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

The transgene insertional mutation 9257 on mouse chromosome 18 was original ly identified by the circling behavior caused by vestibular abnormalities i n heterozygous mutants. To characterize the homozygous phenotype, we genera ted F2 offspring from the cross (C57BL/6J-tg/+ x DBA/2J). Eye defects rangi ng in severity from microphthalmia to anophthalmia were observed in the tg/ tg offspring. Dysmorphic development of the lens was evident as early as E1 0.5 in homozygous transgenic mice. Apparent agenesis of the lateral semicir cular canal was evident at E14.5. Anomalies of:nasomaxillary structures and olfactory neuroepithelium were present in heterozygous and homozygous tran sgenic mice. The 9257 mutation provides a model for analysis of the morphog enesis of these three neurosensory systems and their associated bony struct ures.