Toy J, Yang J M, Leppert G S, Sundin O H
Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287-9289, USA.
Proc Natl Acad Sci U S A. 1998 Sep 1;95(18):10643-8. doi: 10.1073/pnas.95.18.10643.
Vertebrate eye development begins at the gastrula stage, when a region known as the eye field acquires the capacity to generate retina and lens. Optx2, a homeobox gene of the sine oculis-Six family, is selectively expressed in this early eye field and later in the lens placode and optic vesicle. The distal and ventral portion of the optic vesicle are fated to become the retina and optic nerve, whereas the dorsal portion eventually loses its neural characteristics and activates the synthesis of melanin, forming the retinal pigment epithelium. Optx2 expression is turned off in the future pigment epithelium but remains expressed in the proliferating neuroblasts and differentiating cells of the neural retina. When an Optx2-expressing plasmid is transfected into embryonic or mature chicken pigment epithelial cells, these cells adopt a neuronal morphology and express markers characteristic of developing neural retina and photoreceptors. One explanation of these results is that Optx2 functions as a determinant of retinal precursors and that it has induced the transdifferentiation of pigment epithelium into retinal neurons and photoreceptors. We also have isolated optix, a Drosophila gene that is the closest insect homologue of Optx2 and Six3. Optix is expressed during early development of the fly head and eye primordia.
脊椎动物的眼睛发育始于原肠胚阶段，此时一个被称为眼场的区域获得了产生视网膜和晶状体的能力。Optx2是 sine oculis-Six 家族的一个同源异型盒基因，在这个早期眼场中选择性表达，随后在晶状体基板和视泡中表达。视泡的远端和腹侧部分注定会成为视网膜和视神经，而背侧部分最终会失去其神经特征并激活黑色素的合成，形成视网膜色素上皮。Optx2在未来的色素上皮中表达关闭，但在神经视网膜的增殖神经母细胞和分化细胞中仍有表达。当将表达Optx2的质粒转染到胚胎或成熟的鸡色素上皮细胞中时，这些细胞会呈现神经元形态并表达发育中的神经视网膜和光感受器的特征性标志物。对这些结果的一种解释是，Optx2作为视网膜前体的决定因素发挥作用，并且它诱导了色素上皮向视网膜神经元和光感受器的转分化。我们还分离出了optix，它是果蝇中的一个基因，是Optx2和Six3最接近的昆虫同源物。Optix在果蝇头部和眼原基的早期发育过程中表达。
