Phenotypic Expression of an Oxytocin Peptide Null Mutation in Mice

OT has been implicated in several aspects of reproduction including sexual behavior, induction of labor, milk ejection and maternal behavior (Carter, 1992; Witt, 1995). Pharmacological and biochemical studies have also implicated OT in the modulation of separation distress, social preference and aggressive behavior. To further examine the role of endogenous OT in the development and expression of reproductive and other social behavior, a transgenic mouse was engineered to produce deletion of the DNA sequence encoding the OT peptide (Nishimori et al., 1996). In particular, embryonic stem cells were electroporated with the deletion-targeting DNA sequence. Homologous recombination of the targeting sequence with the OT gene resulted in a recombinant allele lacking the DNA sequences coding for the OT peptide, which are located on the first exon. Cell lines with the correct recombination event were injected into blastocysts in order to create chimeras. Chimeras with germ-line transmission were used to create the strain of OT “knockout” mice.