Cell-surface enrichment of fucosylated glycoconjugates in the 8- to 16-cell mouse embryo

Carbohydrate biomarker recognition using synthetic lectin mimics

Carbohydrate biomarkers play very important roles in a wide range of biological and pathological processes. Compounds that can specifically recognize a carbohydrate biomarker are useful for targeted delivery of imaging agents and for development of new diagnostics. Furthermore, such compounds could also be candidates for the development of therapeutic agents. A tremendous amount of active work on synthetic lectin mimics has been reported in recent years. Amongst all the synthetic lectins, boronic-acid-based lectins (boronolectins) have shown great promise. Along this line, four classes of boronolectins including peptide-, nucleic-acid-, polymer-, and small-molecule-based ones are discussed with a focus on the design principles and recent advances. We hope that by presenting the potentials of this field, this review will stimulate more research in this area.

Carbohydrate biomarkers for future disease detection and treatment

Carbohydrates are considered as one of the most important classes of biomarkers for cell types, disease states, protein functions, and developmental states. Carbohydrate "binders" that can specifically recognize a carbohydrate biomarker can be used for developing novel types of site specific delivery methods and imaging agents. In this review, we present selected examples of important carbohydrate biomarkers and how they can be targeted for the development of therapeutic and diagnostic agents. Examples are arranged based on disease categories including (1) infectious diseases, (2) cancer, (3) inflammation and immune responses, (4) signal transduction, (5) stem cell transformation, (6) embryo development, and (7) cardiovascular diseases, though some issues cross therapeutic boundaries.

Ultrastructural localization of lectin receptors in the preimplantation ovine embryo

BACKGROUND

Preimplantation development of mammalia is characterized by cell surface changes functioning in intercellular communication and adhesion. The glycoconjugate role in cellular interactions has been analysed for several groups but not in sheep embryos. The binding patterns of eleven lectins during sheep preimplantation development were investigated and the role of glycoconjugates in early development was discussed.

METHODS

Ultrathin sections from preimplantation ovine embryos (3-7 days) were incubated with different colloidal gold conjugated lectins and the frequency of gold particles on the cell membrane, some organelles, and the zona pellucida was evaluated.

RESULTS AND CONCLUSIONS

We observed a higher staining of WGA, DBA, and SBA lectins in the intercellular contact zone with respect to the free cell surface of blastomeres during cleavage. This indicates that the N-acetyl galactosamine and N-acetyl glucosamine residues may be involved in sheep morula compaction. In contrast, the trophoblast cell displays an increase of staining of some lectins previously identified during cleavage (LcH, WGA, SBA, MPA, and PNA) on the free membrane, and a lack of sugar residues in the intercellular surface. This polarization of the trophoblast cell surface is not observed in the inner cell mass and could provide a mechanism for differentiation within the blastocyst. Intracytoplasmic vesicles show a cytochemical identity with lysosomes in the blastocyst (abundant GlcNAc and Man/Glc residues) that may reflect a functional relationship between both organelles in an intracellular cycle. The zona pellucida presents abundant GalNAc, GlcNAc, and Gal residues during preimplantation ovine development.

Developmental control of human preimplantation embryos: a comparative approach

The period for which oocyte-derived factors are engaged in the control of human embryonic development involves at least the first four cell cycles after fertilization. The maternal-embryonic transition in humans 8- to 16-cell embryos is a relatively vulnerable process, the failure of which entails developmental arrest of the given blastomere. The very early cellular differentiative events in human embryos, including blastomere surface polarization and segregation of the inner cell mass and trophectoderm cell lineages, appear to be dependent largely on the maternal genetic program. However, the embryonic genome is required for the formation of the blastocyst cavity, which is necessary to allow further differentiation of the first two embryonic tissues. Blastomeres with major developmental defects are removed by fragmentation and their loss is compensated by proliferation of remaining normal blastomeres. This mechanism is also mainly responsible for the regulation of ploidy through elimination of aneuploid blastomeres. The data presented suggest that embryos of individual mammalian species may differ in the timing of relevant developmental changes at the cellular and molecular levels. This should be taken into account when findings obtained on embryos of one species are used to anticipate the behavior of embryos of another species under identical conditions.