斑馬魚水解磷酸酯受器4與5之研究

Abstract

水解磷酸酯為一種結構簡單的酯質卻同時調控多種生理功能，包括細胞增生、移動、分化、以及胚胎發育。目前已知之水解磷酸酯受器有五種，其中水解磷酸酯受器一至三屬於內皮細胞分化基因群，而水解磷酸酯受器四至五則屬於另一嘌呤受器基因群。在斑馬魚系統中，水解磷酸酯受器一已知會調控淋巴管發育，而水解磷酸酯受器三則負責神經管發育。此研究中，我們經由TBLASTN演算法比對斑馬魚與小鼠之基因序列，而取得斑馬魚水解磷酸酯受器四與五之序列。將斑馬魚水解磷酸酯受器四與五和所有已知之水解磷酸酯受器與嘌呤受器基因群綜合比對之後，斑馬魚水解磷酸酯受器四與五分別歸屬於水解磷酸酯受器四與五之基因群。斑馬魚水解磷酸酯受器四表現在五天大之魚鰓、睪丸以及脾臟等處。斑馬魚水解磷酸酯受器五則在十八體節發育期之後在全身表現。斑馬魚水解磷酸酯受器四與五異位表現在大鼠細胞株B103中無法接受水解磷酸酯調控細胞內鈣離子濃度。然而在斑馬魚胚胎中降低斑馬魚水解磷酸酯受器四之表現卻明顯的抑制斑馬魚之血管發育，導致胚胎嚴重水腫。綜合以上實驗，斑馬魚水解磷酸酯受器四應為調控斑馬魚循環發育之重要基因。

Lysophosphatidic acid (LPA) is a simple lysophospholipid which regulates various important biological functions such as cell proliferation, migration, differentiation, and morphogenesis. The LPA receptor on cell membrane has been identified and, designated as LPA1-5. LPA1-3 are the major members of the endothelial differentiation gene (EDG) family. LPA4-5, structurally distinct from LPA1-3, were first discovered as purinergic receptors in P2Y family. In zebrafish (Danio rerio), LPA1 and LPA3 have been identified essential for neural tube and lymphatic vessel development, while the function of other LPA receptors are not yet identified. We searched LPA receptors using the TBLASTN algorithm in the zebrafish nucleotide database, and found zLPA4 and one sequence similar to both LPA5 and P2Y5 in mice. After aligning all the known LPA receptors, the sequence showed more similarities with LPA5 than with P2Y5. In zebrafish, zLPA4 is expressed in the gills, testis and spleen after 5 dpf, and zLPA5 is expressed in most tissues after the 18 somites stage. LPA induced Ca++ mobilization in zLPA4 or zLPA5 over-expressed B103 rat neuroblastoma was not observed. This indicates that zebrafish LPA receptors might not trigger the conventional cascade of mammalian LPA receptors. However, down-regulation of zLPA4 leads to defections in vascular development, which needs more evidence to clarify.