The Role of the P53 Family Proteins in Hydroxyurea Induced Embryotoxicity in the Organogenesis Stage Mouse Embryo

Download or read book The Role of the P53 Family Proteins in Hydroxyurea Induced Embryotoxicity in the Organogenesis Stage Mouse Embryo written by Nazem El Husseini and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The embryonic stress response to DNA damage during organogenesis was examined using the model teratogen, hydroxyurea. Intraperitoneal administration of hydroxyurea (400 mg/kg or 600 mg/kg) to timed pregnant CD-1 mice on gestational day 9 significantly affected the expression of ~1300 transcripts in the embryo within three hours. Pathway analysis predicted that the P53 signaling pathway was the most activated in response to hydroxyurea. The steady-state levels of P53 and its phosphorylation increased dramatically in hydroxyurea-exposed embryos. The nuclear localization of phosphorylated P53 was increased significantly in the embryo heart and rostral and caudal neuroepithelia. Hydroxyurea also induced P53 transcriptional activity, leading to the upregulation of P53 downstream targets involved in DNA damage repair, cell cycle arrest and apoptosis. Using a Trp53 null transgenic mouse model, the effects of treatment with hydroxyurea on P53 family members, P63 and P73, were determined in the gestational day 9 embryo. Appreciable amounts of P63 and P73 were detected under normal conditions; hydroxyurea did not affect their steady-state or phosphorylation levels. Trp63 and Trp73 transcript levels were affected by hydroxyurea treatment, although only Trp73 levels were P53-dependent. As transcription factors, neither P63 nor P73 were capable of compensating for the absence of P53 in upregulating the expression of downstream targets involved in cell cycle arrest (Cdkn1a, Rb1) or apoptosis (Fas, Pmaip1) in response to hydroxyurea exposure. Hydroxyurea induction of Caspase-3 and MST-1 cleavage, markers for apoptosis and DNA damage repair, required the presence of P53. Thus, P53 is the main member of the P53 family that responds to genotoxic stress in the organogenesis-stage embryo.To determine whether P53 acts as a suppressor or inducer of hydroxyurea embryotoxicity, Trp53+/+, Trp53+/- and Trp53-/- embryos were exposed in utero on gestational day 9 with saline or hydroxyurea (200 or 400 mg/kg). On gestational day 18, Trp53-/- fetuses from the saline treatment group were found to exhibit a higher rate of malformations compared to their Trp53+/+ littermates. Hydroxyurea treatment induced a dose-dependent increase in resorptions and congenital malformations; these included hypoplastic tails and fore- and hind-limb syndactly, oligodactyly and amelia. In the 200 mg/kg treatment group, hydroxyurea exposed fetuses lacking P53 had a higher rate of malformations than their Trp53+/+ littermates and the rate of resorptions was elevated in these fetuses after exposure to 400 mg/kg hydroxyurea. Thus, the organogenesis stage embryo responds to hydroxyurea-induced stress by activating the P53 signaling pathway that mediates DNA damage repair, cell cycle arrest and apoptotic factors to suppress hydroxyurea embryotoxicity. " --