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>
Subject(s)
Animals , Mice , Fluorescent Antibody Technique , Mice, Inbred C57BL , Optic Chiasm , Cell Biology , Embryology , Metabolism , Optic Nerve , Cell Biology , Embryology , Metabolism , Receptors, G-Protein-Coupled , Retina , Cell Biology , Embryology , Metabolism , Smoothened Receptor , Visual Pathways , Cell Biology , Embryology , MetabolismABSTRACT
<p><b>OBJECTIVE</b>To understand the function of Sonic hedgehog in chiasm development in mouse embryos of embryonic day 13 (E13) to E15.</p><p><b>METHODS</b>Brain slices of E13-E15 mouse embryos containing the optic pathway from the eyes to the optic tract were prepared and cultured in DMEM/F12 in the presence of 10% fetal bovine serum at 37 degrees in a rolling incubator for 5 h. The antibody to Shh was added into the culture medium of the slices in the treatment group, while no additional chemical or only normal mouse IgG was added in the control groups. After culture, the brain slices were fixed and a DiI granule was inserted into the optic disc in one eye. Seven days later, the tissue overlying the chiasm was removed to expose the DiI-labeled chiasm for observation under confocal microscope, and the images were analyzed by METAMORPH software.</p><p><b>RESULTS</b>Shh antibody treatment produced a reduction of crossing of the earliest retinal axons at the midline of E13 chiasm, and the uncrossed axons were also influenced by Shh antibody at E15.</p><p><b>CONCLUSION</b>Shh executes a transient but important function in axon decussation in the early stage of mouse optic chiasm development and signals axon turning in the later stage.</p>