ABSTRACT
<p><b>OBJECTIVE</b>To examine the change of Smoothened (Smo) expression in the retinofugal pathway and in the growth cones during the period of embryonic day 13 (E13) to E15.</p><p><b>METHODS</b>Smo expression in the chiasm and growth cones was observed by fluorescent immunostaining and retinal explant culture.</p><p><b>RESULTS</b>On E13 and E14, Smo was expressed moderately in the retina and optic disc, and in the corner of the retina, Smo expression was especially dense. On E13, Smo expression was detected in the optic nerves and ventral diencephalon, but only in the superficial region of the optic tract on E14. Smo was also detected in the stem and filopodia of the growth cones in the retinal explant culture during this period.</p><p><b>CONCLUSION</b>Smo expression changes in different developmental phases, suggesting that Smo might play a role in signal optic axon growth during the development of the retinofugal pathway.</p>