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Correspondence of gradual developmental increases of expression
of galectin-reactive glycoconjugates with alterations of the total
contents of the two differentially regulated galectins in chicken
intestine and liver as indication for overlapping functions
K.S. Lips1, H. Kaltner1, G. Reuter1, B. Stierstorfer1,
F. Sinowatz2 and H.-J. Gabius1
1Institut für Physiologische Chemie and
2Institut für Tieranatomie, Tierärztliche Fakultät,
Ludwig-Maximilians-Universität, München, Germany
Offprint requests to: Dr.
H.-J. Gabius, Institut für Physiologische Chemie, Tierärztliche
Fakultät, Ludwig-Maximilians-Universität, Veterinär
str. 13, D-80539 München, Germany
Summary. The
duplication of genes for recognition molecules and the ensuing
diversification of the members of such families generate complex
groups of homologous proteins. One example are galactoside-specific
lectins whose sequences display constant features related to sugar
binding, the galectins. Based on the inverse abundance of the
chicken galectins CG-14 and CG-16 in adult intestine and liver,
these two lectins represent a model to comparatively study expression
of the related proteins and the galectin-reactive sites (glycoproteins
and glycolipids) biochemically and histochemically. Functional
overlap and/or acquisition of distinct functions would be reflected
in qualitative and/or quantitative aspects of ligand display.
Using five different stages of embryogenesis, differential regulation
of the two galectins was detected in liver and intestine. The
clear preference for one galectin (CG-14) was observed in intestine
already at rather early stages, whereas equivalence for both proteins
was noted in liver from day 12 to day 18 prior to hatching, as
seen by ELISA assays and Western blot analysis. Presentation of
galectin-reactive glycoproteins showed a tendency for gradual
increase in both organs. Galectin-blotting analysis revealed primarily
very similar patterns of positive bands at the different stages
of development and only few quantitative and qualitative changes.
The reactivity of glycolipids in a solid-phase assay was more
variable, even surpassing the response of extracts of the adult
organ at several embryonic stages. While the localization patterns
of the galectins and galectin-reactive sites were nearly indistinguishable
in the liver, intestinal tissue differed with respect to the placement
and accessibility of binding sites. Thus, the results suggest
a differential regulation of galectin activities in the two organs.
As a sum they resemble the course of development of availability
of glycoprotein ligands in vitro. These findings support the notion
for a partial functional redundancy in this family. The described
approach to employ galectin-specific antibodies and the labeled
galectins as tools to assess presentation of ligands is suggested
to be of general relevance to address the question of distinct
vs. overlapping functions of related recognition molecules. Histol.
Histopathol. 14, 743-760 (1999)
Key words: Agglutinin,
Embryogenesis, Galectin, Glycoprotein, Intestine, Lectin, Liver
DOI: 10.14670/HH-14.743
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