Cellular mechanisms underlying Fgf8-mediated asymmetry of the pharyngeal endoderm

Fgf8介导的咽内胚层不对称性的细胞机制

基本信息

批准号：
10056861
负责人：
Jennifer Leslie Fish
金额：
$ 15.65万
依托单位：
UNIVERSITY OF MASSACHUSETTS LOWELL
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-08-01 至 2022-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10056861
关键词：
Actins Adherens Junction Affect Alleles Apical Apoptosis Bilateral Birds Branchial arch structure Cell Polarity Cell division Cells Cephalic Cre driver Cytoskeleton Data Defect Development DiGeorge Syndrome Disease susceptibility Distal Ear Ectoderm Elements Embryo Endoderm Epithelial Epithelial Cells Epithelium Evolution Exhibits Face Facial asymmetry Failure Genetic Genotype Goals Growth Head Heart Abnormalities Jaw Lateral Left Mammals Mediating Mesenchyme Mesoderm Messenger RNA Modeling Morphogenesis Morphology Mus Mutant Strains Mice Outcome Parathyroid gland Pathway interactions Penetrance Pharyngeal pouch Pharyngeal structure Phenotype Positioning Attribute Process Regulation Research Role Series Severities Severity of illness Shapes Side Signal Transduction Skeleton Source Surface Syndrome Testing Thymus Gland Thyroid Gland Tissues Tonsil Tympanic membrane Variant Work Zebrafish cardiogenesis craniofacial craniofacial disorder dosage first pharyngeal pouch migration mutant neonate paracrine skeletal

项目摘要

PROJECT SUMMARY The pharyngeal pouches develop into the thymus, thyroid and parathyroid glands and contribute to formation of the ear and tonsils. They also provide signals that are essential to the morphogenesis of the craniofacial skeleton. In this latter role, the specific morphology and position of the pouches relative to the mesenchyme of the pharyngeal arches is critical to instruct skeletal formation. Despite these essential roles for proper development of the vertebrate head, pharyngeal pouch development in mammals remains poorly understood. Pharyngeal pouch formation consists of two separate morphogenetic processes, lateral out-pocketing and proximal-distal extension. The work outlined in this proposal focuses on understanding the role of Fgf8 in the latter process. Using an allelic series of Fgf8 mutant mice, embryos of different Fgf8 dosages can be generated, including both a mild and severe mutant. In contrast to zebrafish, in both mouse Fgf8 mutant genotypes, the first pharyngeal pouch (pp1) out-pockets to contact the ectoderm but fails to extend along the proximal-distal axis. In mild mutants, pp1 is reduced in size, but does extend. In the severe mutant, pp1 does not extend proximo-distally and the ectodermal cleft is also hypoplastic and disorganized, contributing to failure of the first and second arches to separate distally. Severe mutants have small, round pouches in which cells appear to stack upon each other. Together, these data suggest that Fgf8 has additional roles in pharyngeal pouch formation beyond directing lateral out-pocketing, which may include proximal-distal extension of both the pharyngeal endoderm and ectoderm. Previous research has suggested that Fgf8 regulates cell polarity, and that polarity of the actin cytoskeleton is essential to pharyngeal pouch extension. The specific hypothesis to be tested by the proposed research is that Fgf8 has a paracrine function regulating proliferation and polarity of pharyngeal pouch epithelial cells. This hypothesis will be tested through two specific aims. In Specific Aim 1, proliferation and polarity in pouch epithelial cells will be quantified in embryos in which Fgf8 has been reduced globally. In Specific Aim 2, pouch shape will be evaluated in embryos in which Fgf8 is specifically ablated in the pharyngeal mesoderm or ectoderm. The future research goals of this work are to investigate genetic and developmental interactions underlying variation in craniofacial morphogenesis, particularly variation in the severity and penetrance of craniofacial disorders. The Fgf8 allelic series exhibits a large range of morphological variation, including the bilateral variation present in both mutant genotypes. Both Fgf8 mutant genotypes exhibit directional asymmetry of the jaw, exemplified by Fgf8Neo/Neo mice in which unilateral fusion of the jaw on the left side only is observed in 33% of neonates. Although it has yet to be shown directly, directional asymmetry is likely due bilateral asymmetry in Fgf8 expression in the cranial mesoderm as a consequence of heart development. Facial asymmetry and heart defects are associated in several syndromes, notably CHARGE and DiGeorge (22q11 deletion) syndrome, which have similar phenotypes to Fgf8 mutants.

项目概要咽囊发育成胸腺、甲状腺和甲状旁腺，并有助于形成耳朵和扁桃体。它们还提供对颅面形态发生至关重要的信号骨骼。在后一个角色中，小袋相对于间充质的特定形态和位置咽弓对于指导骨骼形成至关重要。尽管有这些重要作用脊椎动物头部的发育、哺乳动物咽袋的发育仍然知之甚少。咽袋的形成由两个独立的形态发生过程组成，即横向出袋和近端-远端延伸。本提案中概述的工作重点是了解 Fgf8 在后一个过程。使用一系列等位基因的 Fgf8 突变小鼠，可以将不同 Fgf8 剂量的胚胎产生的，包括轻度和重度突变体。与斑马鱼相比，小鼠 Fgf8 突变体基因型中，第一个咽袋 (pp1) 外袋接触外胚层，但未能沿外胚层延伸近端-远端轴。在轻度突变体中，pp1 的尺寸减小，但确实延伸。在严重突变体中，pp1 确实不向近远端延伸，外胚层裂也发育不全且紊乱，导致失败第一和第二弓向远端分开。严重突变体有小而圆的囊袋，其中细胞似乎相互堆叠。总之，这些数据表明 Fgf8 在咽部中具有其他作用袋的形成超出了定向横向出袋的范围，这可能包括两个袋的近端-远端延伸咽内胚层和外胚层。先前的研究表明 Fgf8 调节细胞极性，并且肌动蛋白细胞骨架的极性对于咽袋的延伸至关重要。具体假设为所提出的研究测试的是Fgf8具有旁分泌功能，调节细胞的增殖和极性。咽囊上皮细胞。这一假设将通过两个具体目标进行检验。在具体目标 1 中，将在 Fgf8 减少的胚胎中对储袋上皮细胞的增殖和极性进行定量全球。在具体目标 2 中，将在胚胎中评估袋形状，其中 Fgf8 在咽中胚层或外胚层。这项工作的未来研究目标是调查遗传和颅面形态发生变化背后的发育相互作用，特别是颅面疾病的严重程度和外显率。 Fgf8 等位基因系列表现出广泛的形态变异，包括两种突变基因型中存在的双边变异。 Fgf8 突变体基因型表现出颌骨的方向不对称性，例如 Fgf8Neo/Neo 小鼠，其中单侧融合 33% 的新生儿仅发现左侧下颌。虽然还没有直接展现出来，方向不对称可能是由于颅中胚层 Fgf8 表达的双侧不对称所致心脏发育的结果。面部不对称和心脏缺陷与多种综合征相关，尤其是 CHARGE 和 DiGeorge（22q11 缺失）综合征，它们与 Fgf8 突变体具有相似的表型。