Stephens Raymond E.

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Stephens
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Raymond E.
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  • Article
    A New invertebrate member of the p53 gene family is developmentally expressed and responds to polychlorinated biphenyls
    (National Institute of Environmental Health Sciences, 2002-03-07) Jessen-Eller, Kathryn ; Kreiling, Jill A. ; Begley, Gail S. ; Steele, Marjorie E. ; Walker, Charles W. ; Stephens, Raymond E. ; Reinisch, Carol L.
    The cell-cycle checkpoint protein p53 both directs terminal differentiation and protects embryos from DNA damage. To study invertebrate p53 during early development, we identified three differentially expressed p53 family members (p53, p97, p120) in the surf clam, Spisula solidissima. In these mollusks, p53 and p97 occur in both embryonic and adult tissue, whereas p120 is exclusively embryonic. We sequenced, cloned, and characterized p120 cDNA. The predicted protein, p120, resembles p53 across all evolutionarily conserved regions and contains a C-terminal extension with a sterile alpha motif (SAM) as in p63 and p73. These vertebrate forms of p53 are required for normal inflammatory, epithelial, and neuronal development. Unlike clam p53 and p97, p120 mRNA and protein levels are temporally expressed in embryos, with mRNA levels decreasing with increasing p120 protein (R2 = 0.97). Highest surf clam p120 mRNA levels coincide with the onset of neuronal growth. In earlier work we have shown that neuronal development is altered by exposure to polychlorinated biphenyls (PCBs), a neurotoxic environmental contaminant. In this study we show that PCBs differentially affect expression of the three surf clam p53 family members. p120 mRNA and protein are reduced the most and earliest in development, p97 protein shows a smaller and later reduction, and p53 protein levels do not change. For the first time we report that unlike p53 and p97, p120 is specifically embryonic and expressed in a time-dependent manner. Furthermore, p120 responds to PCBs by 48 hr when PCB-induced suppression of the serotonergic nervous system occurs.
  • Article
    Detecting p53 family proteins in haemocytic leukemia cells of Mytilus edulis from Pictou Harbour, Nova Scotia, Canada
    (National Research Council Canada, 2005-09-01) St-Jean, Sylvie D. ; Stephens, Raymond E. ; Courtenay, S. C. ; Reinisch, Carol L.
    Evaluating patterns of expression of p53-related proteins in cells is a novel approach in defining environmentally linked diseases. We have examined the induction of haemocytic leukemia in Mytilus edulis by municipal and industrial contaminants in Pictou Harbour, Nova Scotia, Canada. We used a murine monoclonal antibody, 1E10, as a diagnostic reagent to detect leukemic cells. We first characterized the reactivity of 1E10 with both normal and leukemic Mytilus haemocytes by confocal microscopy. We then compared p53 gene family expression (p53, p63–p73, and p97) in normal versus leukemic haemocytes using a panel of monoclonal and polyclonal antibodies to p53 family proteins. The immunochemical data demonstrate that haemocytic leukemia cells of M. edulis differentially express p63–p73 and p97–p120 proteins. We subsequently used 1E10 to diagnose haemocytic leukemia in 500 M. edulis previously deployed 6 months earlier in Pictou Harbour. In the field, Mytilus caged near untreated municipal wastewater and bleached kraft pulpmill effluents have a significantly greater chance of developing haemocytic leukemia than do mussels exposed to reference sites.