Walter Brian E, Tian Yimin, Garlisch Amy K, Carinato Maria E, Elkins Matthew B, Wolfe Adam D, Schaefer Jonathan J, Perry Kimberly J, Henry Jonathan J
Department of Cell and Structural Biology, University of Illinois, Urbana, IL 61801, USA.
Mol Vis. 2004 Mar 24;10:186-98.
Experimental tissue transplant studies reveal that lens development is directed by a series of early and late inductive interactions. These interactions impart a growing lens-forming bias within competent presumptive lens ectoderm that leads to specification and the commitment to lens fate. Relatively few genes are known which control these events. Identification of additional genes expressed during lens development may reveal key players in these processes and help to characterize these tissue properties.
A large suite of genes has been isolated that are expressed during the process of cornea-lens transdifferentiation (lens regeneration) in Xenopus laevis. Many of these genes are also expressed during embryonic lens development. Genes were selected for expression analysis via in situ hybridization. This group consisted of clones with possible roles in cell determination and differentiation as well as novel clones without previous identities. The spatiotemporal expression of these genes in conjunction with previously described genes were correlated with key events during embryonic lens formation.
Eighteen of the thirty clones analyzed via in situ hybridization demonstrated observable expression in the developing lens. These genes were initially expressed in the presumptive lens ectoderm at a variety of timepoints throughout development. Expression is restricted to discrete time intervals during lens development. However, in most cases, expression was maintained throughout lens development after being initially upregulated.
The expression of these genes suggests that a genetic hierarchy exists in which an increasing number of genes are upregulated and their expression is maintained throughout lens development. Suites of genes appear to be upregulated at specific timepoints during development, correlating with stages of lens induction, specification, commitment, lens placode formation, and lens differentiation, while suites at additional timepoints suggest that other, previously unreported stages exist as well. This analysis provides a genetic framework for characterizing these processes of lens development.
实验性组织移植研究表明，晶状体发育受一系列早期和晚期诱导相互作用的指导。这些相互作用在有能力的假定晶状体外胚层内赋予不断增加的晶状体形成倾向，从而导致特化和对晶状体命运的承诺。已知控制这些事件的基因相对较少。鉴定在晶状体发育过程中表达的其他基因可能揭示这些过程中的关键参与者，并有助于表征这些组织特性。
已分离出一大组在非洲爪蟾角膜-晶状体转分化（晶状体再生）过程中表达的基因。这些基因中的许多也在胚胎晶状体发育过程中表达。通过原位杂交选择基因进行表达分析。该组包括可能在细胞决定和分化中起作用的克隆以及以前身份不明的新克隆。这些基因与先前描述的基因一起的时空表达与胚胎晶状体形成过程中的关键事件相关。
通过原位杂交分析的30个克隆中有18个在发育中的晶状体中表现出可观察到的表达。这些基因最初在整个发育过程中的不同时间点在假定的晶状体外胚层中表达。表达在晶状体发育过程中限于离散的时间间隔。然而，在大多数情况下，表达在最初上调后在整个晶状体发育过程中得以维持。
这些基因的表达表明存在一种基因层次结构，其中越来越多的基因被上调，并且它们的表达在整个晶状体发育过程中得以维持。基因组合似乎在发育过程中的特定时间点被上调，与晶状体诱导、特化、承诺、晶状体板形成和晶状体分化的阶段相关，而在其他时间点的基因组合表明还存在其他先前未报道的阶段。该分析为表征晶状体发育的这些过程提供了一个基因框架。
