Disease Pathology In Mice Research Articles

Increased dosage of DYRK1A leads to congenital heart defects in a mouse model of Down syndrome.

Down syndrome (DS) is caused by trisomy of human chromosome 21 (Hsa21). DS is a gene dosage disorder that results in multiple phenotypes including congenital heart defects. This clinically important cardiac pathology is the result of a third copy of one or more of the approximately 230 genes on Hsa21, but the identity of the causative dosage-sensitive genes and hence mechanisms underlying this cardiac pathology remain unclear. Here, we show that hearts from human fetuses with DS and embryonic hearts from the Dp1Tyb mouse model of DS show reduced expression of mitochondrial respiration genes and cell proliferation genes. Using systematic genetic mapping, we determined that three copies of the dual-specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1a) gene, encoding a serine/threonine protein kinase, are associated with congenital heart disease pathology. In embryos from Dp1Tyb mice, reducing Dyrk1a gene copy number from three to two reversed defects in cellular proliferation and mitochondrial respiration in cardiomyocytes and rescued heart septation defects. Increased dosage of DYRK1A protein resulted in impairment of mitochondrial function and congenital heart disease pathology in mice with DS, suggesting that DYRK1A may be a useful therapeutic target for treating this common human condition.

HDAC6 Deficiency Has Moderate Effects on Behaviors and Parkinson's Disease Pathology in Mice.

Histone deacetylase 6 (HDAC6) is involved in the regulation of protein aggregation and neuroinflammation, but its role in Parkinson's disease (PD) remains controversial. In this study, Hdac6-/- mice were generated by CRISPR-Cas9 technology for exploring the effect of HDAC6 on the pathological progression of PD. We found that male Hdac6-/- mice exhibit hyperactivity and certain anxiety. In the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice, though motor injury was slightly alleviated by HDAC6 deficiency, dopamine (DA) depletion in the striatum, the decrease in the number of DA neurons in the substantia nigra (SN) and the reduction in DA neuronal terminals were not affected. In addition, activation of glial cells and the expression of α-synuclein, as well as the levels of apoptosis-related proteins in the nigrostriatal pathway, were not changed in MPTP-injected wild-type and Hdac6-/- mice. Therefore, HDAC6 deficiency leads to moderate alterations of behaviors and Parkinson's disease pathology in mice.

Loss of the m6A methyltransferase METTL3 in monocyte-derived macrophages ameliorates Alzheimer's disease pathology in mice.

Alzheimer's disease (AD) is a heterogeneous disease with complex clinicopathological characteristics. To date, the role of m6A RNA methylation in monocyte-derived macrophages involved in the progression of AD is unknown. In our study, we found that methyltransferase-like 3 (METTL3) deficiency in monocyte-derived macrophages improved cognitive function in an amyloid beta (Aβ)-induced AD mouse model. The mechanistic study showed that that METTL3 ablation attenuated the m6A modification in DNA methyltransferase 3A (Dnmt3a) mRNAs and consequently impaired YTH N6-methyladenosine RNA binding protein 1 (YTHDF1)-mediated translation of DNMT3A. We identified that DNMT3A bound to the promoter region of alpha-tubulin acetyltransferase 1 (Atat1) and maintained its expression. METTL3 depletion resulted in the down-regulation of ATAT1, reduced acetylation of α-tubulin and subsequently enhanced migration of monocyte-derived macrophages and Aβ clearance, which led to the alleviated symptoms of AD. Collectively, our findings demonstrate that m6A methylation could be a promising target for the treatment of AD in the future.

Dual-function AAV gene therapy reverses late-stage Canavan disease pathology in mice.

The leukodystrophy Canavan disease is a fatal white matter disorder caused by loss-of-function mutations of the aspartoacylase-encoding ASPA gene. There are no effective treatments available and experimental gene therapy trials have failed to provide sufficient amelioration from Canavan disease symptoms. Preclinical studies suggest that Canavan disease-like pathology can be addressed by either ASPA gene replacement therapy or by lowering the expression of the N-acetyl-L-aspartate synthesizing enzyme NAT8L. Both approaches individually prevent or even reverse pathological aspects in Canavan disease mice. Here, we combined both strategies and assessed whether intracranial adeno-associated virus-mediated gene delivery to a Canavan disease mouse model at 12 weeks allows for reversal of existing pathology. This was enabled by a single vector dual-function approach. In vitro and in vivo biopotency assessment revealed significant knockdown of neuronal Nat8l paired with robust ectopic aspartoacylase expression. Following nomination of the most efficient cassette designs, we performed proof-of-concept studies in post-symptomatic Aspa-null mice. Late-stage gene therapy resulted in a decrease of brain vacuoles and long-term reversal of all pathological hallmarks, including loss of body weight, locomotor impairments, elevated N-acetyl-L-aspartate levels, astrogliosis, and demyelination. These data suggest feasibility of a dual-function vector combination therapy, directed at replacing aspartoacylase with concomitantly suppressing N-acetyl-L-aspartate production, which holds potential to permanently alleviate Canavan disease symptoms and expands the therapeutic window towards a treatment option for adult subjects.

Combined targeting of pathways regulating synaptic formation and autophagy attenuates Alzheimer's disease pathology in mice.

All drug trials completed to date have fallen short of meeting the clinical endpoint of significantly slowing cognitive decline in Alzheimer’s disease (AD) patients. In this study, we repurposed two FDA-approved drugs, Fasudil and Lonafarnib, targeting synaptic formation (i.e., Wnt signaling) and cellular clearance (i.e., autophagic) pathways respectively, to test their therapeutic potential for attenuating AD-related pathology. We characterized our 3xTg AD mouse colony to select timepoints for separate and combinatorial treatment of both drugs while collecting cerebrospinal fluid (CSF) using an optimized microdialysis method. We found that treatment with Fasudil reduced Aβ at early and later stages of AD, whereas administration of Lonafarnib had no effect on Aβ, but did reduce tau, at early stages of the disease. Induction of autophagy led to increased size of amyloid plaques when administered at late phases of the disease. We show that combinatorial treatment with both drugs was effective at reducing intraneuronal Aβ and led to improved cognitive performance in mice. These findings lend support to regulating Wnt and autophagic pathways in order to attenuate AD-related pathology.

A clinical dose of angiotensin-converting enzyme (ACE) inhibitor and heterozygous ACE deletion exacerbate Alzheimer's disease pathology in mice

Inhibition of angiotensin-converting enzyme (ACE) is a strategy used worldwide for managing hypertension. In addition to converting angiotensin I to angiotensin II, ACE also converts neurotoxic β-amyloid protein 42 (Aβ42) to Aβ40. Because of its neurotoxicity, Aβ42 is believed to play a causative role in the development of Alzheimer's disease (AD), whereas Aβ40 has neuroprotective effects against Aβ42 aggregation and also against metal-induced oxidative damage. Whether ACE inhibition enhances Aβ42 aggregation or impairs human cognitive ability are very important issues for preventing AD onset and for optimal hypertension management. In an 8-year longitudinal study, we found here that the mean intelligence quotient of male, but not female, hypertensive patients taking ACE inhibitors declined more rapidly than that of others taking no ACE inhibitors. Moreover, the sera of all AD patients exhibited a decrease in Aβ42-to-Aβ40-converting activity compared with sera from age-matched healthy individuals. Using human amyloid precursor protein transgenic mice, we found that a clinical dose of an ACE inhibitor was sufficient to increase brain amyloid deposition. We also generated human amyloid precursor protein/ACE+/- mice and found that a decrease in ACE levels promoted Aβ42 deposition and increased the number of apoptotic neurons. These results suggest that inhibition of ACE activity is a risk factor for impaired human cognition and for triggering AD onset.

Nrf2 activation in myeloid cells and endothelial cells differentially mitigates sickle cell disease pathology in mice

AbstractSickle cell disease (SCD) is caused by a monogenic mutation of the β-globin gene and affects millions of people worldwide. SCD is associated with sustained hemolytic anemia, vasoocclusion, ischemia-reperfusion injury, oxidative tissue damage, inflammatory cell activation, and systemic endothelial dysfunction. The transcription factor Nrf2 coordinates the expression of a wide variety of genes encoding antioxidant, detoxification, and metabolic enzymes. Nrf2 participates in suppressing proinflammatory cytokines and organ protection in SCD. However, little is known regarding the mechanisms by which Nrf2 ameliorates SCD pathology or how some cells respond to Nrf2 stimuli to alleviate SCD pathology. Here, we asked whether monocytes/granulocytes and/or endothelial cells are particularly critical in alleviating the pathology of SCD. By targeting these cells with a Cre recombinase system, we generated SCD::Keap1F/F::LysM-Cre and Tie1-Cre mice with constitutive Nrf2 activation in monocytes/granulocytes and endothelial cells, respectively. Analyses of SCD::Keap1F/F::LysM-Cre and SCD::Keap1F/F::Tie1-Cre mice revealed significantly reduced inflammation, along with decreased white blood cell counts and lower Tnfα and Il1β expression in the lungs. Notably, SCD::Keap1F/F::LysM-Cre mice exhibited reduced heme distribution in the liver, consistent with a decrease in the damaged areas. Vascular function in SCD::Keap1F/F::Tie1-Cre mice was significantly improved, with a 50% decrease in vascular leakage and low expression of the adhesion molecules Vcam1 and P-selectin. Thus, Nrf2 activation in monocytes/granulocytes and endothelial cells contributes differentially and cooperatively to the improvement of SCD pathology.

Absence of apolipoprotein E and anti-oxidant defence induces Alzheimer’s disease pathology in mice

Aim: Alzheimer’s disease (AD) is a neurodegenerative disorder associated with ageing and displaying the presence of amyloid-Beta (AB) plaques and neurofibrillary tangles (NFTs) in brain. Cardiovascular risk factors like hypertension and atherosclerosis increases the risk for AD. Apolipoprotein E (major cholesterol carrier in brain) isoforms are considered risk for late-onset AD. Our mice which are double-knockout (dko) for apolipoprotein E (apoE, cholestrol) and PON1 (paroxonase 1, reduces oxidative stress) showed severe atherosclerosis of the arteries carrying blood to the brain even on the normal diet. This prompted us to investigate the possibility of an AD pathology resulting from the deficiency of apoE and induction of oxidative stress.

Kallikrein-8 inhibition attenuates Alzheimer's disease pathology in mice

IntroductionMemory loss and increased anxiety are clinical hallmarks of Alzheimer's disease (AD). Kallikrein-8 is a protease implicated in memory acquisition and anxiety, and its mRNA is known to be up-regulated in AD-affected human hippocampus. Therefore, an involvement of Kallikrein-8 in Alzheimer's pathogenesis is conceivable but remains to be proved. MethodsWe determined the cerebral expression of Kallikrein-8 mRNA and protein during the course of AD in patients and in transgenic mice and tested the impact of Kallikrein-8 inhibition on AD-related pathology in mice and in primary glial cells. ResultsKallikrein-8 mRNA and protein were up-regulated in both species at incipient stages of AD. Kallikrein-8 inhibition impeded amyloidogenic amyloid-precursor-protein processing, facilitated amyloid β (Aβ) clearance across the blood-brain-barrier, boosted autophagy, reduced Aβ load and tau pathology, enhanced neuroplasticity, reversed molecular signatures of anxiety, and ultimately improved memory and reduced fear. DiscussionKallikrein-8 is a promising new therapeutic target against AD.

Adhesion molecule L1 binds to amyloid beta and reduces Alzheimer's disease pathology in mice

Alzheimer's disease (AD) is a devastating neurodegenerative disorder and the most common cause of elderly dementia. In an effort to contribute to the potential of molecular approaches to reduce degenerative processes we have tested the possibility that the neural adhesion molecule L1 ameliorates some characteristic cellular and molecular parameters associated with the disease in a mouse model of AD. Three-month-old mice overexpressing mutated forms of amyloid precursor protein and presenilin-1 under the control of a neuron-specific promoter received an injection of adeno-associated virus encoding the neuronal isoform of full-length L1 (AAV-L1) or, as negative control, green fluorescent protein (AAV-GFP) into the hippocampus and occipital cortex. Four months after virus injection, the mice were analyzed for histological and biochemical parameters of AD. AAV-L1 injection decreased the Aβ plaque load, levels of Aβ42, Aβ42/40 ratio and astrogliosis compared with AAV-GFP controls. AAV-L1 injected mice also had increased densities of inhibitory synaptic terminals on pyramidal cells in the hippocampus when compared with AAV-GFP controls. Numbers of microglial cells/macrophages were similar in both groups, but numbers of microglial cells/macrophages per plaque were increased in AAV-L1 injected mice. To probe for a molecular mechanism that may underlie these effects, we analyzed whether L1 would directly and specifically interact with Aβ. In a label-free binding assay, concentration dependent binding of the extracellular domain of L1, but not of the close homolog of L1 to Aβ40 and Aβ42 was seen, with the fibronectin type III homologous repeats 1–3 of L1 mediating this effect. Aggregation of Aβ42 in vitro was reduced in the presence of the extracellular domain of L1. The combined observations indicate that L1, when overexpressed in neurons and glia, reduces several histopathological hallmarks of AD in mice, possibly by reduction of Aβ aggregation. L1 thus appears to be a candidate molecule to ameliorate the pathology of AD, when applied in therapeutically viable treatment schemes.

Novel Features of a PIWI-Like Protein Homolog in the Parasitic Protozoan Leishmania

In contrast to nearly all eukaryotes, the Old World Leishmania species L. infantum and L. major lack the bona fide RNAi machinery genes. Interestingly, both Leishmania genomes code for an atypical Argonaute-like protein that possesses a PIWI domain but lacks the PAZ domain found in Argonautes from RNAi proficient organisms. Using sub-cellular fractionation and confocal fluorescence microscopy, we show that unlike other eukaryotes, the PIWI-like protein is mainly localized in the single mitochondrion in Leishmania. To predict PIWI function, we generated a knockout mutant for the PIWI gene in both L. infantum (Lin) and L. major species by double-targeted gene replacement. Depletion of PIWI has no effect on the viability of insect promastigote forms but leads to an important growth defect of the mammalian amastigote lifestage in vitro and significantly delays disease pathology in mice, consistent with a higher expression of the PIWI transcript in amastigotes. Moreover, amastigotes lacking PIWI display a higher sensitivity to apoptosis inducing agents than wild type parasites, suggesting that PIWI may be a sensor for apoptotic stimuli. Furthermore, a whole-genome DNA microarray analysis revealed that loss of LinPIWI in Leishmania amastigotes affects mostly the expression of specific subsets of developmentally regulated genes. Several transcripts encoding surface and membrane-bound proteins were found downregulated in the LinPIWI(−/−) mutant whereas all histone transcripts were upregulated in the null mutant, supporting the possibility that PIWI plays a direct or indirect role in the stability of these transcripts. Although our data suggest that PIWI is not involved in the biogenesis or the stability of small noncoding RNAs, additional studies are required to gain further insights into the role of this protein on RNA regulation and amastigote development in Leishmania.

Sera from Preeclampsia Patients Elicit Symptoms of Human Disease in Mice and Provide a Basis for an in Vitro Predictive Assay

Early diagnosis and treatment of preeclampsia would significantly reduce maternal and fetal morbidity and mortality. However, its etiology and prediction have remained elusive. Based on the hypothesis that sera from patients with preeclampsia could function as a "blueprint" of causative factors, we describe a serum-based pregnancy-specific mouse model that closely mirrors the human condition as well as an in vitro predictive assay. We show that a single administration of human preeclampsia serum in pregnant IL-10-/- mice induced the full spectrum of preeclampsia-like symptoms, caused hypoxic injury in uteroplacental tissues, and elevated soluble fms-like tyrosine kinase 1 and soluble endoglin, markers thought to be related to the disease. The same serum sample(s) induced a partial preeclampsia phenotype in wild-type mice. Importantly, preeclampsia serum disrupted cross talk between trophoblasts and endothelial cells in an in vitro model of endovascular activity. Disruption of endovascular activity could be documented in serum samples as early as 12 to 14 weeks of gestation from patients who subsequently developed preeclampsia. These results indicate that preeclampsia patient sera can be used to understand the pregnancy-specific disease pathology in mice and can predict the disorder.

The human genome is composed of viral DNA: Viral homologues of the protein products cause Alzheimer's disease and others via autoimmune mechanisms.

AbstractThe human genome is composed of millions of fragmented contiguous viral DNA sequences, dating from the dawn of evolution and reflecting retroviral insertions over millions of years of coexistence. Herpes and other viral insertion points correspond to the locations of over 120 Alzheimer's disease susceptibility genes and to linkage hotspots. The greater the number of pathogen matches, the more important the gene. These DNA sequences are translated into short contiguous 5-12 amino acid stretches (vatches), identical in viruses and man, and in other pathogens implicated in Alzheimer's disease (Borrelia, Chlamydia, Helicobacter, C. Neoformans , P. Gingivalis). C. Neoformans, which has been associated with a rare but curable form of dementia, expresses the most number of hits to Alzheimer's disease proteins. Vatches are often immunogenic and antibodies to viral proteins may knock down their human counterparts or activate immune responses killing the cells containing their human homologues. This is supported by the presence of the complement membrane attack complex in Alzheimer's disease neurones and by the ability of tau antigens (homologous to pathogen proteins) to promote the formation of neurofibrillary tangles and Alzheimer's disease pathology in mice. Vatches may act as dummy ligands or decoy receptors and interfere with the interactome of their human counterparts. Alzheimer's disease is thus a "pathogenetic" disorder caused by pathogens but dependent on the genes that create these matching sequences. This scenario is relevant to many other, and perhaps most human disorders, given the massive genomic extent of viral coverage. The vatches in the human proteome, dictated by polymorphisms and mutations, may predict, from birth, the spectrum of pathogens that match our proteins and which pathogenetic disease we are likely to develop. These may all be preventable by vaccination, pathogen detection and elimination and curable by immunosuppressant approaches, perhaps with a unique, safe, and effective immunosuppressant panacea.

A dominant vimentin mutant upregulates Hsp70 and the activity of the ubiquitin-proteasome system, and causes posterior cataracts in transgenic mice

Vimentin is the main intermediate filament (IF) protein of mesenchymal cells and tissues. Unlike other IF-/- mice, vimentin-/- mice provided no evidence of an involvement of vimentin in the development of a specific disease. Therefore, we generated two transgenic mouse lines, one with a (R113C) point mutation in the IF-consensus motif in coil1A and one with the complete deletion of coil 2B of the rod domain. In epidermal keratins and desmin, point mutations in these parts of the alpha-helical rod domain cause keratinopathies and desminopathies, respectively. Here, we demonstrate that substoichiometric amounts of vimentin carrying the R113C point mutation disrupted the endogenous vimentin network in all tissues examined but caused a disease phenotype only in the eye lens, leading to a posterior cataract that was paralleled by the formation of extensive protein aggregates in lens fibre cells. Unexpectedly, central, postmitotic fibres became depleted of aggregates, indicating that they were actively removed. In line with an increase in misfolded proteins, the amounts of Hsp70 and ubiquitylated vimentin were increased, and proteasome activity was raised. We demonstrate here for the first time that the expression of mutated vimentin induces a protein-stress response that contributes to disease pathology in mice, and hypothesise that vimentin mutations cause cataracts in humans.

To be or not to be toxic: aggregations in Huntington and Alzheimer disease

Insoluble aggregated proteins in Alzheimer disease and Huntington disease might not be pathogenic. Human studies have poor correlations between aggregates and clinical disease or pathology in these disorders, whereas mouse models have demonstrated that neuronal loss can occur in the absence of detectable aggregates. Furthermore, aggregates can exist in the absence of disease pathology in mice or symptoms in humans. Recent research suggests that soluble protein fragments, not insoluble aggregated proteins, are the toxic species in these disorders.