Browsing by Subject "In Situ Nick-End Labeling"

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    Quantifiable biomarkers of normal aging in the Japanese medaka fish (Oryzias latipes).
    (PLoS One, 2010-10-11) Hinton, DE
    BACKGROUND: Small laboratory fish share many anatomical and histological characteristics with other vertebrates, yet can be maintained in large numbers at low cost for lifetime studies. Here we characterize biomarkers associated with normal aging in the Japanese medaka (Oryzias latipes), a species that has been widely used in toxicology studies and has potential utility as a model organism for experimental aging research. PRINCIPAL FINDINGS: The median lifespan of medaka was approximately 22 months under laboratory conditions. We performed quantitative histological analysis of tissues from age-grouped individuals representing young adults (6 months old), mature adults (16 months old), and adults that had survived beyond the median lifespan (24 months). Livers of 24-month old individuals showed extensive morphologic changes, including spongiosis hepatis, steatosis, ballooning degeneration, inflammation, and nuclear pyknosis. There were also phagolysosomes, vacuoles, and residual bodies in parenchymal cells and congestion of sinusoidal vessels. Livers of aged individuals were characterized by increases in lipofuscin deposits and in the number of TUNEL-positive apoptotic cells. Some of these degenerative characteristics were seen, to a lesser extent, in the livers of 16-month old individuals, but not in 6-month old individuals. The basal layer of the dermis showed an age-dependent decline in the number of dividing cells and an increase in senescence-associated β-galactosidase. The hearts of aged individuals were characterized by fibrosis and lipofuscin deposition. There was also a loss of pigmented cells from the retinal epithelium. By contrast, age-associated changes were not apparent in skeletal muscle, the ocular lens, or the brain. SIGNIFICANCE: The results provide a set of markers that can be used to trace the process of normal tissue aging in medaka and to evaluate the effect of environmental stressors.
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    Targeting A20 decreases glioma stem cell survival and tumor growth.
    (PLoS Biol, 2010-02-23) Hjelmeland, AB; Wu, Q; Wickman, S; Eyler, C; Heddleston, J; Shi, Q; Lathia, JD; Macswords, J; Lee, J; McLendon, RE; Rich, JN
    Glioblastomas are deadly cancers that display a functional cellular hierarchy maintained by self-renewing glioblastoma stem cells (GSCs). GSCs are regulated by molecular pathways distinct from the bulk tumor that may be useful therapeutic targets. We determined that A20 (TNFAIP3), a regulator of cell survival and the NF-kappaB pathway, is overexpressed in GSCs relative to non-stem glioblastoma cells at both the mRNA and protein levels. To determine the functional significance of A20 in GSCs, we targeted A20 expression with lentiviral-mediated delivery of short hairpin RNA (shRNA). Inhibiting A20 expression decreased GSC growth and survival through mechanisms associated with decreased cell-cycle progression and decreased phosphorylation of p65/RelA. Elevated levels of A20 in GSCs contributed to apoptotic resistance: GSCs were less susceptible to TNFalpha-induced cell death than matched non-stem glioma cells, but A20 knockdown sensitized GSCs to TNFalpha-mediated apoptosis. The decreased survival of GSCs upon A20 knockdown contributed to the reduced ability of these cells to self-renew in primary and secondary neurosphere formation assays. The tumorigenic potential of GSCs was decreased with A20 targeting, resulting in increased survival of mice bearing human glioma xenografts. In silico analysis of a glioma patient genomic database indicates that A20 overexpression and amplification is inversely correlated with survival. Together these data indicate that A20 contributes to glioma maintenance through effects on the glioma stem cell subpopulation. Although inactivating mutations in A20 in lymphoma suggest A20 can act as a tumor suppressor, similar point mutations have not been identified through glioma genomic sequencing: in fact, our data suggest A20 may function as a tumor enhancer in glioma through promotion of GSC survival. A20 anticancer therapies should therefore be viewed with caution as effects will likely differ depending on the tumor type.
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    The exon junction complex component Magoh controls brain size by regulating neural stem cell division.
    (Nat Neurosci, 2010-05) Silver, Debra L; Watkins-Chow, Dawn E; Schreck, Karisa C; Pierfelice, Tarran J; Larson, Denise M; Burnetti, Anthony J; Liaw, Hung-Jiun; Myung, Kyungjae; Walsh, Christopher A; Gaiano, Nicholas; Pavan, William J
    Brain structure and size require precise division of neural stem cells (NSCs), which self-renew and generate intermediate neural progenitors (INPs) and neurons. The factors that regulate NSCs remain poorly understood, and mechanistic explanations of how aberrant NSC division causes the reduced brain size seen in microcephaly are lacking. Here we show that Magoh, a component of the exon junction complex (EJC) that binds RNA, controls mouse cerebral cortical size by regulating NSC division. Magoh haploinsufficiency causes microcephaly because of INP depletion and neuronal apoptosis. Defective mitosis underlies these phenotypes, as depletion of EJC components disrupts mitotic spindle orientation and integrity, chromosome number and genomic stability. In utero rescue experiments showed that a key function of Magoh is to control levels of the microcephaly-associated protein Lis1 during neurogenesis. Our results uncover requirements for the EJC in brain development, NSC maintenance and mitosis, thereby implicating this complex in the pathogenesis of microcephaly.