| dc.description.abstract | Galectins are proteins with 15 known members found in nearly all living
organisms. They share a conserved CRD that binds beta-galactoside sugars, and
functions to cross-link glycoproteins as well as glycolipid receptors on the surface of
cells to initiate biological responses. Functional studies on the extracellular and
intracellular roles of galectins implicate them in cell adhesion, chemoattraction and
migration as well as growth, differentiation and apoptosis. Therefore, studies were
conducted to identify functional roles of galectin 15 (LGALS15) during the periimplantation
period of pregnancy in the sheep.
The first study was designed to develop and characterize primary ovine
trophectoderm cell lines for the study of the biological functions of LGALS15. Once
characterized, these cell lines were used to investigate the role of LGALS15 in
trophectoderm gene expression, development, growth, and survival. Two primary
trophectoderm cell lines (oTr1 and oTrF) were developed, and they had characteristics
similar to in vivo conceptus trophectoderm relative to gene expression, morphology, and migration and proved suitable as an in vitro model to investigate functional roles of
LGALS15.
The second study investigated LGALS15 function in trophectoderm cell
adhesion. A dose-dependent increase in oTr cell attachment to LGALS15 was found
that could be inhibited by cyclic GRGDS, but not GRADS, peptides. Mutation of the
LDVRGD integrin binding sequence of LGALS15 to LADRAD decreased its ability to
promote oTr cell attachment, whereas mutation of the CRD had little effect. LGALS15
induced formation of robust focal adhesions in oTr cells that were abolished by mutation
of the LDVRGD sequence.
The third study tested the hypothesis that LGALS15 is a secreted regulator of
trophectoderm development and gene expression, as well as growth, migration, and
apoptosis of trophoblast. LGALS15 moderately increased cellular proliferation, partially
inhibited staurosporine elicited apoptosis, stimulated migration that was dependent on
Jun N-terminal kinase (JNK), and initiated differential gene expression of oTr cells.
Collectively, these results support the hypothesis that LGALS15 has a biological
role in the peri-implantation stage of early pregnancy in the ovine uterus and stimulates
trophectoderm cell gene expression, migration and attachment via integrin binding and
activation which are critical to blastocyst elongation and implantation. | en |
