Sialic acids are involved in many cellular interactions. They can serve as an
adhesion ligand or act as an inhibitor to cellular adhesion by charge repulsion or by
masking potential ligands. Although sialic acids are implicated in the process of
blastocyst implantation, their expression and regulation in uterine epithelium of mice
have not been studied. The lectin, Sambucus nigra (SNA) specifically recognizes
��2,6-linked sialic acids, which are involved in cell recognition phenomena. It was
used to probe frozen uterine sections from mice during days one through six of
pregnancy. SNA staining was most intense at the apical surface of uterine epithelial
cells on day one of pregnancy, decreased gradually through day four, and was
undetectable by day five.
The role of the steroid hormones, estrogen and progesterone, in regulating the
expression of ��2,6-linked sialic acids was studied in uterine sections from mice
during the estrous cycle and in ovariectomized mice given hormone replacement
using SNA. SNA staining of these sections during the estrous cycle showed that the
expression of ��2,6-linked sialic acids was stage dependent. Staining was most
intense in uterine sections from mice in estrus, and was not detected in sections from
mice in diestrus. In ovariectomized mice, staining was most intense in mice injected
with estradiol alone, and no staining was evident in mice injected with progesterone
alone. These results suggest that the expression of ��2,6-linked sialic acids decreases
during the time of implantation and that estrogen stimulates and progesterone inhibits
its expression.
��-Galactoside ��2,6-Sialyltransferase (��2,6-ST) is the enzyme that links sialic
acids to Gal��1-4GlcNAc termini of N-linked oligosaccharides. In order to
investigate the mechanism behind the hormonal regulation of ��2,6-linked sialic
acids, the expression of ��2,6-ST was followed in uterine sections from mice during
early pregnancy, during the estrous cycle, and in ovariectomized mice given hormone
replacement. In-situ hybridization was performed using digoxigenin labeled RNA
probes to characterize ��2,6-ST mRNA levels in uterine sections. Expression of
��2,6-ST protein was also measured in uterine sections with a polyclonal antibody
against ��2,6-ST. The expression of ��2,6-ST mRNA and protein correlated well with
the timing of the appearance of ��2,6-linked sialic acids.
These results show that the expression of ��2,6-linked sialic acids on the
surface of mouse uterine epithelium decreases at the time of implantation and
furthermore, that this decrease is due to the regulation of ��2,6-ST by the steroid
hormones. ��2,6-linked sialic acids may serve to inhibit cellular adhesion by creating
a charge repulsion, or by masking potential binding sites. Removal of this inhibition
may permit blastocyst implantation. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32796 |
| Date | 01 June 2000 |
| Creators | Gaza-Bulseco, Georgeen S. |
| Contributors | Morris, John E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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