title: Eyelid fusion and epithelial differentiation at the ocular surface during mouse embryonic development.
abstract: OBJECTIVE
  To investigate epithelial differentiation at the ocular surface of the developing mouse eye by examining temporal and spatial changes in the expression of specific keratins.
  
  
  METHODS
  Ocular tissues, including the entire eyeball, conjunctiva, and eyelid, of mouse embryos at embryonic day (E) 12.5 to E18.5 as well as of adult mice were examined by hematoxylin-eosin staining and by immunohistochemistry with antibodies to keratins K4, K10, K12, and K14.
  
  
  RESULTS
  Hematoxylin-eosin staining revealed that eyelid fusion occurred at E17.5. Keratin immunohistochemistry demonstrated that: (1) K4 was expressed before K12, which in turn was expressed before K10; (2) expression of K4, K12, and K14 was spatially heterogeneous in the epithelia of the eyelid invaginations before eyelid fusion, but thereafter was continuous and homogeneous in the entire conjunctival epithelium, corneal epithelium, and basal cell layer of the surface epithelia, respectively; and (3) K10 immunoreactivity was not detected before eyelid fusion but was apparent in the epidermis of the eyelid thereafter.
  
  
  CONCLUSIONS
  Eyelid fusion is a critical period for differentiation of the ocular surface ectoderm into the epithelia of the conjunctiva, cornea, and eyelid skin. The conjunctival epithelium differentiates before the corneal epithelium, which in turn differentiates before the eyelid epidermis.
authors.affiliation: Department of Biomolecular Recognition and Ophthalmology, Yamaguchi University School of Medicine, Ube, Japan.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Makiko
authors.initials: M
authors.lastname: Hara
authors.forename: Keisuke
authors.initials: K
authors.lastname: Seki
authors.forename: Ken
authors.initials: K
authors.lastname: Fukuda
authors.forename: Teruo
authors.initials: T
authors.lastname: Nishida
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D003228:Conjunctiva / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D003315:Cornea / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D004475:Ectoderm / Q000166:cytology; D047108:Embryonic Development / Q000502:physiology*; D000078404:Epidermal Cells; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D005143:Eyelids / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D005260:Female; D007150:Immunohistochemistry; D007633:Keratins / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011247:Pregnancy
chemical_list: D007633:Keratins