GENE TRAP CAPTURE OF A NOVEL MOUSE GENE, JUMONJI, REQUIRED FOR NEURAL-TUBE FORMATION

A mouse mutation, termed jumonji (jmj), was generated by a gene trap strategy. Expression of the trapped gene (jmj gene), as monitored by X-gal staining, was detected predominantly at the midbrain-hindbrain boundary and in the cerebellum, depending on the stage of development. All embryos homozygous for the jmj mutation died before embryonic day 15.5. Some, but not all, of the homozygotes developed an abnormal groove in a region just anterior to the midbrain-hindbrain boundary on the neural plate at embryonic day 8-8.5 and showed a defect in neural tube closure in the midbrain region. Analyses of jmj cDNA revealed that the jmj gene is novel, conserved among vertebrates, and disrupted by vector insertion in the jmj homozygotes. The amino acid sequence deduced from the cDNA shared a portion of significant homology with human retinoblastoma-binding protein RBP-2 and with a putative protein encoded by human gene XE169 that escapes X-chromosome inactivation. These results suggest that jmj gene is essential for normal morphogenesis of the neural tube.