[Show abstract][Hide abstract] ABSTRACT: Insulin regulates glycaemia, lipogenesis and increases mRNA translation. Cells with reduced eukaryotic initiation factor 6 (eIF6) do not increase translation in response to insulin. The role of insulin-regulated translation is unknown. Here we show that reduction of insulin-regulated translation in mice heterozygous for eIF6 results in normal glycaemia, but less blood cholesterol and triglycerides. eIF6 controls fatty acid synthesis and glycolysis in a cell autonomous fashion. eIF6 acts by exerting translational control of adipogenic transcription factors like C/EBPβ, C/EBPδ and ATF4 that have G/C rich or uORF sequences in their 5' UTR. The outcome of the translational activation by eIF6 is a reshaping of gene expression with increased levels of lipogenic and glycolytic enzymes. Finally, eIF6 levels modulate histone acetylation and amounts of rate-limiting fatty acid synthase (Fasn) mRNA. Since obesity, type 2 diabetes, and cancer require a Fasn-driven lipogenic state, we propose that eIF6 could be a therapeutic target for these diseases.
[Show abstract][Hide abstract] ABSTRACT: Microphthalmos is a rare congenital anomaly characterized by reduced eye size and visual deficits of variable degree. Sporadic and hereditary microphthalmos have been associated with heterozygous mutations in genes fundamental for eye development. Yet, many cases are idiopathic or await the identification of molecular causes. Here we show that haploinsufficiency of Meis1 , which encodes a transcription factor with evolutionarily conserved expression in the embryonic trunk, brain and sensory organs, including the eye, causes microphthalmic traits and visual impairment in adult mice. By combining analysis of Meis1 loss-of-function and conditional Meis1 functional rescue with ChIP-seq and RNA-seq approaches we show that, in contrast to its preferential association with Hox-Pbx BSs in the trunk, Meis1 binds to Hox/Pbx-independent sites during optic cup development. In the eye primordium, Meis1 coordinates, in a dose-dependent manner, retinal proliferation and differentiation by regulating genes responsible for human microphthalmia and components of the Notch signaling pathway. In addition, Meis1 is required for eye patterning by controlling a set of eye territory-specific transcription factors, so that in Meis1−/− embryos boundaries among the different eye territories are shifted or blurred. We propose that Meis1 is at the core of a genetic network implicated in eye patterning/microphthalmia, and represents an additional candidate for syndromic cases of these ocular malformations.
Development 09/2015; 142(17). DOI:10.1242/dev.122176 · 6.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Ubiquitous deletion of thioredoxin reductase 2 (Txnrd2) in mice is embryonically lethal and associated with abnormal heart development, while constitutive, heart-specific Txnrd2 inactivation leads to dilated cardiomyopathy and perinatal death. The significance of Txnrd2 in aging cardiomyocytes, however, has not yet been examined.
Methods and results:
The tamoxifen-inducible heart-specific αMHC-MerCreMer transgene was used to inactivate loxP-flanked Txnrd2 alleles in adult mice. Hearts and isolated mitochondria from aged knockout mice were morphologically and functionally analyzed. Echocardiography revealed a significant increase in left ventricular end-systolic diameters in knockouts. Fractional shortening and ejection fraction were decreased compared with controls. Ultrastructural analysis of cardiomyocytes of aged mice showed mitochondrial degeneration and accumulation of autophagic bodies. A dysregulated autophagic activity was supported by higher levels of lysosome-associated membrane protein 1 (LAMP1), microtubule-associated protein 1A/1B-light chain 3-I (LC3-I), and p62 in knockout hearts. Isolated Txnrd2-deficient mitochondria used less oxygen and tended to produce more reactive oxygen species. Chronic hypoxia inducible factor 1, α subunit stabilization and altered transcriptional and metabolic signatures indicated that energy metabolism is deregulated.
These results imply a novel role of Txnrd2 in sustaining heart function during aging and suggest that Txnrd2 may be a modifier of heart failure.
Journal of the American Heart Association 07/2015; 4(7). DOI:10.1161/JAHA.115.002153 · 4.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: With the advent of modern developmental biology and molecular genetics, the scientific community has generated thousands of newly genetically altered strains of laboratory mice with the aim of elucidating gene function. To this end, a large group of Institutions which form the International Mouse Phenotyping Consortium is generating and phenotyping a knockout mouse strain for each of the ~20,000 protein-coding genes using the mutant ES cell resource produced by the International Knockout Mouse Consortium. These strains are made available to the research community via public repositories, mostly as cryopreserved sperm or embryos. To ensure the quality of this frozen resource there is a requirement that for each strain the frozen sperm/embryos are proven able to produce viable mutant progeny, before the live animal resource is removed from cages. Given the current requirement to generate live pups to demonstrate their mutant genotype, this quality control check necessitates the use and generation of many animals and requires considerable time, cage space, technical and economic resources. Here, we describe a simple and efficient method of genotyping pre-implantation stage blastocysts with significant ethical and economic advantages especially beneficial for current and future large-scale mouse mutagenesis projects.
Transgenic Research 07/2015; 24(5). DOI:10.1007/s11248-015-9897-1 · 2.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: DNase I hypersensitive sites (DHSs) are a hallmark of chromatin regions containing regulatory DNA such as enhancers and promoters; however, the factors affecting the establishment and maintenance of these sites are not fully understood. We now show that HMGN1 and HMGN2, nucleosome-binding proteins that are ubiquitously expressed in vertebrate cells, maintain the DHSs landscape of mouse embryonic fibroblasts (MEFs) synergistically. Loss of one of these HMGN variants led to a compensatory increase of binding of the remaining variant. Genome wide mapping of the DHSs in Hmgn1-/-, Hmgn2-/- and Hmgn1-/-n2-/- MEFs reveals that loss of both, but not a single HMGN variant, leads to significant remodeling of the DHSs landscape, especially at enhancer regions marked by H3K4me1 and H3K27ac. Loss of HMGN variants affects the induced expression of stress responsive genes in MEFs, the transcription profiles of several mouse tissues, and leads to altered phenotypes that are not seen in mice lacking only one variant. We conclude that the compensatory binding of HMGN variants to chromatin maintains the DHSs landscape and the transcription fidelity and is necessary to retain wild type phenotypes. Our study provides insights into mechanisms that maintain regulatory sites in chromatin and into functional compensation among nucleosome binding architectural proteins.
Published by Cold Spring Harbor Laboratory Press.
Genome Research 07/2015; 25(9). DOI:10.1101/gr.192229.115 · 14.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently, several proteins of the extracellular matrix have been characterised as active contributors to allergic airway disease. Microfibrillar-associated protein 4 (MFAP4) is an extracellular matrix protein abundant in the lung, whose biological functions remain poorly understood. In the current study we investigated the role of MFAP4 in experimental allergic asthma.
MFAP4-deficient mice were subjected to alum/ovalbumin and house dust mite induced models of allergic airway disease. In addition, human healthy and asthmatic primary bronchial smooth muscle cell cultures were used to evaluate MFAP4-dependent airway smooth muscle responses.
MFAP4 deficiency attenuated classical hallmarks of asthma, such as eosinophilic inflammation, eotaxin production, airway remodelling and hyperresponsiveness. In wild-type mice, serum MFAP4 was increased after disease development and correlated with local eotaxin levels. MFAP4 was expressed in human bronchial smooth muscle cells and its expression was upregulated in asthmatic cells. Regarding the underlying mechanism, we showed that MFAP4 interacted with integrin αvβ5 and promoted asthmatic bronchial smooth muscle cell proliferation and CCL11 release dependent on phosphatidyloinositol-3-kinase but not extracellular signal-regulated kinase pathway.
MFAP4 promoted the development of asthmatic airway disease in vivo and pro-asthmatic functions of bronchial smooth muscle cells in vitro. Collectively, our results identify MFAP4 as a novel contributor to experimental asthma, acting through modulation of airway smooth muscle cells.
Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
[Show abstract][Hide abstract] ABSTRACT: The IKMC is analyzing multiple phenotypes in adult KO mice for all 20,000+ protein-coding genes. Data are available at the International Mouse Phenotyping Consortium (IMPC) website and KO mice generated can be readily obtained. KO of approximately 30% of genes results in lethality. Body BMD values for males and females provide an initial characterization of skeletal KO phenotypes. High-resolution radiographs provide dysmorphology information, such as digit, spine and craniofacial abnormalities. The MGI Gene Expression Database (GXD) provides RNA expression profiles for multiple tissues, including bone. The JAX Cre Repository contains over 300 Cre tool mouse strains. Mutant mice available are listed on websites of the IMPC, MGI and Mutant Mouse Regional Resource Centers. JAX, Welcome Trust Sanger Institute, MRC Harwell, and German Mouse Clinic websites, among others, often have more comprehensive data than the IMPC website.
These resources provide valuable information to the bone community. For any candidate gene of interest, IMPC data showing lethality, the lack of a bone phenotype, the presence of a bone phenotype, and/or the presence of non-skeletal phenotypes can guide decisions for individual laboratories. The IMPC database currently provides complete phenotype data for 1410 KO mouse genes with phenotyping underway for an additional 703 KOs. The number of genes examined is anticipated to increase rapidly during the next few years. Efforts are underway with BoneKEy to develop an annotated web database focused on IMPC bone data.
Two examples are informative. Confirming published data on Lrrk1 osteopetrotic KO mice, body BMD is elevated in IMPC KO mice. A separate KO mouse, available from JAX and involving a different KO strategy, shows neonatal lethality. Confirming published data on Wnt16 KO mice suffering spontaneous fractures from reduced cortical bone mass, IMPC KO mice also exhibit spontaneous fractures. Wnt16 expression is restricted to bone, testes and the vasculature.
Fourth Joint Meeting of the European Calcified Tissue Society and the International Bone and Mineral Society, Rotterdam, The Netherlands; 04/2015
[Show abstract][Hide abstract] ABSTRACT: Iron is essential for numerous cellular processes. For diagnostic purposes iron-related parameters in patients are assessed by clinical chemical blood analysis including the analysis of ferritin, transferrin and iron levels. Here, we retrospectively evaluated the use of these parameters in the phenotype-driven Munich N-ethyl-N-nitrosourea mouse mutagenesis project for the generation of novel animal models for human diseases. The clinical chemical blood analysis was carried out on more than 10,700 G1 and G3 offspring of chemically mutagenized inbred C3H mice to detect dominant and recessive mutations leading to deviations in the plasma levels of iron-related plasma parameters. We identified animals consistently exhibiting altered plasma ferritin or transferrin values. Transmission of the phenotypic deviations to the subsequent generations led to the successful establishment of three mutant lines with increased plasma ferritin levels. For two of these lines the causative mutations were identified in the Fth1gene and the Ireb2 gene, respectively. Thus, novel mouse models for the functional analysis of iron homeostasis were established by a phenotype-driven screen for mutant mice.
[Show abstract][Hide abstract] ABSTRACT: A significant challenge facing high-throughput phenotyping of in-vivo knockout mice is ensuring phenotype calls are robust and reliable. Central to this problem is selecting an appropriate statistical analysis that models both the experimental design (the workflow and the way control mice are selected for comparison with knockout animals) and the sources of variation. Recently we proposed a mixed model suitable for small batch-oriented studies, where controls are not phenotyped concurrently with mutants. Here we evaluate this method both for its sensitivity to detect phenotypic effects and to control false positives, across a range of workflows used at mouse phenotyping centers. We found the sensitivity and control of false positives depend on the workflow. We show that the phenotypes in control mice fluctuate unexpectedly between batches and this can cause the false positive rate of phenotype calls to be inflated when only a small number of batches are tested, when the effect of knockout becomes confounded with temporal fluctuations in control mice. This effect was observed in both behavioural and physiological assays. Based on this analysis, we recommend two approaches (workflow and accompanying control strategy) and associated analyses, which would be robust, for use in high-throughput phenotyping pipelines. Our results show the importance in modelling all sources of variability in high-throughput phenotyping studies.
PLoS ONE 10/2014; 9(10):e111239. DOI:10.1371/journal.pone.0111239 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
Type I Bartter syndrome is a recessive human nephropathy caused by loss-of-function mutations in the SLC12A1 gene coding for the Na+-K+-2Cl¿ cotransporter NKCC2. We recently established the mutant mouse line Slc12a1 I299F exhibiting kidney defects highly similar to the late-onset manifestation of this hereditary human disease. Besides the kidney defects, low blood pressure and osteopenia were revealed in the homozygous mutant mice which were also described in humans. Beside its strong expression in the kidney, NKCC2 has been also shown to be expressed in other tissues in rodents i.e. the gastrointestinal tract, pancreatic beta cells, and specific compartments of the ear, nasal tissue and eye.ResultsTo examine if, besides kidney defects, further organ systems and/or metabolic pathways are affected by the Slc12a1 I299F mutation as primary or secondary effects, we describe a standardized, systemic phenotypic analysis of the mutant mouse line Slc12a1 I299F in the German Mouse Clinic. Slc12a1 I299F homozygous mutant mice and Slc12a1 I299F heterozygous mutant littermates as controls were tested at the age of 4¿6 months. Beside the already published changes in blood pressure and bone metabolism, a significantly lower body weight and fat content were found as new phenotypes for Slc12a1 I299F homozygous mutant mice. Small additional effects included a mild erythropenic anemia in homozygous mutant males as well as a slight hyperalgesia in homozygous mutant females. For other functions, such as immunology, lung function and neurology, no distinct alterations were observed.Conclusions
In this systemic analysis no clear primary effects of the Slc12a1 I299F mutation appeared for the organs other than the kidneys where Slc12a1 expression has been described. On the other hand, long-term effects additional and/or secondary to the kidney lesions might also appear in humans harboring SLC12A1 mutations.
[Show abstract][Hide abstract] ABSTRACT: Combined use of metformin and a sodium glucose cotransporter 2 inhibitor (SGLT2I) is a promising treatment strategy for type 2 diabetes. The mechanism by which combination treatment provides better glycemic control than metformin or SGLT2I monotherapy remains elusive.Therefore, we investigated the physiological mechanism, by which both compounds lower blood glucose concentrations in diabetic mice.We compared the potential of metformin and the SGLT2I AVE2268 alone or in combination to mitigate hyperglycemia and modulate glucose fluxes in diabetic db/db and Tallyho/JngJ mice.SGLT2I treatment alone elicited a rapid decline in circulating blood glucose levels, which appeared to induce endogenous glucose production. Supplementation of metformin dampened this counter-response and, therefore, combination therapy more efficiently maintained glycemic control. Finally, combination treatment blunted postprandial glucose excursions and improved HbA1c levels within two weeks.Taken together, we conclude that co-application of metformin enhances the glucose-lowering actions of SGLT2I by restraining endogenous glucose production what may provide long-term improvement of glycemic control in type 2 diabetic patients.
[Show abstract][Hide abstract] ABSTRACT: A combinatory approach using metabolomics and gut microbiome analysis techniques was performed to unravel the nature and specificity of metabolic profiles related to gut ecology in obesity. This study focused on gut and liver metabolomics of two different mouse strains, the C57BL/6J (C57J) and the C57BL/6N (C57N) fed with high-fat diet (HFD) for 3 weeks, causing diet-induced obesity in C57N, but not in C57J mice. Furthermore, a 16S-ribosomal RNA comparative sequence analysis using 454 pyrosequencing detected significant differences between the microbiome of the two strains on phylum level for Firmicutes, Deferribacteres and Proteobacteria that propose an essential role of the microbiome in obesity susceptibility. Gut microbial and liver metabolomics were followed by a combinatory approach using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and ultra performance liquid chromatography time of tlight MS/MS with subsequent multivariate statistical analysis, revealing distinctive host and microbial metabolome patterns between the C57J and the C57N strain. Many taurine-conjugated bile acids (TBAs) were significantly elevated in the cecum and decreased in liver samples from the C57J phenotype likely displaying different energy utilization behavior by the bacterial community and the host. Furthermore, several metabolite groups could specifically be associated with the C57N phenotype involving fatty acids, eicosanoids and urobilinoids. The mass differences based metabolite network approach enabled to extend the range of known metabolites to important bile acids (BAs) and novel taurine conjugates specific for both strains. In summary, our study showed clear alterations of the metabolome in the gastrointestinal tract and liver within a HFD-induced obesity mouse model in relation to the host-microbial nutritional adaptation.The ISME Journal advance online publication, 6 June 2014; doi:10.1038/ismej.2014.79.
The ISME Journal 06/2014; 8(12). DOI:10.1038/ismej.2014.79 · 9.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Emerging technologies based on mass spectrometry or nuclear magnetic resonance enable the monitoring of hundreds of small metabolites from tissues or body fluids. Profiling of metabolites can help elucidate causal pathways linking established genetic variants to known disease risk factors such as blood lipid traits.
We applied statistical methodology to dissect causal relationships between single nucleotide polymorphisms, metabolite concentrations and serum lipid traits, focusing on 95 genetic loci reproducibly associated with the four main serum lipids (total-, low-density lipoprotein- and high-density lipoprotein- cholesterol and triglycerides). The dataset used included 2,973 individuals from two independent population-based cohorts with data for 151 small molecule metabolites and four main serum lipids. Three statistical approaches, namely conditional analysis, Mendelian Randomization and Structural Equation Modelling, were compared to investigate causal relationship at sets of a single nucleotide polymorphism, a metabolite and a lipid trait associated with one another.
A subset of three lipid-associated loci (FADS1, GCKR and LPA) have a statistically significant association with at least one main lipid and one metabolite concentration in our data, defining a total of 38 cross-associated sets of a single nucleotide polymorphism, a metabolite and a lipid trait. Structural Equation Modelling provided sufficient discrimination to indicate that the association of a single nucleotide polymorphism with a lipid trait was mediated through a metabolite at 15 of the 38 sets, and involving variants at the FADS1 and GCKR loci.
These data provide a framework for evaluating the causal role of components of the metabolome (or other intermediate factors) in mediating the association between established genetic variants and diseases or traits.
Genome Medicine 03/2014; 6(3):25. DOI:10.1186/gm542 · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies (GWAS) identified the MEIS1 locus for Restless Legs Syndrome (RLS), but causal single nucleotide polymorphisms (SNPs) and their functional relevance remain unknown. This locus contains a large number of highly conserved noncoding regions (HCNRs) potentially functioning as cis-regulatory modules. We analyzed these HCNRs for allele-dependent enhancer activity in zebrafish and mice and found that the risk allele of the lead SNP rs12469063 reduces enhancer activity in the Meis1 expression domain of the murine embryonic ganglionic eminences (GE). CREB1 binds this enhancer and rs12469063 affects its binding in vitro. In addition, MEIS1 target genes suggest a role in the specification of neuronal progenitors in the GE, and heterozygous Meis1-deficient mice exhibit hyperactivity, resembling the RLS phenotype. Thus, in vivo and in vitro analysis of a common SNP with small effect size showed allele-dependent function in the prospective basal ganglia representing the first neurodevelopmental region implicated in RLS.
Genome Research 03/2014; 24(4). DOI:10.1101/gr.166751.113 · 14.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Loss-of-function mutations protective against human disease provide in vivo validation of therapeutic targets, but none have yet been described for type 2 diabetes (T2D). Through sequencing or genotyping of ~150,000 individuals across 5 ancestry groups, we identified 12 rare protein-truncating variants in SLC30A8, which encodes an islet zinc transporter (ZnT8) and harbors a common variant (p.Trp325Arg) associated with T2D risk and glucose and proinsulin levels. Collectively, carriers of protein-truncating variants had 65% reduced T2D risk (P = 1.7 × 10−6), and non-diabetic Icelandic carriers of a frameshift variant (p.Lys34Serfs*50) demonstrated reduced glucose levels (−0.17 s.d., P = 4.6 × 10−4). The two most common protein-truncating variants (p.Arg138* and p.Lys34Serfs*50) individually associate with T2D protection and encode unstable ZnT8 proteins. Previous functional study of SLC30A8 suggested that reduced zinc transport increases T2D risk, and phenotypic heterogeneity was observed in mouse Slc30a8 knockouts. In contrast, loss-of-function mutations in humans provide strong evidence that SLC30A8 haploinsufficiency protects against T2D, suggesting ZnT8 inhibition as a therapeutic strategy in T2D prevention.