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Thomas Rülicke

Publications and source records attributed to Thomas Rülicke.

17 recordsLinked to original sources
PubMed2006

A time- and dose-dependent STAT1 expression system.

BACKGROUND: 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. RESULTS: 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 regulated in a dose-dependent manner. Furthermore we show that in transgenic mice STAT1 can be induced upon stimulation with the dimerizer, although only at low levels. CONCLUSION: These results prove that the dimerizer-induced system is a powerful tool for STAT1 analysis in vitro and provide evidence that the system is suitable for the use in transgenic mice. To our knowledge this is the first report for inducible STAT1 expression in a time- and dose-dependent manner.

Animals↗
PubMed2006

Functional CD8+ but not CD4+ T cell responses develop independent of thymic epithelial MHC.

The role of nonthymic epithelial (non-TE) MHC in T cell repertoire selection remains controversial. To analyze the relative roles of thymic epithelial (TE) and non-TE MHC in T cell repertoire selection, we have generated tetraparental aggregation chimeras (B6-nude<=>BALB/c and B6<=>BALB/c-nude) harboring T and B cells from both parents, whereas TE cells originated exclusively from the non-nude donor. These chimeras mounted protective virus-specific TE and non-TE MHC-restricted T cell responses. To further evaluate whether non-TE MHC alone was sufficient to generate a functional T cell repertoire, we generated tetraparental aggregation chimeras lacking MHC class II (B6-nude<=>MHCII(-/-)) or both MHC molecules (B6-nude<=>MHCI(-/-)II(-/-)) on TE cells, but not on cells of B6-nude origin. Chimeras with MHC-deficient TE cells mounted functional virus-specific CD8+ but not CD4+ T cell responses. Thus, maturation of functional CD4+ T cell responses required MHC class II on thymic epithelium, whereas CD8+ T cells matured in the absence of TE MHC.

Animals↗
PubMed2006

No transuterine migration of fertilised ova after unilateral embryo transfer in mice.

Transuterine migration is the passage of fertilised ova from one uterine horn into the other. The phenomenon has been described for animals of different species with a bicornuate type of uterus. Whether or not it occurs in rodents is questionable, but could have an impact on the way embryo transfers are carried out, i.e. unilaterally or bilaterally. The aim of this study was to examine the occurrence of transuterine migrations in nulliparous and multiparous mice after unilateral embryo transfer. Sixteen two-cell embryos were transferred into either the left or the right oviduct of mice with different genetic origin. With the exception of one reabsorption site in the opposite uterine horn, we never found evidence for the occurrence of transuterine migration. This is also true for embryo transfers carried out after parturition of the surrogate mother. Even the successful development of up to 13 embryos in one uterine horn did not result in transmigration but may be the reason for the widespread assumption that transuterine migration occurs after unilateral embryo transfers. The separation of the uterine body and the prevaginal portion of the uterine cervix into two canals by a septum seems to be the main reason for the absence of successful transuterine migration in mice.

Animals↗
PubMed2006

Peroxiredoxin 6 is a potent cytoprotective enzyme in the epidermis.

Peroxiredoxin 6 is an enzyme that detoxifies hydrogen peroxide and various organic peroxides. In previous studies we found strongly increased expression of peroxiredoxin 6 in the hyperproliferative epidermis of wounded and psoriatic skin, suggesting a role of this enzyme in epidermal homeostasis. To address this question, we generated transgenic mice overexpressing peroxiredoxin 6 in the epidermis. Cultured keratinocytes from transgenic mice showed enhanced resistance to the toxicity of various agents that induce oxidative stress. However, overexpression of peroxiredoxin 6 did not affect skin morphogenesis or homeostasis. On skin injury, enhancement of wound closure was observed in aged animals. Most importantly, peroxiredoxin 6 overexpression strongly reduced the number of apoptotic cells after UVA or UVB irradiation. These findings demonstrate that peroxiredoxin 6 protects keratinocytes from cell death induced by reactive oxygen species in vitro and in vivo, suggesting that activation of this enzyme could be a novel strategy for skin protection under stress conditions.

Animals↗
PubMed2005

Astrogliosis in epilepsy leads to overexpression of adenosine kinase, resulting in seizure aggravation.

Adenosine kinase (ADK) is considered to be the key regulator of the brain's endogenous anticonvulsant, adenosine. In adult brain, ADK is primarily expressed in a subpopulation of astrocytes and striking upregulation of ADK in these cells has been associated with astrogliosis after kainic acid-induced status epilepticus (KASE) in the kainic acid mouse model of temporal lobe epilepsy. To investigate the causal relationship between KASE-induced astrogliosis, upregulation of ADK and seizure activity, we have developed a novel mouse model [the Adktm1(-/-)-Tg(UbiAdk) mouse] lacking the endogenous astrocytic enzyme due to a targeted disruption of the endogenous gene, but containing an Adk transgene under the control of a human ubiquitin promoter. Mutant Adktm1(-/-)-Tg(UbiAdk) mice were characterized by increased brain ADK activity and constitutive overexpression of transgenic ADK throughout the brain, with particularly high levels in hippocampal pyramidal neurons. This ADK overexpression was associated with increased baseline levels of locomotion. Most importantly, two-thirds of the mutant mice analysed exhibited spontaneous seizure activity in the hippocampus and cortex. This was the direct consequence of transgene expression, since this seizure activity could be prevented by systemic application of the ADK inhibitor 5-iodotubercidin. Intrahippocampal injection of kainate in the mutant mice resulted in astrogliosis to the same extent as that observed in wild-type mice despite the absence of endogenous astrocytic ADK. Therefore, KASE-induced upregulation of endogenous ADK in wild-type mice is a consequence of astrogliosis. However, seizures in kainic acid-injected mutants displayed increased intra-ictal spike frequency compared with wild-type mice, indicating that, once epilepsy is established, increased levels of ADK aggravate seizure severity. We therefore conclude that therapeutic strategies that augment the adenosine system after astrogliosis-induced upregulation of ADK constitute a neurochemical rationale for the prevention of seizures in epilepsy.

Adenosine Kinase↗
PubMed2005

Experimental autoimmune encephalomyelitis repressed by microglial paralysis.

Although microglial activation occurs in inflammatory, degenerative and neoplastic central nervous system (CNS) disorders, its role in pathogenesis is unclear. We studied this question by generating CD11b-HSVTK transgenic mice, which express herpes simplex thymidine kinase in macrophages and microglia. Ganciclovir treatment of organotypic brain slice cultures derived from CD11b-HSVTK mice abolished microglial release of nitrite, proinflammatory cytokines and chemokines. Systemic ganciclovir administration to CD11b-HSVTK mice elicited hematopoietic toxicity, which was prevented by transfer of wild-type bone marrow. In bone marrow chimeras, ganciclovir blocked microglial activation in the facial nucleus upon axotomy and repressed the development of experimental autoimmune encephalomyelitis. We conclude that microglial paralysis inhibits the development and maintenance of inflammatory CNS lesions. The microglial compartment thus provides a potential therapeutic target in inflammatory CNS disorders. These results validate CD11b-HSVTK mice as a tool to study the impact of microglial activation on CNS diseases in vivo.

Animals↗
PubMed2005

Activin controls skin morphogenesis and wound repair predominantly via stromal cells and in a concentration-dependent manner via keratinocytes.

The transforming growth factor-beta family member activin is a potent regulator of skin morphogenesis and repair. Transgenic mice overexpressing activin in keratinocytes display epidermal hyper-thickening and dermal fibrosis in normal skin and enhanced granulation tissue formation after wounding. Mice overexpressing the secreted activin antagonist follistatin, however, have the opposite wound-healing phenotype. To determine whether activin affects skin morphogenesis and repair via activation of keratinocytes and/or stromal cells, we generated transgenic mice expressing a dominant-negative activin receptor IB mutant (dnActRIB) in keratinocytes. The architecture of adult skin was unaltered in these mice, but delays were observed in postnatal pelage hair follicle morphogenesis and in the first catagen-telogen transformation of hair follicles. Although dnActRIB-transgenic mice showed slightly delayed wound re-epithelialization after skin injury, the strong inhibition of granulation tissue formation seen in follistatin-transgenic mice was not observed. Therefore, although endogenous activin appeared to affect skin morphogenesis and repair predominantly via stromal cells, overexpressed activin strongly affected the epidermis. The epidermal phenotype of activin-overexpressing mice was partially rescued by breeding these animals with dnActRIB-transgenic mice. These results demonstrate that activin affects both stromal cells and keratinocytes in normal and wounded skin and that the effect on keratinocytes is dose-dependent in vivo.

Activins↗
PubMed2004

Activities of the matrix metalloproteinase stromelysin-2 (MMP-10) in matrix degradation and keratinocyte organization in wounded skin.

The matrix metalloproteinase stromelysin-2 is expressed in keratinocytes of the epithelial tongue of skin wounds, suggesting a role in keratinocyte migration. Here, we show that stromelysin-2 enhances migration of cultured keratinocytes. To gain insight into the in vivo activities of stromelysin-2 in epithelial repair, we generated transgenic mice expressing a constitutively active stromelysin-2 mutant in keratinocytes. These animals had no alterations in skin architecture, and the healing rate of skin wounds was normal. Histologically, however, we found abnormalities in the organization of the wound epithelium. Keratinocytes at the migrating epidermal tip were scattered in most sections of mice with high expression level, and there was a reduced deposition of new matrix. In particular, the staining pattern of laminin-5 at the wound site was altered. This may be due to proteolytic processing of laminin-5 by stromelysin-2, because degradation of laminin-5 by this enzyme was observed in vitro. The inappropriate matrix contact of keratinocytes was accompanied by aberrant localization of beta1-integrins and phosphorylated focal adhesion kinase, as well as by increased apoptosis of wound keratinocytes. These results suggest that a tightly regulated expression level of stromelysin-2 is required for limited matrix degradation at the wound site, thereby controlling keratinocyte migration.

Animals↗
PubMed2004

Intrinsic resistance of oligodendrocytes to prion infection.

Within the CNS, the normal form of cellular prion protein (PrP(C)) is expressed on neurons, oligodendrocytes, and astrocytes. The contribution of these cell types to prion replication and pathogenesis is unclear. To assess the role of oligodendrocytes, we expressed PrP(C) under the control of the myelin basic protein (MBP) promoter in mice lacking endogenous PrP(C). PrP(C) was detected in oligodendrocytes and Schwann cells but not in neurons and astrocytes. MBP-PrP mice never developed scrapie after intracerebral, intraperitoneal, or intraocular challenge with scrapie prions. Transgenic brains did not contain protease-resistant prion protein and did not transmit scrapie when inoculated into PrP(C)-overexpressing indicator mice. To investigate whether prion spread within the CNS depends on oligodendrocytic PrP(C), we implanted PrP(C)-overexpressing neuroectodermal grafts into MBP-PrP brains. After intraocular prion inoculation, none of the grafts showed spongiform encephalopathy or prion infectivity. Hence oligodendrocytes do not support cell-autonomous prion replication, establishment of subclinical disease, and neural spread of prions. Prion resistance sets oligodendrocytes aside from both neurons and astrocytes.

Animals↗
PubMed2004

Metal-responsive transcription factor-1 (MTF-1) is essential for embryonic liver development and heavy metal detoxification in the adult liver.

Metal-responsive transcription factor-1 (MTF-1) activates the transcription of metallothionein genes and other target genes in response to heavy metal load and other stresses such as hypoxia and oxidative stress. It also has an essential function during embryogenesis: targeted disruption of Mtf1 in the mouse results in lethal liver degeneration on day 14 of gestation. Here we studied Mtf1 knockout mice at embryonic and adult stages, the latter by means of conditional knockout. Hepatocytes from Mtf1 null mutant and wild-type embryos were taken into culture on day 12.5 of gestation. Both initially appeared normal, but mutant cells were lost within a few days. Furthermore, Mtf1 null hepatocytes were poorly, if at all, rescued by cocultivation with wild-type rat embryo hepatocytes, indicating a cell-autonomous defect. When the Mtf1 gene was excised by Cre recombinase after birth in liver and bone marrow and to a lesser extent in other organs, mice were viable under non-stress conditions but highly susceptible to cadmium toxicity, in support of a role of MTF-1 in coping with heavy metal stress. An additional MTF-1 function was revealed upon analysis of the hematopoietic system in conditional knockout mice where leukocytes, especially lymphocytes, were found to be severely underrepresented. Together, these findings point to a critical role of MTF-1 in embryonic liver formation, heavy metal toxicity, and hematopoiesis.

Animals↗
PubMed2003

Expression of truncated PrP targeted to Purkinje cells of PrP knockout mice causes Purkinje cell death and ataxia.

PrP knockout mice with disruption of only the PrP-encoding region (Zürich I-type) remain healthy, whereas mice with deletions extending upstream of the PrP-encoding exon (Nagasaki-type) suffer Purkinje cell loss and ataxia, associated with ectopic expression of Doppel in brain, particularly in Purkinje cells. The phenotype is abrogated by co-expression of full-length PrP. Doppel is 25% similar to PrP, has the same globular fold, but lacks the flexible N-terminal tail. We now show that in Zürich I-type PrP-null mice, expression of N-terminally truncated PrP targeted to Purkinje cells also leads to Purkinje cell loss and ataxia, which are reversed by PrP. Doppel and truncated PrP probably cause Purkinje cell degeneration by the same mechanism.

Alleles↗
PubMed2003

Soluble dimeric prion protein binds PrP(Sc) in vivo and antagonizes prion disease.

Conversion of cellular prion protein (PrP(C)) into a pathological conformer (PrP(Sc)) is thought to be promoted by PrP(Sc) in a poorly understood process. Here, we report that in wild-type mice, the expression of PrP(C) rendered soluble and dimeric by fusion to immunoglobulin Fcgamma (PrP-Fc(2)) delays PrP(Sc) accumulation, agent replication, and onset of disease following inoculation with infective prions. In infected PrP-expressing brains, PrP-Fc(2) relocates to lipid rafts and associates with PrP(Sc) without acquiring protease resistance, indicating that PrP-Fc(2) resists conversion. Accordingly, mice expressing PrP-Fc(2) but lacking endogenous PrP(C) are resistant to scrapie, do not accumulate PrP-Fc(2)(Sc), and do not transmit disease to others. These results indicate that various PrP isoforms engage in a complex in vivo, whose distortion by PrP-Fc(2) affects prion propagation and scrapie pathogenesis. The unique properties of PrP-Fc(2) suggest that soluble PrP derivatives may represent a new class of prion replication antagonists.

Animals↗
PubMed2003

Efficient T cell repertoire selection in tetraparental chimeric mice independent of thymic epithelial MHC.

Nonthymic epithelial cells were compared with thymic epithelial cells for their role in T cell repertoire selection. Tetraparental aggregation chimeras were generated from T and B cell-deficient mice (H-2(d) SCID or H-2(b) Rag-/-) and thymus-deficient nude mice (H-2(b) or H-2(d)). These tetraparental mice showed primary protective CD8(+) T cell responses, after lymphocytic choriomeningitis virus infection, that were peptide-specifically restricted to either thymic or nonthymic epithelial MHC at comparable levels. These chimeras also mounted neutralizing IgG responses dependent on cognate CD4(+) T helper cell activity restricted to nonthymic epithelial MHC. Therefore, in contrast to earlier results with irradiation or thymus chimeras, these relatively undisturbed tetraparental mice reveal that the MHC of nonthymic epithelial cells efficiently selects a functional T cell repertoire.

Animals↗
PubMed2002

Nogo-A expressed in Schwann cells impairs axonal regeneration after peripheral nerve injury.

Injured axons in mammalian peripheral nerves often regenerate successfully over long distances, in contrast to axons in the brain and spinal cord (CNS). Neurite growth-inhibitory proteins, including the recently cloned membrane protein Nogo-A, are enriched in the CNS, in particular in myelin. Nogo-A is not detectable in peripheral nerve myelin. Using regulated transgenic expression of Nogo-A in peripheral nerve Schwann cells, we show that axonal regeneration and functional recovery are impaired after a sciatic nerve crush. Nogo-A thus overrides the growth-permissive and -promoting effects of the lesioned peripheral nerve, demonstrating its in vivo potency as an inhibitor of axonal regeneration.

Animals↗
PubMed2002

Absence of the prion protein homologue Doppel causes male sterility.

The agent that causes prion diseases is thought to be identical with PrP(Sc), a conformer of the normal prion protein PrP(C). PrP(C)-deficient mice do not exhibit major pathologies, perhaps because they express a protein termed Dpl, which shares significant biochemical and structural homology with PrP(C). To investigate the physiological function of Dpl, we generated mice harbouring a homozygous disruption of the Prnd gene that encodes Dpl. Dpl deficiency did not interfere with embryonic and postnatal development, but resulted in male sterility. Dpl protein was expressed at late stages of spermiogenesis, and spermatids of Dpl mutants were reduced in numbers, immobile, malformed and unable to fertilize oocytes in vitro. Mechanical dissection of the zona pellucida partially restored in vitro fertilization. We conclude that Dpl regulates male fertility by controlling several aspects of male gametogenesis and sperm-egg interaction.

Animals↗
PubMed2002

Neonatal hepatic steatosis by disruption of the adenosine kinase gene.

Neonatal hepatic steatosis (OMIM 228100) is a fatal condition of unknown etiology characterized by a pale and yellow liver and early postnatal mortality. In the present study, a deficit in adenosine-dependent metabolism is proposed as a causative factor. Physiologically, adenosine is efficiently metabolized to AMP by adenosine kinase (ADK), an enzyme highly expressed in liver. ADK not only ensures normal adenine nucleotide levels but also is essential for maintaining S-adenosylmethionine-dependent transmethylation processes, where adenosine, an obligatory product, has to be constantly removed. Homozygous Adk(-/-) mutants developed normally during embryogenesis. However, within 4 days after birth they displayed microvesicular hepatic steatosis and died within 14 days with fatty liver. Adenine nucleotides were decreased and S-adenosylhomocysteine, a potent inhibitor of transmethylation reactions, was increased in the mutant liver. Thus, a deficiency in adenosine metabolism is identified as a powerful contributor to the development of neonatal hepatic steatosis, providing a model for the rapid development of postnatally lethal fatty liver.

Adenine Nucleotides↗