investigated the temporal precision of action potential firing in the anterior cingulate cortex (ACC) by using both in vivo and in vitro electrophysiological approaches. We found that peripheral inflammation caused by complete Freund's adjuvant (CFA) increased the standard deviation (SD) of spikes latency (also called jitter) of ∼51% of recorded neurons in the ACC of adult rats in vivo. Similar increases in jitter were found in ACC neurons using in vitro brain slices from adult mice with peripheral inflammation or nerve injury. Bath application of glutamate receptor antagonists CNQX and AP5 abolished the enhancement of jitter induced by CFA injection or nerve injury, suggesting that the increased jitter depends on the glutamatergic synaptic transmission. Activation of adenylyl cyclases (ACs) by bath application of forskolin increased jitter, whereas genetic deletion of AC1 abolished the change of jitter caused by CFA inflammation. Our study provides strong evidence for long-term changes of temporal precision of information coding in cortical neurons after peripheral injuries and explains neuronal mechanism for chronic pain caused cognitive and emotional impairment.

Comprehensive identification of MHC class II alleles in a cohort of Chinese rhesus macaques

Rhesus macaque is a very important animal model for various human diseases, especially for AIDS and vaccine research. The susceptibility and/or resistance to some of these diseases are related to the major histocompatibility complex (MHC). To gain insight into the MHC background and to facilitate the experimental use of Chinese rhesus macaques, Mamu-DPB1, Mamu-DQB1, and Mamu-DRB alleles were investigated in 30 Chinese rhesus macaques through gene cloning and sequencing. A total of 66 alleles were identified in this study, including 14 Mamu-DPB1, 20 Mamu-DQB1, and 30 Mamu-DRB alleles as well as 2 high-frequency Mamu-DPB1 alleles. Interestingly, one of the high-frequency Mamu-DPB1 alleles had been undocumented in earlier studies. Eleven of the other alleles, including four Mamu-DPB1, three Mamu-DQB1, and four Mamu-DRB alleles were also novel. Importantly, like MHC-DRB, more than two Mamu-DPB1 sequences per animal were detected in 13 monkeys, which suggested that they might represent gene duplication. Our data also indicated quite a few differences in the distribution of MHC class II alleles between the Chinese rhesus macaques and the previously reported Indian rhesus macaques. To our knowledge, our results revealed comprehensively the combination of MHC II alleles. This information will not only promote the understanding of Chinese rhesus macaque MHC polymorphism but will also facilitate the use of Chinese rhesus macaques in studies of human disease.

Pharmacological rescue of cortical synaptic and network potentiation in a mouse model for fragile X syndrome

Fragile X syndrome, caused by the mutation of the Fmr1 gene, is characterized by deficits of attention and learning ability. In the hippocampus of Fmr1 knockout mice (KO), long-term depression is enhanced whereas long-term potentiation (LTP) including late-phase LTP (L-LTP) is reduced or unaffected. Here we examined L-LTP in the anterior cingulate cortex (ACC) in Fmr1 KO mice by using a 64-electrode array recording system. In wild-type mice, theta-burst stimulation induced L-LTP that does not occur in all active electrodes/channels within the cingulate circuit and is typically detected in ∼75% of active channels. Furthermore, L-LTP recruited new responses from previous inactive channels. Both L-LTP and the recruitment of inactive responses were blocked in the ACC slices of Fmr1 KO mice. Bath application of metabotropic glutamate receptor 5 (mGluR5) antagonist or glycogen synthase kinase-3 (GSK3) inhibitors rescued the L-LTP and network recruitment. Our results demonstrate that loss of FMRP will greatly impair L-LTP and recruitment of cortical network in the ACC that can be rescued by pharmacological inhibition of mGluR5 or GSK3. This study is the first report of the network properties of L-LTP in the ACC, and provides basic mechanisms for future treatment of cortex-related cognitive defects in fragile X patients.

Effects of NB001 and gabapentin on irritable bowel syndrome-induced behavioral anxiety and spontaneous pain

Irritable bowel syndrome (IBS) is characterized by recurrent abdominal discomfort, spontaneous pain, colorectal hypersensitivity and bowel dysfunction. Patients with IBS also suffer from emotional anxiety and depression. However, few animal studies have investigated IBS-induced spontaneous pain and behavioral anxiety. In this study, we assessed spontaneous pain and anxiety behaviors in an adult mouse model of IBS induced by zymosan administration. By using Fos protein as a marker, we found that sensory and emotion related brain regions were activated at day 7 after the treatment with zymosan; these regions include the prefrontal cortex, anterior cingulate cortex, insular cortex and amygdala. Behaviorally, zymosan administration triggered spontaneous pain (decreased spontaneous activities in the open field test) and increased anxiety-like behaviors in three different tests (the open field, elevated plus maze and light/dark box tests). Intraperitoneal injection of NB001, an adenylyl cyclase 1 (AC1) inhibitor, reduced spontaneous pain but had no significant effect on behavioral anxiety. In contrast, gabapentin reduced both spontaneous pain and behavioral anxiety. These results indicate that NB001 and gabapentin may inhibit spontaneous pain and anxiety-like behaviors through different mechanisms.

Postsynaptic potentiation of corticospinal projecting neurons in the anterior cingulate cortex after nerve injury

Long-term potentiation (LTP) is the key cellular mechanism for physiological learning and pathological chronic pain. In the anterior cingulate cortex (ACC), postsynaptic recruitment or modification of AMPA receptor (AMPAR) GluA1 contribute to the expression of LTP. Here we report that pyramidal cells in the deep layers of the ACC send direct descending projecting terminals to the dorsal horn of the spinal cord (lamina I-III). After peripheral nerve injury, these projection cells are activated, and postsynaptic excitatory responses of these descending projecting neurons were significantly enhanced. Newly recruited AMPARs contribute to the potentiated synaptic transmission of cingulate neurons. PKA-dependent phosphorylation of GluA1 is important, since enhanced synaptic transmission was abolished in GluA1 phosphorylation site serine-845 mutant mice. Our findings provide strong evidence that peripheral nerve injury induce long-term enhancement of cortical-spinal projecting cells in the ACC. Direct top-down projection system provides rapid and profound modulation of spinal sensory transmission, including painful information. Inhibiting cortical top-down descending facilitation may serve as a novel target for treating neuropathic pain.

No requirement of TRPV1 in long-term potentiation or long-term depression in the anterior cingulate cortex

One major interest in the study of transient receptor potential vanilloid type 1 (TRPV1) in sensory system is that it may serve as a drug target for treating chronic pain. While the roles of TRPV1 in peripheral nociception and sensitization have been well documented, less is known about its contribution to pain-related cortical plasticity. Here, we used 64 multi-electrode array recording to examine the potential role of TRPV1 in two major forms of synaptic plasticity, long-term potentiation (LTP) and long-term depression (LTD), in the anterior cingulate cortex (ACC). We found that pharmacological blockade of TRPV1 with either [(E)-3-(4-t-Butylphenyl)-N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)acrylamide] (AMG9810, 10 μM) or N-(3-methoxyphenyl)-4-chlorocinnamide (SB366791, 20 μM) failed to affect LTP induced by strong theta burst stimulation in the ACC of adult mice. Similarly, neither AMG9810 nor SB366791 blocked the cingulate LTD induced by low-frequency stimulation. Analysis of the results from different layers of the ACC obtained the same conclusions. Spatial distribution of LTP or LTD-showing channels among the ACC network was also unaltered by the TRPV1 antagonists. Since cortical LTP and LTD in the ACC play critical roles in chronic pain triggered by inflammation or nerve injury, our findings suggest that TRPV1 may not be a viable target for treating chronic pain, especially at the cortical level.

Comprehensive cysteine-scanning mutagenesis reveals Claudin-2 pore-lining residues with different intrapore locations

The first extracellular loop (ECL1) of claudins forms paracellular pores in the tight junction that determine ion permselectivity. We aimed to map the pore-lining residues of claudin-2 by comprehensive cysteine-scanning mutagenesis of ECL1. We screened 45 cysteine mutations within the ECL1 by expression in polyclonal Madin-Darby canine kidney II Tet-Off cells and found nine mutants that displayed a significant decrease of conductance after treatment with the thiol-reactive reagent 2-(trimethylammonium)ethyl methanethiosulfonate, indicating the location of candidate pore-lining residues. Next, we stably expressed these candidates in monoclonal Madin-Darby canine kidney I Tet-Off cells and exposed them to thiol-reactive reagents. The maximum degree of inhibition of conductance, size selectivity of degree of inhibition, and size dependence of the kinetics of reaction were used to deduce the location of residues within the pore. Our data support the following sequence of pore-lining residues located from the narrowest to the widest part of the pore: Ser(68), Ser(47), Thr(62)/Ile(66), Thr(56), Thr(32)/Gly(45), and Met(52). The paracellular pore appears to primarily be lined by polar side chains, as expected for a predominantly aqueous environment. Furthermore, our results strongly suggest the existence of a continuous sequence of residues in the ECL1 centered around Asp(65)-Ser(68) that form a major part of the lining of the pore.

Loss of long-term depression in the insular cortex after tail amputation in adult mice

The insular cortex (IC) is an important forebrain structure involved in pain perception and taste memory formation. Using a 64-channel multi-electrode array system, we recently identified and characterized two major forms of synaptic plasticity in the adult mouse IC: long-term potentiation (LTP) and long-term depression (LTD). In this study, we investigate injury-related metaplastic changes in insular synaptic plasticity after distal tail amputation. We found that tail amputation in adult mice produced a selective loss of low frequency stimulation-induced LTD in the IC, without affecting (RS)-3,5-dihydroxyphenylglycine (DHPG)-evoked LTD. The impaired insular LTD could be pharmacologically rescued by priming the IC slices with a lower dose of DHPG application, a form of metaplasticity which involves activation of protein kinase C but not protein kinase A or calcium/calmodulin-dependent protein kinase II. These findings provide important insights into the synaptic mechanisms of cortical changes after peripheral amputation and suggest that restoration of insular LTD may represent a novel therapeutic strategy against the synaptic dysfunctions underlying the pathophysiology of phantom pain.

Comparative microRNA expression profiles of cynomolgus monkeys, rat, and human reveal that mir-182 is involved in T2D pathogenic processes

Type 2 diabetes (T2D) is a prevalent disease that happens around the world and usually happens with insulin resistance. MicroRNAs (miRNAs) represented important roles in the suppression of gene expression and were proven to be related to human diseases. In this study, we used cynomolgus monkey fed with normal and high fatty diet (HFD), respectively, to analyze the miRNA expression profile in whole blood by deep sequencing. Finally in total 24 miRNAs with differential expression were filtered. Among them, miR-182 related to the insulin resistance by modulating FOXO1 and PI3K/AKT cascade and had the greatest copy number in the whole blood. Decrease of miR-182 in T2D cynomolgus individuals is completely consistent with the previous studies in human and rat. Integrating miR-182 tissue expression profile, target genes, and copy number in blood reveals that miR-182 plays a key role in crucial genes modulation, such as FOXO1 and BHLHE22, which leads to potential hyperglycemia and modulates the insulin secretion. In addition, miR-182 might regulate the processes of both cell proliferation and apoptosis that play crucial role in determining the cells' fate. Therefore, miR-182 can be a biomarker in diagnosis of the potential T2D that has benefits for medical purpose.

NMDA receptor-dependent long-term potentiation comprises a family of temporally overlapping forms of synaptic plasticity that are induced by different patterns of stimulation

N-methyl-d-aspartate receptor (NMDAR)-dependent long-term potentiation (LTP) is extensively studied since it is believed to use the same molecular mechanisms that are required for many forms of learning and memory. Unfortunately, many controversies exist, not least the seemingly simple issue concerning the locus of expression of LTP. Here, we review our recent work and some of the extensive literature on this topic and present new data that collectively suggest that LTP can be explained, during its first few hours, by the coexistence of at least three mechanistically distinct processes that are all triggered by the synaptic activation of NMDARs.

Long-term potentiation in the anterior cingulate cortex and chronic pain

Glutamate is the primary excitatory transmitter of sensory transmission and perception in the central nervous system. Painful or noxious stimuli from the periphery ‘teach’ humans and animals to avoid potentially dangerous objects or environments, whereas tissue injury itself causes unnecessary chronic pain that can even last for long periods of time. Conventional pain medicines often fail to control chronic pain. Recent neurobiological studies suggest that synaptic plasticity taking place in sensory pathways, from spinal dorsal horn to cortical areas, contributes to chronic pain. Injuries trigger long-term potentiation of synaptic transmission in the spinal cord dorsal horn and anterior cingulate cortex, and such persistent potentiation does not require continuous neuronal activity from the periphery. At the synaptic level, potentiation of excitatory transmission caused by injuries may be mediated by the enhancement of glutamate release from presynaptic terminals and potentiated postsynaptic responses of AMPA receptors. Preventing, ‘erasing’ or reducing such potentiation may serve as a new mechanism to inhibit chronic pain in patients in the future.

N-type voltage gated calcium channels mediate excitatory synaptic transmission in the anterior cingulate cortex of adult mice

Voltage gated calcium channels (VGCCs) are well known for its importance in synaptic transmission in the peripheral and central nervous system. However, the role of different VGCCs in the anterior cingulate cortex (ACC) has not been studied. Here, we use a multi-electrode array recording system (MED64) to study the contribution of different types of calcium channels in glutamatergic excitatory synaptic transmission in the ACC. We found that only the N-type calcium channel blocker ω-conotoxin-GVIA (ω-Ctx-GVIA) produced a great inhibition of basal synaptic transmission, especially in the superficial layer. Other calcium channel blockers that act on L-, P/Q-, R-, and T-type had no effect. We also tested the effects of several neuromodulators with or without ω-Ctx-GVIA. We found that N-type VGCC contributed partially to (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid- and (R)-Baclofen-induced synaptic inhibition. By contrast, the inhibitory effects of 2-Chloroadenosine and carbamoylcholine chloride did not differ with or without ω-Ctx-GVIA, indicating that they may act through other mechanisms. Our results provide strong evidence that N-type VGCCs mediate fast synaptic transmission in the ACC.

Identification of Mamu-DPA1, Mamu-DQA1, and Mamu-DRA alleles in a cohort of Chinese rhesus macaques

Rhesus macaques have long been used as animal models for various human diseases; the susceptibility and/or resistance to some of these diseases are related to the major histocompatibility complex (MHC). To gain insight into the MHC background and to facilitate the experimental use of Chinese rhesus macaques, Mamu-DPA1, Mamu-DQA1, and Mamu-DRA alleles were investigated in 30 Chinese rhesus macaques by gene cloning and sequencing. A total of 14 Mamu-DPA1, 17 Mamu-DQA1, and 9 Mamu-DRA alleles were identified in this study. Of these alleles, 22 novel sequences have not been documented in earlier studies, including nine Mamu-DPA1, ten Mamu-DQA1, and three Mamu-DRA alleles. Interestingly, like Mafa-DQA1 and Mafa-DPA1, more than two Mamu-DQA1 and Mamu-DPA1 alleles were detected in one animal in this study, which suggested that they might represent gene duplication. If our findings can be validated by other studies, it will further increase the number of known Mamu-DPA1 and Mamu-DQA1 polymorphisms. Our data also indicated significant differences in MHC class II allele distribution among the Chinese rhesus macaques, Vietnamese cynomolgus macaques, and the previously reported rhesus macaques, which were mostly of Indian origin. This information will not only promote the understanding of Chinese rhesus macaque MHC diversity and polymorphism but will also facilitate the use of Chinese rhesus macaques in studies of human disease.

TRIM5α polymorphism identification in cynomolgus macaques of Vietnamese origin and Chinese rhesus macaques

TRIM5α is a retroviral restriction factor, in which the B30.2 (SPRY) and coiled-coil domains cooperate to determine the specificity of TRIM5α-mediated capture of retroviral capsids. Here, all exons of TRIM5α were analyzed in 39 Vietnamese cynomolgus macaques (VCE) and 29 Chinese rhesus macaques (CR). Our results revealed the presence of 22 alleles using the PHASE 2.0 software package (PHylogenetics And Sequence Evolution), including two novel species-specific alleles with a low frequency in VCE in exons 4 and 8, which encoded the coiled-coil and B30.2 (SPRY) domains, respectively. Nine alleles were detected in both VCE and CR, while four alleles were likely shared between the species. Of these alleles, the highest frequencies of 38% and 26% occurred in VCE and CR, respectively. Importantly, we found that some alleles encoded the same coiled-coil domain, but not the SPRY domain. In contrast, other alleles encoded the same SPRY domain, but not the coiled-coil domain. Our findings will contribute to the understanding of the interaction between the two domains and the determination of the specificity of TRIM5α-mediated capture of retroviral capsids. Our results from the phylogenetic trees constructed for VCE and CR suggested that the macaques' ability to inhibit SIV replication became gradually stronger if they carried corresponding alleles in four clades (clades4-7). More interesting, in clade3, both novel allele pairs (4E100a, 10E147a) and allele pairs (7R17b and 13R11b), which had the strong ability to inhibit SIV replication, originated from the same ancestral allele, suggesting that the novel alleles might play a key role to determine an animal's ability to inhibit SIV/HIV replication. However, further studies are needed to increase our understanding of the genetic background of TRIM5α in these two macaque species.

Long-term depression of synaptic transmission in the adult mouse insular cortex in vitro

The insular cortex (IC) is known to play important roles in higher brain functions such as memory and pain. Activity-dependent long-term depression (LTD) is a major form of synaptic plasticity related to memory and chronic pain. Previous studies of LTD have mainly focused on the hippocampus, and no study in the IC has been reported. In this study, using a 64-channel recording system, we show for the first time that repetitive low-frequency stimulation (LFS) can elicit frequency-dependent LTD of glutamate receptor-mediated excitatory synaptic transmission in both superficial and deep layers of the IC of adult mice. The induction of LTD in the IC required activation of the N-methyl-d-aspartate (NMDA) receptor, metabotropic glutamate receptor (mGluR)5, and L-type voltage-gated calcium channel. Protein phosphatase 1/2A and endocannabinoid signaling are also critical for the induction of LTD. In contrast, inhibiting protein kinase C, protein kinase A, protein kinase Mζ or calcium/calmodulin-dependent protein kinase II did not affect LFS-evoked LTD in the IC. Bath application of the group I mGluR agonist (RS)-3,5-dihydroxyphenylglycine produced another form of LTD in the IC, which was NMDA receptor-independent and could not be occluded by LFS-induced LTD. Our studies have characterised the basic mechanisms of LTD in the IC at the network level, and suggest that two different forms of LTD may co-exist in the same population of IC synapses.

Comprehensive identification of high-frequency and co-occurring Mafa-DPA1, Mafa-DQA1, Mafa-DRA, and Mafa-DOA alleles in Vietnamese cynomolgus macaques

High-frequency alleles and/or co-occurring human leukocyte antigen alleles across loci appear to be more important than individual alleles as markers of disease risk and have clinical value as biomarkers for targeted screening or the development of new disease therapies. To better elucidate the major histocompatibility complex (MHC) background and to facilitate the experimental use of cynomolgus macaques, Mafa-DPA1, Mafa-DQA1, Mafa-DRA, and Mafa-DOA alleles were characterized, and their combinations were investigated in 30 Vietnamese macaques by gene cloning and sequencing. A total of 26 Mafa-DPA1, 18 Mafa-DQA1, 9 Mafa-DRA, and 15 Mafa-DOA alleles, including 7 high-frequency alleles, were identified in this study, respectively. In addition, 15 Mafa-DQA1, 17 Mafa-DPA1, 15 Mafa-DOA, and 2 Mafa-DRA alleles represented novel sequences that had not been documented in earlier studies. Our results also showed that the Vietnamese macaques might be valuable because no less than 30% of the test animals possessed Mafa-DRA*01:02:01 (90%), -DQA1*26:01:03 (37%), -DOA*01:02:07 (34%), and -DQA1*01:03:03 (30%). We previously reported that the combinations of MHC class II alleles, including the combination of DOA*01:02:07-DPA1*02:09 and DOA*01:02:07-DQA1*01:03:03, were detected in 17 and 14% of the animals, respectively. Interestingly, more than two Mafa-DQA1 and Mafa-DPA1 alleles were detected in one animal in this study, which suggested that they might be caused by a chromosomal duplication. If our findings can be validated by other studies, it will further enrich the number of known Mafa-DPA1 and Mafa-DQA1 polymorphisms. Our results identified the co-occurring MHC alleles across loci in a cohort of Vietnamese cynomolgus macaques, which emphasized the value of this species as a model for biomedical research.

Conserved aromatic residue confers cation selectivity in claudin-2 and claudin-10b

In tight junctions, both claudin-2 and claudin-10b form paracellular cation-selective pores by the interaction of the first ECL 1 with permeating ions. We hypothesized that a highly conserved aromatic residue near the pore selectivity filter of claudins contributes to cation selectivity by cation-π interaction with the permeating cation. To test this, we generated MDCK I Tet-off cells stably transfected with claudin-2 Tyr(67) mutants. The Y67L mutant showed reduced cation selectivity compared with wild-type claudin-2 due to a decrease in Na(+) permeability, without affecting the Cl(-) permeability. The Y67A mutant enlarged the pore size and further decreased the charge selectivity due to an increase in Cl(-) permeability. The Y67F mutant restored the Na(+) permeability, Cl(-) permeability, and pore size back to wild-type. The accessibility of Y67C to methanethiosulfonate modification indicated that its side chain faces the lumen of the pore. In claudin-10b, the F66L mutant reduced cation selectivity, and the F66A mutant lost pore conductance. We conclude that the conserved aromatic residue near the cation pore domain of claudins contributes to cation selectivity by a dual role of cation-π interaction and a luminal steric effect. Our findings provide new insight into how ion selectivity is achieved in the paracellular pore.

Claudin-2 pore function requires an intramolecular disulfide bond between two conserved extracellular cysteines

Claudins constitute a family of tight junction transmembrane proteins whose first extracellular loop (ECL1) determines the paracellular permeability and ion selectivity in epithelia. There are two cysteines in the ECL1 that are conserved among all claudins. We hypothesized that these extracellular cysteines are linked by an intramolecular disulfide bond that is necessary for correct pore folding and function. To test this, we mutated C54 and C64 in claudin-2, either individually or together to alanine or serine, and generated stable Madin-Darby canine kidney (MDCK) I Tet-off cell lines. Immunoblotting showed a higher molecular mass band in the mutants with a single cysteine mutation, consistent with a claudin-2 dimer, suggesting that the two conserved cysteines normally form an intramolecular disulfide bond in wild-type claudin-2. By immunofluorescent staining, the alanine mutants were mislocalized intracellularly, while the serine mutants were expressed at the tight junction. Thus dimerization of both C54A and C64A did not require tight junction expression, suggesting that C54 and C64 are located near an intermolecular interface involved in cis-interaction. The conductance and Na(+) permeability of the serine mutants were markedly lower than the wild type, but there was no difference between the single mutants and the double mutant. We conclude that the disulfide bond between the conserved extracellular cysteines in claudin-2 is necessary for pore formation, probably by stabilizing the ECL1 fold, but is not required for correct protein trafficking. We further speculate that this role is generalizable to other claudin family members.

An increase in synaptic NMDA receptors in the insular cortex contributes to neuropathic pain

Neurons in the insular cortex are activated by acute and chronic pain, and inhibition of neuronal activity in the insular cortex has analgesic effects. We found that in a mouse model in which peripheral nerve injury leads to the development of neuropathic pain, the insular cortex showed changes in synaptic plasticity, which were associated with a long-term increase in the amount of synaptic N-methyl-d-aspartate receptors (NMDARs), but not that of extrasynaptic NMDARs. Activation of cyclic adenosine monophosphate (cAMP)-dependent signaling enhanced the amount of synaptic NMDARs in acutely isolated insular cortical slices and increased the surface localization of NMDARs in cultured cortical neurons. We found that the increase in the amount of NMDARs required phosphorylation of the NMDAR subunit GluN2B at Tyr(1472) by a pathway involving adenylyl cyclase subtype 1 (AC1), protein kinase A (PKA), and Src family kinases. Finally, injecting NMDAR or GluN2B-specific antagonists into the insular cortex reduced behavioral responses to normally nonnoxious stimuli in the mouse model of neuropathic pain. Our results suggest that activity-dependent plasticity takes place in the insular cortex after nerve injury and that inhibiting the increase in NMDAR function may help to prevent or treat neuropathic pain.

Long-term potentiation of synaptic transmission in the adult mouse insular cortex: multielectrode array recordings

The insular cortex (IC) is widely believed to be an important forebrain structure involved in cognitive and sensory processes such as memory and pain. However, little work has been performed at the cellular level to investigate the synaptic basis of IC-related brain functions. To bridge the gap, the present study was designed to characterize the basic synaptic mechanisms for insular long-term potentiation (LTP). Using a 64-channel recording system, we found that an enduring form of late-phase LTP (L-LTP) could be reliably recorded for at least 3 h in different layers of IC slices after theta burst stimulation. The induction of insular LTP is protein synthesis dependent and requires activation of both GluN2A and GluN2B subunits of the NMDA receptor, L-type voltage-gated calcium channels, and metabotropic glutamate receptor 1. The paired-pulse facilitation ratio was unaffected by insular L-LTP induction, and expression of insular L-LTP required the recruitment of postsynaptic calcium-permeable AMPA receptors. Our results provide the first in vitro report of long-term multichannel recordings of L-LTP in the IC in adult mice and suggest its potential important roles in insula-related memory and chronic pain.

Delay-dependent impairment of spatial working memory with inhibition of NR2B-containing NMDA receptors in hippocampal CA1 region of rats

Hippocampal N-methyl-D-aspartate receptor (NMDAR) is required for spatial working memory. Although evidence from genetic manipulation mice suggests an important role of hippocampal NMDAR NR2B subunits (NR2B-NMDARs) in spatial working memory, it remains unclear whether or not the requirement of hippocampal NR2B-NMDARs for spatial working memory depends on the time of spatial information maintained. Here, we investigate the contribution of hippocampal NR2B-NMDARs to spatial working memory on delayed alternation task in T-maze (DAT task) and delayed matched-to-place task in water maze (DMP task). Our data show that infusions of the NR2B-NMDAR selective antagonists, Ro25-6981 or ifenprodil, directly into the CA1 region, impair spatial working memory in DAT task with 30-s delay (not 5-s delay), but severely impair error-correction capability in both 5-s and 30-s delay task. Furthermore, intra-CA1 inhibition of NR2B-NMDARs impairs spatial working memory in DMP task with 10-min delay (not 30-s delay). Our results suggest that hippocampal NR2B-NMDARs are required for spatial working memory in long-delay task, whereas spare for spatial working memory in short-delay task. We conclude that the requirement of NR2B-NMDARs for spatial working memory is delay-dependent in the CA1 region.

Alteration of neuronal activity after digit amputation in rat anterior cingulate cortex

Phantom limb pain is experienced by nearly 50 - 80% of the patients following limb amputation. The anterior cingulate cortex (ACC) is a part of the limbic system that is an essential component in mediating the affective and emotional component of pain responses. To explore the role of ACC in the phantom limb pain, we recorded evoked excitatory postsynaptic potentials (EPSPs), cortical network activity and electrophysiological properties of pyramid neurons in adult rat ACC before and after a third hind paw digit amputation using in vivo intracellular or extracellular recording and staining techniques. The recorded neurons were morphologically identified as pyramidal neurons in the ACC region. The spontaneous activity of ACC neurons significantly reduced with a more percentage of down state after amputation, this is correlated with a decrease in spontaneous spikes in medial thalamus. However, the amplitude of the evoked EPSPs was increased significantly shortly after amputation and lasted for up to 7 days. This potentiation is associated with an increase of paired-pulse facilitation (PPF), suggesting the involvement of presynaptic component in this process. No significant difference in membrane properties was observed after amputation. On the other hand, administration of Complete Freund's Adjuvant (CFA) into the hind paw, a model of inflammatory pain, induced the potentiation of EPSPs in ACC neurons at 7 days after injection. These results demonstrate that digit amputation induced a long-lasting potentiation of synaptic transmission and decrease of cortical network activity in ACC in rats, which might contribute to the phantom limb pain.

Characterization of the major histocompatibility complex class I A alleles in cynomolgus macaques of Vietnamese origin

Cynomolgus macaques (Macaca fascicularis, Mafa) have emerged as an important animal model for infectious disease and transplantation research. Extensive characterization of their major histocompatibility complex (MHC) polymorphism regions therefore becomes urgently required. In this study, we identified 41 MHC class I A nucleotide sequences in 34 unrelated cynomolgus macaques of Vietnamese origin farmed in Southern China, including eight novel Mafa-A sequences. We found two sequences with perfect identity and six sequences with close similarity to previously defined MHC class I alleles from other populations, especially from Indonesian-origin macaques. We also found three Vietnamese-origin cynomolgus macaque MHC class I sequences for which the predicted protein sequences identical throughout their B and F binding pockets to Mamu-A1*001:01 and Mamu-A3*13:03, respectively. This is important because Mamu-A1*001:01 and Mamu-A3*13:03 are associated with longer survival and lower set-point viral load in simian immunodeficiency virus (SIV)-infected rhesus monkeys. These findings have implications for the evolutionary history of Vietnamese-origin cynomolgus macaque as well as for the use of this model in SIV/SHIV (a virus combining parts of the HIV and SIV genomes) research.

Identifying candidate genes for Type 2 Diabetes Mellitus and obesity through gene expression profiling in multiple tissues or cells

Type 2 Diabetes Mellitus (T2DM) and obesity have become increasingly prevalent in recent years. Recent studies have focused on identifying causal variations or candidate genes for obesity and T2DM via analysis of expression quantitative trait loci (eQTL) within a single tissue. T2DM and obesity are affected by comprehensive sets of genes in multiple tissues. In the current study, gene expression levels in multiple human tissues from GEO datasets were analyzed, and 21 candidate genes displaying high percentages of differential expression were filtered out. Specifically, DENND1B, LYN, MRPL30, POC1B, PRKCB, RP4-655J12.3, HIBADH, and TMBIM4 were identified from the T2DM-control study, and BCAT1, BMP2K, CSRNP2, MYNN, NCKAP5L, SAP30BP, SLC35B4, SP1, BAP1, GRB14, HSP90AB1, ITGA5, and TOMM5 were identified from the obesity-control study. The majority of these genes are known to be involved in T2DM and obesity. Therefore, analysis of gene expression in various tissues using GEO datasets may be an effective and feasible method to determine novel or causal genes associated with T2DM and obesity.

Reviewer acknowledgement

Contributing reviewers

The editors of Molecular Brain would like to thank all our reviewers who have contributed to the journal in Volume 5 (2012).

Reviewer Acknowledgement

Contributing reviewers

The editors of Molecular Pain would like to thank all the reviewers who have contributed to the journal in Volume 8 (2012).

Genetic enhancement of neuropathic and inflammatory pain by forebrain upregulation of CREB-mediated transcription

CREB has been reported to be activated by injury and is commonly used as marker for pain-related plasticity changes in somatosensory pathways, including spinal dorsal horn neurons and the anterior cingulate cortex (ACC). However no evidence has been reported to support the direct role of activated CREB in injury-related behavioral sensitization (or allodynia). Here we report that genetic enhancement of CREB-mediated transcription selectively in forebrain areas enhanced behavioral responses to non-noxious stimuli after chronic inflammation (CFA model) or nerve injury. In contrast, behavioral acute responses to peripheral subcutaneous injection of formalin did not show any significant difference. Furthermore, acute pain responses to noxious thermal stimuli were also not affected. Our results thus provide direct evidence that cortical CREB-mediated transcription contributes to behavioral allodynia in animal models of chronic inflammatory or neuropathic pain.

Cortical depression and potentiation: basic mechanisms for phantom pain

People experience the feeling of the missing body part long after it has been removed after amputation are known as phantom limb sensations. These sensations can be painful, sometimes becoming chronic and lasting for several years (or called phantom pain). Medical treatment for these individuals is limited. Recent neurobiological investigations of brain plasticity after amputation have revealed new insights into the changes in the brain that may cause phantom limb sensations and phantom pain. In this article, I review recent progresses of the cortical plasticity in the anterior cingulate cortex (ACC), a critical cortical area for pain sensation, and explore how they are related to abnormal sensory sensations such as phantom pain. An understanding of these alterations may guide future research into medical treatment for these disorders.

Group I metabotropic glutamate receptor-mediated gene transcription and implications for synaptic plasticity and diseases

Stimulation of group I metabotropic glutamate receptors (mGluRs) initiates a wide variety of signaling pathways. Group I mGluR activation can regulate gene expression at both translational and transcriptional levels, and induces translation or transcription-dependent synaptic plastic changes in neurons. The group I mGluR-mediated translation-dependent neural plasticity has been well reviewed. In this review, we will highlight group I mGluR-induced gene transcription and its role in synaptic plasticity. The signaling pathways (PKA, CaMKs, and MAPKs) which have been shown to link group I mGluRs to gene transcription, the relevant transcription factors (CREB and NF-κB), and target proteins (FMRP and ARC) will be documented. The significance and future direction for characterizing group I mGluR-mediated gene transcription in fragile X syndrome, schizophrenia, drug addiction, and other neurological disorders will also be discussed.

Kainate receptor-mediated synaptic transmissions in the adult rodent insular cortex

Kainate (KA) receptors are expressed widely in the central nervous system and regulate both excitatory and inhibitory synaptic transmission. KA receptors play important roles in fear memory, anxiety, and pain. However, little is known about their function in synaptic transmission in the insular cortex (IC), a critical region for taste, memory, and pain. Using whole cell patch-clamp recordings, we have shown that KA receptors contribute to fast synaptic transmission in neurons in all layers of the IC. In the presence of the GABA(A) receptor antagonist picrotoxin, the NMDA receptor antagonist AP-5, and the selective AMPA receptor antagonist GYKI 53655, KA receptor-mediated excitatory postsynaptic currents (KA EPSCs) were revealed. We found that KA EPSCs are ~5-10% of AMPA/KA EPSCs in all layers of the adult mouse IC. Similar results were found in adult rat IC. KA EPSCs had a significantly slower rise time course and decay time constant compared with AMPA receptor-mediated EPSCs. High-frequency repetitive stimulations at 200 Hz significantly facilitated the summation of KA EPSCs. In addition, genetic deletion of GluK1 or GluK2 subunit partially reduced postsynaptic KA EPSCs, and exposure of GluK2 knockout mice to the selective GluK1 antagonist UBP 302 could significantly reduce the KA EPSCs. These data suggest that both GluK1 and GluK2 play functional roles in the IC. Our study may provide the synaptic basis for the physiology and pathology of KA receptors in the IC-related functions.

Roles of CREB in the regulation of FMRP by group I metabotropic glutamate receptors in cingulate cortex

Background

Fragile X syndrome is caused by lack of fragile X mental retardation protein (FMRP) due to silencing of the FMR1 gene. The metabotropic glutamate receptors (mGluRs) in the central nervous system contribute to higher brain functions including learning/memory, mental disorders and persistent pain. The transcription factor cyclic AMP-responsive element binding protein (CREB) is involved in important neuronal functions, such as synaptic plasticity and neuronal survival. Our recent study has shown that stimulation of Group I mGluRs upregulated FMRP and activated CREB in anterior cingulate cortex (ACC), a key region for brain cognitive and executive functions, suggesting that activation of Group I mGluRs may upregulate FMRP through CREB signaling pathway.

Results

In this study, we demonstrate that CREB contributes to the regulation of FMRP by Group I mGluRs. In ACC neurons of adult mice overexpressing dominant active CREB mutant, the upregulation of FMRP by stimulating Group I mGluR is enhanced compared to wild-type mice. However, the regulation of FMRP by Group I mGluRs is not altered by overexpression of Ca²⁺-insensitive mutant form of downstream regulatory element antagonist modulator (DREAM), a transcriptional repressor involved in synaptic transmission and plasticity.

Conclusion

Our study has provided further evidence for CREB involvement in regulation of FMRP by Group I mGluRs in ACC neurons, and may help to elucidate the pathogenesis of fragile X syndrome.

Characterization of neuronal intrinsic properties and synaptic transmission in layer I of anterior cingulate cortex from adult mice

The neurons in neocortex layer I (LI) provide inhibition to the cortical networks. Despite increasing use of mice for the study of brain functions, few studies were reported about mouse LI neurons. In the present study, we characterized intrinsic properties of LI neurons of the anterior cingulate cortex (ACC), a key cortical area for sensory and cognitive functions, by using whole-cell patch clamp recording approach. Seventy one neurons in LI and 12 pyramidal neurons in LII/III were recorded. Although all of the LI neurons expressed continuous adapting firing characteristics, the unsupervised clustering results revealed five groups in the ACC, including: Spontaneous firing neurons; Delay-sAHP neurons, Delay-fAHP neurons, and two groups of neurons with ADP, named ADP1 and ADP2, respectively. Using pharmacological approaches, we found that LI neurons received both excitatory (mediated by AMPA, kainate and NMDA receptors), and inhibitory inputs (which were mediated by GABA_A receptors). Our studies provide the first report characterizing the electrophysiological properties of neurons in LI of the ACC from adult mice.

The Jak/STAT pathway is involved in synaptic plasticity

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is involved in many cellular processes, including cell growth and differentiation, immune functions and cancer. It is activated by various cytokines, growth factors, and protein tyrosine kinases (PTKs) and regulates the transcription of many genes. Of the four JAK isoforms and seven STAT isoforms known, JAK2 and STAT3 are highly expressed in the brain where they are present in the postsynaptic density (PSD). Here, we demonstrate a new neuronal function for the JAK/STAT pathway. Using a variety of complementary approaches, we show that the JAK/STAT pathway plays an essential role in the induction of NMDA-receptor dependent long-term depression (NMDAR-LTD) in the hippocampus. Therefore, in addition to established roles in cytokine signaling, the JAK/STAT pathway is involved in synaptic plasticity in the brain.

Identification of MhcMafa-DRB alleles in a cohort of cynomolgus macaques of Vietnamese origin

Cynomolgus macaques have been used widely to build a research model of infectious and chronic diseases, as well as in transplantation studies, where disease susceptibility and/or resistance are associated with the major histocompatibility complex (MHC). To better elucidate polymorphisms and genetic differences in the Mafa-DRB locus, and facilitate the experimental use of cynomolgus macaques, we used pool screening combined with cloning and direct sequencing of polymerase chain reaction products to characterize MhcMafa-DRB gene alleles in 153 Vietnamese cynomolgus macaques. We identified 30 Mafa-DRB alleles belonging to 17 allelic lineages, including four novel sequences that had not been documented in earlier reports. The highest frequency allele was Mafa-DRB*W27:04, which was present in 7 of 35 (20%) monkeys. The next most frequent alleles were Mafa-DRB*3:07 and Mafa-DRB*W7:01, which were detected in 5 of 35 (14.3%) and 4 of 35 (11.4%) of the monkeys, respectively. The high-frequency alleles in this Vietnamese population may be high priority targets for additional characterization of immune functions. Only the DRB1*03 and DRB1*10 lineages were also present in humans, whereas the remaining alleles were monkey-specific lineages. We found 25 variable sites by aligning the deduced amino acid sequences of 29 identified alleles. Evolutionary and population analyses based on these sequences showed that human, rhesus, and cynomolgus macaques share several Mhc-DRB lineages and the shared polymorphisms in the DRB region may be attributable to the existence of interbreeding between rhesus and cynomolgus macaques. This information will promote the understanding of MHC diversity and polymorphism in cynomolgus macaques and increase the value of this species as a model for biomedical research.

[Research progress on influenza antiviral small RNAs]

Worldwide influenza caused by influenza virus is a respiratory disease which threats the public health by seasonal epidemics or global influenza outbreak. Vaccines and drugs are current therapies, but there are many restricted factors such as neurotoxicity, side effects of gastrointestinal, and drug resistance. New technologies, particularly RNAi mediated by small RNAs, has become a potential and robust method in influenza antiviral research for its high efficiency, specific, and speedy. Following the spread and epidemic of the influenza virus, application of small RNAs into influenza antiviral research has been reported increasingly. The small RNAs, PA-2087, NP-1496, and M-950, which targets PA, NP, and M2 genes, respectively, are the most effective anti-influenza siRNAs up to now. siRNA of targeting conservative region of different influenza viral genes has broader effect on virus inhibition. The combination of siRNAs of targeting different genes can achieve better virus inhibition. In this review, we mainly described the progress of siRNAs and miRNAs for anti-influenza virus, and the prospects and hurdles of influenza RNAi therapy as well.

Translational investigation and treatment of neuropathic pain

Neuropathic pain develops from a lesion or disease affecting the somatosensory system. Translational investigations of neuropathic pain by using different animal models reveal that peripheral sensitization, spinal and cortical plasticity may play critical roles in neuropathic pain. Furthermore, descending facilitatory or excitatory modulation may also act to enhance chronic pain. Current clinical therapy for neuropathic pain includes the use of pharmacological and nonpharmacological (psychological, physical, and surgical treatment) methods. However, there is substantial need to better medicine for treating neuropathic pain. Future translational researchers and clinicians will greatly facilitate the development of novel drugs for treating chronic pain including neuropathic pain.

Comprehensive identification of high-frequency and co-occurring Mafa-B, Mafa-DQB1, and Mafa-DRB alleles in cynomolgus macaques of Vietnamese origin

High-frequency alleles and/or co-occurring human leukocyte antigen (HLA) alleles across loci appear to be more important than individual alleles, because they might be markers of disease risk that have clinical value as biomarkers for targeted screening or the development of new therapies. To better elucidate the major histocompatibility complex background and to facilitate the experimental use of cynomolgus macaques, Mafa-B, Mafa-DQB1, and Mafa-DRB alleles were characterized and their combinations were investigated from 30 macaques of Vietnamese origin by cloning and sequencing. A total of 48 Mafa-B, 22 Mafa-DQB1, and 42 Mafa-DRB alleles, were detected in this study, respectively. In addition, two Mafa-DQB1 and eight Mafa-DRB alleles represented novel sequences that had not been documented in earlier studies. Our results also showed that the macaque from Vietnam might be valuable because >30% of the test animals possessed Mafa-DRB*w304 (30%) and -DQB1*0616 (30%). We report that the combination of major histocompatibility complex (MHC) class I and II alleles, including the combination of DRB3*0403-DRB*w304, DRB1*1013-DRB*w304, and Mafa-B*007:01:01-DRB*w304, which was in 17%, 13%, and 13% of the animals, respectively. Interesting, more than two Mafa-DQB1 alleles detected in one animal in this study suggest that Mafa-DQB1, like Mafa-DRB, might be a duplication in the chromosome, which have ever been documented in cynomolgus monkeys but has not yet been observed in rhesus macaques or other primates. Our results for the high frequency of commonly co-occurring MHC alleles across loci in a cohort of the Vietnamese cynomolgus macaque emphasized the value of this species as a model for biomedical research.

Rapid synaptic potentiation within the anterior cingulate cortex mediates trace fear learning

Although the cortex has been extensively studied in long-term memory storage, less emphasis has been placed on immediate cortical contributions to fear memory formation. AMPA receptor plasticity is strongly implicated in learning and memory, and studies have identified calcium permeable AMPA receptors (CP-AMPARs) as mediators of synaptic strengthening. Trace fear learning engages the anterior cingulate cortex (ACC), but whether plastic events occur within the ACC in response to trace fear learning, and whether GluN2B subunits are required remains unknown. Here we show that the ACC is necessary for trace fear learning, and shows a rapid 20% upregulation of membrane AMPA receptor GluA1 subunits that is evident immediately after conditioning. Inhibition of NMDA receptor GluN2B subunits during training prevented the upregulation, and disrupted trace fear memory retrieval 48 h later. Furthermore, intra-ACC injections of the CP-AMPAR channel antagonist, 1-naphthylacetyl spermine (NASPM) immediately following trace fear conditioning blocked 24 h fear memory retrieval. Accordingly, whole cell patch clamp recordings from c-fos positive and c-fos negative neurons within the ACC in response to trace fear learning revealed an increased sensitivity to NASPM in recently activated neurons that was reversed by reconsolidation update extinction. Our results suggest that trace fear learning is mediated through rapid GluN2B dependent trafficking of CP-AMPARs, and present in vivo evidence that CP-AMPAR activity within the ACC immediately after conditioning is necessary for subsequent memory consolidation processes.

Targeting neuronal adenylyl cyclase for the treatment of chronic pain

Pain research is currently undergoing dramatic changes. In the area of basic pain research, new discoveries have been made towards the understanding of pain transmission, modulation and plasticity. However, many of these basic discoveries have not yet led to the development of new drugs for the treatment of chronic pain. One major reason for this disconnection is the lack of translational research and drug discovery based directly on the novel pain mechanism. In this review, I focus on activity-dependent potentiation in pain-related cortical areas and recent translational research on adenylyl cyclase subtype 1 (AC1) as a novel target for treating chronic pain. In particular, I discuss the AC1 inhibitor, NB001, which produces powerful analgesic effects in animal models of chronic pain by inhibiting chronic pain-related cortical potentiation.

Genetic enhancement of behavioral itch responses in mice lacking phosphoinositide 3-kinase-γ (PI3Kγ)

Phosphoinositide 3-kinases (PI3Ks) are important for synaptic plasticity and various brain functions. The only class IB isoform of PI3K, PI3Kγ, has received the most attention due to its unique roles in synaptic plasticity and cognition. However, the potential role of PI3Kγ in sensory transmission, such as pain and itch has not been examined. In this study, we present the evidence for the first time, that genetic deletion of PI3Kγ enhanced scratching behaviours in histamine-dependent and protease-activated receptor 2 (PAR-2)-dependent itch. In contrast, PI3Kγ-deficient mice did not exhibit enhanced scratching in chloroquine-induced itch, suggesting that PI3Kγ selectively contributes to certain types of behavioal itch response. Furthermore, PI3Kγ-deficient mice exhibited normal acute nociceptive responses to thermal and mechanical noxious stimuli. Behavioral licking responses to intraplantar injections of formalin and mechanical allodynia in a chronic inflammatory pain model (CFA) were also not affected by PI3Kγ gene deletion. Our findings indicate that PI3Kγ selectively contributes to behavioral itching induced by histamine and PAR-2 agonist, but not chloroquine agonist.

PI3Kγ is required for NMDA receptor-dependent long-term depression and behavioral flexibility

Phosphatidylinositol 3-kinase (PI3K) has been implicated in synaptic plasticity and other neural functions in the brain. However, the role of individual PI3K isoforms in the brain is unclear. We investigated the role of PI3Kγ in hippocampal-dependent synaptic plasticity and cognitive functions. We found that PI3Kγ has a crucial and specific role in NMDA receptor (NMDAR)-mediated synaptic plasticity at mouse Schaffer collateral-commissural synapses. Both genetic deletion and pharmacological inhibition of PI3Kγ disrupted NMDAR long-term depression (LTD) while leaving other forms of synaptic plasticity intact. Accompanying this physiological deficit, the impairment of NMDAR LTD by PI3Kγ blockade was specifically correlated with deficits in behavioral flexibility. These findings suggest that a specific PI3K isoform, PI3Kγ, is critical for NMDAR LTD and some forms of cognitive function. Thus, individual isoforms of PI3Ks may have distinct roles in different types of synaptic plasticity and may therefore influence various kinds of behavior.

Genome sequencing and comparison of two nonhuman primate animal models, the cynomolgus and Chinese rhesus macaques

The nonhuman primates most commonly used in medical research are from the genus Macaca. To better understand the genetic differences between these animal models, we present high-quality draft genome sequences from two macaque species, the cynomolgus/crab-eating macaque and the Chinese rhesus macaque. Comparison with the previously sequenced Indian rhesus macaque reveals that all three macaques maintain abundant genetic heterogeneity, including millions of single-nucleotide substitutions and many insertions, deletions and gross chromosomal rearrangements. By assessing genetic regions with reduced variability, we identify genes in each macaque species that may have experienced positive selection. Genetic divergence patterns suggest that the cynomolgus macaque genome has been shaped by introgression after hybridization with the Chinese rhesus macaque. Macaque genes display a high degree of sequence similarity with human disease gene orthologs and drug targets. However, we identify several putatively dysfunctional genetic differences between the three macaque species, which may explain functional differences between them previously observed in clinical studies.

Eighteen novel MHC class I A alleles identified in Vietnamese-origin cynomolgus macaques

We report herein the identification of 18 novel Mafa-A alleles in cynomolgus macaques of Vietnamese origin.

Neuronal and microglial mechanisms of neuropathic pain

Neuropathic pain is generally defined as a chronic pain state resulting from peripheral and/or central nerve injury. Effective treatment for neuropathic pain is still lacking, due in part to poor understanding of pathological mechanisms at the molecular level. Neuronal mechanisms of neuropathic pain, especially synaptic plasticity, are the major focus of many investigators. N-methyl-D-aspartate (NMDA) receptor dependent synaptic plasticity at the spinal and cortical levels is believed to contribute to enhanced sensory responses after injury. Glial cells, including astrocytes and microglia, have recently been implicated in neuropathic pain. These glial cells form close interactions with neurons and thus may modulate nociceptive transmission under pathological conditions. In this review, we present recent progress in the study of neuronal and microglial mechanisms underlying neuropathic pain. We propose that activity-dependent neuronal plasticity is a key target for treatment in neuropathic pain.