SJLB mice develop tauopathy-induced parkinsonism

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) is an inherited dementia caused by tauopathy. Recently, we established the N279K mutant human tau transgenic mice SJLB. Although SJLB mice show cognitive dysfunction with insoluble tau in the brain, it has remained unclear whether they show signs of parkinsonism. To clarify this issue, we studied whether SJLB mice in fact develop parkinsonism. Behavioral analysis showed shorter stride length than that of non-transgenic control mice in the footprint test and movement disorder in the pole test, thus mimicking some features of human parkinsonism. We also found that these symptoms were not affected by dopamine treatment. These results indicate that SJLB mice show signs of parkinsonism and they could be of usefulness not only for studies of dementing disease but also of parkinsonism induced by tauopathy.     

The catecholamine uptake blocker nomifensine protects against MPTP-induced parkinsonism in monkeys

Summary Administration of MPTP (1-methyl-1,2,3,6-tetrahydropyridine) to Macaca fascicularis monkeys produced severe parkinsonism (hypokinesia, tremor, rigidity, aphagia, adipsia) and more than 90% loss of nigral dopamine neurons, striatal dopamine content and striatal ³H-mazindol binding. Treatment with the catecholamine uptake blocker nomifensine counteracted the behavioral, histological and neurochemical effects induced by MPTP. For obtaining best protection, nomifensine had to be administered for weeks after MPTP. The results suggest that the selective target-directed neurotoxic action of MPTP on dopamine neurons in monkeys is mediated via the dopamine uptake mechanism.     

Screening for FMR1 expanded alleles in patients with parkinsonism in mainland China

Expanded alleles of the fragile X mental retardation 1 (FMR1) gene are generally divided into four classes based on the abundance of unstable CGG repeat expansions (CGGs) in its 5′-untranslated region. It has recently been reported that two of the four classes, premutation (55–200 CGGs) and gray zone (GZ, 40–54 CGGs) alleles, was potentially associated with parkinsonism. To investigate this association in patients in mainland China, a total of 360 Chinese patients with parkinsonism and 295 gender and age matched controls were recruited in this study. Indeed, no premutation or full mutation alleles (>200 CGGs) was detected among all the subjects. A total of 11 patients with parkinsonism were identified to have GZ alleles compared with only 1 carrier among the controls (P < 0.05). Notably, 10 of the 11 GZ alleles carriers with parkinsonism were female, which was 6.8% of all 147 female patients compared with none in the control females (P < 0.05). No significant difference was detected between the male groups of patients and controls. Therefore, our results indicate that FMR1 GZ allele is potentially associated with parkinsonism in mainland China, and the association is only present in the female patients, but not in the male.     

Seizure resistance without parkinsonism in aged mice after tau reduction

Tau is an emerging target for Alzheimer's disease (AD) and other conditions with epileptiform activity. Genetic tau reduction (in Tau^+/− and Tau^−/− mice) prevents deficits in AD models and has an excitoprotective effect, increasing resistance to seizures, without causing apparent neuronal dysfunction. However, most studies of tau reduction have been conducted in <1-year-old mice, and the effects of tau reduction in aged mice are less clear. Specifically, whether the excitoprotective effects of tau reduction persist with aging is unknown and whether tau reduction causes neuronal dysfunction, including parkinsonism, with aging is controversial. Here, we performed a comprehensive analysis of 2-year-old Tau^+/+, Tau^+/−, and Tau^−/− mice. In aged mice, tau reduction still conferred resistance to pentylenetetrazole-induced seizures. Moreover, tau reduction did not cause parkinsonian abnormalities in dopamine levels or motor function and did not cause iron accumulation or impaired cognition, although Tau^−/− mice had mild hyperactivity and decreased brain weight. Importantly, the excitoprotective effect in aged Tau^+/− mice was not accompanied by detectable abnormalities, indicating that partially reducing tau or blocking its function may be a safe and effective therapeutic approach for AD and other conditions with increased excitability.     

Plaques,Tangles, and Memory Loss in Mouse Models of Neurodegeneration

Within the past decade, our understanding of the pathogenic mechanisms in Alzheimer’s disease (AD) has dramatically advanced because of the development of transgenic mouse models that recapitulate the key pathological and behavioral phenotypes of the disease. These mouse models have allowed investigators to test detailed questions about how pathology develops and to evaluate potential therapeutic approaches that could slow down the development of this disease. In this review, we discuss the status of transgenic mouse models and review the complex relationship between pathology and behavior in the development of neuropathological syndromes in AD. Edited by Andrew Holmes     

Loss of cell polarity causes severe brain dysplasia in Lgl1 knockout mice

Disruption of cell polarity is seen in many cancers; however, it is generally considered a late event in tumor progression. Lethal giant larvae (Lgl) has been implicated in maintenance of cell polarity in Drosophila and cultured mammalian cells. We now show that loss of Lgl1 in mice results in formation of neuroepithelial rosette-like structures, similar to the neuroblastic rosettes in human primitive neuroectodermal tumors. The newborn Lgl1(-/-) pups develop severe hydrocephalus and die neonatally. A large proportion of Lgl1(-/-) neural progenitor cells fail to exit the cell cycle and differentiate, and, instead, continue to proliferate and die by apoptosis. Dividing Lgl1(-/-) cells are unable to asymmetrically localize the Notch inhibitor Numb, and the resulting failure of asymmetric cell divisions may be responsible for the hyperproliferation and the lack of differentiation. These results reveal a critical role for mammalian Lgl1 in regulating of proliferation, differentiation, and tissue organization and demonstrate a potential causative role of disruption of cell polarity in neoplastic transformation of neuroepithelial cells.     

Age-related decline in white matter integrity in a mouse model of tauopathy: an in vivo diffusion tensor magnetic resonance imaging study

Elevated expression of human hyperphosphorylated tau is associated with neuronal loss and white matter (WM) pathology in Alzheimer's disease (AD) and related neurodegenerative disorders. Using in vivo diffusion tensor magnetic resonance imaging (DT-MRI) at 11.1 Tesla we measured age-related alterations in WM diffusion anisotropy indices in a mouse model of human tauopathy (rTg4510) and nontransgenic (nonTg) control mice at the age of 2.5, 4.5, and 8 months. Similar to previous DT-MRI studies in AD subjects, 8-month-old rTg4510 mice showed lower fractional anisotropy (FA) values in WM structures than nonTg. The low WM FA in rTg4510 mice was observed in the genu and splenium of the corpus callosum, anterior commissure, fimbria, and internal capsule and was associated with a higher radial diffusivity than nonTg. Interestingly, rTg4510 mice showed lower estimates for the mode of anisotropy than controls at 2.5 months suggesting that changes in this diffusivity metric are detectable at an early stage preceding severe tauopathy. Immunogold electron microscopy partly supports our diffusion tensor imaging findings. At the age of 4 months, rTg4510 mice show axonal tau inclusions and unmyelinated processes. At later ages (12 months and 14 months) we observed inclusions in myelin sheath, axons, and unmyelinated processes, and a “disorganized” pattern of myelinated fiber arrangement with enlarged inter-axonal spaces in rTg4510 but not in nonTg mice. Our data support a role for the progression of tau pathology in reduced WM integrity measured by DT-MRI. Further in vivo DT-MRI studies in the rTg4510 mouse should help better discern the detailed mechanisms of reduced FA and anisotropy mode, and the specific role of tau during neurodegeneration.     

Localization of septin 8 in murine retina, and spatiotemporal expression of septin 8 in a murine model of photoreceptor cell degeneration

The septins, which form a conserved family of cytoskeletal GTP-binding proteins in mammals, comprise stable heteromeric complexes and have diverse roles in protein scaffolding, cytokinesis, vesicle trafficking and plasma membrane integrity following cell division. The goal of this study was to determine the localization of septin 8 in murine adult retina, and analyze the spatiotemporal expression of septin 8 in a murine model of photoreceptor cell degeneration. Expression of septin 8 in the normal retina of mouse and rat was observed by using immunohistochemistry and Western blotting. Furthermore, time course of the expression of septin 8 in mouse photoreceptor cell degeneration were examined by immunohistochemistry combined with hematoxylin and eosin staining, and in situ DNA fragment labeling method. In normal mouse and rat retina, localization of septin 8 is restricted in nuclei of photoreceptor cells. 96 h after intravitreal injection of cobalt chloride most photoreceptor cells lost septin 8 immunostaining at the same time as nuclear DNA fragmentation. The results of this study show that septin 8 protein is present in the specific location within the retina. Furthermore, the disappearance of septin 8 in the nuclei of photoreceptor cells is concomitant with nuclear DNA fragmentation. This suggests that loss of septin 8 could be a useful prognostic indicator for photoreceptor cell degeneration.     

Fine structure and fluoride resistant acid phosphatase activity of electron dense sinusoid terminals in the substantia gelatinosa Rolandi of the rat after dorsal root transection

Summary Fluoride resistant acid phosphatase (FRAP) activity of the rat substantia gelatinosa Rolandi is confined to electron dense sinusoid terminals under normal conditions. Transection of dorsal roots or removal of dorsal root ganglia results in a rapid degeneration of more than half of the electron dense sinusoid axon terminals. First signs of degeneration ensue 20 hours after surgery; at the 24 hours state osmiophilic degeneration bodies develop that are translocated into glial elements in the course of the second postoperative day. At the same time, light microscopically visible FRAP-activity of the Rolando substance disappears. Electron histochemical investigations reveal that decreased enzyme activity is due to degeneration of FRAP-positive terminals. It is concluded that FRAP-positive terminals, representing the majority of electron dense sinusoids in the Rolando substance, are dorsal root collaterals; the origin of non-degenerating FRAP-negative electron dense terminals remains unknown for the time being.     

Tau accumulation causes mitochondrial distribution deficits in neurons in a mouse model of tauopathy and in human Alzheimer's disease brain

Neurofibrillary tangles (NFT), intracellular inclusions of abnormal fibrillar forms of microtubule associated protein tau, accumulate in Alzheimer's disease (AD) and other tauopathies and are believed to cause neuronal dysfunction, but the mechanism of tau-mediated toxicity are uncertain. Tau overexpression in cell culture impairs localization and trafficking of organelles. Here we tested the hypothesis that, in the intact brain, changes in mitochondrial distribution occur secondary to pathological changes in tau. Array tomography, a high-resolution imaging technique, was used to examine mitochondria in the reversible transgenic (rTg)4510, a regulatable transgenic, mouse model and AD brain tissue. Mitochondrial distribution is progressively disrupted with age in rTg4510 brain, particularly in somata and neurites containing Alz50-positive tau aggregates. Suppression of soluble tau expression with doxycycline resulted in complete recovery of mitochondrial distribution, despite the continued presence of aggregated tau. The effect on mitochondrial distribution occurs without concomitant alterations in neuropil mitochondrial size, as assessed by both array tomography and electron microscopy. Similar mitochondrial localization alterations were also observed in human AD tissue in Alz50+ neurons, confirming the relevance of tau to mitochondrial trafficking observed in this animal model. Because abnormalities reverted to normal if soluble tau was suppressed in rTg4510 mice, even in the continued presence of fibrillar tau inclusions, we suggest that soluble tau plays an important role in mitochondrial abnormalities, which likely contribute to neuronal dysfunction in AD.     

Loss of GATA4 causes ectopic pancreas in the stomach

Pancreatic heterotopia is defined as pancreatic tissue outside its normal location in the body and anatomically separated from the pancreas. In this work we have analyzed the stomach glandular epithelium of Gata4 ^flox/flox; Pdx1-Cre mice (Gata4KO mice). We found that Gata4KO glandular epithelium displays an atypical morphology similar to the cornified squamous epithelium and exhibits upregulation of forestomach markers. The developing gastric units fail to form properly, and the glandular epithelial cells do not express markers of gastric gland in the absence of GATA4. Of interest, the developing glands of the Gata4KO stomach express pancreatic cell markers. Furthermore, a mass of pancreatic tissue located in the subserosa of the Gata4KO stomach is observed at adult stages. Heterotopic pancreas found in Gata4-deficient mice contains all three pancreatic cell lineages: ductal, acinar, and endocrine. Moreover, Gata4 expression is downregulated in ectopic pancreatic tissue of some human biopsy samples. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Loss of pRB causes centromere dysfunction and chromosomal instability

Chromosome instability (CIN) is a common feature of tumor cells. By monitoring chromosome segregation, we show that depletion of the retinoblastoma protein (pRB) causes rates of missegregation comparable with those seen in CIN tumor cells. The retinoblastoma tumor suppressor is frequently inactivated in human cancers and is best known for its regulation of the G1/S-phase transition. Recent studies have shown that pRB inactivation also slows mitotic progression and promotes aneuploidy, but reasons for these phenotypes are not well understood. Here we describe the underlying mitotic defects of pRB-deficient cells that cause chromosome missegregation. Analysis of mitotic cells reveals that pRB depletion compromises centromeric localization of CAP-D3/condensin II and chromosome cohesion, leading to an increase in intercentromeric distance and deformation of centromeric structure. These defects promote merotelic attachment, resulting in failure of chromosome congression and an increased propensity for lagging chromosomes following mitotic delay. While complete loss of centromere function or chromosome cohesion would have catastrophic consequences, these more moderate defects allow pRB-deficient cells to proliferate but undermine the fidelity of mitosis, leading to whole-chromosome gains and losses. These observations explain an important consequence of RB1 inactivation, and suggest that subtle defects in centromere function are a frequent source of merotely and CIN in cancer.     

On the survival time of a tangled neuron in the hippocampal CA4 region in parkinsonism dementia complex of Guam.

In diseases such as the Parkinson dementia complex of Guam (PDC) or Alzheimer's disease, susceptible neurons develop intracellular tangles (iNFTs) and then die, leaving behind extracellular tangles (eNFTs). We performed counts of healthy neurons, iNFTs, and eNFTs in the hippocampus of Guamanian Chamorros who were neurologically normal or who suffered from PDC. The total of surviving and dead neurons in the CA4 region was remarkably constant from case to case, indicating that eNFTs are not phagocytosed. Since cases of recent PDC showed only marginal tangle formation in CA4, we concluded that tangle development in CA4 commenced close to the onset of the disease. Based on this assumption, as well as the further assumption that the average rate of tangle development and the average lifetime of a tangled neuron do not alter as the disease progresses, we derived equations to determine the average lifetime of tangled neurons. The results varied from 0.13 years for the most rapidly progressing case to 7.98 years for the most slowly developing case. The average for 8 cases was 2.51 years.     

Loss of the anaphase-promoting complex in quiescent cells causes unscheduled hepatocyte proliferation

The anaphase-promoting complex or cyclosome (APC/C) is an ubiquitin protein ligase that together with Cdc20 and Cdh1 targets mitotic proteins for degradation by the proteosome. APC-Cdc20 activity during mitosis triggers anaphase by destroying securin and cyclins. APC-Cdh1 promotes degradation of cyclins and other proteins during G(1). We show that loss of APC/C during embryogenesis is early lethal before embryonic day E6.5 (E6.5). To investigate the role of APC/C in quiescent cells, we conditionally inactivated the subunit Apc2 in mice. Deletion of Apc2 in quiescent hepatocytes caused re-entry into the cell cycle and arrest in metaphase, resulting in liver failure. Re-entry into the cell cycle either occurred without any proliferative stimulus or could be easily induced. We demonstrate that the APC has an additional function to prevent hepatocytes from unscheduled re-entry into the cell cycle.     

Biallelic variant in AGTPBP1 causes infantile lower motor neuron degeneration and cerebellar atrophy

Infantile hereditary lower motor neuron disorders beyond 5q–spinal muscular atrophy (5q‐SMA) are usually caused by mutations other than deletions or mutations in SMN1. In addition to motor neuron degeneration, further neurologic or multisystemic pathologies in non‐5q‐SMAs are not seldom. Some of the non‐5q‐SMA phenotypes, such as pontocerebellar hypoplasia (PCH1), have been classified later as a different disease group due to distinctive primary pathologies. Likewise, a novel phenotype, childhood‐onset neurodegeneration with cerebellar atrophy (CONDCA) has been described recently in individuals with lower motor neuron disorder and cerebellar atrophy due to biallelic loss‐of‐function variants in AGTPBP1 that encodes cytosolic carboxypeptidase 1 (CCP1). Here we present two individuals with CONDCA in whom a biallelic missense AGTPBP1 variant (NM_001330701.1:c.2396G>T, p.Arg799Leu) was identified by whole exome sequencing. Affected individuals in this report correspond to the severe infantile spectrum of the disease and underline the severe pathogenic effect of this missense variant. This report is the second in the literature that delineates the pathogenic effects of biallelic AGTPBP1 variants presenting the recently described CONDCA disease.     

Loss of Rb proteins causes genomic instability in the absence of mitogenic signaling

Loss of G1/S control is a hallmark of cancer, and is often caused by inactivation of the retinoblastoma pathway. However, mouse embryonic fibroblasts lacking the retinoblastoma genes RB1, p107, and p130 (TKO MEFs) are still subject to cell cycle control: Upon mitogen deprivation, they enter and complete S phase, but then firmly arrest in G2. We now show that G2-arrested TKO MEFs have accumulated DNA damage. Upon mitogen readdition, cells resume proliferation, although only part of the damage is repaired. As a result, mitotic cells show chromatid breaks and chromatid cohesion defects. These aberrations lead to aneuploidy in the descendent cell population. Thus, our results demonstrate that unfavorable growth conditions can cause genomic instability in cells lacking G1/S control. This mechanism may allow premalignant tumor cells to acquire additional genetic alterations that promote tumorigenesis.     

中脑神经干细胞分化的神经元体外表达突触素的动态分析

目的：观察中脑神经干细胞(NSCs)分化的神经元在不同条件下及不同时间内表达突触素的动态变化。方法：使用骨髓基质细胞(BMSCs)的条件液培养中脑NSCs,免疫细胞化学染色方法观察NSCs分化的神经元表达突触素的状态。结果：在NSCs分化后的12d,可观察到神经元能够表达突触素,但水平较低;18d,NSCs分化的神经元表达突触素的水平接近体外培养3d的海马神经元,并且也呈现典型的串珠样分布。结论：中脑NSCs分化而来的神经元在体外能够表达突触素,但与原代海马神经元相比,则需要更长的体外培养时间,提示NSCs分化的神经元发育成熟可能需要一定时间。     

尼古丁在人椎间盘髓核细胞退变中的作用

目的探讨不同浓度及时间的尼古丁在人椎间盘髓核细胞退变中的作用。方法随机选择5例腰椎骨折患者的椎间盘髓核组织进行体外细胞培养,种于12孔板中,按照0、1、33.3、100、200、500ng/m L的尼古丁浓度以及1、2、3、7、10天加入来培养,每组细胞用Trizol法提取总RNA,用荧光定量PCR测定AQP1,AQP3和II型胶原(Collagen)以及蛋白多糖(Aggrecan)的m RNA表达。用SPSS19.0进行统计分析。结果随着尼古丁浓度升高及培养时间的延长,髓核细胞形态变化明显,贴壁能力减弱,胞质减少,胞核萎缩,空泡形成,凋亡增加。且细胞AQP1及AQP3的m RNA水平随着尼古丁浓度及时间的增加而降低,II型胶原及蛋白聚糖m RNA水平也降低,细胞发生退变。结论尼古丁会降低人椎间盘髓核细胞AQP1和AQP3的表达,进而降低髓核细胞II型胶原和蛋白聚糖的表达,促进椎间盘退变,且作用时间越长,浓度越高,细胞退变越严重。     

Severe amygdala dysfunction in a MAPT transgenic mouse model of frontotemporal dementia

Frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) is a neurodegenerative tauopathy caused by mutations in the tau gene (MAPT). Individuals with FTDP-17 have deficits in learning, memory, and language, in addition to personality and behavioral changes that are often characterized by a lack of social inhibition. Several transgenic mouse models expressing tau mutations have been tested extensively for memory or motor impairments, though reports of amygdala-dependent behaviors are lacking. To this end, we tested the rTg4510 mouse model on a behavioral battery that included amygdala-dependent tasks of exploration. As expected, rTg4510 mice exhibit profound impairments in hippocampal-dependent learning and memory tests, including contextual fear conditioning. However, rTg4510 mice also display an abnormal hyperexploratory phenotype in the open-field assay, elevated plus maze, light-dark exploration, and cued fear conditioning, indicative of amygdala dysfunction. Furthermore, significant tau burden is detected in the amygdala of both rTg4510 mice and human FTDP-17 patients, suggesting that the rTg4510 mouse model recapitulates the behavioral disturbances and neurodegeneration of the amygdala characteristic of FTDP-17.     

Loss of dystrophin and the microtubule‐binding protein ELP‐1 causes progressive paralysis and death of adult C. elegans

EMAP‐like proteins (ELPs) are conserved microtubule‐binding proteins that function during cell division and in the behavior of post‐mitotic cells. In Caenorhabditis elegans, ELP‐1 is broadly expressed in many cells and tissues including the touch receptor neurons and body wall muscle. Within muscle, ELP‐1 is associated with a microtubule network that is closely opposed to the integrin‐based adhesion sites called dense bodies. To examine ELP‐1 function, we utilized an elp‐1 RNA interference assay and screened for synthetic interactions with mutated adhesion site proteins. We reveal a synthetic lethal relationship between ELP‐1 and the dystrophin‐like protein, DYS‐1. Reduction of ELP‐1 in a dystrophin [dys‐1(cx18)] mutant results in adult animals with motility defects, splayed and hypercontracted muscle with altered cholinergic signaling. Worms fill with vesicles, become flaccid, and die. We conclude that ELP‐1 is a genetic modifier of a C. elegans model of muscular dystrophy. Developmental Dynamics, 2009. © 2009 Wiley‐Liss, Inc.