Insertional mutation in the intron 1 of Unc5h3 gene induces ataxic, lean and hyperactive phenotype in mice

Mice carrying a mutation in the first intron of Unc5h3 were accidentally produced by transgenic insertion and characterized for their homozygous mutant phenotypes. Morphological and histological analysis revealed cerebellar and midbrain abnormalities, which are similar to the previously reported phenotypes of the Unc5h3 mutant. Behavioral analysis showed higher ambulatory activity and circling, and defects in habituation in a novel environment. Their body weights were 10-30% less than wildtype mice from 2-3 weeks of age to 22 months possibly due to reduced accumulation of adipose tissues. The transgenic insertion site was identified and mapped to the intron 1 of Unc5h3 gene with approximately 50 kb deletion of the intron sequence. This intronic mutation interfered with the mRNA expression of the Unc5h3 gene not in testes, but in many tissues including the brain, implying that this intronic region may play a role in regulating tissue-specific transcription of Unc5h3.