The role of the Pax1/9 gene in the early development of amphioxus pharyngeal gill slits.
The role of the Pax1/9 gene in the early development of amphioxus pharyngeal gill slits.
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DOI：
10.1002/jez.b.22596
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Xin Liu;Guang Li;Xian Liu;Yiquan Wang
中科院分区：
文献类型：
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作者：
Xin Liu;Guang Li;Xian Liu;Yiquan Wang
咽是脊索动物的一个主要特征。与脊椎动物相比，文昌鱼在研究咽发育方面具有优势，胚胎缺乏神经嵴，咽主要来源于内胚层细胞。Pax1/9亚家族基因在脊椎动物咽部发育中起着重要作用，但Pax1/9基因在文文鱼咽部发育中是否具有类似的功能尚不清楚。为了回答这个问题，我们检测了文昌鱼胚胎在不同发育阶段的Pax1/9基因表达模式，并观察了Pax1/9基因敲除后的形态学变化。RT-qPCR分析表明，Pax1/9在神经发育早期开始表达，并在神经发育中期迅速达到峰值。此外，原位杂交分析表明，Pax1/9转录本仅定位于早期神经期胚胎发育中的咽部最内胚层区域；然而，Pax1/9在随后发育阶段由内胚层和外胚层融合形成的鳃缝区域的表达明显下调，并在相邻鳃缝之间的边界区域保持表达。使用morpholino和siRNA两种方法敲低Pax1/9的功能导致了前三个鳃缝的胚胎缺陷，以及前两个鳃缝的融合。在Pax1/9基因敲低的胚胎中，咽部标记基因Six1/2和Tbx1/10的表达水平降低。从这些观察结果，我们得出结论，Pax1/9基因在文文鱼咽内胚层的初始分化和鳃缝的形成中起重要作用，最可能是通过调节Six1/2和Tbx1/10的表达。
The pharynx is a major characteristic of chordates. Compared with vertebrates, amphioxus has an advantage for the study of pharynx development, as embryos lack neural crest, and the pharynx is mainly derived from endoderm cells. The Pax1/9 subfamily genes have essential roles in vertebrate pharyngeal patterning, but it is not known if the Pax1/9 gene has similar functions in amphioxus pharynx development. To answer this question, we examined the Pax1/9 gene expression pattern in amphioxus embryos at different developmental stages, and observed morphological changes following Pax1/9 knockdown. RT-qPCR analysis indicated that Pax1/9 expression was initiated during early neurula stage and rapidly peaked during mid-neurula stage. Furthermore, in situ hybridization analysis showed that Pax1/9 transcripts were localized exclusively in the most endodermal region of the developing pharynx in early neurula stage embryos; however, Pax1/9 expression was strikingly down-regulated in the region where gill slits would form from the fusion of endoderm and ectoderm in subsequent developmental stages and was maintained in the border regions between adjacent gill slits. Knockdown of Pax1/9 function using both morpholino and siRNA approaches led to embryonic defects in the first three gill slits, and fusion of the first two gill slits. Moreover, the expression levels of the pharyngeal marker genes Six1/2 and Tbx1/10 were reduced in Pax1/9 knockdown embryos. From these observations, we concluded that the Pax1/9 gene has an important role in the initial differentiation of amphioxus pharyngeal endoderm and in the formation of gill slits, most likely via modulation of Six1/2 and Tbx1/10 expression.