趋化因子在生物体的整个生命周期中都发挥着独一无二的重要作用。它们能够使特定的受体细胞定向迁移，从而调控个体的发育、稳态维持、免疫应答等生命过程，近期也发现与癌症转移等疾病过程息息相关。尽管对于趋化因子的功能性研究已经较为透彻，但作为分泌型蛋白，它们是如何被释放出细胞的则鲜被研究。Cxcl12，是趋化因子中的一员，被发现存在于斑马鱼原肠期迁移细胞的迁移小体中。这一发现标志着趋化因子分泌途径新假说的诞生。本课题以纯化Cxcl12蛋白进行体外实验为主，并辅助以细胞显微荧光成像，致力于揭示介导Cxcl12蛋白进入迁移小体的机制。结果表明，Tspan4作为迁移小体膜上的重要分子，可能不参与Cxcl12进入迁移小体的过程。

Chemokines play indispensable roles during the whole lifetime of organisms. They are capable of attracting receptor cells towards the high-chemokine direction, and then, regulate the development, homeostasis and immune response. They are also found to be highly related with metastasis and other diseases. However, as a group of secretion proteins, the mechanism of their releasing pathway has not been deeply probed, even though their functions are studied broadly. Cxcl12, a member of chemokine, was discovered in the migrasomes of migrating cells of zebrafish gastrulation stage. This discovery marks the birth of a novel hypothesis for chemokine secretion. Here, applying Cxcl12 protein purification with in vitro pull down assay, and combining in vivo fluorescence microscopy, I found that Tspan4, a fundamental migrasome membrane protein, might not participate in the process of Cxcl12 trafficking into migrasome. The project provides a method to purify Cxcl12 protein in mammalian cells and a new insight for chemokine secretion.