Expression and role of sugar-recognition molecule galectin in the digestive tract

半乳糖凝集素是一种动物凝集素，可识别糖结合物的β-半乳糖苷类，在肠道和泌尿生殖道中含量丰富。本研究用原位杂交和免疫组织化学方法研究了半乳糖凝集素亚型在小鼠消化道、肾脏和卵巢中的细胞表达。Galectin-2、Galectin-3、Galectin-4/6和Galectin-7五种亚型的信号仅在消化道上皮细胞中检测到。在腺胃中，Galectin-2和Galectin-4/6主要表达于胃小凹至胃腺颈，其中粘液细胞是主要的细胞来源。小肠中Galectin-2、Galectin-3和Galectin-4/6的表达与成熟有关。在大肠中Galectin-4/6占主导地位，隐窝的上半部分同时含有Galectin-3的转录本。从唇部到前胃和肛门的复层上皮强表达Galectin-7，弱表达Galectin-3。在泌尿系统中，Galectin-3亚型主要表达于集合管和移行上皮，从肾脏到尿路远端，提示Galectin-3在尿蕾上皮和泄殖腔衍生细胞中有选择性表达。卵巢中以Galectin-1和Galectin-3为主。黄体在退化的特定阶段强烈表达这两种半乳糖凝集素。Galectin-3仅限于黄体退行性变，并且总是与孕酮降解酶的表达一致。Galectin-1的信号强度在回归的起始点首先增加，随后Galectin-3的表达增加。这一发现提示Galectin-1和Galectin-3可能通过不同的机制在黄体细胞中介导孕酮的产生和代谢。由于Galectins具有多种功能，了解其细胞/阶段特异性表达的信息有助于更好地了解Galectins的功能和病理参与。

Galectin is an animal lectin that recognizes β-galatosides of glycoconjugates and is abundant in the gut and urogenital tract. This study revealed the cellular expression of galectin subtypes in the digestive tract, kidney and ovary of mice by in situ hybridization and immunohistochemistry. Signals for five subtypes (galectin-2,-3,-4/6, and-7) were detected exclusively in the epithelia of digestive tract. In the glandular stomach, galectin-2 and-4/6 were predominantly expressed from the gastric pits to neck of gastric glands, where mucous cells were the main cellular sources. The small intestine exhibited intense, maturation-associated expressions of galectin-2,-3, and-4/6. In the large intestine, galectin-4/6 were predominated, and the upper half of crypts simultaneously contained transcripts of galectin-3. Stratified epithelium from the lip to forestomach and anus intensely expressed galectin-7 with weak expressions of galectin-3. In the urinary system, the major subtype was galectin-3, which was expressed in the collecting ducts and transitional epithelium continuously from the kidney to the distal end of the urethra, suggesting selective expression of galectin-3 in epithelia of uretic bud and cloaca-derivatives. Galectin-1 and-3 were predominant in the ovary. The corpus luteum at particular stages of regression intensely expressed both types of galectins. Galectin-3 was restricted to regressing corpus luteum and always coincident to the expression of a progesterone degradation enzyme. The signal intensity of galectin-1 first increased at the starting point of regression followed by increasing expression of galectin-3. This finding suggest that galectin-1 and-3 may mediate the progesterone production and metabolism in luteal cells via different mechanisms. Because multi-functions of galectins, information on their cell/stage-specific expression contributes to a better understanding of the functions and pathological involvements of galectins.