Correlation between cognitive deficits and Abeta deposits in transgenic APP+PS1 mice

Doubly transgenic mAPP+mPS1 mice (15-16 months) had impaired cognitive function in a spatial learning and memory task that combined features of a water maze and a radial arm maze. Nontransgenic mice learned a new platform location each day during 4 consecutive acquisition trials, and exhibited memory for this location in a retention trial administered 30 min later. In contrast, transgenic mice were, on average, unable to improve their performance in finding the hidden platform over trials. The cognitive performance of individual mice within the transgenic group were inversely related to the amount of Abeta deposited in the frontal cortex and hippocampus. These findings imply that mAPP+mPS1 transgenic mice develop deficits in cognitive ability as Abeta deposits increase. These data argue that radial arm water maze testing of doubly transgenic mice may be a useful behavioral endpoint in evaluating the functional consequences of potential AD therapies, especially those designed to reduce Abeta load.     

The effects of piracetam on cognitive performance in a mouse model of Down's syndrome

Piracetam is a nootropic agent that has been shown to improve cognitive performance in a number of animal model systems. Piracetam is reported to be used widely as a means of improving cognitive function in children with Down's syndrome (DS). In order to provide a preclinical assessment of the potential efficacy of piracetam, we examined the effects of a dose range of piracetam in the Ts65Dn mouse model of DS. Ts65Dn mice are trisomic for a region of mouse chromosome 16 with homology to human chromosome 21. Daily piracetam treatment at doses of 0, 75, 150, and 300 mg/kg ip was initiated in 6-week-old male Ts65Dn and euploid control mice. Following 4 weeks of treatment, mice were tested in the visible and hidden-platform components of the Morris water maze and were placed overnight in computerized activity chambers to assess effects on overall activity. Piracetam treatment was continued through the 4 weeks of testing. In control mice, 75 and 150 mg/kg/day piracetam improved performance in both the visible- and hidden-platform tasks. Although low doses of piracetam reduced search time in the visible-platform component in Ts65Dn mice, all piracetam doses prevented trial-related improvements in performance in Ts65Dn mice. The 300-mg/kg/day-piracetam dose was associated with a reversal of the nocturnal spontaneous hyperactivity in Ts65Dn. These data do not provide support for piracetam treatment for individuals with DS.     

Haploinsufficiency of Dyrk1A in mice leads to specific alterations in the development and regulation of motor activity

DYRK1A is a protein kinase proposed to be involved in neurogenesis. Gene-targeting disruption of Dyrk1A in mice leads to decreased body and brain size, with no severe disturbance of behavior. In this study, the authors focused on the motor profile of Dyrk1A(+/-) mice. These mice presented impairment of neuromotor development with decreased activity, suggesting a physiological role of Dyrk1A in the maturation of the neuromotor system. In the adult, a marked hypoactivity and alteration of specific motor parameters were detected. These results are in agreement with the significant expression of Dyrk1A in structures related to motor function and support a role of Dyrk1A in the control of motor function.     

Molecular mechanisms of bladder outlet obstruction in transgenic male mice overexpressing aromatase (Cyp19a1)

We investigated the etiology and molecular mechanisms of bladder outlet obstruction (BOO). Transgenic (Tg) male mice overexpressing aromatase (Cyp19a1) under the ubiquitin C promoter in the estrogen-susceptible C57Bl/6J genetic background (AROM+/6J) developed inguinal hernia by 2 months and severe BOO by 9 to 10 months, with 100% penetrance. These mice gradually developed uremia, renal failure, renal retention, and finally died. The BOO bladders were threefold larger than in age-matched wild-type (WT) males and were filled with urine on necropsy. Hypotrophic smooth muscle cells formed the thin detrusor urinae muscle, and collagen III accumulation contributed to the reduced compliance of the bladder. p-AKT and ERα expression were up-regulated and Pten expression was down-regulated in the BOO bladder urothelium. Expression of only ERα in the intradetrusor fibroblasts suggests a specific role of this estrogen receptor form in urothelial proliferation. Inactivation of Pten, which in turn activated the p-AKT pathway, was strictly related to the activation of the ERα pathway in the BOO bladders. Human relevance for these findings was provided by increased expression of p-AKT, PCNA, and ERα and decreased expression of PTEN in severe human BOO samples, compared with subnormal to mild samples. These findings clarify the involvement of estrogen excess and/or imbalance of the androgen/estrogen ratio in the molecular pathogenetic mechanisms of BOO and provide a novel lead into potential treatment strategies for BOO.     

Coenzyme Q10 and remacemide hydrochloride ameliorate motor deficits in a Huntington's disease transgenic mouse model.

Huntington's disease (HD) is a progressive inherited neurodegenerative disorder, for which there is no effective therapy. The CARE-HD study, recently published, evaluated the ability of a combination of coenzyme Q10 (CoQ10) and remacemide hydrochloride (R) to ameliorate symptoms, which might arise from glutamate-mediated excitotoxicity and abnormalities in mitochondrial energy production. In this study, we examined the efficacy of CoQ10/R therapy on ameliorating the motor dysfunction and premature death of HD-N171-82Q transgenic mice. Motor performance, measured on the Rotarod, was specifically but transiently improved beginning 3 weeks after initiating the CoQ10/R therapy. Survival, however was not prolonged. Our findings suggest that further study of CoQ10/R in mouse models is warranted to investigate whether this therapeutic approach can ameliorate the symptoms of HD in early stages of the disease.     

Motor discoordination of transgenic mice overexpressing a microtubule destabilizer, stathmin, specifically in Purkinje cells

The proper regulation of microtubule (MT) structure is important for dendritic and neural circuit development. However, the relationship between the regulation of the MTs in dendrites and the formation of neural function is still unclear. Stathmin is a MT destabilizer, and we have previously reported that the expression and the activity of stathmin is downregulated during cerebellar Purkinje cell (PC) development. In this study, we generated transgenic mice that specifically overexpress the constitutively active form of stathmin in the PCs. These mutant mice did not show any obvious morphological or excitatory transmission abnormalities in the cerebellum. In contrast, we observed a decline in the expression of MAP2 and KIF5 signal in the PC dendrites and a discoordination of motor function in the mutant mice, although they displayed normal general behavior. These data indicate that the overexpression of stathmin disrupts dendritic MT organization, motor protein distribution, and neural function in PCs.     

Mild impairment of learning and memory in mice overexpressing the mSim2 gene located on chromosome 16: an animal model of Down's syndrome.

Human Sim2 is a product of one of the genes located on human chromosome 21q22 and is a homolog of Drosophila single-minded ( sim ) which is a critical player in midline development of the central nervous system of the fly. Since Sim2 mRNA is expressed in facial, skull, palate and vertebra primordia in human and rodent embryos, features that are associated with phenotypes of Down's syndrome (DS), its trisomic state is suspected to contribute to the symptoms of DS. Here we describe that mSim2 mRNA is expressed in hippocampus and amygdala of adult mice, and that while mice overexpressing mSim2 under the control of the beta-actin promoter are viable and fertile and have superficially normal skeletal, brain and heart structures, they exhibit a moderate defect in context-dependent fear conditioning and a mild defect in the Morris water maze test. Taken together, our data show that overdosage of Sim2 may be important for the pathogenesis of Down's syndrome, especially mental retardation.     

Down's syndrome: morphological remodelling and increased complexity in the neuromuscular junction of transgenic CuZn-superoxide dismutase mice

Summary Transgenic mice carrying the human CuZn-superoxide dismutase gene were used to investigate whether CuZn-superoxide dismutase gene dosage is involved in the signs of neuromuscular junction deterioration associated with Down's syndrome. Three parameters of neuromuscular junction morphology were studied in hindlimb muscles of CuZn-superoxide dismutase-transgenic mice and their non-transgenic littermates: nerve terminal length, number of nerve terminal branching points and incidence of sprouting that results in synapse formation. These parameters increased with advanced age and the increase occurred earlier in CuZn-superoxide dismutase-transgenic mice. Therefore, the data is in line with the possibility that CuZn-superoxide dismutase-transgenic mice are undergoing premature ageing with respect to neuromuscular junction morphology, most probably owing to a gene dosage effect of CuZn-superoxide dismutase.     

Cocaine increases mortality and cardiac mass in a murine transgenic model of acquired immune deficiency syndrome

Cardiac dysfunction in AIDS is an important problem. Cocaine is an epidemic associated with sudden death, cardiac dysfunction, and congestive heart failure. Cocaine use and HIV infection frequently coexist in the same patient, yet the combined impact of both is poorly understood. The present study uses cocaine treatment of an established murine AIDS transgenic model (NL4-3Delta gag/pol; TG) to define the combined effects of AIDS and cocaine on cardiac pathophysiology. To determine the effects of cocaine and HIV-1 proteins on mortality, wild-type and NL4-3Delta gag/pol mice received saline or cocaine via continuous infusion by Alzet osmotic pumps for 28 days (chronic). Acute cocaine administration (10 days; 40 mg/kg/day) was used to study the nonlethal effects of cocaine in TGs. Echocardiograms and single time point electrocardiograms were performed at the termination of each experiment. Hearts were removed and examined histopathologically. Chronic cocaine treatment (80 mg/kg/day; 28 days) markedly decreased median survival in both wild-type and TG; however, TG survival was significantly more decreased. In acute studies, TG echocardiographic changes included increased left ventricular mass and increased left ventricular fractional shortening compared with all cohorts. Electrocardiographic changes were absent among the groups. Histopathologically, perivascular fibrosis and interstitial fibrosis were evident in cocaine-treated TG. Data suggest that additive cardiac insults (from AIDS and cocaine) result in combined deleterious effects.     

Time-course and characterization of orolingual motor deficits in B6SJL-Tg(SOD1-G93A)1Gur/J mice

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease affecting upper and lower motor neurons. Symptom onset may occur in the muscles of the limbs (spinal onset) or those of the head and neck (bulbar onset). Bulbar involvement is particularly important in ALS as it is associated with increased morbidity and mortality. The purpose of this study was to characterize bulbar motor deficits in the B6SJL-Tg(SOD1-G93A)1Gur/J (SOD1-G93A) mouse model of familial ALS. We measured orolingual motor function by placing thirsty mice in a customized operant chamber that allows for measurement of tongue force and lick rhythm as animals lick water from an isometric disc. Testing spanned the pre-symptomatic, symptomatic, and end-stage segments of the disease. Rotarod performance, fore- and hindlimb grip strength, and locomotor activity were also monitored regularly during this period. We found that spinal involvement was apparent first, with both fore- and hindlimb grip strength being affected in SOD1-G93A mice from the onset of testing (64 days of age). Rotarod performance was affected by 71 days of age. Locomotor activity was not affected, even near end-stage. Bulbar involvement appeared much later, with tongue motility being affected by 100 days of age. Tongue force was affected by 115 days of age. To our knowledge, these findings are the first to describe the onset of bulbar versus spinal motor signs and characterize orolingual motor deficits in this preclinical model of ALS.     

Behavioral and anatomical abnormalities in Mecp2 mutant mice: a model for Rett syndrome

Over 90% of Rett syndrome (RTT) cases have a mutation in the X-linked gene encoding methyl CpG binding-protein 2 (MeCP2). A mouse model that reprises clinical manifestations of the disease would be valuable for examining disease mechanisms. Here, we characterize physical and behavioral measures, as well as brain region volumes in young adult mice that have mutations in mouse methyl CpG binding-protein 2 gene (Mecp2) to serve as a baseline for other studies. Hemizygous males, which produce no functional protein, exhibit hypoactivity and abnormalities in locomotion, stereotypies, and anxiety reminiscent of the clinical condition. The mutant males also exhibit cognitive deficits in fear conditioning and object recognition relative to wildtypes. Volumetric analyses of male brains revealed a 25% reduction in whole brain volume in mutants relative to wildtypes; regional differences were also apparent. Mutants had decreased volumes in three specific brain regions: the amygdala (39%), hippocampus (21%), and striatum (29%). Heterozygous females, which produce varying amounts of functional protein, displayed a less severe behavioral phenotype. The mutant females exhibit abnormalities in locomotion, anxiety measures, and cognitive deficits in object recognition in an open field. This study provides the first evidence that the abnormal motor and cognitive behavioral phenotype in Mecp2 mice is consistent with specific volume reductions in brain regions associated with these behaviors, and shows how these data parallel the human condition. The Mecp2 mutant mice provide a very good model in which to examine molecular and behavioral mechanisms, as well as potential therapeutic interventions in RTT.     

Phospholipase A2 reduction ameliorates cognitive deficits in a mouse model of Alzheimer's disease

Neuronal expression of familial Alzheimer's disease-mutant human amyloid precursor protein (hAPP) and hAPP-derived amyloid-beta (Abeta) peptides causes synaptic dysfunction, inflammation and abnormal cerebrovascular tone in transgenic mice. Fatty acids may be involved in these processes, but their contribution to Alzheimer's disease pathogenesis is uncertain. We used a lipidomics approach to generate a broad profile of fatty acids in brain tissues of hAPP-expressing mice and found an increase in arachidonic acid and its metabolites, suggesting increased activity of the group IV isoform of phospholipase A(2) (GIVA-PLA(2)). The levels of activated GIVA-PLA(2) in the hippocampus were increased in individuals with Alzheimer's disease and in hAPP mice. Abeta caused a dose-dependent increase in GIVA-PLA(2) phosphorylation in neuronal cultures. Inhibition of GIVA-PLA(2) diminished Abeta-induced neurotoxicity. Genetic ablation or reduction of GIVA-PLA(2) protected hAPP mice against Abeta-dependent deficits in learning and memory, behavioral alterations and premature mortality. Inhibition of GIVA-PLA(2) may be beneficial in the treatment and prevention of Alzheimer's disease.     

Comparison of HLA-DR1-restricted T cell response induced in HLA-DR1 transgenic mice deficient for murine MHC class II and HLA-DR1 transgenic mice expressing endogenous murine MHC class II molecules

Transgenic mice expressing human HLA class II molecules provide a useful model for identifying HLA-restricted CD4+ epitopes. However, the influence of endogenous murine H-2-restricted T cell responses on HLA-restricted responses is not known. In the present study, we show that HLA-DR1 transgenic mice deficient for H-2 class II expression (HLA-DR1+/+/IAbeta0/0) exhibit an equivalent expression level of the transgene HLA-DR1 and a similar diversity in the TCR repertoire, but a slightly different number of CD4+ peripheral T cells, when compared to HLA-DR1 transgenic mice in which H-2 class II molecules were retained (HLA-DR1+/+/IAbeta+/+). More importantly, a strong antigen-specific HLA-DR1-restricted response was observed in nearly all HLA-DR1+/+/IAbeta0/0 mice immunized with HBV envelope protein (HBs) or capsid protein (HBc), whereas weak HBs- or HBc-specific HLA-DR1-restricted responses were detected in half of the immunized HLA-DR1+/+/IAbeta+/+ mice. Conversely, strong HBs- or HBc-specific H-2-restricted T cell responses were detected in HLA-DR1+/+/IAbeta+/+ mice but not in HLA-DR1+/+/IAbeta0/0 mice. Our results indicate that the coexpression of endogenous H-2 class II molecules reduces the intensity of HLA-DR1-restricted antigen-specific responses in transgenic mice, by favoring murine over human MHC recognition and education. Thus, HLA-DR1+/+/IAbeta0/0 mice represent a better model for identifying and characterizing HLA-DR1-restricted epitopes relevant for human disease.     

Levodopa ameliorates learning and memory deficits in a murine model of Alzheimer's disease

Dopamine plays an important role in learning and memory processes. A deficit of this neurotransmitter as it is apparent in Alzheimer's disease (AD) may contribute to cognitive decline, a major symptom of AD patients. The aim of this study was to elucidate whether or not stimulation of the dopaminergic system leads to an improvement of cognitive function and reduction of non-cognitive behavioral alterations in a murine model of AD. Transgenic and wild type male mice of the TgCRND8 line were treated either with the dopamine precursor levodopa or vehicle and tested in two learning tasks, the object-recognition task and the Barnes maze test. Additionally 24 h spontaneous behavior in the home cage was analyzed. In both memory tasks wild type mice performed significantly better than transgenics. However, transgenics treated with levodopa showed a significant object recognition memory and improved acquisition of spatial memory in the Barnes maze compared to vehicle treated transgenics. Concerning spontaneous behavior transgenic mice performed much more stereotypies than wild types. However, there was a trend for reduced stereotypies in the levodopa group in the time the drug was active. Neurochemical analysis revealed elevated levels of dopamine in the neostriata and frontal cortices and reduced levels in the hippocampi of transgenic mice compared to wild types. Thus cognitive deficits and stereotypies may be due to changes in the dopaminergic system as they could be ameliorated by levodopa treatment, that might also have a therapeutic significance for AD.     

Enzyme replacement therapy in a murine model of Morquio A syndrome

Mucopolysaccharidosis IVA (MPS IVA) is an autosomal recessive disorder caused by a deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS), leading to accumulation of keratan sulfate (KS) and chrondroitin-6-sulfate. The pharmacokinetics and biodistributions were determined for two recombinant human GALNSs produced in CHO cell lines: native GALNS and sulfatase-modifier-factor 1 (SUMF1) modified GALNS. Preclinical studies of enzyme replacement therapy (ERT) by using two GALNS enzymes were performed on MPS IVA mice. The half-lives in blood circulation of two phosphorylated GALNS enzymes were similar (native, 2.4 min; SUMF1, 3.3 min). After intravenous doses of 250 units/g body weight were administered, each enzyme was primarily recovered in liver and spleen, with detectable activity in other tissues including bone and bone marrow. At 4 h post-injection, enzyme activity was retained in the liver, spleen, bone and bone marrow at levels that were 20-850% of enzyme activity in the wild-type mice. After intravenous doses of 250 units/g of native GALNS, and 250, 600 or 1000 units/g of SUMF1-GALNS were administered weekly for 12 weeks, MPS IVA mice showed marked reduction of storage in visceral organs, sinus lining cells in bone marrow, heart valves, ligaments and connective tissues. A dose-dependent clearance of storage material was observed in brain. The blood KS level assayed by tandem mass spectrometry was reduced nearly to normal level. These preclinical studies demonstrate the clearance of tissue and blood KS by administered GALNS, providing the in vivo rationale for the design of ERT trials in MPS IVA.     

A study of digestive absorption in four cases of Down's syndrome. Down's syndrome, malnutrition, malabsorption, and Alzheimer's disease

Many data suggest that patients with Down's syndrome (DS) suffer from digestive malabsorption. A fecal test of absorption (search for undigested meat fibers following the ingestion of a measured diet) was conducted in 4 patients with DS. The results point to malabsorption in these patients and support the hypothesis of malabsorption in DS. The etiology of probable malabsorption in DS is discussed. Data are presented suggesting that chronic malnutrition caused by malabsorption could be the cause of the neuropathologic signs of Alzheimer's disease occurring at or slightly before the fourth decade in all patients with DS.     

Stage-specific apoptosis, developmental delay, and embryonic lethality in mice homozygous for a targeted disruption in the murine Bloom’s syndrome gene

Bloom’s syndrome is a human autosomal genetic disorder characterized at the cellular level by genome instability and increased sister chomatid exchanges (SCEs). Clinical features of the disease include proportional dwarfism and a predisposition to develop a wide variety of malignancies. The human BLM gene has been cloned recently and encodes a DNA helicase. Mouse embryos homozygous for a targeted mutation in the murine Bloom’s syndrome gene (Blm) are developmentally delayed and die by embryonic day 13.5. The fact that the interrupted gene is the homolog of the human BLM gene was confirmed by its homologous sequence, its chromosomal location, and by demonstrating high numbers of SCEs in cultured murine Blm^−/− fibroblasts. The proportional dwarfism seen in the human is consistent with the small size and developmental delay (12–24 hr) seen during mid-gestation in murine Blm^−/− embryos. Interestingly, the growth retardation in mutant embryos can be accounted for by a wave of increased apoptosis in the epiblast restricted to early post-implantation embryogenesis. Mutant embryos do not survive past day 13.5, and at this time exhibit severe anemia. Red blood cells and their precursors from Blm^−/− embryos are heterogeneous in appearance and have increased numbers of macrocytes and micronuclei. Both the apoptotic wave and the appearance of micronuclei in red blood cells are likely cellular consequences of damaged DNA caused by effects on replicating or segregating chromosomes.     

HLA—Ⅱ类基因DRα,DRB1＊0401转基因鼠模型的建立及体内表 …

OBJECTIVE: To construct transgenic mice model on DR alpha and DRB1*0401 of human MHC-II molecules. METHODS: By microinjection techniques on germ nucleus of zygotes, DRalpha and DRB1*0401 genes were injected into zygotes of C57BL/6 x DBA/1 hybrid mice and transplanted into the oviducts of pseudopregnancy female mice. The integration and expression of exogenous genes in offspring were detected by PCR, Southern blot and Northern blot, RT-PCR analysis. RESULTS: There were 5 founders of all injected mice, which had steadily inherited to the fifth generation. It was found that 95 mice were positive by PCR and 68 mice were integrated exogenous gene by Southern blot analysis. DRalpha and DRB1*0401 genes were expressed on spleen and kidney of transgenic mice. CONCLUSION: This experiment on the construction of DRalpha and DRB1*0401 transgenic mice model is a success.