LPA1為斑馬魚淋巴管發育之必需因子

Abstract

Lysophosphatidic acid (LPA) 是一種具有生物活性的小分子，可以專一地與一種G蛋白耦合性受體 (G protein-coupled receptor) 結合，進而調控生物體的許多生理反應。內皮細胞 (endothelial cells) 是構成血管系統的主要細胞，存在內皮細胞中的LPA受體，常久以來便被認為與血管新生 (angiogenesis) 的現象有關；然而在以小鼠為材料的研究中，卻發現缺少LPA1受體的鼠胚並不具有明顯的血管系統缺陷。為了釐清這個問題，我利用斑馬魚 (Danio rerio) 為材料，來探討LPA1受體在斑馬魚發育過程中所扮演的角色。利用morpholino oligonucleotides抑制lpa1表現，斑馬魚胚隨著劑量造成程度不同的心血管機能失調，例如心跳減緩、心室停止搏動，以及血流停滯等，甚至導致全身性的水腫。進一步利用螢光轉基因斑馬魚 (Tg(fli1:EGFP)y1)，發現抑制了LPA1生成後，魚體最大的淋巴管—胸導管的生成也隨之受到抑制，但可以藉由異位表現LPA1而回復。而異位表現一種淋巴管新生的必需因子VEGF-C之後，缺乏的胸導管也會部份回復生長。本研究結果顯示，LPA1在斑馬魚淋巴管的發育過程中扮演著不可或缺的角色。

Lysophosphatidic acid (LPA) is a small bioactive molecule which binds to its specific G protein-coupled receptors (GPCRs) to mediate a variety of physiological responses of organisms. The existence of LPA receptor in endothelial cells (ECs), which are a main component of the vascular system, has long been considered to relate to angiogenesis. However, no significant defect in vascular system was observed in mouse embryos lacking either or a combinator of LPA receptors, LPA1 and LPA2. To verify the previous result, I use zebrafish to study the role of LPA1 during embryonic development. I found that knockdown lpa1 by morpholino oligonucleotides (MO) caused cardiovascular dysfunctions including weaker contractility of ventricle and static blood flow in a dose-dependent manner. In addition, edema also appeared globally. Using the transgenic zebrafish (Tg(fli1:EGFP)y1) to observe vasculature, the development of the major lymphatic vessel, thoracic duct, was impaired or even absent in the LPA1 morphants and these defects could be rescued fully or partially by ectopic expression lpa1 or vegf-c, respectively. Taken together, these results demonstrated that LPA1 is indispensable to lymphatic development in zebrafish.