Chn1flox mice possess loxP sites flanking exons 2-3 of the chimerin 1 (Chn1) gene. CHN1 is a GTPase-activating protein for the receptor tyrosine kinase EphA4, which is predominantly expressed in neurons and is involved in controlling multiple axonal guidance steps, most prominently in the locomotor circuits. Chimerin 1 plays an important role in neuronal signal-transduction mechanisms and ocular motor axon pathfinding. Mutations in this gene are associated with Duane's retraction syndrome 2, which is characterized by limited outward movement of the affected eye. This is caused by miswiring of the eye muscles or misdirected or absent ocular nerves. Mice that are homozygous for this allele are viable and fertile. When bred to mice that express tissue-specific Cre recombinase, resulting offspring will have exons 2-3 deleted in the cre-expressing tissues.
For example, when bred to B6.C-Tg(CMV-cre)1Cgn/J mice (Stock No. 006054), resulting Chn1 KO mice resulting offspring exhibit a rabbit-like hopping gait with synchronous hindlimb movements, similar to that seen in EphA4 KO mice.
