The objective of the study was to examine variability across multiple prospective cohort studies in level and rate of cognitive decline by race/ethnicity and years of education. We compare data ...across studies, we harmonized estimates of common latent factors representing overall or general cognitive performance, memory, and executive function derived from the: (a) Washington Heights, Hamilton Heights, Inwood Columbia Aging Project (N = 4,115), (b) Spanish and English Neuropsychological Assessment Scales (N = 525), (c) Duke Memory, Health, and Aging study (N = 578), and (d) Neurocognitive Outcomes of Depression in the Elderly (N = 585). We modeled cognitive change over age for cognitive outcomes by race, education, and study. We adjusted models for sex, dementia status, and study-specific characteristics. The results found that for baseline levels of overall cognitive performance, memory, and executive function, differences in race and education tended to be larger than between-study differences and consistent across studies. This pattern did not hold for rate of cognitive decline: effects of education and race/ethnicity on cognitive change were not consistently observed across studies, and when present were small, with racial/ethnic minorities and those with lower education declining at faster rates. In this diverse set of datasets, non-Hispanic Whites and those with higher education had substantially higher baseline cognitive test scores. However, differences in the rate of cognitive decline by race/ethnicity and education did not follow this pattern. This study suggests that baseline test scores and longitudinal change have different determinants, and future studies to examine similarities and differences of causes of cognitive decline in racially/ethnically and educationally diverse older groups is needed.
Abstract
Aims
Mitochondrial Complex I assembly (MCIA) is a multi-step process that necessitates the involvement of a variety of assembly factors and chaperones to ensure that the final active enzyme ...is correctly assembled. The role of the assembly factor evolutionarily conserved signalling intermediate in the toll (ECSIT) pathway was studied across various murine tissues to determine its role in this process and how this varied between tissues of varying energetic demands. We hypothesized that many of the known functions of ECSIT were unhindered by the introduction of an ENU-induced mutation, while its role in Complex I assembly was affected on a tissue-specific basis.
Methods and results
Here, we describe a mutation in the MCIA factor ECSIT that reveals tissue-specific requirements for ECSIT in Complex I assembly. MCIA is a multi-step process dependent on assembly factors that organize and arrange the individual subunits, allowing for their incorporation into the complete enzyme complex. We have identified an ENU-induced mutation in ECSIT (N209I) that exhibits a profound effect on Complex I component expression and assembly in heart tissue, resulting in hypertrophic cardiomyopathy in the absence of other phenotypes. The dysfunction of Complex I appears to be cardiac specific, leading to a loss of mitochondrial output as measured by Seahorse extracellular flux and various biochemical assays in heart tissue, while mitochondria from other tissues were unaffected.
Conclusions
These data suggest that the mechanisms underlying Complex I assembly and activity may have tissue-specific elements tailored to the specific demands of cells and tissues. Our data suggest that tissues with high-energy demands, such as the heart, may utilize assembly factors in different ways to low-energy tissues in order to improve mitochondrial output. These data have implications for the diagnosis and treatment of various disorders of mitochondrial function as well as cardiac hypertrophy with no identifiable underlying genetic cause.
Graphical Abstract
Graphical Abstract
Two bottlenecks impeding the genetic analysis of complex traits in rodents are access to mapping populations able to deliver gene-level mapping resolution and the need for population-specific ...genotyping arrays and haplotype reference panels. Here we combine low-coverage (0.15×) sequencing with a new method to impute the ancestral haplotype space in 1,887 commercially available outbred mice. We mapped 156 unique quantitative trait loci for 92 phenotypes at a 5% false discovery rate. Gene-level mapping resolution was achieved at about one-fifth of the loci, implicating Unc13c and Pgc1a at loci for the quality of sleep, Adarb2 for home cage activity, Rtkn2 for intensity of reaction to startle, Bmp2 for wound healing, Il15 and Id2 for several T cell measures and Prkca for bone mineral content. These findings have implications for diverse areas of mammalian biology and demonstrate how genome-wide association studies can be extended via low-coverage sequencing to species with highly recombinant outbred populations.
Nephrotic syndrome is characterized by severe proteinuria, hypoalbuminaemia, edema and hyperlipidaemia. Genetic studies of nephrotic syndrome have led to the identification of proteins playing a ...crucial role in slit diaphragm signaling, regulation of actin cytoskeleton dynamics and cell-matrix interactions. The laminin α5 chain is essential for embryonic development and, in association with laminin β2 and laminin γ1, is a major component of the glomerular basement membrane, a critical component of the glomerular filtration barrier. Mutations in LAMA5 were recently identified in children with nephrotic syndrome. Here, we have identified a novel missense mutation (E884G) in the uncharacterized L4a domain of LAMA5 where homozygous mice develop nephrotic syndrome with severe proteinuria with histological and ultrastructural changes in the glomerulus mimicking the progression seen in most patients. The levels of LAMA5 are reduced in vivo and the assembly of the laminin 521 heterotrimer significantly reduced in vitro. Proteomic analysis of the glomerular extracellular fraction revealed changes in the matrix composition. Importantly, the genetic background of the mice had a significant effect on aspects of disease progression from proteinuria to changes in podocyte morphology. Thus, our novel model will provide insights into pathologic mechanisms of nephrotic syndrome and pathways that influence the response to a dysfunctional glomerular basement membrane that may be important in a range of kidney diseases.
Display omitted
Abstract
Aims
Cardiac arrhythmias comprise a major health and economic burden and are associated with significant morbidity and mortality, including cardiac failure, stroke, and sudden cardiac death ...(SCD). Development of efficient preventive and therapeutic strategies is hampered by incomplete knowledge of disease mechanisms and pathways. Our aim is to identify novel mechanisms underlying cardiac arrhythmia and SCD using an unbiased approach.
Methods and results
We employed a phenotype-driven N-ethyl-N-nitrosourea mutagenesis screen and identified a mouse line with a high incidence of sudden death at young age (6–9 weeks) in the absence of prior symptoms. Affected mice were found to be homozygous for the nonsense mutation Bcat2p.Q300*/p.Q300* in the Bcat2 gene encoding branched chain amino acid transaminase 2. At the age of 4–5 weeks, Bcat2p.Q300*/p.Q300* mice displayed drastic increase of plasma levels of branch chain amino acids (BCAAs—leucine, isoleucine, valine) due to the incomplete catabolism of BCAAs, in addition to inducible arrhythmias ex vivo as well as cardiac conduction and repolarization disturbances. In line with these findings, plasma BCAA levels were positively correlated to electrocardiogram indices of conduction and repolarization in the German community-based KORA F4 Study. Isolated cardiomyocytes from Bcat2p.Q300*/p.Q300* mice revealed action potential (AP) prolongation, pro-arrhythmic events (early and late afterdepolarizations, triggered APs), and dysregulated calcium homeostasis. Incubation of human pluripotent stem cell-derived cardiomyocytes with elevated concentration of BCAAs induced similar calcium dysregulation and pro-arrhythmic events which were prevented by rapamycin, demonstrating the crucial involvement of mTOR pathway activation.
Conclusions
Our findings identify for the first time a causative link between elevated BCAAs and arrhythmia, which has implications for arrhythmogenesis in conditions associated with BCAA metabolism dysregulation such as diabetes, metabolic syndrome, and heart failure.
Graphical Abstract
Graphical Abstract
The link between mutations in collagen genes and the development of Alport Syndrome has been clearly established and a number of animal models, including knock-out mouse lines, have been developed ...that mirror disease observed in patients. However, it is clear from both patients and animal models that the progression of disease can vary greatly and can be modified genetically. We have identified a point mutation in Col4a4 in mice where disease is modified by strain background, providing further evidence of the genetic modification of disease symptoms. Our results indicate that C57BL/6J is a protective background and postpones end stage renal failure from 7 weeks, as seen on a C3H background, to several months. We have identified early differences in disease progression, including expression of podocyte-specific genes and podocyte morphology. In C57BL/6J mice podocyte effacement is delayed, prolonging normal renal function. The slower disease progression has allowed us to begin dissecting the pathogenesis of murine Alport Syndrome in detail. We find that there is evidence of differential gene expression during disease on the two genetic backgrounds, and that disease diverges by 4 weeks of age. We also show that an inflammatory response with increasing MCP-1 and KIM-1 levels precedes loss of renal function.
Otitis media with effusion (OME) is the commonest cause of hearing loss in children, yet the underlying genetic pathways and mechanisms involved are incompletely understood. Ventilation of the middle ...ear with tympanostomy tubes is the commonest surgical procedure in children and the best treatment for chronic OME, but the mechanism by which they work remains uncertain. As hypoxia is a common feature of inflamed microenvironments, moderation of hypoxia may be a significant contributory mechanism. We have investigated the occurrence of hypoxia and hypoxia-inducible factor (HIF) mediated responses in Junbo and Jeff mouse mutant models, which develop spontaneous chronic otitis media. We found that Jeff and Junbo mice labeled in vivo with pimonidazole showed cellular hypoxia in inflammatory cells in the bulla lumen, and in Junbo the middle ear mucosa was also hypoxic. The bulla fluid inflammatory cell numbers were greater and the upregulation of inflammatory gene networks were more pronounced in Junbo than Jeff. Hif-1α gene expression was elevated in bulla fluid inflammatory cells, and there was upregulation of its target genes including Vegfa in Junbo and Jeff. We therefore investigated the effects in Junbo of small-molecule inhibitors of VEGFR signaling (PTK787, SU-11248, and BAY 43-9006) and destabilizing HIF by inhibiting its chaperone HSP90 with 17-DMAG. We found that both classes of inhibitor significantly reduced hearing loss and the occurrence of bulla fluid and that VEGFR inhibitors moderated angiogenesis and lymphangiogenesis in the inflamed middle ear mucosa. The effectiveness of HSP90 and VEGFR signaling inhibitors in suppressing OM in the Junbo model implicates HIF-mediated VEGF as playing a pivotal role in OM pathogenesis. Our analysis of the Junbo and Jeff mutants highlights the role of hypoxia and HIF-mediated pathways, and we conclude that targeting molecules in HIF-VEGF signaling pathways has therapeutic potential in the treatment of chronic OM.
Isocitrate dehydrogenase (IDH) is an enzyme required for the production of α-ketoglutarate from isocitrate. IDH3 generates the NADH used in the mitochondria for ATP production, and is a tetramer made ...up of two α, one β and one γ subunit. Loss-of-function and missense mutations in both
and
have previously been implicated in families exhibiting retinal degeneration. Using mouse models, we investigated the role of IDH3 in retinal disease and mitochondrial function. We identified mice with late-onset retinal degeneration in a screen of ageing mice carrying an ENU-induced mutation, E229K, in
Mice homozygous for this mutation exhibit signs of retinal stress, indicated by GFAP staining, as early as 3 months, but no other tissues appear to be affected. We produced a knockout of
and found that homozygous mice do not survive past early embryogenesis.
compound heterozygous mutants exhibit a more severe retinal degeneration compared with
homozygous mutants. Analysis of mitochondrial function in mutant cell lines highlighted a reduction in mitochondrial maximal respiration and reserve capacity levels in both
and
cells. Loss-of-function
mutants do not exhibit the same retinal degeneration phenotype, with no signs of retinal stress or reduction in mitochondrial respiration. It has previously been reported that the retina operates with a limited mitochondrial reserve capacity and we suggest that this, in combination with the reduced reserve capacity in mutants, explains the degenerative phenotype observed in
mutant mice.This article has an associated First Person interview with the first author of the paper.
Soluble molecules including complement components have been shown to facilitate the clearance of dying cells by phagocytes, a process that is important in preventing tissue damage and autoimmunity. ...However, the extent to which complement is involved in this process and the relative contribution of each of the complement activation pathways is not fully understood. We examined the role of complement in the recognition/uptake of apoptotic thymocytes by murine bone marrow‐derived macrophages (BMDM) in vitro using sera from gene‐targeted mice. We found this process to be IgM‐ and complement‐dependent, especially when the apoptotic cell‐to‐BMDM ratio was low, and the level of C3 deposition on apoptotic cells correlated closely with their uptake. The addition of C1q rectified the phagocytic defect seen in the presence of C1q‐deficient serum in vitro but had no effect on the phagocytic defect observed with serum deficient in both IgM antibodies and C1q. Similarly, complement activation by IgM antibodies was essential for in vivo C3 deposition on apoptotic cells and their uptake by peritoneal macrophages. Hence, the efficient uptake of dying cells by BMDM requires IgM antibodies and complement.
PDF
