垂体-甲状腺轴即TSH（促甲状腺素）/TSHR（促甲状腺素受体）信号通路存在于包括七鳃鳗在内的所有脊椎动物中，但其起源和演化迄今仍是一个未解之谜。鉴于文昌鱼存在类似垂体的同源器官哈氏窝和类似甲状腺的同源器官内柱，因此我们推测TSH/TSHR信号通路可能已出现于文昌鱼中。有报道表明文昌鱼存在类似TSHR基因。新近，我们发现文昌鱼也有TSHβ亚基。但是，关于文昌鱼TSHβ和TSHR的功能一直缺乏研究。我们拟（1）采用原位杂交和免疫组化技术，研究TSHβ和TSHR组织分布和定位；（2）采用ELISA以及配体、受体和报告基因共转染技术，分析TSHβ和TSHR的互作及TSHβ和融合激素GpA2/TSHβTSHR的活化作用；（3）采用体内实验确立TSHβ和GpA2/TSHβ的生理功能。由此，确定文昌鱼是否存在类似脊椎动物的TSH/TSHR信号通路，进而描绘出脊椎动物垂体-甲状腺轴起源与演化图景。

The pituitary-thyroid axis, or thyroid-stimulating hormone (TSH)/TSH receptor (TSHR) system, has been identified in all vertebrate species including lamprey, however, its origin remains a mystery. Given that amphioxus has the Hatschek's pit, a pituitary-like organ, and the endostyle, a thyroid gland-like organ, we thus propose that a TSH/TSHR system might have emerged in this basal chordate. In accordance with our hypothesis above, TSHR gene has been identified in the genome database of Florida amphioxus. In addition, we have also identified a gene encoding β subunit of TSH (TSHβ) in the genome databases of Florida amphioxus and Xiamen amphioxus. However, functional characterization of both TSHβ and TSHR remains open in amphioxus. We have successfully cloned both TSHβ and TSHR genes from the amphioxus Branchiostoma japonicum. Next, we plan to perform the following experiments: (1) RT-PCR analysis and whole mount hybridization of TSHβ and TSHR genes in adult and embryos/larvae; (2) Recombinant expression and purification of TSHβ and TSHR proteins, and preparation of antibodies; (3) Immunohistochemical localization of TSHβ with TSHR; (4) Binding analysis of recombinant TSHβ with TSHR; (5) Activation of TSHR by recombinant TSHβ or/and fusion hormone GpA2/TSHβ; and (6) Examination in vivo of TSHβ and/or GpA2/TSHβ. Based on the experiments above, we will conclude if the TSH/TSHR system or pituitary-thyroid axis already emerged in amphioxus. This study will certainly enrich and deepen our understanding of the origin and evolution of endocrine system in vertebrates.