A SUBSET OF P53-DEFICIENT EMBRYOS EXHIBIT EXENCEPHALY

Defects in neural tube formation are among the most common malformatio ns leading to infant mortality. Although numerous genetic loci appear to contribute to the defects observed in humans and in animal model sy stems, few of the genes involved have been characterized at the molecu lar level, Mice lacking the p53 tumour suppressor gene are predisposed to tumours, but the viability of these animals indicates that p53 fun ction is not essential for embryonic development. Here, we demonstrate that a fraction of p53-deficient embryos in fact do not develop norma lly. These animals display defects in neural tube closure resulting in an overgrowth of neural tissue in the region of the midbrain, a condi tion known as exencephaly.