title: Expression of the transmembrane mucins, MUC1, MUC4 and MUC16, in normal endometrium and in endometriosis.
abstract: OBJECTIVE
  Are the transmembrane mucins, MUC1, MUC4 and MUC16, differentially expressed in endometriosis compared with normal endometrium?
  
  
  CONCLUSIONS
  This study revealed that transmembrane mucin expression does not vary significantly in normal endometrium during the menstrual cycle and is not altered in endometriosis relative to the epithelial marker, cytokeratin-18 (KRT18).
  
  
  BACKGROUND
  Increased serum levels of the transmembrane mucin fragments MUC1, MUC4 and MUC16 that normally dominate the apical surface of simple epithelia are found in several pathological conditions, including endometriosis. Altered mucin expression in gynecologic diseases may promote infertility or endometrial pathologies.
  
  
  METHODS
  This was a laboratory-based study of samples from 12 endometriosis patients as well as non-endometriosis control samples obtained from 31 patients.
  
  
  METHODS
  Total RNA was isolated from endometrial biopsies of ectopic and eutopic endometrium from women with endometriosis and control patients from different stages of the menstrual cycle. Quantitative (q)-RT-PCR analyses were performed for the mucins, MUC1, MUC4 and MUC16, relative to the epithelial marker, cytokeratin-18 (KRT18), or β-actin (ACTB). Frozen sections from endometrial biopsies of proliferative and mid-secretory stage women with endometriosis were immunostained for MUC1, MUC4 and MUC16.
  
  
  RESULTS
  qRT-PCR analyses of MUC1 and MUC16 mRNA revealed that these mucins do not vary significantly during the menstrual cycle nor are they altered in women with endometriosis relative to the epithelial marker, KRT18. MUC4 mRNA is expressed at very low levels relative to MUC1 and MUC16 under all conditions. There was little difference in MUC1 and MUC16 expression between eutopic endometrial and ectopic endometriotic tissues. MUC4 expression also was not significantly higher in the ectopic endometriotic tissues. Immunostaining for all three mucins reveals robust expression of MUC1 and MUC16 at the apical surfaces of endometrial epithelia, but little to no staining for MUC4.
  
  
  CONCLUSIONS
  qRT-PCR analysis was the main method used for mucin detection. Additional studies with stage III-IV endometriotic tissue would be useful to determine if changes in MUC1 and MUC16 expression occur, or if MUC4 expression increases, at later stages of endometriosis.
  
  
  CONCLUSIONS
  We report a comprehensive comparative profile of the major transmembrane mucins, MUC1, MUC4 and MUC16, relative to the epithelial marker, KRT18, in normal cycling endometrium and in endometriosis, and indicate constitutive expression. Previous studies have profiled the expression of individual mucins relative to β-actin and indicate accumulation in the luteal phase. Thus, these differences in interpretation appear to reflect the increased epithelial content of endometrium during the luteal phase.
  
  
  BACKGROUND
  This study was supported by: NIH R01HD29963 to D.D.C.; NIH U54HD007495 to S.M.H.; and NIH R01HD067721 to S.L.Y. and B.A.L. The authors have no competing interests to declare.
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA.
authors.forename: N
authors.initials: N
authors.lastname: Dharmaraj
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Chapela
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA.
authors.forename: M
authors.initials: M
authors.lastname: Morgado
authors.affiliation: Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Hawkins
authors.affiliation: Department of Obstetrics and Gynecology, Greenville Health System, Greenville, SC 29650, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Lessey
authors.affiliation: Department of Obstetrics and Gynecology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Young
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA Department of Biochemistry and Molecular Biology, M.D. Anderson Cancer Center, Houston, TX 77030, USA dcarson@rice.edu.
authors.forename: D D
authors.initials: DD
authors.lastname: Carson
mesh_terms: D018394:CA-125 Antigen / Q000378:metabolism*; D004715:Endometriosis / Q000378:metabolism*; D004717:Endometrium / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008597:Menstrual Cycle / Q000378:metabolism; D018396:Mucin-1 / Q000378:metabolism*; D055264:Mucin-4 / Q000378:metabolism*
chemical_list: D018394:CA-125 Antigen; C060192:MUC1 protein, human; C451759:MUC16 protein, human; C524658:MUC4 protein, human; D008565:Membrane Proteins; D018396:Mucin-1; D055264:Mucin-4
keywords: cytokeratin-18; endometriosis; endometrium; mucins