CONTROL OF EARLY EYE DEVELOPMENT BY BMP'S

本提案的长期目标是确定骨形态发生蛋白（BMPs）在哺乳动物眼睛发育过程中的作用，BMPs是TGF-分泌信号分子超家族的成员。bmp在胚胎诱导组织相互作用的许多方面都有牵连。特别是，我们最近发现家族成员Bmp4在小鼠胚胎晶状体诱导过程中起着重要作用。在最近的研究中，人类14q22- q23 （BMP4基因的定位位置）的染色体缺失与显性眼盲和垂体发育不全有关。此外，研究表明，另一个家族成员Bmp7对于小鼠的正常眼睛发育是必需的。然而，bmp调节脊椎动物眼睛发育特定过程的分子机制尚不清楚。在这里，我们提出了遗传和实验胚胎学方法来解决这个问题，重点关注Bmp4和i型Bmp受体Alk3的作用。我们将检验以下三个假设：(1) Bmp4不仅在晶状体诱导过程中发挥作用，而且在眼睛形成的后续步骤中也需要发挥作用；(2)Bmp4和另一种信号因子Fgf15直接介导视神经泡的晶状体诱导信号；(3)在眼睛发育早期晶状体外胚层和视网膜神经外胚层都需要独立的Bmp信号。我们的策略利用我们已经建立的胚胎眼外植体培养技术。我们将用外源性Bmp4和/或Fgf15蛋白治疗突变型和野生型胚胎眼组织，以探索它们在眼睛形成中的功能。此外，我们将使用Cre-loxP系统进行条件性基因破坏，在发育中的眼睛中产生特异性缺乏Alk3受体功能的小鼠胚胎。原始的纯合子AIk3突变会导致原肠胚形成前的胚胎致死性，因此眼睛特异性基因的破坏对于研究该基因在胚胎眼睛发育过程中的功能至关重要。该技术产生的胚胎将提供突变眼组织，用于重组器官培养，以研究BMP信号的组织类型特异性功能。这些研究将有助于我们理解分泌信号分子在哺乳动物眼睛发育中的基本作用。此外，该结果将揭示细胞间信号的异常调节导致人类先天性眼缺陷和相关的出生后眼功能障碍的可能性。

The long term goal of this proposal is to define the roles of Bone Morphogenetic Proteins (BMPs), members of the TGF- superfamily of secreted signaling molecules, during mammalian eye development. BMPs have been implicated in many aspects of embryonic inductive tissue interactions. In particular, we have recently shown that one family member, Bmp4, plays an essential role during lens induction in the mouse embryo. In recent studies, chromosomal deletions in humans at 14q22- q23, where the BMP4 gene is mapped, have been linked with dominant anopthalmia and pituitary hypoplasia. Moreover, it has been shown that another family member, Bmp7, is required for normal eye development in the mouse. However, the molecular mechanisms by which BMPs regulate specific processes in vertebrate eye development are poorly understood. Here, we propose genetic and experimental embryological approaches to address this question, focusing on the roles of Bmp4 and a type-I Bmp receptor, Alk3. We will test the following three hypotheses; (1) that Bmp4 function is required, not only during lens induction, but also during subsequent steps in eye formation, (2) that Bmp4 and another signaling factor, Fgf15, directly mediate the lens inductive signal of the optic vesicle, (3) and that Bmp signaling is required independently in both the lens ectoderm and the retinal neuroectoderm during early eye development. Our strategy utilizes an embryonic eye explant culture technique we have established. We will treat both mutant and wildtype embryonic eye tissues with exogenous Bmp4 and/or Fgf15 proteins to explore their functions in eye formation. Furthermore, we will generate mouse embryos that lack Alk3 receptor function specifically in the developing eye using the Cre-loxP system for conditional gene disruption. The original homozygous AIk3 mutation causes pre-gastrulation embryonic lethality, and therefore the eye specific gene disruption is crucial for studying function of this gene during embryonic eye development. The embryos generated by this technique will provide mutant eye tissues which will be used for recombination organ cultures to study tissue-type specific functions of BMP signaling. These studies will contribute significantly to our understanding of the fundamental roles of secreted signaling molecules in mammalian eye development. Moreover, the results will shed light on the possibility that abnormal regulation of intercellular signaling contributes to congenital eye defects and associated postnatal eye dysfunctions in humans.