Optic, olfactory, and vestibular dysmorphogenesis in the homozygous mouse insertional mutant Tg9257.

The transgene insertional mutation 9257 on mouse chromosome 18 was originally identified by the circling behavior caused by vestibular abnormalities in heterozygous mutants. To characterize the homozygous phenotype, we generated F2 offspring from the cross (C57BL/6J-tg/+ x DBA/2J). Eye defects ranging in severity from microphthalmia to anophthalmia were observed in the tg/tg offspring. Dysmorphic development of the lens was evident as early as E10.5 in homozygous transgenic mice. Apparent agenesis of the lateral semicircular canal was evident at E14.5. Anomalies of nasomaxillary structures and olfactory neuroepithelium were present in heterozygous and homozygous transgenic mice. The 9257 mutation provides a model for analysis of the morphogenesis of these three neurosensory systems and their associated bony structures.