The galectins constitute a large family of carbohydrate-binding proteins with specificity for N‑acetyl‑lactosamine‑containing glycoproteins. At least 14 mammalian galectins, which share structural similarities in their carbohydrate recognition domains (CRD), have been identified. The galectins have been classified into the prototype galectins (-1, -2, -5, -7, -10, -11, -13, -14), which contain one CRD and exist either as a monomer or a noncovalent homodimer; the chimera galectins (Galectin-3) containing one CRD linked to a nonlectin domain; and the tandem-repeat galectins (-4, -6, -8, -9, -12) consisting of two CRDs joined by a linker peptide. Galectins lack a classical signal peptide and can be localized to the cytosolic compartments where they have intracellular functions. However, via one or more as yet unidentified non-classical secretory pathways, galectins can also be secreted to function extracellularly. Individual members of the galectin family have different tissue distribution profiles and exhibit subtle differences in their carbohydrate-binding specificities. Each family member may preferentially bind to a unique subset of cell-surface glycoproteins (1-4).

Human Galectin-7 is a prototype monomeric galectin. It is specifically expressed in stratified epithelia, notably in epidermis, but is barely detectable in epidermal tumors and significantly down-regulated or absent from squamous carconima cell lines. The Galectin-7 gene is induced by tumor suppressor protein p53 transcriptional activity following genotoxic events. A pro-apoptotic protein, Galectin-7 functions intracellularly upstream of JNK activation and cytochrome-c release. This protein has been shown to increase the susceptibility of keratinocytes to UVB induced apoptosis, an essential processss in the maintenance of epidermal homeostasis. Cell lines transfected with the Galectin-7 gene localized the protein in the nucleus and intracellularly. Human and mouse Galectin-7 share 79% amino acid homology (4-6).