Modeling the impact of neuromorphological alterations in Down syndrome on fast neural oscillations.

Cognitive disorders, including Down syndrome (DS), present significant morphological alterations in neuron architectural complexity. However, the relationship between neuromorphological alterations and impaired brain function is not fully understood. To address this gap, we propose a novel computational model that accounts for the observed cell deformations in DS. The model consists of a cross-sectional layer of the mouse motor cortex, composed of 3000 neurons. The network connectivity is obtained by accounting explicitly for two single-neuron morphological parameters: the mean dendritic tree radius and the spine density in excitatory pyramidal cells. We obtained these values by fitting reconstructed neuron data corresponding to three mouse models: wild-type (WT), transgenic (TgDyrk1A), and trisomic (Ts65Dn). Our findings reveal a dynamic interplay between pyramidal and fast-spiking interneurons leading to the emergence of gamma activity (∼40 Hz). In the DS models this gamma activity is diminished, corroborating experimental observations and validating our computational methodology. We further explore the impact of disrupted excitation-inhibition balance by mimicking the reduction recurrent inhibition present in DS. In this case, gamma power exhibits variable responses as a function of the external input to the network. Finally, we perform a numerical exploration of the morphological parameter space, unveiling the direct influence of each structural parameter on gamma frequency and power. Our research demonstrates a clear link between changes in morphology and the disruption of gamma oscillations in DS. This work underscores the potential of computational modeling to elucidate the relationship between neuron architecture and brain function, and ultimately improve our understanding of cognitive disorders.

Astrocytic metabolic control of orexinergic activity in the lateral hypothalamus regulates sleep and wake architecture.

Neuronal activity undergoes significant changes during vigilance states, accompanied by an accommodation of energy demands. While the astrocyte-neuron lactate shuttle has shown that lactate is the primary energy substrate for sustaining neuronal activity in multiple brain regions, its role in regulating sleep/wake architecture is not fully understood. Here we investigated the involvement of astrocytic lactate supply in maintaining consolidated wakefulness by downregulating, in a cell-specific manner, the expression of monocarboxylate transporters (MCTs) in the lateral hypothalamus of transgenic mice. Our results demonstrate that reduced expression of MCT4 in astrocytes disrupts lactate supply to wake-promoting orexin neurons, impairing wakefulness stability. Additionally, we show that MCT2-mediated lactate uptake is necessary for maintaining tonic firing of orexin neurons and stabilizing wakefulness. Our findings provide both in vivo and in vitro evidence supporting the role of astrocyte-to-orexinergic neuron lactate shuttle in regulating proper sleep/wake stability.

Neddylation inhibition prevents acetaminophen-induced liver damage by enhancing the anabolic cardiolipin pathway.

Drug-induced liver injury (DILI) is a significant cause of acute liver failure (ALF) and liver transplantation in the Western world. Acetaminophen (APAP) overdose is a main contributor of DILI, leading to hepatocyte cell death through necrosis. Here, we identified that neddylation, an essential post-translational modification involved in the mitochondria function, was upregulated in liver biopsies from patients with APAP-induced liver injury (AILI) and in mice treated with an APAP overdose. MLN4924, an inhibitor of the neuronal precursor cell-expressed developmentally downregulated protein 8 (NEDD8)-activating enzyme (NAE-1), ameliorated necrosis and boosted liver regeneration in AILI. To understand how neddylation interferes in AILI, whole-body biotinylated NEDD8 (bioNEDD8) and ubiquitin (bioUB) transgenic mice were investigated under APAP overdose with and without MLN4924. The cytidine diphosphate diacylglycerol (CDP-DAG) synthase TAM41, responsible for producing cardiolipin essential for mitochondrial activity, was found modulated under AILI and restored its levels by inhibiting neddylation. Understanding this ubiquitin-like crosstalk in AILI is essential for developing promising targeted inhibitors for DILI treatment.

Impact of RAAS Receptors and Membrane-Bound Transporter System in the Left Ventricle during the Long-Term Control of Hypertension.

The Renin-Angiotensin-Aldosterone System (RAAS) has been implicated in systemic and neurogenic hypertension. The infusion of RAAS inhibitors blunted arterial pressure and efficacy of use-dependent synaptic transmission in sympathetic ganglia. The current investigation aims to elucidate the impact of RAAS-mediated receptors on left ventricular cardiomyocytes and the role of the sarcolemma-bound carrier system in the heart of the hypertensive transgene model. A significant increase in mRNA and the protein expression for angiotensin II (AngII) receptor subtype-1 (AT1R) was observed in (mREN2)27 transgenic compared to the normotensive rodents. Concurrently, there was an upregulation in AT1R and a downregulation in the MAS1 proto-oncogene protein receptor as well as the AngII subtype-2 receptor in hypertensive rodents. There were modifications in the expressions of sarcolemma Na+-K+-ATPase, Na+-Ca2+ exchanger, and Sarcoendoplasmic Reticulum Calcium ATPase in the transgenic hypertensive model. These observations suggest chronic RAAS activation led to a shift in receptor balance favoring augmented cardiac contractility and disruption in calcium handling through modifications of membrane-bound carrier proteins and blood pressure. The study provides insight into mechanisms underlying RAAS-mediated cardiac dysfunction and highlights the potential value of targeting the protective arm of AngII in hypertension.

Ectopic Activation of Fgf8 in Dental Mesenchyme Causes Incisor Agenesis and Molar Microdontia.

Putatively, tooth agenesis was attributed to the initiation failure of tooth germs, though little is known about the histological and molecular alterations. To address if constitutively active FGF signaling is associated with tooth agenesis, we activated Fgf8 in dental mesenchyme with Osr-cre knock-in allele in mice (Osr2-creKI; Rosa26R-Fgf8) and found incisor agenesis and molar microdontia. The cell survival assay showed tremendous apoptosis in both the Osr2-creKI; Rosa26R-Fgf8 incisor epithelium and mesenchyme, which initiated incisor regression from cap stage. In situ hybridization displayed vanished Shh transcription, and immunostaining exhibited reduced Runx2 expression and enlarged mesenchymal Lef1 domain in Osr2-creKI; Rosa26R-Fgf8 incisors, both of which were suggested to enhance apoptosis. In contrast, Osr2-creKI; Rosa26R-Fgf8 molar germs displayed mildly suppressed Shh transcription, and the increased expression of Ectodin, Runx2 and Lef1. Although mildly smaller than WT controls prenatally, the Osr2-creKI; Rosa26R-Fgf8 molar germs produced a miniature tooth with impaired mineralization after a 6-week sub-renal culture. Intriguingly, the implanted Osr2-creKI; Rosa26R-Fgf8 molar germs exhibited delayed odontoblast differentiation and accelerated ameloblast maturation. Collectively, the ectopically activated Fgf8 in dental mesenchyme caused incisor agenesis by triggering incisor regression and postnatal molar microdontia. Our findings reported tooth agenesis resulting from the regression from the early bell stage and implicated a correlation between tooth agenesis and microdontia.

c-KIT inhibitors reduce pathology and improve behavior in the Tg(SwDI) model of Alzheimer's disease.

Treatments for Alzheimer's disease have primarily focused on removing brain amyloid plaques to improve cognitive outcomes in patients. We developed small compounds, known as BK40143 and BK40197, and we hypothesize that these drugs alleviate microglial-mediated neuroinflammation and induce autophagic clearance of neurotoxic proteins to improve behavior in models of neurodegeneration. Specificity binding assays of BK40143 and BK40197 showed primary binding to c-KIT/Platelet Derived Growth Factor Receptors (PDGFR)α/ß, whereas BK40197 also differentially binds to FYVE finger-containing phosphoinositide kinase (PIKFYVE). Both compounds penetrate the CNS, and treatment with these drugs inhibited the maturation of peripheral mast cells in transgenic mice, correlating with cognitive improvements on measures of memory and anxiety. In the brain, microglial activation was profoundly attenuated and amyloid-beta and tau were reduced via autophagy. Multi-kinase inhibition, including c-KIT, exerts multifunctional effects to reduce neurodegenerative pathology via autophagy and microglial activity and may represent a potential therapeutic option for neurodegeneration.

CRY2 mediates the cognitive decline induced by sleep deprivation in 5xFAD mice.

BACKGROUND: Cryptochrome-2 (CRY2) is a core rhythm gene that plays a crucial role in DNA damage repair. The present study investigated the potential role of CRY2 in mediating sleep deprivation-induced cognitive decline in 5xFAD mice. METHODS: To assess the effects of SD on different brain regions of the mouse brain, we used 18F FDG PET-CT. Cognitive function was evaluated using the Morris water maze test and Y-maze. Lentivirus was used for the overexpression of CRY2, and small interfering RNA (siRNA) was used for the downregulation of CRY2 to verify the effect of CRY2. We used qRT‒PCR and Western blotting to identify the downstream factors of CRY2 and evaluated the cognitive function of mice to confirm the effects of these factors. RESULTS: The AD mice exhibited cognitive decline after 21 days of SD and had higher expression of CRY2 compared to AD mice with normal sleep. Overexpression of CRY2 led to decreased cognitive function in AD mice, and the downregulation of CRY2 attenuated the SD-induced cognitive decline in AD mice. CRY2 reduced the expression and function of CISH, which reduced the inhibition of STAT1 phosphorylation and led to synaptic dysfunction. CISH overexpression attenuated the impairing effect of sleep deprivation on cognitive function in AD mice. Furthermore, 18F FDG PET-CT revealed that SD significantly reduced glucose metabolism in different brain regions of AD mice. CONCLUSION: Our study demonstrated that sleep deprivation upregulated CRY2 in the hippocampus of AD mice, which resulted in synaptic dysfunction by decreasing CISH-mediated STAT1 phosphorylation.

Rotating magnetic field inhibits Aß protein aggregation and alleviates cognitive impairment in Alzheimer's disease mice.

Amyloid beta (Aß) monomers aggregate to form fibrils and amyloid plaques, which are critical mechanisms in the pathogenesis of Alzheimer's disease (AD). Given the important role of Aß1-42 aggregation in plaque formation, leading to brain lesions and cognitive impairment, numerous studies have aimed to reduce Aß aggregation and slow AD progression. The diphenylalanine (FF) sequence is critical for amyloid aggregation, and magnetic fields can affect peptide alignment due to the diamagnetic anisotropy of aromatic rings. In this study, we examined the effects of a moderate-intensity rotating magnetic field (RMF) on Aß aggregation and AD pathogenesis. Results indicated that the RMF directly inhibited Aß amyloid fibril formation and reduced Aß-induced cytotoxicity in neural cells in vitro. Using the AD mouse model APP/PS1, RMF restored motor abilities to healthy control levels and significantly alleviated cognitive impairments, including exploration and spatial and non-spatial memory abilities. Tissue examinations demonstrated that RMF reduced amyloid plaque accumulation, attenuated microglial activation, and reduced oxidative stress in the APP/PS1 mouse brain. These findings suggest that RMF holds considerable potential as a non-invasive, high-penetration physical approach for AD treatment.

Systemic inflammation enhances metastatic growth in a syngeneic neuroblastoma mouse model.

BACKGROUND: We previously showed that total tumor resection enhances metastatic growth in a syngeneic metastatic mouse model of neuroblastoma. In this study, we further investigated which surgical factors contributed most to metastatic growth. METHODS: Tumor cells derived from MYCN transgenic mice were subcutaneously injected into wild-type mice. Mice were randomly assigned to receive partial resection (PR group), subcutaneous implantation of a sponge (Sp group), or observation (Obs group). The lymph node metastasis volume and the frequency of lung metastasis were compared 14 days after assignment by measuring C-reactive protein (CRP) and interleukin-6 (IL-6) levels. RESULTS: The lymph node metastasis volume in the Sp group was larger than in the Obs group (148.4 [standard deviation {SD}: 209.5] vs. 10.2 [SD 12.8] mm3). The frequency of lung metastasis was greater in the Sp group than in the PR group (11.9 [SD 12.2] vs. 6.6 [SD 4.0] counts/slide). The CRP level in the Sp group was higher than in the PR group (2.3 [SD 0.5] vs. 1.5 [SD 0.4] µg/mL), and the IL-6 level in the Sp group was higher than in the PR or Obs groups (28.4 [SD 34.5] vs. 12.4 [SD 19.0] vs. 5.4 [SD 8.1] pg/mL). CONCLUSION: Metastatic growth may be enhanced by systemic inflammation.

B Cell Receptor Transgenic Mice as Tools to Study Memory B Cells.

B cell receptor (BCR) transgenic mice allow the control of the initial target (antigen) specificity of naïve B cells and to investigate their properties following activation. Here, I describe how BCR transgenic B cells can be used in combination with adoptive cell transfer and immunization models to study memory B cell formation and reactivation.

Different localization of P2X4 and P2X7 receptors in native mouse lung - lack of evidence for a direct P2X4-P2X7 receptor interaction.

Introduction: P2X receptors are a family of homo- and heterotrimeric cation channels gated by extracellular ATP. The P2X4 and P2X7 subunits show overlapping expression patterns and have been involved in similar physiological processes, such as pain and inflammation as well as various immune cell functions. While formation of P2X2/P2X3 heterotrimers produces a distinct pharmacological phenotype and has been well established, functional identification of a P2X4/P2X7 heteromer has been difficult and evidence for and against a physical association has been found. Most of this evidence stems, however, from in vitro model systems. Methods: Here, we used a P2X7-EGFP BAC transgenic mouse model as well as P2X4 and P2X7 knock-out mice to re-investigate a P2X4-P2X7 interaction in mouse lung by biochemical and immunohistochemical experiments as well as quantitative expression analysis. Results: No detectable amounts of P2X4 could be co-purified from mouse lung via P2X7-EGFP. In agreement with these findings, immuno-histochemical analysis using a P2X7-specific nanobody revealed only limited overlap in the cellular and subcellular localizations of P2X4 and P2X7 in both the native lung tissue and primary cells. Comparison of P2X4 and P2X7 transcript and protein levels in the respective gene-deficient and wild type mice showed no mutual interrelation between their expression levels in whole lungs. However, a significantly reduced P2rx7 expression was found in alveolar macrophages of P2rx4 -/- mice. Discussion: In summary, our detailed analysis of the cellular and subcellular P2X4 and P2X7 localization and expression does not support a physiologically relevant direct association of P2X4 and P2X7 subunits or receptors in vivo.

Impaired myoblast differentiation and muscle IGF-1 receptor signaling pathway activation after N-glycosylation inhibition.

The role of N-glycosylation in the myogenic process remains poorly understood. Here, we evaluated the impact of N-glycosylation inhibition by Tunicamycin (TUN) or by phosphomannomutase 2 (PMM2) gene knockdown, which encodes an enzyme essential for catalyzing an early step of the N-glycosylation pathway, on C2C12 myoblast differentiation. The effect of chronic treatment with TUN on tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of WT and MLC/mIgf-1 transgenic mice, which overexpress muscle Igf-1Ea mRNA isoform, was also investigated. TUN-treated and PMM2 knockdown C2C12 cells showed reduced ConA, PHA-L, and AAL lectin binding and increased ER-stress-related gene expression (Chop and Hspa5 mRNAs and s/uXbp1 ratio) compared to controls. Myogenic markers (MyoD, myogenin, and Mrf4 mRNAs and MF20 protein) and myotube formation were reduced in both TUN-treated and PMM2 knockdown C2C12 cells. Body and TA weight of WT and MLC/mIgf-1 mice were not modified by TUN treatment, while lectin binding slightly decreased in the TA muscle of WT (ConA and AAL) and MLC/mIgf-1 (ConA) mice. The ER-stress-related gene expression did not change in the TA muscle of WT and MLC/mIgf-1 mice after TUN treatment. TUN treatment decreased myogenin mRNA and increased atrogen-1 mRNA, particularly in the TA muscle of WT mice. Finally, the IGF-1 production and IGF1R signaling pathways activation were reduced due to N-glycosylation inhibition in TA and EDL muscles. Decreased IGF1R expression was found in TUN-treated C2C12 myoblasts which was associated with lower IGF-1-induced IGF1R, AKT, and ERK1/2 phosphorylation compared to CTR cells. Chronic TUN-challenge models can help to elucidate the molecular mechanisms through which diseases associated with aberrant N-glycosylation, such as Congenital Disorders of Glycosylation (CDG), affect muscle and other tissue functions.

Chronic stress dysregulates the Hippo/YAP/14-3-3η pathway and induces mitochondrial damage in basolateral amygdala in a mouse model of depression.

Rationale: Recent evidence highlights the pivotal role of mitochondrial dysfunction in mood disorders, but the mechanism involved remains unclear. We studied whether the Hippo/YAP/14-3-3η signaling pathway mediates mitochondrial abnormalities that result in the onset of major depressive disorder (MDD) in a mouse model. Methods: The ROC algorithm was used to identify a subpopulation of mice that were exposed to chronic unpredictable mild stress (CUMS) and exhibited the most prominent depressive phenotype (Dep). Electron microscopy, biochemical assays, quantitative PCR, and immunoblotting were used to evaluate synaptic and mitochondrial changes in the basolateral amygdala (BLA). RNA sequencing was used to explore changes in the Hippo pathway and downstream target genes. In vitro pharmacological inhibition and immunoprecipitation was used to confirm YAP/14-3-3η interaction and its role in neuronal mitochondrial dysfunction. We used virus-mediated gene overexpression and knockout in YAP transgenic mice to verify the regulatory effect of the Hippo/YAP/14-3-3η pathway on depressive-like behavior. Results: Transcriptomic data identified a large number of genes and signaling pathways that were specifically altered from the BLA of Dep mice. Dep mice showed notable synaptic impairment in BLA neurons, as well as mitochondrial damage characterized by abnormal mitochondrial morphology, compromised function, impaired biogenesis, and alterations in mitochondrial marker proteins. The Hippo signaling pathway was activated in Dep mice during CUMS, and the transcriptional regulatory activity of YAP was suppressed by phosphorylation of its Ser127 site. 14-3-3η was identified as an important co-regulatory factor of the Hippo/YAP pathway, as it can respond to chronic stress and regulate cytoplasmic retention of YAP. Importantly, the integrated Hippo/YAP/14-3-3η pathway mediated neuronal mitochondrial dysfunction and depressive behavior in Dep mice. Conclusion: The integrated Hippo/YAP/14-3-3η pathway in the BLA neuron is critical in mediating depressive-like behaviors in mice, suggesting a causal role for this pathway in susceptibility to chronic stress-induced depression. This pathway therefore may present a therapeutic target against mitochondrial dysfunction and synaptic impairment in MDD.

Fast and efficient isolation of murine circulating tumor cells using screencell technology for pre-clinical analyzes.

Circulating tumor cells (CTCs) represent a rare and heterogeneous population of cancer cells that are detached from the tumor site and entered blood or lymphatic circulation. Once disseminated in distant tissues, CTCs could remain dormant or create a tumor mass causing serious danger for patients. Many technologies exist to isolate CTCs from patients' blood samples, mostly based on microfluidic systems or by sorting them according to their surface antigens, notably EpCAM, and/or cytokeratins for carcinoma. ScreenCell has developed an easy-to-use, antigen-independent, rapid, cost-effective, and efficient technology that isolates CTCs according to their bigger size compared to the blood cells. This study provides the technical information necessary to isolate and characterize CTCs from mouse blood. By using blood samples from transgenic mice with breast cancer or from WT mice in which we spiked cancer cells, we showed that ScreenCell technology is compatible with standard EDTA blood collection tubes. Furthermore, the ScreenCell Cyto kit could treat up to 500 µl and the ScreenCell MB kit up to 200 µl of mouse blood. As the ScreenCell MB kit captures unaltered live CTCs, we have shown that their DNA could be efficiently extracted, and the isolated cells could be grown in culture. In conclusion, ScreenCell provides a rapid, easy, antigen-independent, cost-effective, and efficient technology to isolate and characterize CTCs from the blood samples of cancer patients and murine models. Thanks to this technology CTCs could be captured fixed or alive. Murine cancer models are extensively used in pre-clinical studies. Therefore, this study demonstrates the crucial technical points necessary while manipulating mouse blood samples using ScreenCell technology.

Nasal tau immunotherapy clears intracellular tau pathology and improves cognitive functions in aged tauopathy mice.

Pathological tau aggregates cause cognitive decline in neurodegenerative tauopathies, including Alzheimer's disease (AD). These aggregates are prevalent within intracellular compartments. Current tau immunotherapies have shown limited efficacy in clearing intracellular tau aggregates and improving cognition in clinical trials. In this study, we developed toxic tau conformation-specific monoclonal antibody-2 (TTCM2), which selectively recognized pathological tau aggregates in brain tissues from patients with AD, dementia with Lewy bodies (DLB), and progressive supranuclear palsy (PSP). TTCM2 potently inhibited tau-seeding activity, an essential mechanism underlying tauopathy progression. To effectively target intracellular tau aggregates and ensure rapid delivery to the brain, TTCM2 was loaded in micelles (TTCM2-ms) and administered through the intranasal route. We found that intranasally administered TTCM2-ms efficiently entered the brain in hTau-tauopathy mice, targeting pathological tau in intracellular compartments. Moreover, a single intranasal dose of TTCM2-ms effectively cleared pathological tau, elevated synaptic proteins, and improved cognitive functions in aged tauopathy mice. Mechanistic studies revealed that TTCM2-ms cleared intracellular, synaptic, and seed-competent tau aggregates through tripartite motif-containing 21 (TRIM21), an intracellular antibody receptor and E3 ubiquitin ligase known to facilitate proteasomal degradation of cytosolic antibody-bound proteins. TRIM21 was found to be essential for TTCM2-ms-mediated clearance of tau pathology. Our study collectively provides evidence of the effectiveness of nasal tau immunotherapy in targeting and clearing intracellular tau pathology through TRIM21 and enhancing cognition in aged tauopathy mice. This study could be valuable in designing effective tau immunotherapies for AD and other tauopathies.

HBx promotes glomerular podocyte-induced immune cell responses.

BACKGROUND: Podocytes, as intrinsic renal cells, can also express MHC-II and costimulatory molecules under inflammatory conditions, suggesting that they may act as antigen-presenting cells (APCs) to activate immune cell responses and then lead to immune-mediated renal injury. They are already recognized as main targets in the pathogenic mechanism of hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN). Previous studies also have indicated that inflammatory cells infiltration and immune-mediated tissue injury are evident in the kidney samples of patients with HBV-GN. However, the role of podocytes immune disorder in the pathogenic mechanism of HBV-GN remains unclear. METHODS: Renal function and inflammatory cells infiltration were measured in HBV transgenic (HBV-Tg) mice. In vitro, podocytes/CD4+ T cells or macrophages co-culture system was established. Then, the expression of HBx, CD4, and CD68 was determined by immunohistochemistry, while the expression of MHC-II, CD40, and CD40L was determined by immunofluorescence. Co-stimulatory molecules expression was examined by flow cytometry. The levels of inflammatory factors were detected by ELISA. RESULTS: In vivo, renal function was obviously impaired in HBV-Tg mice. HBx was significantly upregulated and immune cells infiltrated in the glomerulus of HBV-Tg mice. Expression of MHC-II and costimulatory molecule CD40 increased in the podocytes of HBV-Tg mice; CD4+ T cells exhibited increased CD40L expression in glomerulus. In vitro, CD40 expression was markedly elevated in HBx-podocytes. In co-culture systems, HBx-podocytes stimulated CD4+ T cells activation and caused the imbalance between IFN-γ and IL-4. HBx-podocytes also enhanced the adhesion ability of macrophages and induced the release of proinflammatory mediators. CONCLUSION: Taken together, these podocyte-related immune disorder may be involved in the pathogenic mechanism of HBV-GN.

Apolipoprotein E polymorphisms and female fertility in a transgenic mouse model of Alzheimer's disease.

Apolipoprotein E (APOE) is a major cholesterol carrier responsible for lipid transport and injury repair in the brain. The human APOE gene (h-APOE) has 3 naturally occurring alleles: ε3, the common allele; ε4, which increases Alzheimer's disease (AD) risk up to 15-fold; and ε2, the rare allele which protects against AD. Although APOE4 has negative effects on neurocognition in old age, its persistence in the population suggests a survival advantage. We investigated the relationship between APOE genotypes and fertility in EFAD mice, a transgenic mouse model expressing h-APOE. We show that APOE4 transgenic mice had the highest level of reproductive performance, followed by APOE3 and APOE2. Intriguingly, APOE3 pregnancies had more fetal resorptions and reduced fetal weights relative to APOE4 pregnancies. In conclusion, APOE genotypes impact fertility and pregnancy outcomes in female mice, in concordance with findings in human populations. These mouse models may help elucidate how h-APOE4 promotes reproductive fitness at the cost of AD in later life.

MHC heterozygosity limits T cell receptor variability in CD4 T cells.

αß T cell receptor (TCR) V(D)J genes code for billions of TCR combinations. However, only some appear on peripheral T cells in any individual because, to mature, thymocytes must react with low affinity but not high affinity with thymus expressed major histocompatibility (MHC)/peptides. MHC proteins are very polymorphic. Different alleles bind different peptides. Therefore, any individual might express many different MHC alleles to ensure that some peptides from an invader are bound to MHC and activate T cells. However, most individuals express limited numbers of MHC alleles. To explore this, we compared the TCR repertoires of naïve CD4 T cells in mice expressing one or two MHC alleles. Unexpectedly, the TCRs in heterozygotes were less diverse that those in the sum of their MHC homozygous relatives. Our results suggest that thymus negative selection cancels out the advantages of increased thymic positive selection in the MHC heterozygotes.

Norwegian moose CWD induces clinical disease and neuroinvasion in gene-targeted mice expressing cervid S138N prion protein.

Chronic wasting disease (CWD) is a prion disease affecting deer, elk and moose in North America and reindeer, moose and red deer in Northern Europe. Pathogenesis is driven by the accumulation of PrPSc, a pathological form of the host's cellular prion protein (PrPC), in the brain. CWD is contagious among North American cervids and Norwegian reindeer, with prions commonly found in lymphatic tissue. In Nordic moose and red deer CWD appears exclusively in older animals, and prions are confined to the CNS and undetectable in lymphatic tissues, indicating a sporadic origin. We aimed to determine transmissibility, neuroinvasion and lymphotropism of Nordic CWD isolates using gene-targeted mice expressing either wild-type (138SS/226QQ) or S138N (138NN/226QQ) deer PrP. When challenged with North American CWD strains, mice expressing S138N PrP did not develop clinical disease but harbored prion seeding activity in brain and spleen. Here, we infected these models intracerebrally or intraperitoneally with Norwegian moose, red deer and reindeer CWD isolates. The moose isolate was the first CWD type to cause full-blown disease in the 138NN/226QQ model in the first passage, with 100% attack rate and shortened survival times upon second passage. Furthermore, we detected prion seeding activity or PrPSc in brains and spinal cords, but not spleens, of 138NN/226QQ mice inoculated intraperitoneally with the moose isolate, providing evidence of prion neuroinvasion. We also demonstrate, for the first time, that transmissibility of the red deer CWD isolate was restricted to transgenic mice overexpressing elk PrPC (138SS/226EE), identical to the PrP primary structure of the inoculum. Our findings highlight that susceptibility to clinical disease is determined by the conformational compatibility between prion inoculum and host PrP primary structure. Our study indicates that neuroinvasion of Norwegian moose prions can occur without, or only very limited, replication in the spleen, an unprecedented finding for CWD.

Age-related differences in retinal function and structure in C57BL/6J and Thy1-YFPh mice.

Age-related neuronal adaptations are known to help maintain function. This study aims to examine gross age-related in vivo retinal functional adaptations (using electroretinography) in young and middle aged C57BL/6J and Thy1-YFPh mice and to relate this to in vivo retinal structure (using optical coherence tomography). Electroretinography responses were generally larger in Thy1-YFPh mice than in C57BL/6J mice, with similar in vivo retinal layer thicknesses except for longer inner/outer photoreceptor segment in Thy1-YFPh mice. Relative to 3-month-old mice, 12-month-old mice showed reduced photoreceptor (C57BL/6J 84.0±2.5 %; Thy1-YFPh 80.2±5.2 %) and bipolar cell (C57BL/6J 75.6±2.3 %; Thy1-YFPh 68.1±5.5 %) function. There was relative preservation of ganglion cell function (C57BL/6J 79.7±3.7 %; Thy1-YFPh 91.7±5.0 %) with age, which was associated with increased b-wave (bipolar cell) sensitivities to light. Ganglion cell function was correlated with both b-wave amplitude and sensitivity. This study shows that there are normal age-related adaptations to preserve functional output. Different mouse strains may have varied age-related adaptation capacity and should be taken into consideration when examining age-related susceptibility to injury.