Disease Phenotype In Mice Research Articles

N6-methyladenosine modification-tuned lipid metabolism controls skin immune homeostasis via regulating neutrophil chemotaxis.

Disrupted N6-methyladenosine (m6A) modification modulates various inflammatory disorders. However, the role of m6A in regulating cutaneous inflammation remains elusive. Here, we reveal that the m6A and its methyltransferase METTL3 are down-regulated in keratinocytes in inflammatory skin diseases. Inducible deletion of Mettl3 in murine keratinocytes results in spontaneous skin inflammation and increases susceptibility to cutaneous inflammation with activation of neutrophil recruitment. Therapeutically, restoration of m6A alleviates the disease phenotypes in mice and suppresses inflammation in human biopsy specimens. We support a model in which m6A modification stabilizes the mRNA of the lipid-metabolizing enzyme ELOVL6 via the m6A reader IGF2BP3, leading to a rewiring of fatty acid metabolism with a reduction in palmitic acid accumulation and, consequently, suppressing neutrophil chemotaxis in cutaneous inflammation. Our findings highlight a previously unrecognized epithelial-intrinsic m6A modification-lipid metabolism pathway that is essential for maintaining epidermal and immune homeostasis and lay the basis for potential therapeutic targeting of m6A modulators to attenuate inflammatory skin diseases.

Retinol dehydrogenase 12 (RDH12) knock out may cause hyperuricemia phenotype in mice

Hyperuricemia is a chronic metabolic disease caused by purine metabolism disorder. And several gene loci and transporter proteins that associated with uric acid transport functions have been identified. Retinol Dehydrogenase 12 (RDH12), recognized for its role in safeguarding photoreceptors, and our study investigated the potential impact of Rdh12 mutations on other organs and diseases, particularly hyperuricemia. We assessed Rdh12 mRNA expression levels in various tissues and conducted serum biochemical analyses in Rdh12−/− mice. Compared with the wild type, significant alterations in serum uric acid levels and kidney-related biochemical indicators have been revealed. Then further analysis, including quantitative RT-PCR of gene expression in the liver and kidney, highlighted variations in the expression levels of specific genes linked to hyperuricemia. And renal histology assessment exposed mild pathological lesions in the kidneys of Rdh12−/− mice.In summary, our study suggests that Rdh12 mutations impact not only retinal function but also contribute to hyperuricemia and renal disease phenotypes in mice. Our finding implies that individuals with Rdh12 mutations may be prone to hyperuricemia and gout, emphasizing the significance of preventive measures and regular examinations in daily life.

Divergent pathogenetic outcomes in BALB/c mice following Omicron subvariant infection

Following the emergence of B.1.1.529 Omicron, the SARS-CoV-2 virus evolved into a significant number of sublineage variants that possessed numerous mutations throughout the genome, but particularly within the spike glycoprotein (S) gene. For example, the BQ.1.1 and the XBB.1 and XBB.1.5 subvariants contained 34 and 41 mutations in S, respectively. However, these variants elicited largely replication only or mild disease phenotypes in mice. To better model pathogenic outcomes and measure countermeasure performance, we developed mouse adapted versions (BQ.1.1 MA; XBB.1 MA; XBB.1.5 MA) that reflect more pathogenic acute phase pulmonary disease symptoms of SARS-CoV-2, as well as derivative strains expressing nano-luciferase (nLuc) in place of ORF7 (BQ.1.1 nLuc; XBB.1 nLuc; XBB.1.5 nLuc). Amongst the mouse adapted (MA) viruses, a wide range of disease outcomes were observed including mortality, weight loss, lung dysfunction, and tissue viral loads in the lung and nasal turbinates. Intriguingly, XBB.1 MA and XBB.1.5 MA strains, which contained identical mutations throughout except at position F486S/P in S, exhibited divergent disease outcomes in mice (Ao et al., 2023). XBB.1.5 MA infection was associated with significant weight loss and ∼45 % mortality across two independent studies, while XBB.1 MA infected animals suffered from mild weight loss and only 10 % mortality across the same two independent studies. Additionally, the development and use of nanoluciferase expressing strains provided moderate throughput for live virus neutralization assays. The availability of small animal models for the assessment of Omicron VOC disease potential will enable refined capacity to evaluate the efficacy of on market and pre-clinical therapeutics and interventions.

Specific quinone reductase 2 inhibitors reduce metabolic burden and reverse Alzheimer's disease phenotype in mice.

Biological aging can be described as accumulative, prolonged metabolic stress and is the major risk factor for cognitive decline and Alzheimer's disease (AD). Recently, we identified and described a quinone reductase 2 (QR2) pathway in the brain, in which QR2 acts as a removable memory constraint and metabolic buffer within neurons. QR2 becomes overexpressed with age, and it is possibly a novel contributing factor to age-related metabolic stress and cognitive deficit. We found that, in human cells, genetic removal of QR2 produced a shift in the proteome opposing that found in AD brains while simultaneously reducing oxidative stress. We therefore created highly specific QR2 inhibitors (QR2is) to enable evaluation of chronic QR2 inhibition as a means to reduce biological age-related metabolic stress and cognitive decline. QR2is replicated results obtained by genetic removal of QR2, while local QR2i microinjection improved hippocampal and cortical-dependent learning in rats and mice. Continuous consumption of QR2is in drinking water improved cognition and reduced pathology in the brains of AD-model mice (5xFAD), with a noticeable between-sex effect on treatment duration. These results demonstrate the importance of QR2 activity and pathway function in the healthy and neurodegenerative brain and what we believe to be the great therapeutic potential of QR2is as first-in-class drugs.

Abstract P2091: Histone Deacetylase 6 (HDAC6) Inhibitor Improves Stress-Induced Cardiomyocyte Restructuring in Heart Failure with Preserved Ejection Fraction (HFpEF) in a Multimodal Manner Based on Single Nucleus RNA-seq (snRNA-seq) Analyses

In the high fat diet (HFD)/L-NAME mouse model of HFpEF, Ranjbarvaziri et al from Tenaya Therapeutics have previously shown that pharmacological inhibition of HDAC6 improves functional and structural cardiac metrics, together with improved oxidative phosphorylation, improved contraction, and reduced fibrosis. Tissue level as well as single cell level transcriptional studies of control, HFD + L-NAME HFpEF, and HFD + L-NAME HFpEF treated with either HDAC6 inhibitor TYA-018 or SGLT2 inhibitor empagliflozin, demonstrated extensive reversal of disease phenotypes in mice treated with TYA-018. Based on snRNA-Seq analyses, we report characterization of cardiomyocyte (CM) subtypes in HFpEF that establish specific and substantial cell-cell interactions with their surrounding fibroblasts and endothelial cells. These interactions initiate CM-subtype-specific signaling cascades, leading to emergence of ‘stressed’ hypoxic CM and hypercontractile CM subtypes. We show that these cell types increase in the HFpEF disease state. The proportion of ‘stressed’ CMs at tissue level corresponds to the worsening cardiac functional measures, and their composing fractions in left ventricle tissue decline and normalize after TYA-018 treatment. These findings suggest HDAC6 inhibition may regulate undesirable HFpEF phenotype characteristics such as dysregulated metabolism, fibrosis and hypertrophy, and also present detailed cell-level evidence of HDAC6 inhibition’s favorable effects in metabolic syndrome.

Estrogen receptor alpha signaling in dendritic cells modulates autoimmune disease phenotype in mice.

Estrogen is a disease-modifying factor in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) via estrogen receptor alpha (ERα). However, the mechanisms by which ERα signaling contributes to changes in disease pathogenesis have not been completely elucidated. Here, we demonstrate that ERα deletion in dendritic cells (DCs) of mice induces severe neurodegeneration in the central nervous system in a mouse EAE model and resistance to interferon beta (IFNβ), a first-line MS treatment. Estrogen synthesized by extragonadal sources is crucial for controlling disease phenotypes. Mechanistically, activated ERα directly interacts with TRAF3, a TLR4 downstream signaling molecule, to degrade TRAF3 via ubiquitination, resulting in reduced IRF3 nuclear translocation and transcription of membrane lymphotoxin (mLT) and IFNβ components. Diminished ERα signaling in DCs generates neurotoxic effector CD4+ T cells via mLT-lymphotoxin beta receptor (LTβR) signaling. Lymphotoxin beta receptor antagonist abolished EAE disease symptoms in the DC-specific ERα-deficient mice. These findings indicate that estrogen derived from extragonadal sources, such as lymph nodes, controls TRAF3-mediated cytokine production in DCs to modulate the EAE disease phenotype.

Tmprss6 Depletion-Mediated Iron Deficiency Attenuates the Clinical Course of Plasmodium Berghei Infection in Mice

Background Anaemia and malaria cause a great burden of disease and commonly co-exist. Field studies have linked iron deficiency with decreased malaria risk but may be confounded. We aimed to define the association between iron status and malaria risk in an in vivo experimental system. Using the P. berghei mouse malaria model, we assessed the impact of both severe iron overload and iron deficiency using inducible hepcidin (Hamp) knockout (iHamp-KO), Tmprss6 knockout (Tmprss6-KO) and Tmprss6 knockdown (Tmprss6-KD) mouse models. Homozygous mutations of HAMP (encoding hepcidin) cause severe iron overload, while homozygous inactivation of TMPRSS6 leads to hepcidin overexpression and iron deficiency. MethodsP. berghei infection of C57BL/6 mice is an experimental model of cerebral and severe malaria. The majority of mice develop neurological symptoms between day 6-10 post infection, surviving mice usually develop hyperparasitaemia and symptoms of severe anaemia by day 20. Mice were infected with PbmCherryLuci sporozoites by intravenous injection. Luciferase activity was used to assess liver infection and egress. Mice were analysed by IVIS at 24, 36, 52 and 55/56 hours post infection. From day 3 post infection peripheral parasitaemia was assessed daily. Mice were euthanised if they showed signs of cerebral malaria (such as loss of self-righting reflex and hind-limb paresis), severe anaemia, or if parasitaemia reached >20% (iHamp-KO and Tmprss6-KO) or >30% (Tmprss6-KD) in line with animal ethics requirements. iHamp-KO mice received tamoxifen intraperitoneally daily for 5 days 3 months prior to infection to induce Hamp deletion. Controls were iHamp-KO littermates that received vehicle alone. Tmprss6-KO mice were infected at about 24 weeks of age and compared to littermate heterozygote controls which are known to have a negligible phenotype. Tmprss6-KD was achieved through treatment of WT mice with siTMP, a GalNAc siRNA conjugate targeting Tmprss6. Mice received siTMP 5mg/kg s.c. 3 weekly starting 8 weeks prior to P. berghei infection, or a single treatment on day 3 (expected onset of blood stage infection) or day 6 (expected onset of high risk period for cerebral malaria), while controls received PBS. Results iHamp-KO mice had lower peak liver infection (p=0.0097), but egress was not affected, and there was no effect on overall survival or survival from cerebral malaria. Tmprss6-KO mice showed higher liver infection compared with heterozygous littermate controls at all timepoints, but egress was not different. Tmprss6-KO mice had improved overall survival compared with heterozygous controls (p=0.0004) and improved survival from cerebral malaria (p=0.0004). All 7 heterozygous controls succumbed to cerebral malaria by day 10, compared to 1 of 6 Tmprss6-KO animals (Figure 1). We further investigated effects of iron deficiency on malaria severity using Tmprss6 knockdown. Mice treated with siTMP for 8-10 weeks had markedly reduced Tmprss6 and elevated Hamp expression in the liver, and lower haemoglobin, MCV, and plasma iron. Tmprss6-KD mice, treated 8 weeks prior to P. berghei infection exhibited reduced parasitaemia, and took longer to reach 10%, 20% and 30% parasitaemia (Figure 2). There was no change in survival from cerebral malaria. Tmprss6-KD after infection did not change parasitaemia or survival. Conclusion Experimental iron deficiency via Tmprss6 downregulation attenuated malaria disease phenotype in mice. These data provide experimental evidence to support observational data that iron deficiency provides protection against malaria infection. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Multi-phenotype analysis for enhanced classification of 11 herpes simplex virus 1 strains.

Herpes simplex virus 1 (HSV1) is best known for causing oral lesions and mild clinical symptoms, but it can produce a significant range of disease severities and rates of reactivation. To better understand this phenotypic variation, we characterized 11 HSV1 strains that were isolated from individuals with diverse infection outcomes. We provide new data on genomic and in vitro plaque phenotype analysis for these isolates and compare these data to previously reported quantitation of the disease phenotype of each strain in a murine animal model. We show that integration of these three types of data permitted clustering of these HSV1 strains into four groups that were not distinguishable by any single dataset alone, highlighting the benefits of combinatorial multi-parameter phenotyping. Two strains (group 1) produced a partially or largely syncytial plaque phenotype and attenuated disease phenotypes in mice. Three strains of intermediate plaque size, causing severe disease in mice, were genetically clustered to a second group (group 2). Six strains with the smallest average plaque sizes were separated into two subgroups (groups 3 and 4) based on their different genetic clustering and disease severity in mice. Comparative genomics and network graph analysis suggested a separation of HSV1 isolates with attenuated vs. virulent phenotypes. These observations imply that virulence phenotypes of these strains may be traceable to genetic variation within the HSV1 population.

Kruppel-like factor 1–GATA1 fusion protein improves the sickle cell disease phenotype in mice both in vitro and in vivo

AbstractSickle cell disease (SCD) and β-thalassemia are among the most common genetic disorders worldwide, affecting global health and mortality. Hemoglobin A2 (HbA2, α2δ2) is expressed at a low level in adult blood due to the lack of the Kruppel-like factor 1 (KLF1) binding motif in the δ-globin promoter region. However, HbA2 is fully functional as an oxygen transporter, and could be a valid antisickling agent in SCD, as well as a substitute for hemoglobin A in β-thalassemia. We have previously demonstrated that KLF1-GATA1 fusion protein could interact with the δ-globin promoter and increase δ-globin expression in human primary CD34+ cells. We report the effects of 2 KLF1-GATA1 fusion proteins on hemoglobin expression, as well as SCD phenotypic correction in vitro and in vivo. Forced expression of KLF1-GATA1 fusion protein enhanced δ-globin gene and HbA2 expression, as well as reduced hypoxia-related sickling, in erythroid cells cultured from both human sickle CD34+ cells and SCD mouse hematopoietic stem cells (HSCs). The fusion proteins had no impact on erythroid cell differentiation, proliferation, and enucleation. Transplantation of highly purified SCD mouse HSCs expressing KLF1-GATA1 fusion protein into SCD mice lessened the severity of the anemia, reduced the sickling of red blood cells, improved SCD-related pathological alterations in spleen, kidney, and liver, and restored urine-concentrating ability in recipient mice. Taken together, these results indicate that the use of KLF1-GATA1 fusion constructs may represent a new gene therapy approach for hemoglobinopathies.

Cross-species genetic screens identify transglutaminase 5 as a regulator of polyglutamine-expanded ataxin-1.

Many neurodegenerative disorders are caused by abnormal accumulation of misfolded proteins. In spinocerebellar ataxia type 1 (SCA1), accumulation of polyglutamine-expanded (polyQ-expanded) ataxin-1 (ATXN1) causes neuronal toxicity. Lowering total ATXN1, especially the polyQ-expanded form, alleviates disease phenotypes in mice, but the molecular mechanism by which the mutant ATXN1 is specifically modulated is not understood. Here, we identified 22 mutant ATXN1 regulators by performing a cross-species screen of 7787 and 2144 genes in human cells and Drosophila eyes, respectively. Among them, transglutaminase 5 (TG5) preferentially regulated mutant ATXN1 over the WT protein. TG enzymes catalyzed cross-linking of ATXN1 in a polyQ-length–dependent manner, thereby preferentially modulating mutant ATXN1 stability and oligomerization. Perturbing Tg in Drosophila SCA1 models modulated mutant ATXN1 toxicity. Moreover, TG5 was enriched in the nuclei of SCA1-affected neurons and colocalized with nuclear ATXN1 inclusions in brain tissue from patients with SCA1. Our work provides a molecular insight into SCA1 pathogenesis and an opportunity for allele-specific targeting for neurodegenerative disorders.

Correction: Defining α-synuclein species responsible for Parkinson's disease phenotypes in mice.

VOLUME 294 (2019) PAGES 10392–10406 In the published article, there was an inadvertent error in Fig. 5. The panel for the retrobeads (red) and p-α-synuclein inclusions (green) in the cortex at 1 week post-injection was the same as 2 weeks post-injection. The 1-week post-injection panel was incorrect and has been corrected. There are no phosphorylated α-synuclein inclusions or retrotracer beads present in the cortex (or amygdala or SNc) 1 week post-injection.

H7N9 Influenza Virus Containing a Polybasic HA Cleavage Site Requires Minimal Host Adaptation to Obtain a Highly Pathogenic Disease Phenotype in Mice.

Low pathogenic avian influenza (LPAI) H7N9 viruses have recently evolved to gain a polybasic cleavage site in the hemagglutinin (HA) protein, resulting in variants with increased lethality in poultry that meet the criteria for highly pathogenic avian influenza (HPAI) viruses. Both LPAI and HPAI variants can cause severe disease in humans (case fatality rate of ~40%). Here, we investigated the virulence of HPAI H7N9 viruses containing a polybasic HA cleavage site (H7N9-PBC) in mice. Inoculation of mice with H7N9-PBC did not result in observable disease; however, mice inoculated with a mouse-adapted version of this virus, generated by a single passage in mice, caused uniformly lethal disease. In addition to the PBC site, we identified three other mutations that are important for host-adaptation and virulence in mice: HA (A452T), PA (D347G), and PB2 (M483K). Using reverse genetics, we confirmed that the HA mutation was the most critical for increased virulence in mice. Our study identifies additional disease determinants in a mammalian model for HPAI H7N9 virus. Furthermore, the ease displayed by the virus to adapt to a new host highlights the potential for H7N9-PBC viruses to rapidly acquire mutations that may enhance their risk to humans or other animal species.

P.104Skeletal muscle reduction of Dnm2 with antisense oligonucleotides in myotubular myopathy

Centronuclear myopathies (CNM) are a group of severe muscle diseases for which no effective therapy is currently available. The most severe and neonatal X-linked form is known as myotubular myopathy and caused by loss-of-function mutations in Myotubularin (MTM1), while the main autosomal dominant form is due to mutations in Dynamin 2 (DNM2). We previously showed that genetic reduction of DNM2 expression in Mtm1 knockout (Mtm1KO) mice prevents development of muscle pathology. We are now investigating skeletal muscle targeting of Dnm2 reduction in mice. Indeed specific muscle isoforms are expressed during muscle maturation and in adulthood, through alternative splicing. A single intraperitoneal injection of 25mg/kg of antisense oligonucleotides targeting the total pool of Dnm2 increased the lifespan, whole body strength, and reduced disease severity in Mtm1KO mice, however a single injection alone was not sufficient to rescue the disease for the lifespan of the mice. Repeated injections of ASO was able to revert the disease phenotype in mice within 2 weeks, and the effects lasted several months after the final injection. ASO was still detected in skeletal muscles at this time point, but not in key tissues such as the liver, which may explain in part the longterm improvement in the myopathic phenotype. New ligand-conjugated antisense (LICA) oligonucleotides targeting Dnm2 are now being tested in Mtm1KO mice for potency and efficacy. ASO-mediated Dnm2 knockdown can efficiently correct skeletal muscle defects due to loss of MTM1, providing an attractive therapeutic strategy for this disease. Effective muscle targeting will be an important step in translation of this approach to the clinic for patients.

Recent Advances in Understanding Mammalian Prion Structure: A Mini Review.

Prions are lethal pathogens, which cause fatal neurodegenerative diseases in mammals. They are unique infectious agents and are composed of self-propagating multi-chain assemblies of misfolded host-encoded prion protein (PrP). Understanding prion structure is fundamental to understanding prion disease pathogenesis however to date, the high-resolution structure of authentic ex vivo infectious prions remains unknown. Advances in determining prion structure have been severely impeded by the difficulty in recovering relatively homogeneous prion particles from infected brain and definitively associating infectivity with the PrP assembly state. Recently, however, images of highly infectious ex vivo PrP rods that produce prion-strain specific disease phenotypes in mice have been obtained using cryo-electron microscopy and atomic force microscopy. These images have provided the most detailed description of ex vivo mammalian prions reported to date and have established that prions isolated from multiple strains have a common hierarchical structure. Misfolded PrP is assembled into 20 nm wide rods containing two fibers, each with double helical repeating substructure, separated by a characteristic central gap 8–10 nm in width. Irregularly structured material with adhesive properties distinct to that of the fibers is present within the central gap of the rod. Prions are clearly distinguishable from non-infectious recombinant PrP fibrils generated in vitro and from all other propagating protein structures so far described in other neurodegenerative diseases. The basic architecture of mammalian prions appears to be exceptional and fundamental to their lethal pathogenicity.

Defining α-synuclein species responsible for Parkinson’s disease phenotypes in mice

Parkinson's disease (PD) is a neurodegenerative disorder characterized by fibrillar neuronal inclusions composed of aggregated α-synuclein (α-syn). These inclusions are associated with behavioral and pathological PD phenotypes. One strategy for therapeutic interventions is to prevent the formation of these inclusions to halt disease progression. α-Synuclein exists in multiple structural forms, including disordered, nonamyloid oligomers, ordered amyloid oligomers, and fibrils. It is critical to understand which conformers contribute to specific PD phenotypes. Here, we utilized a mouse model to explore the pathological effects of stable β-amyloid-sheet oligomers compared with those of fibrillar α-synuclein. We biophysically characterized these species with transmission EM, atomic-force microscopy, CD spectroscopy, FTIR spectroscopy, analytical ultracentrifugation, and thioflavin T assays. We then injected these different α-synuclein forms into the mouse striatum to determine their ability to induce PD-related phenotypes. We found that β-sheet oligomers produce a small but significant loss of dopamine neurons in the substantia nigra pars compacta (SNc). Injection of small β-sheet fibril fragments, however, produced the most robust phenotypes, including reduction of striatal dopamine terminals, SNc loss of dopamine neurons, and motor-behavior defects. We conclude that although the β-sheet oligomers cause some toxicity, the potent effects of the short fibrillar fragments can be attributed to their ability to recruit monomeric α-synuclein and spread in vivo and hence contribute to the development of PD-like phenotypes. These results suggest that strategies to reduce the formation and propagation of β-sheet fibrillar species could be an important route for therapeutic intervention in PD and related disorders.

High Saturated and Unsaturated Fat Diets Yield Different Disease Phenotypes in Mice

Excessive consumption of unsaturated or saturated fatty acids have adverse effects on certain health parameters, namely increased risk of obesity, diabetes, and cardiovascular disease. Specifically, saturated fats are linked to increased cardiovascular risk while unsaturated fats are suggested to protect against cardiovascular disease. Our previous work suggested that various high fat diets have differential effects on cardiac hypertrophy and function. However, it was not clear whether a high saturated fat diet (HSFD) or high unsaturated fat diet (HUFD) could elicit different disease phenotypes. Therefore, the purpose of this study was to evaluate the effects of HSFD or HUFD on the development of obesity, diabetes, and cardiac lipotoxicity in mice. Male, C57BL/6J mice received normal chow (CON, n=12), HSFD (n=15) or HUFD (n=15) for 12 weeks. Body weight and food intake were measured weekly. After 12 weeks, the adipose tissue and heart were removed and weighed. Glucose, fatty acids, and cholesterol were analyzed in serum using biochemical assays. Cardiac triglycerides (TG) were measured in heart tissue extracts. Both HSFD and HUFD significantly increased body weight above CON. Interestingly, body weight increased by ~63% in the HUFD while the HSFD increased ~41% (P<0.05). Adipose tissue mass was increased 5‐fold in both HFD groups and was ~10% greater in the HUFD. Surprisingly, caloric intake was higher in the HSFD (15.3±0.8) compared to HUFD (12.8±0.1) and CON (11.9±0.7). Serum cholesterol levels were elevated in both HSFD and HUFD. Blood glucose was significantly increased only in the HUFD while serum fatty acids were increased only in the HSFD. Cardiac hypertrophy, assessed by the heart weight to tibia length ratio, was increased in the HSFD but not HUFD group. Cardiac TGs were ~25% higher in HSFD but <10% in HUFD compared to CON. These data show that excess consumption of saturated or unsaturated fats increased body weight and adiposity in mice. However, high consumption of unsaturated fatty acids resulted in a pronounced increase in body weight, body fat, and hyperglycemia, consistent with an obese and diabetic phenotype. Conversely, high consumption of saturated fatty acids caused elevated serum lipids, cardiac hypertrophy, and cardiac lipid accumulation, consistent with cardiac lipotoxicity. In conclusion, the fatty acid composition of diets may be critical in the development of disease phenotypes resulting from high fat feeding in mice.Support or Funding InformationThis work was supported by funding from the American Heart Association and Ursinus College.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Control of the innate immune response by the mevalonate pathway.

Deficiency of mevalonate kinase (MVK) causes systemic inflammation. However, the molecular mechanisms linking the mevalonate pathway to inflammation remain obscure. Geranylgeranyl pyrophosphate (GGPP), a non-sterol intermediate of the mevalonate pathway, is the substrate for protein geranylgeranylation, protein post-translational modification catalyzed by protein geranylgeranyl transferase I (GGTase I). Pyrin is an innate immune sensor that forms an active inflammasome in response to bacterial toxins. Mutations in MEFV (encoding human PYRIN) cause autoinflammatory Familial Mediterranean Fever (FMF) syndrome. Here, we show that protein geranylgeranylation enables Toll-like receptor (TLR)-induced phosphatidylinositol-3-OH kinase PI(3)K) activation by promoting the interaction between the small GTPase Kras and the PI(3)K catalytic subunit p110δ. Macrophages deficient for GGTase I or p110δ exhibited constitutive interleukin-1β release that was MEFV-dependent, but NLRP3-, AIM2- and NLRC4- inflammasome independent. In the absence of protein geranylgeranylation, compromised PI(3)K activity allows for an unchecked TLR-induced inflammatory responses and constitutive activation of the Pyrin inflammasome.

Arginase-1 deficiency.

Arginase-1 (ARG1) deficiency is a rare autosomal recessive disorder that affects the liver-based urea cycle, leading to impaired ureagenesis. This genetic disorder is caused by 40+ mutations found fairly uniformly spread throughout the ARG1 gene, resulting in partial or complete loss of enzyme function, which catalyzes the hydrolysis of arginine to ornithine and urea. ARG1-deficient patients exhibit hyperargininemia with spastic paraparesis, progressive neurological and intellectual impairment, persistent growth retardation, and infrequent episodes of hyperammonemia, a clinical pattern that differs strikingly from other urea cycle disorders. This review briefly highlights the current understanding of the etiology and pathophysiology of ARG1 deficiency derived from clinical case reports and therapeutic strategies stretching over several decades and reports on several exciting new developments regarding the pathophysiology of the disorder using ARG1 global and inducible knockout mouse models. Gene transfer studies in these mice are revealing potential therapeutic options that can be exploited in the future. However, caution is advised in extrapolating results since the lethal disease phenotype in mice is much more severe than in humans indicating that the mouse models may not precisely recapitulate human disease etiology. Finally, some of the functions and implications of ARG1 in non-urea cycle activities are considered. Lingering questions and future areas to be addressed relating to the clinical manifestations of ARG1 deficiency in liver and brain are also presented. Hopefully, this review will spark invigorated research efforts that lead to treatments with better clinical outcomes.

A thioredoxin fold protein Sh3bgr regulates Enah and is necessary for proper sarcomere formation

The sh3bgr (SH3 domain binding glutamate-rich) gene encodes a small protein containing a thioredoxin-like fold, SH3 binding domain, and glutamate-rich domain. Originally, it was suggested that increased expression of Sh3bgr may cause the cardiac phenotypes in Down's syndrome. However, it was recently reported that the overexpression of Sh3bgr did not cause any disease phenotypes in mice. In this study, we have discovered that Sh3bgr is critical for sarcomere formation in striated muscle tissues and also for heart development. Sh3bgr is strongly expressed in the developing somites and heart in Xenopus. Morpholino mediated-knockdown of sh3bgr caused severe malformation of heart tissue and disrupted segmentation of the somites. Further analysis revealed that Sh3bgr specifically localized to the Z-line in mature sarcomeres and that knockdown of Sh3bgr completely disrupted sarcomere formation in the somites. Moreover, overexpression of Sh3bgr resulted in abnormally discontinues thick firmaments in the somitic sarcomeres. We suggest that Sh3bgr does its function at least partly by regulating localization of Enah for the sarcomere formation. In addition, we provide the data supporting Sh3bgr is also necessary for proper heart development in part by affecting the Enah protein level.

OP24 – 2321: FINGORETT – An ongoing phase I clinical study to assess safety and efficacy of oral fingolimod (FTY720) in children with Rett syndrome

Objectives Rett syndrome is a neurodevelopmental disorder characterized by normal early psychomotor development followed by the loss of acquired skills. Phenotypic reversal by activation of MECP2 (see Guy et al. Science 2007) triggered hope towards possible therapeutic options for this disease. BDNF (brain-derived neurotrophic factor) levels were identified to influence disease phenotype in mice (Chang et al. Neuron 2006). FTY720 (fingolimod) is an oral modulator of S1P (sphingosine-1 phosphate) receptors. It increases BDNF levels and improved symptoms of a mouse model of Rett syndrome (Deogracias et al. Proc Natl Acad Sci USA 2012). Our study has been designed to assess safety of oral FTY720 and to study some outcome measures in order to evaluate a possible efficacy of FTY720 in children with Rett Syndrome. Methods 6 children with Rett-Syndrome (confirmed MECP2-Mutation) older than 6 years will be included into this study. Children will be treated with oral FTY720 once daily. Safety will be assessed by clinical visits and by blood sampling. Efficacy will be measured by comparing BDNF-levels in blood and cerebrospinal fluid (CSF) before and under treatment and by measuring development of general as well as focal brain atrophy/volume by MRI (Magnetic Resonance Imaging) during the treatment period of one year. Clinical Scales will be used to study the children's skills before, under and after treatment. Results The study is ongoing with no safety concerns so far. Conclusions FINGORETT is a first phase I clinical study to assess safety and efficacy in children with Rett Syndrome. First results from this ongoing study show, that FTY720 is safe in children with Rett Syndrome above 6 years of age. FTY720 could be a possible treatment option for children with Rett Syndrome.