Abnormal nuclear morphology is independent of longevity in a zmpste24-deficient fish model of Hutchinson-Gilford progeria syndrome (HGPS).

Lamin is an intermediate protein underlying the nuclear envelope and it plays a key role in maintaining the integrity of the nucleus. A defect in the processing of its precursor by a metalloprotease, ZMPSTE24, results in the accumulation of farnesylated prelamin in the nucleus and causes various diseases, including Hutchinson-Gilford progeria syndrome (HGPS). However, the role of lamin processing is unclear in fish species. Here, we generated zmpste24-deficient medaka and evaluated their phenotype. Unlike humans and mice, homozygous mutants did not show growth defects or lifespan shortening, despite lamin precursor accumulation. Gonadosomatic indices, blood glucose levels, and regenerative capacity of fins were similar in 1-year-old mutants and their wild-type (WT) siblings. Histological examination showed that the muscles, subcutaneous fat tissues, and gonads were normal in the mutants at the age of 1 year. However, the mutants showed hypersensitivity to X-ray irradiation, although p53target genes, p21 and mdm2, were induced 6 h after irradiation. Immunostaining of primary cultured cells from caudal fins and visualization of nuclei using H2B-GFP fusion proteins revealed an abnormal nuclear shape in the mutants both in vitro and in vivo. The telomere lengths were significantly shorter in the mutants compared to WT. Taken together, these results suggest that zmpste24-deficient medaka phenocopied HGPS only partially and that abnormal nuclear morphology and lifespan shortening are two independent events in vertebrates.

Plant microtubules reorganization under the indirect UV-B exposure and during UV-B-induced programmed cell death.

The role of microtubules in cellular pathways of UV-B signaling in plants as well as in related structural cell response become into focus of few last publications. As microtubules in plant cell reorient/reorganize (become randomized, fragmented or depolymerized) in a response to direct UV-B exposure, these cytoskeletal components could be involved into UV-B signaling pathways as highly responsive players. In the current addendum, indirect UV-B-induced microtubules reorganization in cells of shielded Arabidopsis thaliana (GFP-MAP4) primary roots and the correspondence of microtubules depolymerization with the typical hallmarks of the programmed cell death in Nicotiana tabacum BY-2 (GFP-MBD) cells are discussed.

Apaf-1 deficiency confers resistance to ultraviolet-induced apoptosis in mouse embryonic fibroblasts by disrupting reactive oxygen species amplification production and mitochondrial pathway.

Apoptosis requires tightly regulated cell death pathways. The signaling pathways that trigger a cell to undergo apoptosis after UV radiation are cell type specific and are currently being defined. Here, we have used pharmacological and genetic tools to demonstrate the decisive part of the mitochondrial pathway in UVC-induced apoptosis in mouse embryo fibroblasts (MEFs). UVC-induced apoptosis proceeded independent of the activation of death receptor components. In contrast, soon after UV radiation, MAPK activation and generation of reactive oxygen species (ROS) increased, followed by a decline in mitochondrial membrane potential (MMP) and cytochrome c release, as well as activation of caspase-9 and -3 and the upregulation of p47-phox. Deficiency of apaf-1, a critical member of the apoptosome, dramatically abolished all the UV-induced signal deterioration and cell death. In parallel, UVC-induced apoptosis was largely attenuated by either DN-caspase-9 or Bcl-X(L) overexpression. Pretreatment of cells with N-acetylcysteine or catalase but not Tempol decreased UVC-induced MAPK activation and apoptosis. Inhibition of JNK and caspase attenuated p47-phox upregulation. Altogether, we have for the first time demonstrated the critical role of Apaf-1 in the regulation of MAPK, ROS, and MMP in UVC-radiated MEFs and propose that the amplification feedback loop among mitochondrial signal molecules culminates in the demise of the cell.

Confocal microscopy for modeling electron microbeam irradiation of skin.

For radiation exposures employing targeted sources such as particle microbeams, the deposition of energy and dose will depend on the spatial heterogeneity of the sample. Although cell structural variations are relatively minor for two-dimensional cell cultures, they can vary significantly for fully differentiated tissues. Employing high-resolution confocal microscopy, we have determined the spatial distribution, size, and shape of epidermal keratinocyte nuclei for the full-thickness EpiDerm™ skin model (MatTek, Ashland, VA). Application of these data to calculate the microdosimetry and microdistribution of energy deposition by an electron microbeam is discussed.

Relative biological effectiveness of high-energy iron ions for micronucleus formation at low doses.

Dose-response curves for micronucleus (MN) formation were measured in Chinese hamster V79 and xrs6 (Ku80(-)) cells and in human mammary epithelial MCF10A cells in the dose range of 0.05-1 Gy. The Chinese hamster cells were exposed to 1 GeV/nucleon iron ions, 600 MeV/nucleon iron ions, and 300 MeV/nucleon iron ions (LETs of 151, 176 and 235 keV/microm, respectively) as well as with 320 kVp X rays as reference. Second-order polynomials were fitted to the induction curves, and the initial slopes (the alpha values) were used to calculate RBE. For the repair-proficient V79 cells, the RBE at these low doses increased with LET. The values obtained were 3.1 +/- 0.8 (LET = 151 keV/microm), 4.3 +/- 0.5 (LET = 176 keV/microm), and 5.7 +/- 0.6 (LET = 235 keV/microm), while the RBE was close to 1 for the repair-deficient xrs6 cells regardless of LET. For the MCF10A cells, the RBE was determined for 1 GeV/nucleon iron ions and was found to be 5.5 +/- 0.9, slightly higher than for V79 cells. To test the effect of shielding, the 1 GeV/nucleon iron-ion beam was intercepted by various thicknesses of high-density polyethylene plastic absorbers, which resulted in energy loss and fragmentation. It was found that the MN yield for V79 cells placed behind the absorbers decreased in proportion to the decrease in dose both before and after the iron-ion Bragg peak, indicating that RBE did not change significantly due to shielding except in the Bragg peak region. At the Bragg peak itself with an entrance dose of 0.5 Gy, where the LET is very high from stopping low-energy iron ions, the effectiveness for MN formation per unit dose was decreased compared to non-Bragg peak areas.