The linkage disequilibrium maps of three human chromosomes across four populations reflect their demographic history and a common underlying recombination pattern

The extent and patterns of linkage disequilibrium (LD) determine the feasibility of association studies to map genes that underlie complex traits. Here we present a comparison of the patterns of LD across four major human populations (African-American, Caucasian, Chinese, and Japanese) with a high-resolution single-nucleotide polymorphism (SNP) map covering almost the entire length of chromosomes 6, 21, and 22. We constructed metric LD maps formulated such that the units measure the extent of useful LD for association mapping. LD reaches almost twice as far in chromosome 6 as in chromosomes 21 or 22, in agreement with their differences in recombination rates. By all measures used, out-of-Africa populations showed over a third more LD than African-Americans, highlighting the role of the population's demography in shaping the patterns of LD. Despite those differences, the long-range contour of the LD maps is remarkably similar across the four populations, presumably reflecting common localization of recombination hot spots. Our results have practical implications for the rational design and selection of SNPs for disease association studies.     

Molecular cloning and characterization of a novel adenylate kinase 3 gene from Clonorchis sinensis

Adenylate kinase (AK) is a ubiquitous enzyme that contributes to the homeostasis of adenine nucleotides in living cells. AK catalyzes reversible high energy phosphoryl transfer reactions between ATP (or GTP) and AMP to generate ADP (or GDP). From a Clonorchis sinensis adult worm cDNA library, we isolated a cDNA clone encoding a novel AK3 isozyme. The 956 bp cDNA encodes a putative protein of 228 amino acids with a predicted molecular mass of 26.2 kDa. The recombinant CsAK3 protein produced in Escherichia coli can be refolded into a functional protein with AK3 activity. The optimum pH and temperature for the enzyme are 8.5 and 40°C, respectively. The calculated activation energy is 56.04 kJ mol^–1. The K_m of the CsAK3 for AMP and GTP are 118 M and 359 M, respectively. CsAK3 is inhibited by Ap₅A (>70% inhibition by 2.0 mM AP₅A). Ap₅A may be a potential lead compound acting on C. sinensis in which AK3 as a drug target.     

Sodium salicylate reduces gamma aminobutyric acid-induced current in rat spinal dorsal horn neurons

Sodium salicylate is one of the nonsteroidal antiinflammatory drugs and is clinically used for antiinflammation and chronic pain relief. In the present study, we investigated the actions of sodium salicylate on gamma-aminobutyric acid type A receptor (GABA(A)) current in cultured rat spinal dorsal horn neurons. Sodium salicylate was found to reduce GABA(A) current in a reversible and concentration-dependent manner, but did not change its ion selectivity. Sodium salicylate was effective only when GABA and sodium salicylate were applied together. Application of sodium salicylate immediately before, but not during, the application of GABA did not result in a significant reduction of GABA(A) current. Our results demonstrate that sodium salicylate reversibly attenuates the GABA(A) response of dorsal horn neurons, suggesting that GABA(A) receptors in the region are pharmacological targets of sodium salicylate.     

Cystatin C prevents degeneration of rat nigral dopaminergic neurons: in vitro and in vivo studies

Destruction of nigrostriatal dopaminergic (DA) pathway triggers various persistent responses, such as inflammation and increased synthesis of neural growth factors, both in striatum and in substantia nigra. The pathological processes involved in such responses are poorly characterized and could contribute to secondary damage and/or regeneration in the central nervous system (CNS). Cystatin C was previously implicated in the process of neurodegeneration. However, its biological role during neurodegeneration is not understood and remains controversial. The present study identified an increased cystatin C mRNA level in the DA-depleted rat striatum, starting from the second week following a 6-OHDA-induced lesion. Immunohistochemical analysis confirmed the increase in cystatin C protein level in the striatum following DA depletion. Double-labeled fluorescence immunohistochemistry revealed that nigrostriatal neurons, astrocytes, and microglia contributed to the elevated level of cystatin C. Exposure to 6-hydroxydopamine, a DA-specific neurotoxin, resulted in DA neurons loss in the fetal mesencephalic cultures, an effect which could be partially reversed by treatment with cystatin C. Moreover, in vivo DA neurons survival study showed that administration of cystatin C in rats with 6-OHDA-induced lesion partially rescued the nigral DA neurons. The results indicate that the 6-OHDA lesioning induced a relatively slow but sustained up-regulation of cystatin C expression and suggest that the inhibitor may exert a neuroprotective action on DA neurons. The findings raise the possibility that cysteine proteinase inhibitors may be new candidates for neuroprotective treatment of Parkinson's disease. Cystatin C may be useful therapeutically in limiting neuropathy in Parkinson's disease.     

Neuroprotection by neuregulin-1 following focal stroke is associated with the attenuation of ischemia-induced pro-inflammatory and stress gene expression

Neuregulins are a family of growth factors with potent neuroprotective properties. We recently demonstrated that neuregulin-1 blocked delayed neuronal death following focal ischemic stroke in the rat. Focal ischemia results in the release of pro-inflammatory cytokines that produce profound changes in gene expression and contribute to cell death associated with stroke. Inflammatory and stress mediators are involved in the pathogenesis of focal ischemic brain damage. We examined whether neuregulin-1 can influence inflammatory and stress gene expression in the rat brain following transient middle cerebral artery occlusion (MCAO). In this study, we compared gene expression profiles in animals treated with neuregulin-1beta (NRG-1) or vehicle followed by MCAO. We used the Affymetrix GeneChip system to analyze gene expression in focal ischemia of the rat brain. Several inflammatory and stress genes were significantly induced following MCAO compared to sham controls including heat shock protein-70 (HSP70), interleukin-1beta, and macrophage chemotattractant protein-1 (JE/MCP-1). Treatment with NRG-1 attenuated the expression of many of these genes by 50% or more. In vitro studies demonstrated that NRG-1 suppressed inflammatory gene expression in activated macrophages. NRG-1 also prevented neuronal death induced by oxygen-glucose deprivation in a rat neuroblastoma cell line, suggesting that NRG-1 may have both direct and indirect neuroprotective capacity. These results demonstrate that NRG-1 can regulate inflammatory and stress gene expression and may give new insight to the molecular mechanisms involved in the neuroprotective role of neuregulins in stroke.     

Disruption of palladin results in neural tube closure defects in mice

Palladin is a newly identified actin-associated protein which was proposed to be involved in actin cytoskeleton organization and nervous system development. Here, we show that inactivation of palladin leads to embryonic lethality due to severe defects of cranial neural tube closure and herniation of liver and intestine. It was found that palladin(-/-) embryos died around E15.5 and developed cranial neural tube closure defects (NTDs) with 100% penetrance. Whole mount in situ hybridization revealed that expression of palladin in early wild type embryos (E8.5) was specifically restricted in the elevating cranial neural folds where the neural tube closure is initiated. Palladin expression closely mirrors the phenotypic defects observed in palladin(-/-) mutants. While in E 9.5 and E10.5 embryos palladin was ubiquitously expressed. In vitro study revealed that formation of stress fibers in cytoplasm, cell adherent ability to extra-cellular matrix protein fibronectin and cell migration were dramatically disturbed in palladin(-/-) murine embryonic fibroblast cells (MEFs). Our findings suggest that palladin plays important roles in actin stress fiber formation, cell adhesion and migration. We propose that palladin is required for the initiation of neural tube closure and provides an important new candidate that may be implicated in the etiology of human NTDs.     

Effects of unconditioned and conditioned aversive stimuli in an intense fear conditioning paradigm on synaptic plasticity in the hippocampal CA1 area in vivo

Repeated vivid recalls or flashbacks of traumatic memories and memory deficits are the cardinal features of post-traumatic stress disorder (PTSD). The underlying mechanisms are not fully understood yet. Here, we examined the effects of very strong fear conditioning (20 pairings of a light with a 1.5-mA, 0.5-s foot shock) and subsequent reexposure to the conditioning context (chamber A), a similar context (chamber B), and/or to the fear conditioned stimulus (CS) (a light) on synaptic plasticity in the hippocampal CA1 area in anesthetized Sprague-Dawley rats. The conditioning procedure resulted in very strong conditioned fear, as reflected by high levels of persistent freezing, to both the contexts and to the CS, 24 h after fear conditioning. The induction of long-term potentiation (LTP) was blocked immediately after fear conditioning. It was still markedly impaired 24 h after fear conditioning; reexposure to the conditioning chamber A (CA) or to a similar chamber B (CB) did not affect the impairment. However, presentation of the CS in the CA exacerbated the impairment of LTP, whereas the CS presentation in a CB ameliorated the impairment so that LTP induction did not differ from that of control groups. The induction of long-term depression (LTD) was facilitated immediately, but not 24 h, after fear conditioning. Only reexposure to the CS in the CA, but not reexposure to either chamber A or B alone, or the CS in chamber B, 24 h after conditioning, reinstated the facilitation of LTD induction. These data demonstrate that unconditioned and conditioned aversive stimuli in an intense fear conditioning paradigm can have profound effects on hippocampal synaptic plasticity, which may aid to understand the mechanisms underlying impairments of hippocampus-dependent memory by stress or in PTSD.     

Therapeutic benefit of TH-engineered mesenchymal stem cells for Parkinson's disease

The present study was designed to assess the potential of marrow stromal cells (MSCs) to deliver therapeutic genes to the brain and result in biologically significant functional recovery. The tyrosine hydroxylase (TH) gene was transfected to MSCs with an adeno-associated virus (AAV) vector. MSCs expressing TH gene were transplanted into the striatum of Parkinson's disease (PD) rat. The asymmetric rotation of these models after apomorphine administration was detected every week after transplantation. Six weeks after grafting, animals were sacrificed. Some brains were sectioned to do TH immunohistochemistry. The others were used to detect the dopamine levels by high-performance liquid chromatograph and electrochemical detection (HPLC-ECD). The results showed that MSCs multiply rapidly and formed fibroblast colony-forming units in primary culture. The gene expression efficiency was about 75%. The rounds of asymmetric rotation after apomorphine administration decreased after TH-engineered MSCs were grafted. Histological examination showed that TH gene was expressed around the transplantation points. The dopamine level in the lesioned striatum of rats injected with TH-MSCs was significantly greater than that in rats treated with LacZ-MSCs (P < 0.05). All the data demonstrated that MSCs could readily be genetically engineered. Therefore, MSCs could be useful gene delivery vehicles of gene therapy for Parkinson's disease.