Corticosteroid-induced cleft palate in short-ear mice.

Corticosteroid-induced facial clefting was examined in short-ear mice (inbred strain SEA/GnJ from Jackson Laboratory). They were found to be gentle, prolific breeders (average litter size 7.3 +/- 2.6), with no increased fetal loss due to treatment. Although they have the most "resistant" H-2 haplotype (H-2d), they were found to be highly susceptible to corticosteroid-induced clefting, demonstrating that loci other than H-2 are involved in susceptibility. The short-ear locus itself is a plausible candidate, given that this gene on chromosome 9 leads to defective mesenchymal condensation, which in turn may render these mice extremely sensitive to teratogen exposure. Another gene or genes on chromosome 9 are also possibilities.