Murine homodimeric adhesion/growth-regulatory galectins-1, -2 and -7: comparative profiling of gene/ promoter sequences by database mining, of expression by RT-PCR/immunohistochemistry and of contact sites for carbohydrate ligands by computational chemistry.

Following the detection of individual mem- bers of the family of galectins it is an obvious chal- lenge to define the extent of functional overlap/diver- gence among these proteins. As a step to address this issue a comparative profiling has been started in the mouse as a model organism, combining sequence analysis, expression patterns and structural features in the cases of the homodimeric galectins-1, -2 and -7. Close relationship was apparent at the level of glo- bal gene organization. Scrutiny of the proximal pro- moter regions for putative transcription-factor-bind- ing sites by two search algorithms uncovered quali- tative and quantitative differences with potential to influence the combinatorial functionality of regula- tory sequences. RT-PCR mapping with samples from an array of 17 organs revealed significant differen- ces, separating rather ubiquitous gene expression of galectin-1 from the more restricted individual pat- terns of galectins-2 and -7. Using specific antisera obtained by affinity depletion including stringent controls to ascertain lack of cross-reactivity these re- sults were corroborated at the level of galectin locali- zation in fixed tissue sections. Nuclear presence was seen in the case of galectin-1. In addition to non- identical expression profiles the mapping of the car- bohydrate recognition domains of galectins-1 and -7 by homology modelling and docking of naturally oc- curring complex tetra- and pentasaccharides dis- closed a series of sequence deviations which may un- derlie disparate affinities for cell surface glycans/gly- comimetic peptides. In view of applicability the pre- sented data can serve as useful reference to delineate changes with respect to disease and in genetically en- gineered models. To enable more general conclusions on the galectin network it is warranted to further pursue this combined approach within this lectin family.