Fischer Andy J, Foster Shane, Scott Melissa A, Sherwood Patrick
Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210, USA.
J Comp Neurol. 2008 Feb 1;506(4):584-603. doi: 10.1002/cne.21578.
In the retina of warm-blooded vertebrates, photoreceptors are specified many days before the onset of synaptogenesis and the expression of photopigments. The factors that regulate the maturation of photoreceptors in the developing retina remain unknown. We report here that photoreceptors transiently express LIM-domain transcription factors during the development of the chicken retina. We examined the differentiation of photoreceptors through the normal course of embryonic development and at the far periphery of the postnatal retina, where the differentiation of photoreceptors is slowed and persists across a spatial gradient. In the embryonic retina, we find visinin-positive photoreceptors that transiently express Islet2 and Lim3 starting at E8 and ending around E15, but persisting in far peripheral regions of the retina through the first 2 weeks of postnatal development. During early stages of photoreceptor maturation, there is coincident and transient expression of the LIM-domain factors with axonin1, a cell surface glycoprotein that is a member of the immunoglobulin superfamily. Coincident with the downregulation of Islet2 and Lim3, we find the upregulation of calbindin, red/green opsin, rhodopsin, and a synaptic marker in the outer plexiform layer (OPL; dystrophin). In the periphery of the postnatal retina, photoreceptors that express Islet2, Lim3, and axonin1 do not overlap with photoreceptors that express calbindin, red/green opsin, rhodopsin, and dystrophin. We propose that Islet2 and Lim3 may promote the expression of genes that are involved in the early stages of differentiation but may suppress the expression of genes that are required in the mature photoreceptors.
在温血脊椎动物的视网膜中,光感受器在突触发生和光色素表达开始前许多天就已特化。调节发育中视网膜光感受器成熟的因素仍然未知。我们在此报告,在鸡视网膜发育过程中,光感受器会短暂表达含LIM结构域的转录因子。我们通过胚胎发育的正常过程以及出生后视网膜的最周边区域来研究光感受器的分化,在该区域光感受器的分化减缓,并在空间梯度上持续存在。在胚胎视网膜中,我们发现从E8开始到E15左右短暂表达Islet2和Lim3的视宁蛋白阳性光感受器,但在出生后发育的前两周在视网膜的最周边区域持续存在。在光感受器成熟的早期阶段,含LIM结构域的因子与轴突素1同时短暂表达,轴突素1是一种细胞表面糖蛋白,属于免疫球蛋白超家族成员。与Islet2和Lim3的下调同时,我们发现在外网状层(OPL;肌营养不良蛋白)中钙结合蛋白、红/绿视蛋白、视紫红质和一种突触标记物上调。在出生后视网膜的周边区域,表达Islet2、Lim3和轴突素1的光感受器与表达钙结合蛋白、红/绿视蛋白、视紫红质和肌营养不良蛋白的光感受器不重叠。我们提出,Islet2和Lim3可能促进参与分化早期阶段的基因表达,但可能抑制成熟光感受器所需基因的表达。