title: Claudin 7 is reduced in uterine epithelial cells during early pregnancy in the rat.
abstract: The non-receptive uterine luminal epithelium forms an intact polarised epithelial barrier that is refractory to blastocyst invasion. During implantation, organised dismantling of this barrier leads to a receptive state promoting blastocyst attachment. Claudins are tight junction proteins that increase in the uterine epithelium at the time of implantation. Claudin 7 is a member of this family but demonstrates a basolateral localisation pattern that is distinct from other claudins. The present study investigated the localisation, abundance and hormonal regulation of claudin 7 to elucidate a role for the protein during implantation. The results showed that claudin 7 demonstrates a distinct basal and lateral localisation in the uterine luminal and glandular epithelium throughout early pregnancy. On day 1, claudin 7 is abundantly present in response to ovarian estrogen. At the time of implantation, claudin 7 decreases in abundance. This decrease is not dependent on blastocyst presence, as shown by results in pseudopregnant animals. We propose that claudin 7 mediates intercellular adhesions in the uterine epithelium and also may be responsible for stabilising adhesion proteins at the basolateral cell surface. Thus, claudin 7 may function under the maintenance of the uterine luminal epithelial barrier, in the non-receptive state preventing implantation from occurring.
authors.affiliation: Cell and Reproductive Biology Laboratory, School of Medical Sciences (Discipline of Anatomy and Histology) and The Bosch Institute, The University of Sydney, N364, F13 Anderson Stuart Building, Sydney, NSW, 2006, Australia. conniep@anatomy.usyd.edu.au
authors.forename: Connie E
authors.initials: CE
authors.lastname: Poon
authors.forename: Romanthi J
authors.initials: RJ
authors.lastname: Madawala
authors.forename: Margot L
authors.initials: ML
authors.lastname: Day
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Murphy
mesh_terms: D000818:Animals; D001755:Blastocyst; D057167:Claudins / Q000378:metabolism*; D010064:Embryo Implantation; D004717:Endometrium / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism; D005260:Female; D010053:Ovary / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D014599:Uterus / Q000378:metabolism*
chemical_list: D057167:Claudins; C524370:Cldn7 protein, rat; D004967:Estrogens