Positional cloning of a global regulator of anterior-posterior patterning in mice.

Anterior-posterior (A-P) patterning is of fundamental importance throughout vertebrate embryonic development. Murine members of the trithorax (trx) and Polycomb group (Pc-G) of genes regulate A-P patterning of segmented axial structures, demonstrating conserved upstream regulation of homeotic pathways between Drosophila and mouse. Here we report the positional cloning of a classical mouse mutation, eed (for embryonic ectoderm development), which is the highly conserved homologue of the Drosophila Pc-G gene esc (for extra sex combs), a long-term repressor of homeotic genes. Mutants homozygous for a null allele of eed display disrupted A-P patterning of the primitive streak during gastrulation. Mutant embryos lack a node, notochord and somites, and there is no neural induction. In contrast to absence of anterior structures, extra-embryonic mesoderm is abundant. Mice carrying a hypomorphic eed mutation exhibit posterior transformations along the axial skeleton. These results indicate that eed is required globally for A-P patterning throughout embryogenesis.

Intestinal obstruction due to peritoneal adhesions as a complication of peritoneal dialysis for neonatal hyperammonemia.

A male infant with ornithine transcarbamylase deficiency developed massive neonatal hyperammonemia and was treated with peritoneal dialysis. He later developed intestinal obstruction due to peritoneal bands which originated at the site of the previous peritoneal catheter. In this infant the blood concentration of ammonia could not be lowered below 1000 micrograms/dl using peritoneal dialysis, while treatment with sodium benzoate led to control within 24 h. In view of the possibility of this and other complications of peritoneal dialysis, pharmacologic therapy of neonatal hyperammonemia should be considered as an initial modality of treatment.