| Abstract: | 內皮細胞可藉由與組織之間的交互作用來誘導器官發育。腎上腺皮質擁有複雜的血管系統, 其功能和皮質細胞的生長, 組織的維持, 及類固醇的釋放有關。然而在早期器官發生過程中, 血管及腎上腺皮質之間如何交互作用尚有待瞭解。我們過去發現孤獨核接受器蛋白ff1b (nr5a1a), 並因此解明腎間腺 (相當於哺乳類腎上腺) 在斑馬魚胚胎中發生的起源。在發生過程中, 腎間腺依附著鄰近的原腎, 且與內皮細胞呈現緊密連結。最近我們利用遺傳學分析, 闡明了內皮細胞在形成血管前, 會對附近的腎間腺原基細胞發出訊號, 引導兩組原基細胞在胚胎中線區域進行聚合 (Liu & Guo, 2006)。此發現引導我們對其中極可能包含的旁分泌機制, 進行更深入的分子與細胞學分析。在此計畫中, 我們將研究三個課題: (1) 引導腎間腺原基細胞進行聚合的成血管細胞(內皮細胞前身)究竟會形成動脈內皮或靜脈內皮; (2)內皮細胞產生何種訊號?如何產生訊號?及該訊號如何作用之分子機制; (3) 透過研究無血管突變種中所缺少的細胞外基質及聯結蛋白, 以瞭解腎間腺組織及發育中血管如何產生緊密連接。本計畫將有助我們瞭解不同組織附近之內皮細胞如何產生不同訊號; 並且在各種內分泌器官發育過程中, 內皮細胞訊號如何扮演特異性之角色。
Endothelium has been discovered to communicate with organ tissues and provide inductive signals for organ development. The adrenal cortex has a complex vasculature that is essential for growth, tissue maintenance, and access of secreted steroids to the bloodstream. However, the interaction between vasculature and adrenal cortex during early organogenesis remains largely unclear. Our previous identification of orphan nuclear receptor ff1b (nr5a1a) has led to the characterization of zebrafish interrenal tissue, the functional counterpart of mammalian adrenal cortex. The interrenal tissue develops in parallel with the pronephros (embryonic kidney) at early stages, and displays a tight association with the endothelium (Hsu et al., 2003; Chai et al., 2003; Liu and Guo, 2006). As zebrafish embryo does not depend on vasculature to transport oxygen, it is an ideal model for assessing the effects of endothelial dysfunction to interrenal organogenesis, precluding the confounding factor of hypoxia. Recently, we have utilized diverse genetic means in zebrafish to demonstrate that endothelial cells (ECs) intrinsically signal to emergent interrenal primordial cells, prior to vessel formation, to promote their convergence at the embryonic midline (Liu and Guo, 2006). This novel finding is leading to more in-depth analyses for addressing the molecular as well as cellular mechanisms that underlie the putative paracrine signaling. In this proposal, we aim to (1) ascertain whether pre-arterial or pre-venous angioblasts (ECs prior to vessel formation) are involved in the guidance of interrenal movement, and how the molecular heterogeneity of various EC populations would result in different signaling properties; (2) identify the endothelial derived signal(s) and its relevant signaling components from the trunk endothelium, by utilizing fluorescent activated cell sorting (FACS) of cells from transgenic zebrafish coupled with microarray analysis; (3) identify molecular targets which mediate the tight association between interrenal tissue and developing vessels, by morpholino knockdown analysis of extracellular matrix (ECM) and junctional proteins whose expressions are down-regulated in an avascular mutant. In general, this study will help to unravel the complexities of tissue-specific EC-derived signals, as well as their specific roles in various aspects of endocrine organogenesis. |
