I-Scei Meganuclease-mediated transgenesis in the acorn worm, Saccoglossus kowalevskii

Hemichordates are a phylum of marine invertebrate deuterostomes that are closely related to chordates, and represent one of the most promising models to provide insights into early deuterostome evolution. The genome of the hemichordate, Saccoglossus kowalevskii, reveals an extensive set of non-coding elements conserved across all three deuterostome phyla. Functional characterization and cross-phyla comparisons of these putative regulatory elements will enable a better understanding of enhancer evolution, and subsequently how changes in gene regulation give rise to morphological innovation. Here, we describe an efficient method of transgenesis for the characterization of non-coding elements in S. kowalevskii. We first test the capacity of an I-SceI transgenesis system to drive ubiquitous or regionalized gene expression, and to label specific cell types. Finally, we identified a minimal promoter that can be used to test the capacity of putative enhancers in S. kowaleuskii. This work demonstrates that this I-SceI transgenesis technique, when coupled with an understanding of chromatin accessibility, can be a powerful tool for studying how evolutionary changes in gene regulatory mechanisms contributed to the diversification of body plans in deuterostomes.

半索动物是海洋无脊椎后口动物的一个门，与脊索动物密切相关，是深入了解早期后口动物进化的最有前景的模型之一。半索动物（囊舌虫，Saccoglossus kowalevskii）的基因组揭示了一组在所有三个后口动物门中都保守的大量非编码元件。对这些假定的调控元件进行功能鉴定和跨门比较，将有助于更好地理解增强子的进化，以及随后基因调控的变化如何导致形态创新。在此，我们描述了一种用于鉴定囊舌虫中非编码元件的高效转基因方法。我们首先测试了I - SceI转基因系统驱动普遍或区域化基因表达以及标记特定细胞类型的能力。最后，我们确定了一个最小启动子，可用于测试囊舌虫中假定增强子的能力。这项工作表明，这种I - SceI转基因技术，结合对染色质可及性的了解，可以成为研究基因调控机制的进化变化如何促进后口动物身体结构多样化的有力工具。