title: Immunolocalization of matrix proteins in nacre lamellae and their in vivo effects on aragonitic tablet growth.
abstract: How matrix proteins precisely control the growth of nacre lamellae is an open question in biomineralization research. Using the antibodies against matrix proteins for immunolabeling and in vivo experiments, we investigate the structural and functional roles of EDTA-soluble matrix (SM) and EDTA-insoluble matrix (ISM) proteins in nacre biomineralization of the pearl oyster Pinctada fucata. Immunolabeling reveals that a SM protein, nacrein, distributes within aragonitic tablets and intertabular matrix. An ISM protein, which we named P43, has been specifically recognized by polyclonal antibodies raised against the recombinant protein of P. fucata bone morphogenetic protein 2 in immunoblot analysis. Immunolabeling indicates that P43 is localized to interlamellar sheet, and also embedded within aragonitic tablets. Although nacrein and P43 both distribute within aragonitic tablets, they function differently in aragonitic tablet growth. When nacrein is suppressed by the antibodies against it in vivo, crystal overgrowth occurs, indicating that this SM protein is a negative regulator in aragonitic tablet growth. When P43 is suppressed in vivo, the organo-mineral assemblage is disrupted, suggesting that P43 is a framework matrix. Taken together, SM and ISM proteins are indispensable factors for the growth of nacre lamellae, controlling crystal growth and constructing the framework of aragonitic tablets.
authors.affiliation: Department of Biological Sciences and Biotechnology, Institute of Marine Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Ningping
authors.initials: N
authors.lastname: Gong
authors.forename: Junlong
authors.initials: J
authors.lastname: Shangguan
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Liu
authors.forename: Zhenguang
authors.initials: Z
authors.lastname: Yan
authors.forename: Zhuojun
authors.initials: Z
authors.lastname: Ma
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
authors.forename: Rongqing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000032:analysis; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000032:analysis*; D003460:Crystallization; D016326:Extracellular Matrix Proteins / Q000032:analysis*; D007150:Immunohistochemistry; D049911:Pinctada / Q000648:ultrastructure*
chemical_list: D055396:Bone Morphogenetic Protein 2; D016326:Extracellular Matrix Proteins; C101387:nacrein; D002256:Carbonic Anhydrases; D002119:Calcium Carbonate