We have shown that besides a role in eye and nose development, Pax6 is also required for the development of forebrain structures. Loss of Pax6 function causes a failure in the establishment of several expression boundaries that specify longitudinal domains within the developing forebrain (Stoykova et al., 1996). Our findings also indicate that in addition to Pax6, other genes are also required for eye development. Based on existing Drosophila mutants, we have identified the mouse Six3 gene which is a functional homologue of the sine oculis gene involved in the fly eye development. Earlier on, Six3 expression is restricted to the anterior neural plate and is later found in the region of the optic recess, the hypothalamus and optic vesicles. Using a gain-of-function approach, we have demonstrated that Six3 activity in fish embryos is sufficient to promote ectopic lens formation in the absence of an optic vesicle. Our results show that in addition to the lens placode, the ectoderm in the region of the otic placode is competent to respond to a lens promoting signal. These studies identify Six3 as another key player in the development of the vertebrate eye (Oliver et al., 1996). Another gene, Pax2, is also expressed in structures ot the developing visual system. We generated Pax2 mutant mice which reveal the requirement of Pax2 for the establishment of axonal pathways along the optic stalks and ventral diencephalon. In Pax2 mutant brains, the optic tracts remain completely ipsilateral due to the agenesis of the optic chiasm. Pax2 mutants also show extension of the pigmented retina into the oplic stalks and failure of the optic fissure to close resulting in coloboma. Therefore, Pax2 is a major regulator required for the closure of the optic fissure and for the correct optic nerve trajectory (Torres et al., 1996),.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology