水解磷脂酸受器3 (LPA3) 在斑馬魚早期胚發育所扮演角色之探討

Abstract

水解磷脂酸 (Lysophosphatidic acid, LPA) 廣泛存在生物體中，為一具有多種功能的生物活性脂類，其透過LPA受器參與多種生物性機制，包含細胞生長、分化、存活、凋亡。先前研究顯示LPA受器之一lpa3為內皮細胞分化基因，表現在血管內皮細胞，並可能參與血管生成機制。在本研究中，我選殖出一段斑馬魚lpa3基因含全部編碼區域 (coding region)，利用RT-PCR發現lpa3基因表現於各個不同時期之早期胚更廣泛存在不同成體組織中，以原位雜合技術確認了lpa3基因在早期胚均有表現，而在受精後24小時高量表現於頭部及脊索上下區域。利用LPA3反義基因阻斷劑 (anti-sense morpholino oligonucleotides, zlpa3 MO)，我發現zlpa3-MO可造成心臟循環障礙，水腫、血球及神經生成等缺陷。此等缺陷可因異位表現zlpa3而回復，此證明了zlpa3-MO的專一性及LPA3在此等生理作用之必需性。

Lysophosphatidic acid (LPA) is a commonly existing bioactive lipid with multiple functions. Its functions are known to be mediated via its cognate G-protein-coupled receptors. It involves in many biological activities, including cell growth, differentiation, survival, apoptotic, and so on. LPA receptor 3 (EDG7) is a member of endothelial cell differentiation gene (EDG) family, which expresses in blood endothelial cells and is expected to participate in angiogenesis. However, the lpa3-null mice fail to show notable defects in angiogenesis. To further explore the role of LPA3, I have cloned an lpa3 gene with its complete sequence from zebrafish. Expression analysis by RT-PCR showed that zebrafish lpa3 (zlpa3) ubiquitously expresses in early embryos and adult tissues. By whole-mount in situ hybridization, it revealed that zlpa3 expresses abundantly in the head and regions surrounding notochord. Using the zlpa3 anti-sense morpholino oligonucleotides (zlpa3-MO), I observed that knockdown of zlpa3 resulted in defects in heart circulation, blood cell formation and neurogenesis. The zlpa3-MO resultant defects are specific since they could be rescued by ectopic expression of zlpa3. In conclusion, this study suggests that LPA3 plays an important role in regulating circulation, hematopoiesis and neurogenesis.