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Marit Stafsnes

    Marit Stafsnes

    Mutations in the N-myc downstream-regulated gene 1 (NDRG1) cause degenerative polyneuropathy in ways that are poorly understood. We have investigated Alaskan Malamute dogs with neuropathy caused by a missense mutation in NDRG1. In... more
    Mutations in the N-myc downstream-regulated gene 1 (NDRG1) cause degenerative polyneuropathy in ways that are poorly understood. We have investigated Alaskan Malamute dogs with neuropathy caused by a missense mutation in NDRG1. In affected animals, nerve levels of NDRG1 protein were reduced by more than 70% (p< 0.03). Nerve fibers were thinly myelinated, loss of large myelinated fibers was pronounced and teased fiber preparations showed both demyelination and remyelination. Inclusions of filamentous material containing actin were present in adaxonal Schwann cell cytoplasm and Schmidt-Lanterman clefts. This condition strongly resembles the human Charcot-Marie-Tooth type 4D. However, the focally folded myelin with adaxonal infoldings segregating the axon found in this study are ultrastructural changes not described in the human disease. Furthermore, lipidomic analysis revealed a profound loss of peripheral nerve lipids. Our data suggest that the low levels of mutant NDRG1 is insuff...
    IRFs [IFN (interferon) regulatory factors] constitute a family of transcription factors involved in IFN signalling and in the development and differentiation of the immune system. IRF-2 has generally been described as an antagonist of... more
    IRFs [IFN (interferon) regulatory factors] constitute a family of transcription factors involved in IFN signalling and in the development and differentiation of the immune system. IRF-2 has generally been described as an antagonist of IRF-1-mediated transcription of IFN and IFN-inducible genes; however, it has been recently identified as a transcriptional activator of some genes, such as those encoding histone H4, VCAM-1 (vascular cell adhesion molecule-1) and Fas ligand. Biologically, IRF-2 plays an important role in cell growth regulation and has been shown to be a potential oncogene. Studies in knock-out mice have also implicated IRF-2 in the differentiation and functionality of haematopoietic cells. Here we show that IRF-2 expression in a myeloid progenitor cell line leads to reprogramming of these cells towards the megakaryocytic lineage and enables them to respond to thrombopoietin, as assessed by cell morphology and expression of specific differentiation markers. Up-regulatio...
    The yellow-pigmented soil bacterium Corynebacterium glutamicum ATCC13032 is accumulating the cyclic C50 carotenoid decaprenoxanthin and its glucosides. Carotenoid pathway engineering was previously shown to allow for efficient lycopene... more
    The yellow-pigmented soil bacterium Corynebacterium glutamicum ATCC13032 is accumulating the cyclic C50 carotenoid decaprenoxanthin and its glucosides. Carotenoid pathway engineering was previously shown to allow for efficient lycopene production. Here, engineering of C. glutamicum for production of endogenous decaprenoxanthin as well as of the heterologous C50 carotenoids C.p.450 and sarcinaxanthin is described. Plasmid-borne overexpression of genes for lycopene cyclization and hydroxylation from C. glutamicum, Dietzia sp., and Micrococcus luteus, in a lycopene-producing platform strain constructed here, resulted in accumulation of these three C50 carotenoids to concentrations of about 3-4 mg/g CDW. Chromosomal deletion of a putative carotenoid glycosyltransferase gene cg0730/crtX in these strains entailed production of non-glucosylated derivatives of decaprenoxanthin, C.p.450, and sarcinaxanthin, respectively. Upon introduction of glucosyltransferase genes from M. luteus, C. glutamicum, and Pantoea ananatis, these hydroxylated C50 carotenoids were glucosylated. We here also demonstrate production of the C40 carotenoids β-carotene and zeaxanthin in recombinant C. glutamicum strains and co-expression of the P. ananatis crtX gene was used to obtain glucosylated zeaxanthin. Together, our results show that C. glutamicum is a potentially valuable host for production of a wide range of glucosylated C40 and C50 carotenoids.
    ABSTRACTThe induciblePmpromoter integrated into broad-host-range plasmid RK2 replicons can be fine-tuned continuously between the uninduced and maximally induced levels by varying the inducer concentrations. To lower the uninduced... more
    ABSTRACTThe induciblePmpromoter integrated into broad-host-range plasmid RK2 replicons can be fine-tuned continuously between the uninduced and maximally induced levels by varying the inducer concentrations. To lower the uninduced background level while still maintaining the inducibility for applications in, for example, metabolic engineering and synthetic (systems) biology, we report here the use of mutations in thePmDNA region corresponding to the 5′ untranslated region of mRNA (UTR). Five UTR variants obtained by doped oligonucleotide mutagenesis and selection, apparently reducing the efficiency of translation, were all found to display strongly reduced uninduced expression of three different reporter genes (encoding β-lactamase, luciferase, and phosphoglucomutase) inEscherichia coli. The ratio between induced and uninduced expression remained the same or higher compared to cells containing a corresponding plasmid with the wild-type UTR. Interestingly, the UTR variants also displ...