Role of the claudin tight junction protein in tube formation during mammalian organ development

以小鼠颌下腺为模型系统，对哺乳动物发育器官的管状结构进行了研究。研究结果如下：(1)研究了ZO-1、occludin和claudins等主要紧密连接蛋白在颌下腺发育过程中的表达模式。结果表明，ZO-1的表达之后是occludin，然后是claudins。这些紧密连接蛋白在管形成开始之前以点状方式表达，然后随着管形成的进行逐渐以紧密连接分布的细小和线性模式表达。(2)Claudin家族的某些成员与细菌肽毒素(C-CPE)特异性结合，C-CPE的结合导致Claudin表达下调。为了研究Claudins在导管形成中的作用，在C-CPE存在的情况下培养发育中的颌下腺。在小鼠下颌下腺的器官培养中，研究人员先前发现，在发育中的腺体中，Sonic hedgehog(Shh)信号分子的生物活性多肽片段可以促进发育中的腺体上皮管形成和细胞极化，包括紧密连接的形成。在本研究中，研究人员发现，除了Shh，刺猬家族的另外两个成员，印度刺猬(India Hedgehog，IHH)和沙漠刺猬(Desert Hedgehog，DHH)，在发育中的小鼠颌下腺中也有表达。此外，研究人员还发现，IHH肽比Shh肽更有效地促进上皮管形成和细胞极化。(论文正在准备中)

Research on the tube formation in developing organs of mammals was made using the mouse submandibular gland as a model system. The investigator has obtained the results described below.(1) The expression pattern of major tight junction proteins, including ZO-1, occludin and claudins, was examined in developing submandibular gland. It turned out that ZO-1 expression was followed by occludin and then by claudins. These tight junction proteins were expressed in a dot-like manner before the beginning of tube formation and then gradually in a thin and linear pattern typical of the tight junction distribution as tube formation proceeds.(2) Certain members of the claudin family specifically bind to a bacterial peptide toxin (C-CPE) and the binding of C-CPE causes downregulation of claudin expression. To investigate the role of claudins in tube formation, developing submandibular glands were cultured in the presence of C-CPE. Claudin expression and tube formation were inhibited in the treated glands but not the control glands, indicating the involvement of claudins in tube formation.(3) The investigator previously showed in an organ culture of the mouse submandibular gland that epithelial tube formation and cell polarization, including tight junction formation, in the developing gland was promoted in the presence of a biologically active peptide fragment of the Sonic hedgehog (Shh) signaling molecule. In the present study the investigator have revealed that in addition to Shh, two other members of the hedgehog family, Indian hedgehog (Ihh) and Desert hedgehog (Dhh), are expressed in developing submandibular gland of mouse. Furthermore, the investigator has found that Ihh peptide promotes epithelial tube formation and cell polarization more efficiently than Shh peptide. (paper in preparation)