Olfactory ensheathing cells are the main phagocytic cells that remove axon debris during early development of the olfactory system

During development of the primary olfactory system, axon targeting is inaccurate and axons inappropriately project within the target layer or overproject into the deeper layers of the olfactory bulb. As a consequence there is considerable apoptosis of primary olfactory neurons during embryonic and postnatal development and axons of the degraded neurons need to be removed. Olfactory ensheathing cells (OECs) are the glia of the primary olfactory nerve and are known to phagocytose axon debris in the adult and postnatal animal. However, it is unclear when phagocytosis by OECs first commences. We investigated the onset of phagocytosis by OECs in the developing mouse olfactory system by utilizing two transgenic reporter lines: OMP‐ZsGreen mice which express bright green fluorescent protein in primary olfactory neurons, and S100β‐DsRed mice which express red fluorescent protein in OECs. In crosses of these mice, the fate of the degraded axon debris is easily visualized. We found evidence of axon degradation at embryonic day (E)13.5. Phagocytosis of the primary olfactory axon debris by OECs was first detected at E14.5. Phagocytosis of axon debris continued into the postnatal animal during the period when there was extensive mistargeting of olfactory axons. Macrophages were often present in close proximity to OECs but they contributed only a minor role to clearing the axon debris, even after widespread degeneration of olfactory neurons by unilateral bulbectomy and methimazole treatment. These results demonstrate that from early in embryonic development OECs are the primary phagocytic cells of the primary olfactory nerve. J. Comp. Neurol. 523:479–494, 2015. © 2014 Wiley Periodicals, Inc.     

Cell‐specific and developmental expression of lectican‐cleaving proteases in mouse hippocampus and neocortex

Mounting evidence has demonstrated that a specialized extracellular matrix exists in the mammalian brain and that this glycoprotein‐rich matrix contributes to many aspects of brain development and function. The most prominent supramolecular assemblies of these extracellular matrix glycoproteins are perineuronal nets, specialized lattice‐like structures that surround the cell bodies and proximal neurites of select classes of interneurons. Perineuronal nets are composed of lecticans, a family of chondroitin sulfate proteoglycans that includes aggrecan, brevican, neurocan, and versican. These lattice‐like structures emerge late in postnatal brain development, coinciding with the ending of critical periods of brain development. Despite our knowledge of the presence of lecticans in perineuronal nets and their importance in regulating synaptic plasticity, we know little about the development or distribution of the extracellular proteases that are responsible for their cleavage and turnover. A subset of a large family of extracellular proteases (called a disintegrin and metalloproteinase with thrombospondin motifs [ADAMTS]) is responsible for endogenously cleaving lecticans. We therefore explored the expression pattern of two aggrecan‐degrading ADAMTS family members, ADAMTS15 and ADAMTS4, in the hippocampus and neocortex. Here, we show that both lectican‐degrading metalloproteases are present in these brain regions and that each exhibits a distinct temporal and spatial expression pattern. Adamts15 mRNA is expressed exclusively by parvalbumin‐expressing interneurons during synaptogenesis, whereas Adamts4 mRNA is exclusively generated by telencephalic oligodendrocytes during myelination. Thus, ADAMTS15 and ADAMTS4 not only exhibit unique cellular expression patterns but their developmental upregulation by these cell types coincides with critical aspects of neural development. J. Comp. Neurol. 523:629–648, 2015. © 2014 Wiley Periodicals, Inc.     

Amyotrophic lateral sclerosis surveillance in Baltimore and Philadelphia

Introduction: Limited epidemiological data on amyotrophic lateral sclerosis (ALS) exist in defined geographic areas in the United States. Methods: Neurologists submitted case reports for patients under their care between January 1, 2009, and December 31, 2011, who met the El Escorial criteria. Diagnosis was confirmed for a sample of cases by the consulting neurologist. Death certificate data were used for supplemental case identification. Results: The 248 reported cases were most likely to be 50–69 years old, men, white, and non‐Hispanic. The total crude average annual incidence rate was 1.46 per 100,000 person‐years. Conclusions: The reported demographic characteristics were consistent with previously published findings. The crude annual incidence was slightly lower than the expected rate of 1.6 but was within the range reported previously (0.7–2.5). These findings help quantify the burden of ALS in the United States. Muscle Nerve 51 : 815–821, 2015     

Quinolinic acid induces disrupts cytoskeletal homeostasis in striatal neurons. Protective role of astrocyte–neuron interaction

Quinolinic acid (QUIN) is an endogenous metabolite of the kynurenine pathway involved in several neurological disorders. Among the several mechanisms involved in QUIN‐mediated toxicity, disruption of the cytoskeleton has been demonstrated in striatally injected rats and in striatal slices. The present work searched for the actions of QUIN in primary striatal neurons. Neurons exposed to 10 µM QUIN presented hyperphosphorylated neurofilament (NF) subunits (NFL, NFM, and NFH). Hyperphosphorylation was abrogated in the presence of protein kinase A and protein kinase C inhibitors H89 (20 μM) and staurosporine (10 nM), respectively, as well as by specific antagonists to N‐methyl‐D‐aspartate (50 µM DL‐AP5) and metabotropic glutamate receptor 1 (100 µM MPEP). Also, intra‐ and extracellular Ca²⁺ chelators (10 µM BAPTA‐AM and 1 mM EGTA, respectively) and Ca²⁺ influx through L‐type voltage‐dependent Ca²⁺ channel (10 µM verapamil) are implicated in QUIN‐mediated effects. Cells immunostained for the neuronal markers βIII‐tubulin and microtubule‐associated protein 2 showed altered neurite/neuron ratios and neurite outgrowth. NF hyperphosphorylation and morphological alterations were totally prevented by conditioned medium from QUIN‐treated astrocytes. Cocultured astrocytes and neurons interacted with one another reciprocally, protecting them against QUIN injury. Cocultured cells preserved their cytoskeletal organization and cell morphology together with unaltered activity of the phosphorylating system associated with the cytoskeleton. This article describes cytoskeletal disruption as one of the most relevant actions of QUIN toxicity in striatal neurons in culture with soluble factors secreted by astrocytes, with neuron–astrocyte interaction playing a role in neuroprotection. © 2014 Wiley Periodicals, Inc.     

Insulin treatment restores glutamate (α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid) receptor function in the hippocampus of diabetic rats

Type 1 diabetes is associated with cognitive dysfunction. Cognitive processing, particularly memory acquisition, depends on the regulated enhancement of expression and function of glutamate receptor subtypes in the hippocampus. Impairment of memory was been detected in rodent models of type 1 diabetes induced by streptozotocin (STZ). This study examines the functional properties of synaptic α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors and the expression of synaptic molecules that regulate glutamatergic synaptic transmission in the hippocampus of STZ‐diabetic rats. The AMPA receptor‐mediated miniature excitatory postsynaptic currents (mEPSCs) and single‐channel properties of synaptosomal AMPA receptors were examined after 4 weeks of diabetes induction. Results show that amplitude and frequency of mEPSCs recorded from CA1 pyramidal neurons were decreased in diabetic rats. In addition, the single‐channel properties of synaptic AMPA receptors from diabetic rat hippocampi were different from those of controls. These impairments in synaptic currents gated by AMPA receptors were accompanied by decreased protein levels of AMPA receptor subunit GluR1, the presynaptic protein synaptophysin, and the postsynaptic anchor protein postsynaptic density protein 95 in the hippocampus of diabetic rats. Neural cell adhesion molecule (NCAM), an extracellular matrix molecule abundantly expressed in the brain, and the polysialic acid (PSA) attached to NCAM were also downregulated in the hippocampus of diabetic rats. Insulin treatment, when initiated at the onset of diabetes induction, reduced these effects. These findings suggest that STZ‐induced diabetes may result in functional deteriorations in glutamatergic synapses in the hippocampus of rats and that these effects may be reduced by insulin treatment. © 2015 Wiley Periodicals, Inc.     

MiR-124 effect in neurons apoptosis in newborn rat with thyroid hypofunction

Congenital thyroid hypofunction can cause a variety of developmental disorders. Hippocampus is an important structure participating in the cognitive activities. Neural function damage is able to induce hippocampal neuron apoptosis. As a miRNA expressed specifically and abundantly in brain tissue, miR-124 has protective effect to neuron apoptosis caused by cerebral apoplexy. However, its role in neuron apoptosis caused by thyroid hypofunction is still unclear. The rats were divided into four groups including normal group, thyroid hypofunction group, miR-124 negative control group, and miR-124 mimics group. Propylthiouracil (50 mg/d) was injected to the stomach to the rats with 15 d pregnancy till the newborn rats were born. Inducing the thyroid hypofunction rat model and then injecting miR-124 mimics to ventricle. Serum TSH, FT3 and FT4 were detected to confirm the model. Immunohistochemistry was carried out to calculate neuron number. Tunel assay was used to detect neuron apoptosis. Western blot was applied to detect apoptosis related protein Caspase-3, Bcl-2 and Bax expression. After brain injection miR-124 mimics, hippocampal neuron number and morphology both improved in 15 d newborn mice compared with thyroid hypofunction group. Tunel staining found positive neurons reduced, which indicated that miR-124 can inhibit hippocampal neuron apoptosis in thyroid hypofunction rats. Further Western blot results revealed that apoptosis inhibition might be related to down-regulating activated Caspase-3 and Bax levels, and up-regulating tumor-suppressor gene Bcl-2 expression. MiR-124 can protect neuron apoptosis in thyroid hypofunction rat.     

Whether Alzheimer’s diseases related genes also differently express in the hippocampus of Ts65Dn mice?

Background: Down syndrome is a condition which extra genetic material causes delays in child development, both mentally and physically. Strengthening the study of the neural defects of DS is of great significance. Methods: Ts65Dn mice were used in this study. We removed the brain and isolated their hippocampus. We customized 54 genes in one PCR arrays, included some important genes related to Alzheimer’s disease. The expression of genes were detected by RT-PCR. Results: PCR arrays contained 54 genes related to Alzheimer’s disease. After real-time PCR, three genes (Nae1, APP and Mapt) expressed differently in the hippocampus of Ts65Dn, compared with the normal mice. Nae1 was decreased significantly, while APP and Mapt were increased obviously. The levels of fold-changes of Nae1, APP and Mapt were 86.19, 4.49 and 2.89 respectively. Significantly different levels of expression were found in the Ts65Dn mice compared with the normal control group (P=0.00 for Nae1, P=0.02 for APP, P=0.01 for Mapt respectively). Conclusions: There are differential expressed genes in the hippocampus of Ts65Dn mice that may be closely related to Alzheimer’s disease. PCR array technology was used in the screening and identification of these genes.     

Jagged1在大鼠切割穹窿海马伞后海马内的表达变化

目的:探讨切割穹窿海马伞后不同时相点海马内Jagged1的动态表达变化。方法:切割SD大鼠双侧穹窿海马伞,于切割后第3、7、14、21 d分别提取海马组织总RNA和总蛋白,应用RT-PCR和Western Blot的方法分别检测Jagged1基因和蛋白的表达变化;切割SD大鼠右侧穹窿海马伞,7 d后通过免疫组织化学的方法检测海马齿状回颗粒下层和门区中Jagged1阳性细胞的数目和平均光密度值(MOD)。结果:Jagged1基因和蛋白在切割穹窿海马伞后的第3 d表达开始增高,第7 d时达到最高水平,第14 d后表达下降至正常水平;切割穹窿海马伞后的第7 d,切割侧海马齿状回颗粒下层和门区中Jagged1阳性细胞数为167.89±22.11,平均光密度值为0.11±0.02;正常侧阳性细胞数为140.45±22.63,平均光密度值为0.06±0.01;切割侧阳性细胞数和平均光密度值与正常侧均明显增高(P0.05)。结论:切割穹窿海马伞后Jagged1基因和蛋白的表达呈现出先增高后降低的变化趋势,提示Jagged1是切割穹窿海马伞后海马内微环境的重要组成分子。     

GAD67-GFP精神分裂症小鼠行为学改变及海马齿状回颗粒细胞层GABA能神经元的表达

目的:探讨谷氨酸脱羧酶67-绿色荧光蛋白(GAD67-GFP)基因敲入小鼠制备精神分裂症模型后学习与记忆功能的改变及海马齿状回颗粒细胞层GABA能神经元的表达。方法:利用聚合酶链式反应(PCR)鉴定GAD67-GFP基因敲入小鼠,MK-801连续腹腔注射2周制备精神分裂症动物模型,通过悬尾实验、Morris水迷宫实验、免疫荧光标记技术等,观察GAD67-GFP基因敲入小鼠的学习与记忆功能的改变及GABA能神经元在海马齿状回颗粒细胞层的表达。结果:停药后实验组与对照组比较:(1)实验组体重增加明显低于对照组(P0.05);(2)行为学改变:1悬尾实验:实验组不动时间明显小于对照组(P0.05);2Morris水迷宫实验:定位航行实验中实验组逃避潜伏期,游泳总路程明显长于对照组(P0.05),而其平均游泳速度与对照组没有明显差异(P0.05);空间探查实验中实验组经过平台所在点的次数和在平台所在象限的时间明显小于对照组(P0.05);(3)在海马齿状回颗粒细胞层中实验组的GFP阳性细胞明显多于对照组(P0.05)。结论:通过对GAD67-GFP基因敲入小鼠进行腹腔注射MK-801制备精神分裂症模型后,其学习与记忆功能显著下降,且海马齿状回颗粒细胞层GABA能神经元明显增加。提示精神分裂症后学习记忆功能减退可能与GABA能神经元的表达有关。