Used Transgenic Mice (used + transgenic_mouse)

Distribution by Scientific Domains

Selected Abstracts

Mutation spectrum in UVB-exposed skin epidermis of Xpa -knockout mice: Frequent recovery of triplet mutations

Hironobu Ikehata
Abstract Knockout mutations in both alleles of the Xpa gene give rise to a complete deficiency in nucleotide excision repair (NER) in mammalian cells. We used transgenic mice harboring the ,-phage-based lacZ mutational reporter gene to study the effect of Xpa null mutation (Xpa,/,) on damage induction, repair, and mutagenesis in mouse skin epidermis after UVB irradiation. UVB induced equal amounts of cyclobutane pyrimidine dimers (CPDs) and pyrimidine(6-4)pyrimidone photoproducts (64PPs) in mouse skin epidermis of Xpa,/, and wild-type mice. Neither photolesion was removed in the Xpa,/, epidermis by 12 hr after irradiation whereas removal of 64PPs was observed in the epidermis of wild-type mice. Irradiation with 200 and 300 J/m2 UVB increased the lacZ mutant frequency in the epidermis of Xpa,/, mice, but the induced mutant frequencies were not significantly different from those previously determined for wild-type mice. One-hundred lacZ mutants isolated from the UVB-exposed epidermis of Xpa,/, mice were analyzed and compared with mutant sequences previously determined for irradiated wild-type mice. The distribution of the mutations along the lacZ transgene and the preferred dipyrimidine context of the UV-specific mutations were similar in mutants from the Xpa,/, and wild-type mice. The spectra of the mutations in the two genotypes were both highly UV-specific and similar in a dominance of C , T transitions at dipyrimidine sites; however, Xpa,/, mice had a higher frequency than wild-type mice of two-base tandem substitutions, including CC , TT mutations, three-base tandem mutations and double base substitutions that were separated by one unchanged base in a three-base sequence (alternating mutations). These tandem/alternating mutations included a remarkably large number of triplet mutations, a recently reported, novel type of UV-specific mutation, characterized by multiple base substitutions or frameshifts within a three-nucleotide sequence containing a dipyrimidine. We conclude that the triplet mutation is a UV-specific mutation that preferably occurs in NER-deficient genetic backgrounds. Environ. Mol. Mutagen., 2007. 2006 Wiley-Liss, Inc. [source]

T lymphocyte rolling and recruitment into peripheral lymph nodes is regulated by a saturable density of L-selectin (CD62L)

Elena Galkina Dr.
Abstract L-selectin mediates tethering and rolling of lymphocytes in high endothelial venules (HEV) of lymph nodes (LN) and of leukocytes at inflammatory sites. We used transgenic mice expressing varying levels of wild-type or a non-cleavable mutant form of L-selectin on T cells to determine the relationship between L-selectin density, tethering and rolling, and migration into LN. T cells expressing supraphysiological levels of either wild-type or non-cleavable L-selectin showed rolling parameters similar to C57BL/6 T cells in hydrodynamic flow assays and during rolling in Peyer's patch HEV. In contrast, PMA- or antigen-activated T cells and L-selectin+/, T cells expressing subphysiological levels of L-selectin showed reduced numbers of rolling cells with increased rolling velocity. Short-term homing studies showed that elevated expression of L-selectin above physiological levels had no effect on T cell migration to LN; however, low L-selectin expression resulted in reduced T cell homing to LN. Thus, T lymphocyte migration into LN is regulated by the density of cell surface L-selectin. In addition, there is a saturable density of L-selectin required for optimal homing to PLN in C57BL/6 mice, the L-selectin level on circulating naive T cells promotes optimal homing, and increased expression above saturating levels promotes no further increase in T cell recruitment. [source]

Structure of the Mouse Glutamate Decarboxylase 65 Gene and Its Promoter

Preferential Expression of Its Promoter in the GABAergic Neurons of Transgenic Mice
Abstract: GABA is synthesized by glutamate decarboxylase (GAD), which has two forms, GAD65 and GAD67. To elucidate the molecular mechanisms of mouse GAD65 (mGAD65) gene expression, we isolated and characterized the mGAD65 gene. The mGAD65 gene was found to be divided into 16 exons and spread over 75 kb. The sequence of the first exon and the 5,-flanking region indicated the presence of potential neuron-specific cis -regulatory elements. We used transgenic mice to examine the expression pattern conferred by a 9.2-kb promoter-proximal DNA fragment of the mGAD65 gene fused to the bacterial lacZ reporter gene. Transgenic mice showed high ,-galactosidase activity specifically in brain and testis. They also showed characteristic patterns of transgene expression in olfactory bulb, cerebellar cortex, and spinal cord, a similar expression pattern to that of endogenous mGAD65. However, no transgene expression was observed in the ventral thalamus or hypothalamus, in which high mGAD65 gene expression levels have been observed. These results suggest that the 9.2-kb DNA fragment of the mGAD65 gene is associated with its tissue-specific expression and its targeted expression in GABAergic neurons of specific brain regions but that additional regulatory elements are necessary to obtain fully correct expression. [source]

Leukemia inhibitory factor inhibits neuronal development and disrupts synaptic organization in the mouse retina

David M. Sherry
Abstract Leukemia inhibitory factor (LIF) belongs to the interleukin-6 cytokine family, all members of which signal through the common gp130 receptor. Neurotrophic members of this cytokine family are known to arrest photoreceptor maturation and are likely to regulate maturation of other retinal neurons as well. We have used transgenic mice that constitutively express LIF beginning in embryonic development to determine its effects on synaptic organization and molecular maturation of all classes of retinal neurons. LIF reduced the numbers of cells showing markers characteristic of mature cells of all neuronal classes and caused synaptic ectopia. The net effect was disrupted morphological development and disturbed synaptic organization. Our study suggests that cytokines signaling through gp130 are capable of regulating many aspects of neuronal differentiation in the retina, including synaptic targeting. 2005 Wiley-Liss, Inc. [source]