Tbx15/18/22 shares a binding site with Tbx6-r.b to maintain expression of a muscle structural gene in ascidian late embryos
Tbx15/18/22 shares a binding site with Tbx6-r.b to maintain expression of a muscle structural gene in ascidian late embryos
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Tbx15/18/22 与 Tbx6-r.b 共享一个结合位点，以维持海鞘晚期胚胎中肌肉结构基因的表达
DOI：
10.1016/j.ydbio.2021.12.012
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发表时间：
2022
影响因子：
2.7
通讯作者：
Oda-Ishii Izumi
中科院分区：
文献类型：
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作者：
Yu Deli;Iwamura Yuri;Satou Yutaka;Oda-Ishii Izumi
海鞘幼虫的尾巴含有游泳所需的肌肉细胞。这些肌肉细胞大多是自主分化的。这种自主性背后的遗传程序已经被广泛研究，并发现了从母体因素到肌肉结构基因Myl.c开始表达的遗传级联；Myl.c的表达最初由细胞期的转录因子Tbx6-R.b控制，然后由Tbx6-R.b和MRF的联合作用从原肠胚到尾芽早期。在本研究中，我们发现Myl.c在尾芽晚期胚胎和幼虫中持续转录，而Tbx6-R.b和GFP的融合蛋白在尾芽晚期胚胎中几乎检测不到。基因敲除实验、报告实验和体外结合实验表明，在早期胚胎中与Tbx6-Rb结合的Myl.c的一个必要的顺式调节元件与晚期胚胎中的Tbx15/18/22结合以维持Myl.c的表达。我们还发现Tbx15/18/22由Mr f控制，这与Tbx6-R.B.构成了一个调控环。因此，我们的数据表明，Tbx15/18/22最初是在这个调控环的控制下激活的，就像Myl.c一样，然后Tbx15/18/22在Tbx6-R.b消失后维持Myl.c的表达。对Tbx15/18/22变异胚胎的RNA测序表明，许多肌肉结构基因与Tbx15/18/22相似。因此，本研究揭示了Tbx15/18/22替代Tbx6-R.b在晚期胚胎中维持肌肉结构基因转录的机制。
The ascidian larval tail contains muscle cells for swimming. Most of these muscle cells differentiate autonomously. The genetic program behind this autonomy has been studied extensively and the genetic cascade from maternal factors to initiation of expression of a muscle structural gene,Myl.c, has been uncovered;Myl.cexpression is directed initially by transcription factor Tbx6-r.b at the 64-cell stage and then by the combined actions of Tbx6-r.b and Mrf from the gastrula to early tailbud stages. In the present study, we showed that transcription ofMyl.ccontinued in late tailbud embryos and larvae, although a fusion protein of Tbx6-r.b and GFP was hardly detectable in late tailbud embryos. A knockdown experiment, reporter assay, andin vitrobinding assay indicated that an essentialcis-regulatory element ofMyl.cthat bound Tbx6-r.b in early embryos bound Tbx15/18/22 in late embryos to maintain expression ofMyl.c. We also found thatTbx15/18/22was controlled byMrf, which constitutes a regulatory loop withTbx6-r.b. Therefore, our data indicated thatTbx15/18/22was activated initially under control of this regulatory loop as in the case ofMyl.c, and then Tbx15/18/22 maintained the expression ofMyl.cafter Tbx6-r.b had disappeared. RNA-sequencing ofTbx15/18/22morphant embryos revealed that many muscle structural genes were regulated similarly byTbx15/18/22. Thus, the present study revealed the mechanisms of maintenance of transcription of muscle structural genes in late embryos in whichTbx15/18/22takes the place ofTbx6-r.b.