Eph-ephrin signaling in the lens

项目摘要 根据世界卫生组织，年龄相关的透镜病变是导致视力下降的主要原因。 世界上的缺陷。白内障，定义为眼睛透镜中的任何混浊，仍然是白内障的主要原因。 世界上的盲人老花眼是由于透镜在聚焦过程中改变形状的能力降低而引起的 （住宿），并推而广之，需要阅读眼镜。未解决的老花眼是主要的 全球视力障碍的原因。几十年的研究集中在先天性透镜病理学上，因此， 对于促进终身透镜形成的细胞和分子机制，我们知之甚少 体内平衡最近的研究已经报道，EphA 2受体或肝配蛋白-A5配体的突变是 与人类和小鼠的可变先天性和年龄相关性白内障相关，这些双向 信号分子是调节透镜细胞组织和稳定性的关键组分。 我们的小鼠模型揭示EphA 2的缺失导致与人类相似的年龄相关性皮质白内障 EphA 2功能障碍患者。我们将评估白内障的进展，在我们的小鼠系研究细胞， 以及皮质白内障形成过程中发生的分子变化。我们假设EphA 2的缺失导致 在细胞骨架结构的变化或细胞间粘附的外周纤维细胞，导致光学 透镜皮质的不连续性。 我们的新数据表明，透镜利用了经典配体介导的EphA 2双向信号传导， 非典型的配体非依赖性EphA 2信号传导途径。我们假设典型的EphA 2信号传导 在赤道上皮细胞中是必需的，而在纤维细胞中是必需的 分化和成熟，这种受体活性的分离可能解释了大量的分化和成熟。 由EphA 2突变引起的人类先天性和年龄相关性白内障。我们将评估激活 EphA 2的空间和时间模式，并确定已知的下游途径的活性， 不同的透镜细胞群。我们将EphA 2激动剂和拮抗剂肽应用于原代培养小鼠， 透镜上皮细胞以产生微型晶状体作为透镜发育的体外模型。 透镜中心或核的尺寸和硬度增加被假设为非晶状体性眼的关键因素。 仅与年龄相关的总体透镜硬度和老花眼增加，而且营养和废物运输不良 导致与年龄相关的核性白内障我们新的初步数据显示，EphA 2的丢失导致更软， 较小的透镜核。我们假设Eph-ephrin信号传导是正常细胞间粘附所必需的， 细胞骨架重排，驱动核纤维细胞膜重组和压实。该数据 将提供更好的理解协调信号机制，以维持稳态， 正常老化和晶状体透明度和生物力学特性的变化，这可能导致 开发新的非手术方法来延迟或预防与年龄相关的透镜病变。

Project Summary According to the World Health Organization, age-related lens pathologies are the leading cause of visual impairment in the world. Cataracts, defined as any opacity in the eye lens, remain the leading cause of blindness in the world. Presbyopia is caused by a reduction in the lens’ ability to change shape during focusing (accommodation), and, by extension, the need for reading glasses. Unaddressed presbyopia is the leading cause of visual impairment globally. Decades of study have focused on congenital lens pathologies, and thus, very little is known about the underlying cellular and molecular mechanisms that facilitate lifelong lens homeostasis. Recent studies have reported that mutations of the EphA2 receptor or the ephrin-A5 ligand are associated with variable congenital and age-related cataracts in humans and mice, and these bidirectional signaling molecules are key components for regulating lens cell organization and stability. Our mouse models reveal that loss of EphA2 leads to age-related cortical cataracts similar to human patients with EphA2 dysfunction. We will evaluate cataract progression in our mouse line to study the cellular and molecular changes that occur during cortical cataract formation. We hypothesize that loss of EphA2 results in changes in cytoskeletal structures or cell-cell adhesion of peripheral fiber cells leading to optical discontinuities in the lens cortex. Our new data show that the lens utilizes both canonical ligand-mediated EphA2 bidirectional signaling and non-canonical ligand-independent EphA2 signaling pathways. We hypothesize that canonical EphA2 signaling is required in equatorial epithelial cells while non-canonical EphA2 activation is required for fiber cell differentiation and maturation and that this segregation of receptor activity may explain the large variety of human congenital and age-related cataracts caused by EphA2 mutations. We will evaluate the activation pattern of EphA2 spatially and temporally and determine the activity of known downstream pathways in different lens cell populations. We will apply EphA2 agonist and antagonist peptides to primary culture mouse lens epithelial cells to generate mini lenses as an in vitro model for lens development. Increased size and stiffness of the lens center or nucleus has been hypothesized to be a key factor for not only age-related increases in overall lens stiffness and presbyopia, but also poor nutrient and waste transport leading to age-related nuclear cataracts. Our new preliminary data shows that loss of EphA2 leads to softer, smaller lens nuclei. We hypothesize that Eph-ephrin signaling is required for normal cell-cell adhesion and cytoskeleton rearrangement that drives nuclear fiber cell membrane re-organization and compaction. This data will provide a better understanding of coordinated signaling mechanisms for maintaining homeostasis during normal aging and in lenses with changes in transparency and biomechanical properties, which may lead to the development of new non-surgical approaches to delay or prevent age-related lens pathologies.