title: The roles of p53 and p21 in normal development and hyperthermia-induced malformations.
abstract: BACKGROUND
  Hyperthermia (HS) is a well-studied teratogen that induces serious malformations, including neural tube defects. Our previous studies have shown that HS induces apoptosis by activating the mitochondrial apoptotic pathway. Prior to activation of the mitochondrial apoptotic pathway, HS also activates p53 and its target genes. In the present study, we determine whether p53 and/or p21 play a role as teratogen suppressors or inducers of HS-induced malformations.
  
  
  METHODS
  Pregnant mice carrying all three p53 or p21 genotype embryos were exposed to HS on day 8.5. Subsequently, fetuses were collected on day 15.5, and genotyped. In addition to genotype, we also determined the number of resorptions and dead fetuses as well as the number and types of external malformations.
  
  
  RESULTS
  In the absence of HS exposure, fetuses exhibiting exencephaly and spina bifida were observed in approximately 11% of p53 -/- fetuses, whereas no malformations were observed among p21 -/- fetuses. Exposure to HS resulted in an increase in exencephaly and polydactyly in fetuses of all three p53 genotypes. However, the incidence of these malformations was statistically significantly higher in p53 -/- compared to p53 +/- and p53 +/+ fetuses. Exencephaly was the only malformation observed in p21 fetuses exposed to HS, with an approximately 2-fold increase among p21 +/- and a 3-fold increase among p21 -/- compared to p21 +/+ fetuses.
  
  
  CONCLUSIONS
  Our study confirms that p53 plays a role in normal development and has shown, for the first time that p53 and p21 function to suppress HS-induced malformations.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX 77843, USA.hhosako@cvm.tamu.edu
authors.forename: Hiromi
authors.initials: H
authors.lastname: Hosako
authors.forename: Liezl E
authors.initials: LE
authors.lastname: Francisco
authors.forename: Gail S
authors.initials: GS
authors.lastname: Martin
authors.forename: Philip E
authors.initials: PE
authors.lastname: Mirkes
mesh_terms: D000818:Animals; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D047108:Embryonic Development / Q000235:genetics*; D005260:Female; D005334:Fever; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D051379:Mice; D018345:Mice, Knockout; D009436:Neural Tube Defects / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D016135:Spinal Dysraphism / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53