The phenotype of the stargazer 3J mouse has been attributed to an early transposon (ETn) insertion into intron 2, approximately 2 kb downstream from the site of the ETn insertion that gave rise to the original stargazer mutation. RT-PCR analysis demonstrated that in addition to two aberrant transcripts generated by the insertion, some normally spliced mRNA was detected, suggesting that this mutation does not represent a complete null allele. (J:84624)