09-P093 Interplay of Fgfs in pharyngeal endoderm and its potential role in ear development

telencephalon at E9.5–10.5 and cortical ventricular zone later than E12.5. Otx, Tcf, Smad and two sites for unknown transcriptional factors are essential to all these activities. The enhancer is well conserved among tetrapods. The mutant that lacks this enhancer demonstrated that the Emx2 expression under this enhancer is indeed essential to diencephalon, telencephalon and cortical development. However, the Emx2 expression is greatly reduced, but present in the enhancer mutant, indicating the presence of another enhancer. The FB enhancer lacks the activity in cortical hem and does not exhibit a graded activity in dorsal telencephalon. These are unique features of the Emx2 expression in mammalian telencephalon that has Cajal-Retzius cells for the layer formation and exhibits area patterning; the second enhancer is most probably unique to mammal.