Ultrastructural matrix–mineral relationships in avian eggshell, and effects of osteopontin on calcite growth in vitro

Modulation of Calcium Oxalate Dihydrate Growth by Selective Crystal-face Binding of Phosphorylated Osteopontin and Polyaspartate Peptide Showing Occlusion by Sectoral (Compositional) Zoning

“…In regulating biomineralization, intracrystalline proteins likely simultaneously (or uniquely) impart additional functional properties to the final structure of the biomineral, such as, among others, mechanical strength, optical characteristics, or varying textures (82,83). In calcitic avian eggshell, for example, an extremely abundant organic matrix network occludes into the mineral phase, and OPN is a prominent protein of this matrix (84). Intracrystalline organics can also be components of biominerals that dislocate the mineral structure, distorting crystal lattice (85) and modifying their thermodynamic properties (86), thus rendering them more unstable and dissolvable.…”

Intrinsically Disordered Proteins in Biomineralization

“…Its ubiquitous expression pattern and variations in phosphorylation, glycosylation and sulphation suggest that OPN fulfills many different functions (George & Veis, 2008). Moreover, OPN controls the formation of calcium phosphate (Goldberg & Hunter, 1995), calcium carbonate (Chien et al, 2008), and calcium oxalate (Grohe et al, 2007) crystals. NMR, CD and FTIR studies demonstrated that OPN is an IDP in solution (Tab.1) (Fisher et al, 2001;Gorski et al, 1995).…”

“…To produce an eggshell, 5 grams of calcium carbonate must be crystallized within 20 h (Arias et al, 2007;2008). OPN, which is one of the eggshell proteins, was described above and is characterized as an IDP (3.1.4) (Chien et al, 2008;Panheleux et al, 1999). There are some proteins that are unique to eggshells.…”

Dietary calcium deficiency in laying ducks impairs eggshell quality by suppressing the process of shell biomineralization

“…As one of the major phosphorylated proteins of the avian eggshell matrix (Mann et al, 2007), OPN is synthesized in and secreted from the uterus of the laying bird (Fernandez et al, 2003). OPN localizes specifically in the palisade and mammillae layers (mammillary cores) of the shell (Fernandez et al, 2003;Chien et al, 2008). Its gene expression in the uterus of chicken is stimulated by the presence of the egg in the uterus (Lavelin et al, 2000;Brionne et al, 2014) or due to mechanical distension of the uterine wall (Lavelin et al, 1998).…”

“…These observations indicate the importance of OPN in shell calcification. Although the mechanism of shell biomineralization is poorly understood, the involvement of OPN in this mechanism may be mediated via the fabrication of OPNcontaining fibers (Fernandez et al, 2004;Chien et al, 2008Chien et al, , 2009 in the collagen type X net of the outer shell membrane that is formed in the isthmus. In the present study, the decreased mammillary knob thickness and mammillae density induced by calcium deficiency may be associated with the suppression of OPN expression in the uterus (SPP1 expression in the duck).…”