其旁系同源物Chx10/Vsx2对Vsx1的负调控在脊椎动物视网膜中是保守的。

Negative regulation of Vsx1 by its paralog Chx10/Vsx2 is conserved in the vertebrate retina.

作者信息

Clark Anna M, Yun Sanghee, Veien Eric S, Wu Yuan Y, Chow Robert L, Dorsky Richard I, Levine Edward M

机构信息

Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA.

出版信息

Brain Res. 2008 Feb 4;1192:99-113. doi: 10.1016/j.brainres.2007.06.007. Epub 2007 Jun 18.

Abstract

Chx10/Vsx2 and Vsx1 are the only Paired-like CVC (Prd-L:CVC) homeobox genes in the mouse genome. Both are expressed in the retina and have important but distinct roles in retinal development. Mutations in Chx10/Vsx2 cause reduced retinal progenitor cell (RPC) proliferation and an absence of bipolar cells, while mutations in Vsx1 impair differentiation of cone bipolar cells. Given their structural similarities and importance in retinal development, we sought to determine if a regulatory interaction exists between these genes and whether inactivation of both genes blocks initiation of retinal development. We found that Chx10/Vsx2 binds to a specific sequence in the Vsx1 5'-intergenic region and represses the activity of a luciferase reporter under the control of the Vsx1 promoter. This is consistent with our observation that there is an inverse relationship between the levels of Chx10/Vsx2 and Vsx1 immunostaining within the bipolar cell class. Furthermore, Vsx1 mRNA is upregulated in the RPCs of Chx10/Vsx2 deficient mice and zebrafish embryos injected with a chx10/vsx2 morpholino. In mice deficient for both Chx10/Vsx2 and Vsx1 and zebrafish embryos co-injected with chx10/Vsx2 and vsx1 morpholinos, the changes in embryonic retinal development and marker expression are similar in magnitude to embryos with Chx10/Vsx2 loss of function only. From these studies, we propose that Vsx1 is a direct target of Chx10/Vsx2-mediated transcriptional repression. Although Vsx1 mRNA is upregulated in Chx10/Vsx2 deficient RPCs, Vsx1 does not genetically compensate for loss of Chx10/Vsx2, demonstrating that Prd-L:CVC genes, although important, are not absolutely required to initiate retinal development.

摘要

Chx10/Vsx2和Vsx1是小鼠基因组中仅有的配对样CVC(Prd-L:CVC)同源框基因。二者均在视网膜中表达,且在视网膜发育过程中发挥着重要但不同的作用。Chx10/Vsx2的突变会导致视网膜祖细胞(RPC)增殖减少以及双极细胞缺失,而Vsx1的突变则会损害视锥双极细胞的分化。鉴于它们在结构上的相似性以及在视网膜发育中的重要性,我们试图确定这两个基因之间是否存在调控相互作用,以及两个基因的失活是否会阻断视网膜发育的起始。我们发现Chx10/Vsx2与Vsx1 5'-基因间区域的特定序列结合,并抑制在Vsx1启动子控制下的荧光素酶报告基因的活性。这与我们的观察结果一致,即在双极细胞类别中,Chx10/Vsx2和Vsx1免疫染色水平呈负相关。此外,在Chx10/Vsx2缺陷小鼠的RPC以及注射了chx10/vsx2吗啉代寡核苷酸的斑马鱼胚胎中,Vsx1 mRNA上调。在Chx10/Vsx2和Vsx1均缺陷的小鼠以及共同注射chx10/Vsx2和vsx1吗啉代寡核苷酸的斑马鱼胚胎中,胚胎视网膜发育和标志物表达的变化在程度上与仅Chx10/Vsx2功能缺失的胚胎相似。从这些研究中,我们提出Vsx1是Chx10/Vsx2介导的转录抑制的直接靶点。尽管在Chx10/Vsx2缺陷的RPC中Vsx1 mRNA上调,但Vsx1并不能在基因上补偿Chx10/Vsx2的缺失,这表明Prd-L:CVC基因虽然很重要,但并非启动视网膜发育绝对必需的。

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