Effect of the X-linked gene Tabby (Ta) on eyelid opening and incisor eruption in neonatal mice is opposite to that of epidermal growth factor

Studies on eyelid opening and incisor eruption in 216 neonatal Tabby (Ta)-bearing mice and wildtype controls (35 Ta/Y, 62 + /Y, 30 Ta/Ta, 57 Ta/+ and 32 +/+) showed that in animals hemizygous and homozygous for Ta, the timing of eyelid opening and incisor eruption was significantly delayed (P less than 0.05). It was also observed that once open, the eyes of mutant pups do not remain open for long but soon close again for several days before reopening. An iterative eyes open-eyes closed process seems to continue beyond puberty. Studies in 25 epidermal growth factor (EGF)-treated mutants and 23 saline-treated controls showed that neonatal EGF injections (4 micrograms g-1 body weight per day) reversed the delayed timing of eyelid opening and incisor eruption in hemizygote and homozygote Tabby mice. However, both mutant and wildtype EGF-treated mice also showed the eyes open-eyes closed cycle, whereas untreated nonmutant mice did not. Because Tabby appears to be genetically homologous to the gene for human X-linked hypohidrotic ectodermal dysplasia, these results may have potential clinical significance. The eyes open-eyes closed cycle may involve cycling levels of EGF receptor; since the gene for this receptor shows homology with an oncogene, this system may be useful in studies on genetic control of oncogene function.