The Mesoderm-Forming Gene brachyury Regulates Ectoderm-Endoderm Demarcation in the Coral Acropora digitifera
The Mesoderm-Forming Gene brachyury Regulates Ectoderm-Endoderm Demarcation in the Coral Acropora digitifera
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中胚层形成基因 brachyury 调节珊瑚鹿角珊瑚的外胚层-内胚层分界
DOI：
10.1016/j.cub.2016.08.011
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Noriyuki Satoh
中科院分区：
文献类型：
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作者：
Yuuri Yasuoka;Chuya Shinzato;Noriyuki Satoh
在大多数后生动物中，T-box转录因子genebrachyury的胚口表达是保守的[1，2]。其在中胚层形成中的作用已在脊椎动物中被深入研究[3-6]。然而，它的基本功能附近的胚孔是知之甚少，在其他门。刺胞动物是基础的后生动物，对于理解后生动物身体计划的进化很重要[7，8]。因为它们缺乏中胚层，它们已被用于研究中胚层的进化起源[1，9-11]。在这里，我们专注于珊瑚，一个原始的刺胞动物分支，从海葵分化到500百万年[12]。我们开发了一种珊瑚卵的显微注射方法，以检查Brachyury的功能在胚胎发育的石珊瑚，鹿角珊瑚。由于顶孔菌胚胎在胚孔完全关闭后才形成咽[13-15]，因此有助于了解短尾菌在原肠胚形成运动和咽形成中的作用。我们表明，短尾尿的胚口表达直接由珊瑚胚胎外胚层中的Wnt/β-catenin信号传导激活，这表明从Wnt/β-catenin信号传导到短尾尿的调节轴在真后生动物中高度保守。功能丧失分析表明，Brachyury是咽形成所需的，但不是原肠胚运动。全基因组转录组分析表明，Brachyury正调控基因在顶孔绦虫外胚层表达，而负调控基因在内胚层表达。因此，胚孔周围的胚层分界似乎是Brachyury在原肠胚形成过程中进化上保守的作用。与Brachyury在脊椎动物中胚层-外胚层和中胚层-内胚层分界中的功能相比[4-6]，我们的结果表明脊椎动物型中胚层可能起源于与内胚层相邻的表达Brachyury的外胚层。
Blastoporal expression of the T-box transcription factor genebrachyuryis conserved in most metazoans [1, 2]. Its role in mesoderm formation has been intensively studied in vertebrates [3–6]. However, its fundamental function near the blastopore is poorly understood in other phyla. Cnidarians are basal metazoans that are important for understanding evolution of metazoan body plans [7, 8]. Because they lack mesoderm, they have been used to investigate the evolutionary origins of mesoderm [1, 9–11]. Here, we focus on corals, a primitive clade of cnidarians that diverged from sea anemones ∼500 mya [12]. We developed a microinjection method for coral eggs to examine Brachyury functions during embryogenesis of the scleractinian coral,Acropora digitifera. BecauseAcroporaembryos undergo pharynx formation after the blastopore closes completely [13–15], they are useful to understand Brachyury functions in gastrulation movement and pharynx formation. We show that blastoporal expression ofbrachyuryis directly activated by Wnt/β-catenin signaling in the ectoderm of coral embryos, indicating that the regulatory axis from Wnt/β-catenin signaling tobrachyuryis highly conserved among eumetazoans. Loss-of-function analysis demonstrated that Brachyury is required for pharynx formation but not for gastrulation movement. Genome-wide transcriptome analysis demonstrated that genes positively regulated by Brachyury are expressed in the ectoderm ofAcroporagastrulae, while negatively regulated genes are in endoderm. Therefore, germ layer demarcation around the blastopore appears to be the evolutionarily conserved role of Brachyury during gastrulation. Compared with Brachyury functions in vertebrate mesoderm-ectoderm and mesoderm-endoderm demarcation [4–6], our results suggest that the vertebrate-type mesoderm may have originated frombrachyury-expressing ectoderm adjacent to endoderm.