Kobayashi Takuma, Yasuda Kunio, Araki Masasuke
Developmental Neurobiology Laboratory, Department of Biological Sciences, Nara Women's University, Nara 630-8506, Japan.
Dev Growth Differ. 2009 Oct;51(8):723-33. doi: 10.1111/j.1440-169X.2009.01132.x.
Vertebrate ocular morphogenesis requires proper dorso-ventral polarity within the optic vesicle, and loss of dorso-ventral polarity results in failure of optic cup formation and domain specification, as shown by a reverse transplantation of the optic vesicle. We have shown previously that the ocular development depends not only on the signal within the antero-ventral optic vesicle but also on the extraocular signals. In the present study, using embryonic transplantation of a discrete portion of the embryonic chick brain, we demonstrate formation of a second eye from the antero-ventral hemicephalon when it was transplanted in the antero-dorsal hemicephalon of the host embryo. The transplant consists of an antero-ventral quadrant of the optic vesicle and the surrounding part of the anterior cephalon. The original dorso-ventral polarity of the transplant was once cancelled and re-established in accordance with that of the host embryo. Neither dorsal nor ventral cephalic halves in isolation did not develop into entire eye structures under the culture condition; the dorsal halves developed merely into the retinal pigmented epithelium and the ventral halves into the neural retina alone. The present study clearly suggests that extraocular dorsal and ventral signals counterbalance each other to specify the polarity of the optic vesicle.
脊椎动物的眼形态发生需要视泡内正确的背腹极性，视泡背腹极性的丧失会导致视杯形成和区域特化失败，这已通过视泡的反向移植得到证实。我们之前已经表明，眼的发育不仅取决于前腹侧视泡内的信号，还取决于眼外信号。在本研究中，通过对鸡胚脑的离散部分进行胚胎移植，我们证明，当将鸡胚前腹侧半脑移植到宿主胚胎的前背侧半脑时，会从前腹侧半脑形成第二只眼睛。移植组织包括视泡的前腹象限和前脑的周围部分。移植组织原来的背腹极性一度被消除，并根据宿主胚胎的极性重新建立。在培养条件下，单独的背侧或腹侧脑半球都不会发育成完整的眼结构；背侧脑半球仅发育成视网膜色素上皮，腹侧脑半球仅发育成神经视网膜。本研究清楚地表明，眼外的背侧和腹侧信号相互平衡，以确定视泡的极性。
