Animal Models

Nephronophthisis (NPHP), an autosomal recessive kidney disease, is the most frequent genetic cause of end-stage renal failure in the first three decades of life. A mutation of GLIS2 transcriptional repressor was identified as causing an NPHP-like phenotype in humans and mice. Glis2 was identified as a transcription factor mutated in NPHP and it was demonstrated that this gene has an essential role for the maintenance of renal tissue architecture through prevention of apoptosis and fibrosis. Amouse model suitable for kidney disease research was generated by targeted deletion the GLIS2 gene.

The actin cytoskeleton in neurons is a highly dynamic filament system regulating neurite outgrowth and polarity, growth cone motility, dendritic spine motility, as well as neuronal precursor cell migration. In mouse brain profilin1 and profilin2 have distinct roles in regulating synaptic actin polymerization with profilin2 preferring a WAVE-complex-mediated pathway. Mice lacking profilin2 show a block in synaptic actin polymerization in response to depolarization, which is accompanied by increased synaptic excitability of glutamatergic neurons due to higher vesicle exocytosis. These alterations in neurotransmitter release correlate with a hyperactivation of the striatum and enhanced novelty-seeking behavior in profilin2 mutant mice.

Mice lacking p38 alpha MAP kinase die during embryogenesis due to placental defects. Therefore, in order to study the function of p38 alpha in specific cell types of adult mice we used the Cre/loxP system to generate conditional p38 alpha knockout mice. Mice were generated allow studying of the cell-specific function of p38alpha in vivo in both physiological and pathological conditions. Given that the p38 pathway is an attractive drug target for inflammatory diseases and cancer, these mice can be used as a genetic model to validate the effects of p38 alpha inhibition in mouse models of human diseases.

Mice lacking the brain-specific homeobox transcription factor Bsx were generated exhibiting reduced locomotor activity and lower expression of Npy and Agrp, which regulate feeding behavior and body weight. Analysis of these knockout animals revealed that they are prone to obesity when fed a high fat-diet. Molecular characterisation of the phenotype revealed changes in the expression levels of different hormones i.e. NPY and somatostatin in the hypothalamus. The mice serve as attractive model to study the control of food acquisition and body weight regulation.

Multiple sclerosis is the most common inflammatory demyelinating disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) is the best known animal model of multiple sclerosis and can be induced in susceptible rodents and other animals by immunization with myelin antigens such as myelin oligodendrocyte glycoprotein (MOG). CNS-restricted ablation of ‘upstream’ NF-kappaB activators NEMO or IKK2 in mice ameliorated disease pathology in a mouse model of multiple sclerosis, suggesting that ‘canonical’ NF-kappaB activation in cells of the CNS has a mainly pathogenic function in autoimmune demyelinating disease. NF-kappaB inhibition prevented the expression of proinflammatory cytokines, chemokines and the adhesion molecule VCAM-1 from CNS-resident cells. The mice serve as attractive model to study the function of NF-kappaB specifically in neuroectoderm-derived cells.

Acquired mutations affecting the C/EBPalpha transcription factor are common in acute myeloid leukemia (AML), indicating a role for C/EBPalpha in myeloid tumor suppression. Knock-in mice were generated in which p42 translation is specifically ablated. These mice developed lethal acute myeloid leukemia with complete penetrance.

The C/EBPalpha transcription factor regulates hepatic nitrogen, glucose, lipid and iron metabolism. However, how it is able to independently control these processes is not known. In the present research mouse knockin mutagenesis was used to identify C/EBPalpha domains that specifically regulate hepatic gluconeogenesis and lipogenesis, respectively. The characterization of the resulting mice revealed that pathway specific metabolic regulation can be achieved through a single transcription factor containing context-sensitive regulatory domains, and indicates C/EBPalpha phosphorylation as a PGC-1alpha-independent mechanism for regulating hepatic gluconeogenesis.

Long-term potentiation (LTP) is a well-studied form of synaptic plasticity. It is thought to reveal mechanisms for the acquisition and storage of information by synapses in the hippocampus and other selected brain sites. Mice carrying point mutations on specific docking sites of TrkB receptors (trkBSHC, trkBPLC) were generated. The characterization of these mice revealed that the TrkB PLC{gamma}-docking site is necessary for certain forms of learning and hippocampal synaptic plasticity. Mice with a mutation at the TrkB PLC{gamma}-docking site are impaired in the acquisition of trace eyeblink conditioning, and also show impairments in learning-related changes in synaptic efficacy and LTP in the CA3-CA1 region. In contrast, mice with a mutation at the TrkB SHC-docking site showed normal acquisition of trace eyeblink conditioning, but to some extent augmented synaptic efficacy and LTP.

To find effective therapies against chronic inflammations of the intestine, such as Chron’s disease and Ulcerative Colitis, requires an understanding of their underlying molecular mechanisms. Recent studies at the EMBL showed that blocking the signalling molecule NF-kappaB leads to severe intestinal inflammation in mice and reveals molecular mechanisms that are likely to also underpin human inflammatory bowel disease. To investigate the role of NF-kappaB signalling in the gut epithelium mice were generated lacking NEMO specifically in small intestine and colon epithelial cells. These mice revealed signs of severe colitis and pancolitis. This model identifies NF-kappaB signalling in the gut epithelium as a critical regulator of epithelial integrity and intestinal immune homeostasis, and has important implications for understanding the mechanisms controlling the pathogenesis of human inflammatory bowel disease.

Various neuronal diseases such as mental retardation, lissencephaly, epilepsy, and schizophrenia have been linked to neuronal migration defects during development. While the etiology of the cortical disorder lissencephaly (LIS1) has been studied extensively, the underlying mechanisms remain elusive. F-actin depolymerizing factor n-cofilin controls cell migration and cell cycle progression in the cerebral cortex. To study the role of actin remodelling in the development of the brain, mice were generated carrying conditional mutations of n-cofilin. Theses mutants showed impaired radial migration, resulting in the lack of intermediate cortical layers.

To assess whether IKK1 regulates keratinocyte differentiation in a cell-autonomous manner, mice lacking IKK1 specifically in epidermal keratinocytes were generated using keratin 14–Cre transgenics. The characterization of these mice reveal a new role for IKK1 in the epidermis, where it functions in a keratinocyte-autonomous fashion to regulate the formation of a watertight epidermal barrier, by controlling the expression of genes whose products are crucial for epidermal lipid processing and tight-junction integrity.

Insulin-like growth factor 1 (IGF-1) is an important regulator of growth, survival, and differentiation in many tissues. It is produced in several isoforms that differ in their N-terminal signal peptide and C-terminal extension peptide. A transgenic mouse model was generated, in which mIGF-1 expression is driven by the keratin 14 promoter. IGF-1 levels were unchanged in the sera of hemizygous K14/mIGF-1 transgenic animals whose growth was unaffected. A skin analysis of young animals revealed normal architecture and thickness as well as proper expression of differentiation and proliferation markers. No malignant tumors were formed. Normal homeostasis of the putative stem cell compartment was also maintained. Healing of full-thickness excisional wounds was accelerated because of increased proliferation and migration of keratinocytes, whereas inflammation, granulation tissue formation, and scarring were not obviously affected. In addition, mIGF-1 promoted late hair follicle morphogenesis and cycling.

The nuclear factor kB (NF-kB) signaling pathway regulates immune and inflammatory responses and is implicated in the pathogenesis of multiple diseases. The principal mechanism controlling NF-kB activation depends on the association of NF-kB transcription factor dimers with IkB molecules, which prevents the accumulation of NF-kB in the nucleus and the activation of target gene transcription. Knock-in mice were generated, expressing a fusion protein between the green fluorescent protein (GFP) and the p65/RelA NFkB subunit (GFP-p65) from the endogenous p65 genomic locus. Homozygous GFP-p65 mice developed normally and showed normal NF-kB activation, demonstrating that the GFP-p65 fusion protein functionally substitutes for wild-type p65. Live imaging of primary cells from GFP-p65-mice allowed real-time monitoring of p65 nucleo-cytoplasmic shuttling upon NF-kB activation. Therefore, the GFP-p65 knock-in mice constitute an valuable tool for studying the dynamic regulation of NF-kB.