Table S2.xlsx from Head transcriptome profiling of glossiphoniid leech (<i>Helobdella austinensis</i>) reveals clues of proboscis development

Cephalization refers to the evolutionary trend toward concentration of neural tissues, sensory organs, mouth and associated structures at the front end of bilaterian animals. Comprehensive studies on gene expression related to anterior formation in invertebrate models are currently lacking. In this study, we performed <i>de novo</i> transcriptional profiling, on a proboscis-bearing leech <i>Helobdella austinensis</i> to identify differentially expressed genes (DEGs) in the anterior versus other parts of the body, and in particular to find clues as to the development of the proboscis. Between the head and the body, 132 head-specific DEGs were identified, of which we chose 11 to investigate their developmental function during embryogenesis. Analysis of the spatial expression of these genes using <i>in situ</i> hybridization showed that they were characteristically expressed in the anterior region of the developing embryo, including the proboscis. Our results provide information on genes related to head formation and insights into the function of proboscis-related genes during organogenesis with the potential roles of genes not yet characterized.头部化（Cephalization）指两侧对称动物的神经组织、感觉器官、口部及相关结构在身体前端集中的演化趋势。目前针对无脊椎动物模型中前部发育相关基因表达的综合性研究仍较为匮乏。本研究以具吻蛭类*Helobdella austinensis*为实验材料，开展从头（de novo）转录组分析，以鉴定头部与身体其他部位的差异表达基因（differentially expressed genes, DEGs），并特别探寻与吻部发育相关的分子线索。研究共在头部与躯体间鉴定得到132个头部特异性差异表达基因，我们从中选取11个，以探究其在胚胎发生过程中的发育功能。通过原位杂交（in situ hybridization）分析这些基因的空间表达模式，结果显示它们特征性地表达于发育胚胎的前部区域，包括吻部。本研究结果为头部形成相关基因提供了基础数据，同时为器官发生过程中吻部相关基因的功能解析提供了新视角，也为尚未被功能表征的基因的潜在作用研究提供了参考方向。