The role of p53 in normal development and teratogen-induced apoptosis and birth defects in mouse embryos

The Role of p53 in Normal Development and Teratogen-Induced Apoptosis and Birth Defects in Mouse Embryos. (December 2008) Hiromi Hosako, B.S., Texas State University – San Marcos Co-Chairs of Advisory Committee, Dr. Philip E. Mirkes Dr. Stephen H. Safe In the studies described in this dissertation, we investigated the roles of p53 in normal development, teratogen-induced apoptosis, and birth defects. In the first study, the activation of p53 and its target genes, p21, NOXA, and PUMA, were examined during neural tube closure in mouse embryos exposed to hyperthermia (HS) or 4peroxycyclophosphamide (4CP), teratogens known to induce neural tube defects (NTDs). In the second study, using p53-deficient mice, we examined the expression of mRNAs and microRNAs (miRNAs) during neural tube closure. In the third study, the incidence of NTDs was investigated in p53and p21-deficient mouse embryos exposed to HS. Finally, we examined the induction of apoptosis in p53-deficient mouse embryos exposed to HS. HS and 4CP induced the activation of p53 by phosphorylation and accumulation of the protein, leading to an increase in p21 proteins and mRNAs. Although HS and 4CP also induced the expression of Noxa and Puma mRNAs, no significant increases in NOXA and PUMA proteins were observed, suggesting a possible role of transcriptionindependent apoptosis. In the second study, we showed that the expression of 388 genes and 5 miRNAs were significantly altered in p53 -/compared to p53 +/+ embryos. Finally, we showed that 10% of p53 -/pups exhibit exencephaly, spina bifida, and/or preaxial polydactyly, whereas no malformations were observed among p21 -/offspring in the absence of HS. HS resulted in an increased incidence of exencephaly in both p53 and p21 null mice indicating that these two proteins act as teratogen suppressors. Our