Mice with targeted disruption of Hoxb-1 fail to form the motor nucleus of the VIIth nerve.

Mice were generated with targeted disruptions in the hoxb-1 gene. Two separate mutations were created: the first disrupts only the homeodomain and the second inactivates the first exon as well as the homeodomain. The phenotypes associated with these two mutant alleles are indistinguishable in surviving adult mice. The predominant defect in these mutant mice is a failure to form the somatic motor component of the VIIth (facial) nerve, possibly through a failure to specify these neurons. The phenotype of hoxb-1 mutant homozygotes closely resembles features of the clinical profile associated with humans suffering from Bell's Palsy or Moebius Syndrome. These animals should therefore provide a useful animal model for these human diseases.