Shimazaki Aki, Sakai Akiko, Ogasawara Michio
Department of Biology, Faculty of Science, Chiba University, Chiba, Japan.
Dev Dyn. 2006 Feb;235(2):562-9. doi: 10.1002/dvdy.20657.
Gill slits, a series of openings in the pharyngeal epithelium, are characteristic features of the hemichordate and chordate body plans. In ascidians, these openings, called stigmata, are formed in the branchial sac during juvenile development. Multiple whole-mount in situ hybridization analyses based on approximately 1,500 genes expressed in Ciona intestinalis juveniles, identified 28 genes expressed predominantly in the stigmatal cells. Expression patterns of these stigmatal genes were classified into four different categories. On the basis of these findings, we have been able to show that the peripheral region of a stigma consists of at least three different regions. The expression of a Dlk1-like gene was detected in nonciliated cells during the stigma perforation and division and was maintained in the basal region of the elliptical stigma. Expression of meichroacidin, tektin A1, and tektin B1 orthologs during the differentiation of the ciliated stigmatal cells suggests that some of the molecular mechanisms involved in sperm differentiation might be recruited for the stigma development, or vice versa. Components of the cilia such as alpha-tubulin and rootletin were also expressed in the stigmatal cells. These genes might facilitate further analyses regarding the evolution of the branchial fissures and the development of the ascidian stigmata.
鳃裂是咽上皮中的一系列开口，是半索动物和脊索动物身体结构的特征性标志。在海鞘中，这些开口被称为气门，在幼体发育期间在鳃囊中形成。基于约1500个在玻璃海鞘幼体中表达的基因进行的多次全组织原位杂交分析，鉴定出28个主要在气门细胞中表达的基因。这些气门基因的表达模式可分为四类。基于这些发现，我们已经能够表明，气门的周边区域至少由三个不同区域组成。在气门穿孔和分裂期间，在非纤毛细胞中检测到类Dlk1基因的表达，并在椭圆形气门的基部区域维持表达。在纤毛气门细胞分化过程中，美克酸蛋白、微管蛋白A1和微管蛋白B1直系同源物的表达表明，参与精子分化的一些分子机制可能被用于气门发育，反之亦然。纤毛的成分如α-微管蛋白和根蛋白也在气门细胞中表达。这些基因可能有助于进一步分析鳃裂的进化和海鞘气门的发育。
