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  • Title: Developmental expression and vitamin D regulation of calbindin-D28K in chick embryonic yolk sac endoderm.
    Author: Tuan RS, Suyama E.
    Journal: J Nutr; 1996 Apr; 126(4 Suppl):1308S-16S. PubMed ID: 8642477.
    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.
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