title: Transmembrane and truncated (SEC) isoforms of MUC1 in the human endometrium and Fallopian tube.
abstract: The cell surface mucin MUC1 is expressed by endometrial epithelial cells with increased abundance in the secretory phase of the menstrual cycle, when it is found both at the apical cell surface and in secretions. This suggests the presence of a maternal cell surface glycoprotein barrier to embryo implantation, arising from the anti-adhesive property of MUC1. In previous work, we demonstrated alternatively spliced MUC1 variant forms in tumour cells. The variant MUC1/SEC lacks the transmembrane and cytoplasmic sequences found in the full-length variant. We now show that MUC1/SEC mRNA is present in endometrial carcinoma cell lines, endometrial tissue and primary cultured endometrial epithelial cells. The protein can be detected using isoform-specific antibodies in uterine flushings, suggesting release from endometrium in vivo. However, on the basis of immunolocalisation studies, MUC1/SEC also remains associated with the apical epithelial surface both in tissue and in cultured cells. Transmembrane MUC1 and MUC1/SEC are both strikingly localised to the apical surface of tubal epithelium. Thus MUC1 may contribute to the anti-adhesive character of the tubal surface, inhibiting ectopic implantation. The mechanism by which this barrier is overcome in endometrium at implantation is the subject of ongoing investigation.
authors.affiliation: Medical School and School of Biological Sciences, University of Manchester, UK. neil.hey@completemedcomms.com
authors.forename: Neil A
authors.initials: NA
authors.lastname: Hey
authors.forename: Marcos
authors.initials: M
authors.lastname: Meseguer
authors.forename: Carlos
authors.initials: C
authors.lastname: Simón
authors.forename: Nechama I
authors.initials: NI
authors.lastname: Smorodinsky
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Wreschner
authors.forename: María Elena
authors.initials: ME
authors.lastname: Ortíz
authors.forename: John D
authors.initials: JD
authors.lastname: Aplin
mesh_terms: D002277:Carcinoma / Q000737:chemistry* / Q000473:pathology; D002448:Cell Adhesion; D016764:Cell Polarity; D002478:Cells, Cultured / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D016889:Endometrial Neoplasms / Q000737:chemistry* / Q000473:pathology; D004717:Endometrium / Q000737:chemistry*; D004847:Epithelial Cells / Q000737:chemistry; D005187:Fallopian Tubes / Q000737:chemistry*; D005260:Female; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000502:physiology; D018396:Mucin-1 / Q000737:chemistry* / Q000502:physiology; D009363:Neoplasm Proteins / Q000737:chemistry; D020033:Protein Isoforms / Q000737:chemistry; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D018396:Mucin-1; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger