Avian eggshell structure and osteopontin.
The avian eggshell primarily consists of calcium carbonate mineral (calcite) and matrix proteins. Here we review matrix-mineral relationships in the eggshell at the ultrastructural level using scanning and transmission electron microscopy, and describe the distribution of osteopontin (OPN) as determined by colloidal gold immunolabeling for OPN. A rich protein network integrated within the calcitic structure of the eggshell shows variable, region-specific organization that included layered fibrous planar sheets of matrix, thin filamentous threads, thin film-like surface coatings, vesicular structures and isolated proteins residing on cleaved {104} crystallographic faces of the eggshell calcite. Except for the vesicular structures, these matrix structures all immunolabeled strongly for OPN. Given the potent mineralization- inhibiting function of OPN, we discuss how this protein might regulate eggshell growth rate and inhibit calcification at specific compartmental boundaries to provide eggshell form.
Chien
Y-C
YC
Faculty of Dentistry, McGill University, Montreal, Que., Canada.
Hincke
M T
MT
McKee
M D
MD
D000818:Animals; D002645:Chickens / Q000378:metabolism*; D004528:Egg Shell / Q000737:chemistry / Q000648:ultrastructure*; D004847:Epithelial Cells / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000378:metabolism; D008566:Membranes / Q000648:ultrastructure; D008903:Minerals / Q000378:metabolism; D053495:Osteopontin / Q000378:metabolism*
D008903:Minerals; D053495:Osteopontin