Circling behavior exhibited by a transgenic insertional mutant.

We report here of an abnormal circling behavior expressed in the TgX15 transgenic mouse line as a result of insertional mutagenesis. Homozygous transgenic mice expressed the phenotype while heterozygous transgenics were normal. We also found that the dopamine D2 receptor binding sites in the striata of the circling mice were significantly elevated by about 31% compared to normal heterozygous transgenic mice. Other transgenic lines constructed with the same transgene appeared normal suggesting that, in the TgX15 line, a genetic locus significant in mammalian motor behavior has been disrupted.