Thomas Kolbe - Academia.edu (original) (raw)

Papers by Thomas Kolbe

Nature medicine, 2011

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that regulate g... more Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that regulate genes involved in energy metabolism and inflammation. For biological activity, PPARs require cognate lipid ligands, heterodimerization with retinoic X receptors, and coactivation by PPAR-γ coactivator-1α or PPAR-γ coactivator-1β (PGC-1α or PGC-1β, encoded by Ppargc1a and Ppargc1b, respectively). Here we show that lipolysis of cellular triglycerides by adipose triglyceride lipase (patatin-like phospholipase domain containing protein 2, encoded by Pnpla2; hereafter referred to as Atgl) generates essential mediator(s) involved in the generation of lipid ligands for PPAR activation. Atgl deficiency in mice decreases mRNA levels of PPAR-α and PPAR-δ target genes. In the heart, this leads to decreased PGC-1α and PGC-1β expression and severely disrupted mitochondrial substrate oxidation and respiration; this is followed by excessive lipid accumulation, cardiac insufficiency and lethal cardiomyop...

Immunity, Oct 17, 2008

The innate inflammatory immune response must be tightly controlled to avoid damage to the host. H... more The innate inflammatory immune response must be tightly controlled to avoid damage to the host. Here, we showed that the tuberous sclerosis complex-mammalian target of rapamycin (TSC-mTOR) pathway regulated inflammatory responses after bacterial stimulation in monocytes, macrophages, and primary dendritic cells. Inhibition of mTOR by rapamycin promoted production of proinflammatory cytokines via the transcription factor NF-kB but blocked the release of interleukin-10 via the transcription factor STAT3. Conversely, deletion of TSC2, the key negative regulator of mTOR, diminished NF-kB but enhanced STAT3 activity and reversed this proinflammatory cytokine shift. Rapamycin-hyperactivated monocytes displayed a strong T helper 1 (Th1) cell-and Th17 cell-polarizing potency. Inhibition of mTOR in vivo regulated the inflammatory response and protected genetically susceptible mice against lethal Listeria monocytogenes infection. These data identify the TSC2-mTOR pathway as a key regulator of innate immune homeostasis with broad clinical implications for infectious and autoimmune diseases, vaccination, cancer, and transplantation.

Cytokine, 2011

Tyrosine kinase 2 (Tyk2) is one of four mammalian Janus kinases (Jaks) that are specifically enga... more Tyrosine kinase 2 (Tyk2) is one of four mammalian Janus kinases (Jaks) that are specifically engaged by a variety of cytokine receptors. We and others previously identified cell type-specific functions of Tyk2. Here we present the generation of conditional Tyk2 knockout mice (Tyk2fl/fl). We show the integrity of the floxed Tyk2 allele and successful deletion when Tyk2fl/fl mice were crossed with transgenic mice expressing Cre recombinase either under the Lck, CD11c or LysM promoter. We found recently, that Tyk2 is indispensable for splenic interleukin-17 (IL-17) production fol-

Lab Animal, 2015

Superovulation is often used to increase the number of oocytes that can be collected from donor f... more Superovulation is often used to increase the number of oocytes that can be collected from donor females for in vitro fertilization. Donor age can affect the quantity and quality of oocytes produced during superovulation, and in some strains of mice juvenile females are optimal donors. The authors reviewed donor and oocyte records from a breeding program to evaluate how donor age affects the number and fertilization efficiency of oocytes collected from C57BL/6J mice. Generally fewer oocytes per donor were collected from females aged &amp;amp;amp;gt; 32 d than from females aged 21-32 d. Fertilization efficiency of oocytes generally declined with donor age when oocytes were fertilized with fresh or with stored sperm. These findings suggest that the use of younger C57BL/6J donors, instead of older donors, can reduce the number of donors needed for IVF procedures.

ALTEX, 2015

Fluorescence proteins have been useful as genetic reporters for a wide range of applications in b... more Fluorescence proteins have been useful as genetic reporters for a wide range of applications in biomedical research and are frequently used for the analysis of transgene activity. Here, we show that expression levels of the ubiquitously expressed fluorescent proteins eGFP, mCherry, and tdTomato can be measured in transgenic mouse lines with random or targeted integrations. We identified the tail of the mouse as the tissue best suited for quantifying fluorescence intensity and show that expression levels in the tail correlate with gene dose. This allows for instant non-invasive determination of the genetic condition at the transgenic locus (hemizygous/heterozygous and homozygous), while simultaneously providing an objective comparison for transgene expression levels among different mouse lines. In summary, we demonstrate for the first time that the gene dose of a ubiquitously expressed fluorescence reporter can be reliably quantified and directly linked to the genotype of transgenic ...

eLife, 2015

Dangerous damage to mitochondrial DNA (mtDNA) can be ameliorated during mammalian development thr... more Dangerous damage to mitochondrial DNA (mtDNA) can be ameliorated during mammalian development through a highly debated mechanism called the mtDNA bottleneck. Uncertainty surrounding this process limits our ability to address inherited mtDNA diseases. We produce a new, physically motivated, generalisable theoretical model for mtDNA populations during development, allowing the first statistical comparison of proposed bottleneck mechanisms. Using approximate Bayesian computation and mouse data, we find most statistical support for a combination of binomial partitioning of mtDNAs at cell divisions and random mtDNA turnover, meaning that the debated exact magnitude of mtDNA copy number depletion is flexible. New experimental measurements from a wild-derived mtDNA pairing in mice confirm the theoretical predictions of this model. We analytically solve a mathematical description of this mechanism, computing probabilities of mtDNA disease onset, efficacy of clinical sampling strategies, and effects of potential dynamic interventions, thus developing a quantitative and experimentally-supported stochastic theory of the bottleneck.

Surgical endoscopy, 2010

The number of mesh-based therapies of inguinal hernias is increasing compared with the classical ... more The number of mesh-based therapies of inguinal hernias is increasing compared with the classical suture techniques such as Shouldice and Bassini. Many different types of meshes with regard to material, pore size and surface coating are available. A recently offered mesh (Parietene Progrip) combines the properties of a standard lightweight polypropylene mesh with a whole surface fixation by incorporation of micro hooks. Therefore, additional fixation elements such as screws, tacks or clips become redundant when using this material. However, in treated male patients the micro hooks will also come into contact with the ductus deferens. As the sensitivity of this structure is known, the question arises of whether this new self-gripping mesh might damage susceptible tissue layers and impair male fertility. Two different meshes, a standard lightweight polypropylene mesh (Parietene-Light) and a new self-gripping polypropylene mesh (Parietene Progrip) with absorbable micro hooks were wrappe...

Methods in molecular biology (Clifton, N.J.), 2015

Heteroplasmic mice represent a valuable tool to study the segregation of different mtDNA haplotyp... more Heteroplasmic mice represent a valuable tool to study the segregation of different mtDNA haplotypes (mtDNAs with differing alleles) in vivo against a defined nuclear background. We describe two methods for the creation of such models, differing in the resulting initial heteroplasmy levels: (1) transfer of ooplasm and (2) fusion of two blastomeres. These methods result in typical heteroplasmy of 5 % and 50 % donor mtDNA, respectively. The choice of method depends on the aim of the study. By means of breeding, even 100 % donor mtDNA can be reached within few generations.

Oncotarget, 2011

Multiparous Stat1-/- mice spontaneously develop mammary tumors with increased incidence: at an av... more Multiparous Stat1-/- mice spontaneously develop mammary tumors with increased incidence: at an average age of 12 months, 55% of the animals suffer from mammary cancer, although the histopathology is heterogeneous. We consistently observed mosaic expression or down-regulation of STAT1 protein in wild-type mammary cancer evolving in the control group. Transplantation experiments show that tumorigenesis in Stat1-/- mice is partially influenced by impaired CTL mediated tumor surveillance. Additionally, STAT1 exerts an intrinsic tumor suppressing role by controlling and blocking proliferation of the mammary epithelium. Loss of STAT1 in epithelial cells enhances cell growth in both transformed and primary cells. The increased proliferative capacity leads to the loss of structured acini formation in 3D-cultures. Analogous effects were observed when Irf1-/- epithelial cells were used. Accordingly, the rate of mammary intraepithelial neoplasias (MINs) is increased in Stat1-/- animals: MINs r...

BMC biotechnology, 2006

The signal transducer and activator of transcription (STAT) family of transcription factors media... more The signal transducer and activator of transcription (STAT) family of transcription factors mediates a variety of cytokine dependent gene regulations. STAT1 has been mainly characterized by its role in interferon (IFN) type I and II signaling and STAT1 deficiency leads to high susceptibility to several pathogens. For fine-tuned analysis of STAT1 function we established a dimerizer-inducible system for STAT1 expression in vitro and in vivo. The functionality of the dimerizer-induced STAT1 system is demonstrated in vitro in mouse embryonic fibroblasts and embryonic stem cells. We show that this two-vector based system is highly inducible and does not show any STAT1 expression in the absence of the inducer. Reconstitution of STAT1 deficient cells with inducible STAT1 restores IFNgamma-mediated gene induction, antiviral responses and STAT1 activation remains dependent on cytokine stimulation. STAT1 expression is induced rapidly upon addition of dimerizer and expression levels can be reg...

Cell Reports, 2014

The dynamics by which mitochondrial DNA (mtDNA) evolves within organisms are still poorly underst... more The dynamics by which mitochondrial DNA (mtDNA) evolves within organisms are still poorly understood, despite the fact that inheritance and proliferation of mutated mtDNA cause fatal and incurable diseases. When two mtDNA haplotypes are present in a cell, it is usually assumed that segregation (the proliferation of one haplotype over another) is negligible. We challenge this assumption by showing that segregation depends on the genetic distance between haplotypes. We provide evidence by creating four mouse models containing mtDNA haplotype pairs of varying diversity. We find tissue-specific segregation in all models over a wide range of tissues. Key findings are segregation in postmitotic tissues (important for disease models) and segregation covering all developmental stages from prenatal to old age. We identify four dynamic regimes of mtDNA segregation. Our findings suggest potential complications for therapies in human populations: we propose ''haplotype matching'' as an approach to avoid these issues.

Reproduction, Fertility and Development, 2014

Superovulation of mice is routinely used to increase the number of obtainable ova per female. Bec... more Superovulation of mice is routinely used to increase the number of obtainable ova per female. Because of the better outcome, prepubescent females are preferentially used. Here, we provide results of the impact of superovulation and mating on the wellbeing of juvenile compared with adult C57BL/6N mice. Two groups of mice (3-4 weeks vs 7-8 weeks old) were superovulated and mated. Observation of mating behaviour showed that reluctant adult females tended to fight the male's approach, whereas juveniles preferred to take flight. Faeces were collected daily for the analysis of stress hormones. There was no difference in the levels of glucocorticoid metabolites either between age groups or between treated animals and their controls. Histology after mating revealed intact vaginal mucosa without any detectable lesions in all animals regardless of age. In contrast to adults, almost all juveniles were synchronised in oestrus and produced significantly more ova. Taken together, our results reveal no increased welfare problem from using juvenile mice for superovulation and mating. Considering the higher yield of fertilisable oocytes and zygotes, it is advisable to use C57BL/6N prepubescent mice in order to reduce the number of donor females required.

Transgenic Research, 2014

Tyrosine kinase 2 (TYK2) has a pivotal role in immunity to infection and tumor surveillance. It i... more Tyrosine kinase 2 (TYK2) has a pivotal role in immunity to infection and tumor surveillance. It is associated with several cytokine receptor chains including type I interferon (IFN) receptor 1 (IFNAR1), interleukin-(IL-) 12 receptor beta 1 (IL-12Rb1) and IL-10R2. We have generated a mouse with a conditional Tyk2 null allele and proved integrity of the conditional Tyk2 locus. TYK2 was successfully removed by the use of ubiquitous and tissue-specific Cre-expressing mouse strains. Myeloid TYK2 was found to critically contribute to the defense against murine cytomegalovirus. Ubiquitous TYK2 ablation severely impaired tumor immunosurveillance, while deletion in myeloid, dendritic or T cells alone showed no effect. The conditional Tyk2 mouse strain will be instrumental to further dissect TYK2 functions in infection, inflammation and cancer.

Transgenic Research, 2012

are key cytokines in the innate immune response that also bridge the gap to adaptive immunity. Si... more are key cytokines in the innate immune response that also bridge the gap to adaptive immunity. Signaling upon stimulation by IFN type I, II and III is mediated by the Jak-Stat pathway. STAT1 is activated by all three IFN receptor complexes and absence of STAT1 from mice increases their susceptibility to pathogens. In addition, depending on the setting, STAT1 can act as tumor suppressor or oncogene. Here we report the generation and detailed functional characterization of a conditional Stat1 knockout mouse. We show the integrity of the conditional Stat1 locus and report successful in vivo deletion by means of a ubiquitous and a tissue-specific Cre recombinase. The conditional Stat1 null allele represents an important tool for identifying novel and cell-autonomous STAT1 functions in infection and cancer.

Surgical Endoscopy, 2010

Background Mesh tearoff from the tissue is the most common reason for hernia recurrence after her... more Background Mesh tearoff from the tissue is the most common reason for hernia recurrence after hernia surgery involving the use of a synthetic mesh. Various fixation systems were critically compared in terms of their retention strength and the formation of adhesions. Methods In a prospective study with 25 Sprague-Dawley rats, two pieces of Parietex composite meshes measuring 2 9 3 cm were fixed intraperitoneally in a paramedian location. The randomized mesh fixation groups included transfascial fixed suture, ProTack, AbsorbaTack, and I-Clip. Of the 25 rats, 12 were killed and analyzed 1 week after implantation, with the remaining 13 rats killed and analyzed after 2 months. Adhesions observed at the time of mesh removal were measured according to an adhesion scoring system, and the fixation strengths of the individual fixation systems were tested. Additionally, the foreign body reaction to the mesh and fixation systems was measured as well as their potential degradation. Results After 1 week, the retention strength of transfascial fixed suture was significantly higher (8.7 N/cm 2 ) than that of ProTack (5.6 N/cm 2 ) or AbsorbaTack (5.7 N/cm 2 ). After 2 months, the retention strength had increased to 13.2 N/cm 2 in the transfascial fixed suture group, which was significantly higher than in the ProTack (9.7 N/cm 2 )or AbsorbaTack (8.7 N/cm 2 ) groups. In contrast, the mesh could be fixed with the I-Clip only in 56% of the cases, and then achieved rather poor retention strength. Adhesion was significantly greater in the ProTack group than in any of the other groups (p \ 0.001). At 2 months, scanning electron microscopy showed only marginal degradation of the absorbable elements. Conclusions Suture fixation led to satisfactory attachment of the prosthesis. Additional widespread anchorage of the mesh was achieved with ProTack or AbsorbaTack. The feasibility and retention strength of the I-Clip were poor.

Shock, 2007

Previously, we have shown that the JakYsignal transducer and activator of transcription signaling... more Previously, we have shown that the JakYsignal transducer and activator of transcription signaling constituents Tyk2 and STAT1 play a role in the development of multiple organ failure during endotoxin shock. Here, we report that Tyk2 and STAT1 contribute to death caused by intestinal I/R injury. Tyk2-and STAT1-deficient mice showed increased survival to I/R because their intestines were protected from gross histomorphological tissue destruction and neutrophil infiltration. On the molecular level, the reduced ischemia induced inflammatory response in mutant versus wildtype mice was accompanied by an impaired up-regulation of the adhesion molecules P-selectin and intercellular adhesion molecule 1 and of the matrix metalloproteinases (MMPs) MMP-2, MMP-9, and MMP-14 in the reperfused intestine. In conclusion, this study demonstrates for the first time that Tyk2 or STAT1 promote intestinal I/R-induced shock based on a deregulated local inflammatory response and a destruction of the gut intestinal barrier.

PROTEOMICS, 2008

Tyrosine kinase 2 (Tyk2) belongs to the Janus kinase (Jak) family and is involved in signalling v... more Tyrosine kinase 2 (Tyk2) belongs to the Janus kinase (Jak) family and is involved in signalling via a number of cytokines. Tyk2-deficient mice are highly resistant to lipopolysaccharide (LPS)-induced endotoxin shock. Macrophages are key players in the pathogenesis of endotoxin shock and, accordingly, defects in the LPS responses of Tyk2(-/-) macrophages have been reported. In the present study, the molecular role of Tyk2 is investigated in more detail using a proteomics approach. 2-D DIGE was applied to compare protein patterns from wild-type and Tyk2(-/-) macrophages and revealed significant differences in protein expression patterns between the genotypes before and after LPS treatment. Twenty-one proteins deriving from 25 differentially expressed spots were identified by MALDI/ESI MS. Among them, we show for N-myc interactor that its mRNA transcription/stability is positively influenced by Tyk2. In contrast, LPS-induced expression of plasminogen activator 2 protein but not mRNA is strongly enhanced in the absence of Tyk2. Our data furthermore suggest an influence of Tyk2 on the subcellular distribution of elongation factor 2 and on LPS-mediated changes in the peroxiredoxin 1 spot pattern. Thus, our results imply regulatory roles of Tyk2 at multiple levels and establish novel connections between Tyk2 and several cellular proteins.

Proceedings of the National Academy of Sciences, 2008

Transcriptional pathways controlling the development of CD44 hi memory phenotype (MP) T cells wit... more Transcriptional pathways controlling the development of CD44 hi memory phenotype (MP) T cells with ''innate-like'' functions are not well understood. Here we show that the BTB (bric-a-brac, tramtrack, broad complex) domain-containing protein promyelocytic leukemia zinc finger (PLZF) is expressed in CD44 hi , but not in CD44 lo , CD4 ؉ T cells. Transgenic expression of PLZF during T cell development and in CD4 ؉ and CD8 ؉ T cells induced a T cell intrinsic program leading to an increase in peripheral CD44 hi MP CD4 ؉ and CD8 ؉ T cells and a corresponding decrease of naïve CD44 lo T cells.

Proceedings of the National Academy of Sciences, 2005

Human coronavirus (HCoV) 229E is a group 1 coronavirus and is specific to humans. So far, no anim... more Human coronavirus (HCoV) 229E is a group 1 coronavirus and is specific to humans. So far, no animal model is available to study the pathogenesis of infection by HCoV-229E. We show here that the expression of aminopeptidase N (APN, also termed CD13), the receptor for HCoV-229E, is required but not sufficient to confer susceptibility in vivo. HCoV-229E infection was facilitated by crossing APN transgenic mice into signal transducers and activators of transcription (Stat) 1 null mice and by adaptation of HCoV-229E to grow in primary APN transgenic, Stat1 null fibroblasts. Double transgenic mice allow the study of human coronavirus group 1 infections in an animal model, in particular, viral tropism, replication, recombination, and spread in an immunocompromised situation. Furthermore, these mice provide an important tool for the evaluation of biosafety and efficacy of coronavirus-based vectors.