Braga V M, Pemberton L F, Duhig T, Gendler S J
Imperial Cancer Research Fund, London, UK.
Development. 1992 Jun;115(2):427-37. doi: 10.1242/dev.115.2.427.
The Muc-1 mucin is found as a transmembrane protein in the apical surface of glandular epithelia. To provide insight into possible functions, we have assessed the timing of expression and the distribution of the Muc-1 protein during mouse embryogenesis using three different techniques: RT-PCR, northern blots and immunohistochemistry. Our results indicate that Muc-1 expression correlates with epithelial differentiation in stomach, pancreas, lung, trachea, kidney and salivary glands. Once started, Muc-1 synthesis continually increases with time, mainly due to epithelial area growth. Our data suggest that expression of the Muc-1 gene is under spatial and temporal control during organogenesis. Although Muc-1 is present in different organs, its expression is not induced systemically, but according to the particular onset of epithelial polarization and branching morphogenesis of each individual organ. It is of particular interest that Muc-1 protein can be detected lining the apical surfaces of the developing lumens when the epithelium of these organs is still undergoing folding and branching, and glandular activity has not yet started. We speculate that Muc-1 may participate in epithelial sheet differentiation/lumen formation during early development of the organs known to express it. This speculation is based on: (1) the detection of Muc-1 expression early during organogenesis, (2) the defined apical localization in different epithelia, (3) the decrease in cell-cell interactions when Muc-1 protein is highly expressed and (4) the possible interaction of its cytoplasmic tail with the actin cytoskeleton. However, it remains to be established using in vitro systems, whether the temporal and local expression of the Muc-1 gene coincident with the morphogenetic events described here is relevant for the process.
Muc-1粘蛋白作为一种跨膜蛋白存在于腺上皮的顶端表面。为深入了解其可能的功能，我们运用三种不同技术，即逆转录聚合酶链反应（RT-PCR）、Northern印迹法和免疫组织化学，评估了Muc-1蛋白在小鼠胚胎发育过程中的表达时间和分布情况。我们的结果表明，Muc-1的表达与胃、胰腺、肺、气管、肾脏和唾液腺中的上皮分化相关。一旦开始表达，Muc-1的合成会随着时间持续增加，这主要是由于上皮面积的增长。我们的数据表明，Muc-1基因的表达在器官发生过程中受到空间和时间的控制。尽管Muc-1存在于不同器官中，但其表达并非全身性诱导，而是根据每个器官上皮极化和分支形态发生的特定起始情况而定。特别有趣的是，当这些器官的上皮仍在进行折叠和分支且腺活动尚未开始时，就可以检测到Muc-1蛋白排列在发育中管腔的顶端表面。我们推测，Muc-1可能在已知表达它的器官早期发育过程中参与上皮细胞层分化/管腔形成。这一推测基于以下几点：（1）在器官发生早期检测到Muc-1的表达；（2）在不同上皮细胞中明确的顶端定位；（3）当Muc-1蛋白高度表达时细胞间相互作用的减少；（4）其细胞质尾巴与肌动蛋白细胞骨架的可能相互作用。然而，使用体外系统来确定与这里描述的形态发生事件同时发生的Muc-1基因的时间和局部表达是否与该过程相关，仍有待确定。
