Differential expression of galectin-1 and galectin-3 during first trimester human embryogenesis.

Development of complex organisms requires specific temporospatial differentiation and expression of the correct phenotype through activation of a variety of genes. Galectins are mammalian lectins able to interact with various extracellular matrix glycoconjugates and have been implicated in several biological events including cell attachment, differentiation, apoptosis, embryogenesis, and cancer invasion and metastasis. In this study, we have examined the expression of galectin-1 and galectin-3 during human first trimester embryogenesis using immunohistochemistry and Western blotting. Variable amounts of galectin-1 and galectin-3 were detected in all tissue protein extracts. Galectin-1 expression was demonstrated in the connective tissue and derived tissues such as smooth and striated muscle cells, and in some epithelia, such as in the basal layers of the skin after 14 weeks and in the epithelial cells of the gonads. Galectin-3 was detected mainly in epithelia, such as the skin, epithelial lining of the digestive and respiratory tract, and urothelium and excretory tubes of the kidney, but also in the myocardial cells, in the peripheral and preossifying hypertrophic chondrocytes, and in the notochord and in the liver. Our study constitutes the first demonstration of galectin-1 and galectin-3 during human embryogenesis. The differential expression of these two lectins suggests that they could participate in the complex processes of tissue differentiation.