title: Developmental expression and vitamin D regulation of calbindin-D28K in chick embryonic yolk sac endoderm.
abstract: The yolk is an important calcium source for the developing chick embryo. The epithelial yolk sac endodermal cells lie in direct contact with the yolk and are the principal nutrient-transporting cell type. We previously reported that vitamin D treatment stimulated yolk calcium mobilization and that the vitamin D-dependent Ca2+-binding protein, calbindin-D28K, is present in the yolk sac. We report here the developmental expression and regulation of calbindin-D28K in the yolk sac. Calbindin-D28K is expressed as early as incubation d 3 and is found exclusively within the cytoplasm of endodermal cells. Comparative protein and mRNA analyses of yolk sac and dissociated yolk sac endodermal cells as a function of development and treatment with calcitriol (1,25-dihydroxyvitamin D3) in vitro and in vivo showed a development-specific and vitamin D-inducible expression of calbindin-D28K. Northern analysis revealed the expression of vitamin D receptor mRNA in the yolk sac, beginning as early as d 3, strongly indicating that the extraembryonic yolk sac is an early vitamin D target tissue. Cultured yolk sac endodermal cells should serve as a useful in vitro cell model for analyzing the cellular and molecular mechanisms of vitamin D action.
authors.affiliation: Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Tuan
authors.forename: E
authors.initials: E
authors.lastname: Suyama
mesh_terms: D000818:Animals; D064026:Calbindins; D002117:Calcitriol / Q000494:pharmacology*; D002642:Chick Embryo; D004707:Endoderm / Q000737:chemistry* / Q000187:drug effects; D007150:Immunohistochemistry; D064030:S100 Calcium Binding Protein G / Q000032:analysis*; D015017:Yolk Sac / Q000737:chemistry* / Q000187:drug effects
chemical_list: D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D002117:Calcitriol