Role of integrin a5b1 in vascular patterning and the formation of the pharyngeal arch arteries

先天性心脏病（CHD）是新生儿死亡和发病的重要原因 国际吧主动脉弓动脉（AAA）及其主要分支的缺陷是最严重的 导致CHD的畸形。腹主动脉瘤及其分支通过腹主动脉瘤的不对称重塑而产生。 三对两侧对称的咽弓动脉（PAA），3、4和6。左侧第4 PAA中的缺陷 特别具有破坏性，导致主动脉弓B型（IAA-B）中断。IAA-B破坏了 体循环，出生后致命。IAA-B的遗传原因大多是未知的，强调了一个 迫切需要了解基因和机制调节形成的左第四PAA。PAA的形成是 一个多步骤的过程：PAA内皮细胞（EC）祖细胞在E7.5时在第二心脏区域（SHF）中出现， 在接下来的两天内填充咽弓，最终形成小SHF丛， E10.0在第4弓间产生血管，随着其形成，EC丛逐渐重塑 在第四个拱门的中间合并成一个大的血管，第四个PAA。Fn 1或整合素a5 b1缺失 在Isl 1谱系中，导致右和左第四PAA的缺陷形成，并导致IAA-B。我的实验室 证实了由Fn 1和整合素a5 b1调节的细胞-ECM相互作用在多个时间点上以粘附方式起作用， 阶段以细胞类型特异性方式调节第四PAA的形成和重塑。在这篇文章中，我们提出 Fn 1和整合素a5 b1在维持SHF衍生血管同侧模式中的数据 在咽部的E9.5我们的数据表明，在Isl 1谱系中Fn 1或整合素a5 b1的缺失破坏了 SHF来源的细胞对称地分配到左侧和右侧咽弓，导致呼吸系统失衡 左侧与右侧的SHF衍生细胞的数量。在稍后阶段，在E10和E10.75之间，Fn 1和整合素 a5 b1通过介导咽EC丛向第4 PAA的重塑来调节血管模式。 我们发表的数据表明，Fn 1和整合素a5 b1介导了EC-非细胞-细胞-细胞间质中丛-PAA的重塑。 通过调节负性血管引导线索的表达和激活 为了明确Fn 1和整合素a5 b1对VEGF 2和Erk 1/2表达的调控机制， SHF衍生的血管系统的图案化，我们将使用实时成像、定量免疫荧光显微镜， 遗传上位性分析和单细胞RNAseq来检验两个假设：1）Fn 1和整合素a5 b1 在Isl 1谱系中表达的SHF通过调节SHF的表达来维持SHF衍生细胞在咽部中的平衡分配。 ECM组装和同侧SHF细胞迁移以及2）Fn 1和整合素a5 b1调节丛至PAA 通过调节EC引导信号的表达和Erk 1/2的激活来重塑。完成 提出的研究将提供重要的见解细胞-ECM相互作用的功能，在发展中的 SHF衍生的血管和CHD发病机制。

PROJECT SUMMARY Congenital heart disease (CHD) is a significant cause of neonatal mortality and morbidity worldwide. Defects in the aortic arch artery (AAA) and its major branches are among the most severe malformations that cause CHD. The AAA and its branches arise through the asymmetrical remodeling of the three bilaterally symmetrical pairs of the pharyngeal arch arteries (PAAs), 3, 4, and 6. Defects in the left 4th PAA are particularly devastating, leading to the interruption of the aortic arch type B (IAA-B). IAA-B disrupts the systemic circulation and is lethal after birth. The genetic causes of IAA-B are mostly unknown, underscoring a critical need to understand genes and mechanisms regulating the formation of the left 4th PAA. PAA formation is a multi-step process: PAA endothelial cell (EC) progenitors arise in the second heart field (SHF) by E7.5 and populate pharyngeal arches within the next two days, culminating in the formation of a plexus of small SHF- derived blood vessels between by E10.0 in the 4th arch. Following its formation, the EC plexus gradually remodels by merging in the middle of the 4th arch into one large vessel, the 4th PAA. The deletion of Fn1 or integrin a5b1 in the Isl1 lineages results in the defective formation of the right and left 4th PAA and leads to IAA-B. My lab has demonstrated that cell-ECM interactions regulated by Fn1 and integrin a5b1 function reiteratively, at multiple stages to regulate the 4th PAAs’ formation and remodeling in a cell-type-specific manner. In this grant, we present data implicating Fn1 and integrin a5b1 in maintaining the ipsilateral patterning of the SHF-derived vasculature in the pharynx at E9.5. Our data show that the deletion of Fn1 or integrin a5b1 in the Isl1 lineage disrupts symmetrical allocation of SHF-derived cells to the left and right pharyngeal arches, causing an imbalance in the number of SHF-derived cells on the left vs. the right. At a later stage, between E10 and E10.75, Fn1 and integrin a5b1 regulate vascular patterning by mediating the remodeling of the pharyngeal EC plexus into the 4th PAA. Our published data show that Fn1 and integrin a5b1 mediate the plexus-to-PAA remodeling in an EC-non-cell- autonomous manner by regulating the expression of negative vascular guidance cues and the activation of VEGFR2 and Erk1/2 in the 4th arch. To determine the mechanisms by which Fn1 and integrin a5b1 regulate the patterning of SHF-derived vasculature, we will use live imaging, quantitative immunofluorescence microscopy, genetic epistasis analysis, and single-cell RNAseq to test two hypotheses 1) that Fn1 and integrin a5b1 expressed in the Isl1 lineage maintain the balanced allocation of SHF-derived cells in the pharynx by regulating ECM assembly and ipsilateral SHF cell migration and 2) that Fn1 and integrin a5b1 regulate plexus-to-PAA remodeling by modulating the expression of EC guidance cues and the activation of Erk1/2. Completing the proposed studies will provide essential insights into the functions of cell-ECM interactions in the development of SHF-derived vasculature and CHD pathogenesis.