Methanol causes posteriorization of cervical vertebrae in mice

Inhalation of methanol by pregnant mice before gestation day nine (gd 9) produces fetal skeletal alterations, principally in the cervical region. The appearance of these defects suggests homeotic shifts in segment identity, patterning, or both. To explore this possibility, detailed morphological analyses of the effects of methanol on fetal skeletal development were done. Pregnant mice were gavaged with 0, 4.0, or 5.0 g/kg methanol (MeOH) split in two doses on gd 7, the most sensitive day for induction of skeletal alterations with methanol. Dams were killed on gd 18 and the fetuses were counted, weighed, and examined externally. Fetuses were double stained with alcian blue and alizarin red for examination of cartilaginous and ossified vertebral and rib characteristics, and in selected fetuses cervical vertebrae were disarticulated for more detailed analysis. Observations indicative of methanol-induced homeotic transformations were as follows: [tabular data: see abstract volume] Examination of disarticulated vertebrae revealed foramina and other distinguishing characteristics on vertebrae anterior to those on which they normally appear. These results demonstrate that maternal methanol exposure can alter segment patterning in the developing mouse embryo, producing posteriorization of cervical vertebrae.