Rb=rabbit; m=mouse; r=rat; h=human; s=sheep; b=bovine; ch=chicken; d=dog; ~CT or ~NT=near C or N-terminus. EC=Extracellular; CL=Cytoplasmic loop.
 

Core Binding Factors, Noggin & Sclerostin Antibodies-General Information

The gene noggin encodes a member of one of at least four distinct gene families encoding secreted polypeptides that bind to members of the transforming growth factor-beta superfamily, such as BMP, and inhibit the function of these signaling proteins by preventing their interaction with receptors on the cell surface. Other antagonists with related functions include Chordin, Follistatin, Sclerostin and members of the DAN family. These BMP antagonists are assumed to be diffusible and therefore potentially important in the establishment of BMP activity gradients in vivo Although structurally distinct, members of these gene families have in some cases similar ligand specificity and overlapping patterns of expression, and in the case of Chordin and Noggin these proteins apparently are capable of at least partial compensation for each other. In addition to these multiple secreted BMP antagonists, there are other secreted proteins whose primary function is to overcome this antagonism. Thus, there is a highly complex system to regulate the bioavailability and consequently the activities of BMPs in the extracellular space.

BMP activities are modulated through gene expression, protein processing and by interaction with antagonists. The interplay between BMPs and their antagonists governs developmental and cellular processes as diverse as establishment of the embryonic dorsal-ventral axis, induction of neuronal tissue, and formation of joints in the skeletal system and the neurogenesis in the adult brain. Noggin inhibits BMP signaling by blocking the molecular interfaces of the binding epitopes for both type-I and -II receptors of BMP.

BMPs are important regulators of key events in the processes of bone formation during embryogenesis, postnatal growth, remodeling and regeneration of the skeleton. The BMPs function by binding to a receptor complex that is found on all normal cells and is composed of type-I and -II receptors. The primary unit of bone formation is osteoblast, the bone-forming cell. These osteoblast cells respond to physical loading by transducing signals that alter gene expression patterns. Cbfa (core binding factor), the osteoblast specific transcription factor plays an important role in osteoblast differentiation and function.

Cbfa1/ Runx2/ OSF2/AML3 (alternatively spliced form 507aa and 522aa in human (chr 6p21) and 528aa or 596aa in mouse) is expressed in bone thymus, testis but not in brain, lung, heart or kidney. It is a transcription factor involved in osteoblastic differentiation and skeletal morphogenesis, essential for the maturation of osteoblast and both intramembranous and endochondral ossification. Defects in Cbfa1 are the cause of cleidocranial dysplasia (CCD), an autosomal dominant skeletal disorder with high penetrance and variable expressivity. It is due to defective endochondral and intramembranous bone formation.

Cbfa 2/ Runx1/ AML 1 (11 spliced forms) a 450aa protein in rat, 451aa in mouse and 453 in human (Chr. 21q22.3), It binds to the core site 5'-PYGPYGGT-3' of a number of enhancers and promoters like murine leukemia virus, T-cell receptor enhancers, expressed in all tissues except brain and heart.

Cbfa 3/ Runx3/ AML 2 (2 spliced forms), A protein 409aa long each in mouse, rat and 415aa long in human (Chr. 1p36). As Cbfa 2 it also bind to the core site of number of enhancers and promoters, interacts with TLE1. Its DNA binding is increased by heterodimerization. It shows subcellular nuclear localization.

Noggin is a homodimer (~32kDa) of two monomeric units linked together by a disulfide bond. The monomeric precursor (232aa, human and mouse) is encoded by NOG gene, mapped at human chromosome 17. The mature protein (28-232aa) is secreted as a glycosylated dimer, which binds to BMPs including BMP-2, -4 and-7. The structure of Noggin is very similar to BMP-7. Mutation in Noggin gene leads to skeletal dysplasias characterized by joint fusions.

Sclerostin (213aa in rat and human (chr 17q12) and 211aa in mouse) is a novel secreted osteoclast-derived BMP antagonist with unique ligand specificity; it negatively regulates the formation of bone by repressing the differentiation and/or function of osteoblasts induced by BMPs. Since sclerostin expression is confined to the bone resorbing osteoclast, it provides a mechanism whereby bone apposition is inhibited in the vicinity of resorption. Indicating the role of sclerostin in bone remodeling and links bone resorption and bone apposition. Defects in SOST are the cause of sclerosteosis, a progressive sclerosing bone dysplasia.
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List of publications using ADI's Antibodies to various Cbfa-Noggin related items

cbfa1
Steinert A, 2003, Chondrogenic differentiation of mesenchymal progenitor cells encapsulated in ultrahigh-viscosity alginate Journal of Orthopaedic Research 21, 1090-1097, IHC

Cbfa-1
Perinpanayagam ,H, 2003, Altered Cbfa1 expression and biomineralization in an osteosarcoma cell line Journal of Orthopaedic Research, 22, 404-410, WB, UMR and B1 Cells/60 kda

Cbfa-1
Rabie ABM,, 2003 Cbfa1 couples chondrocytes maturation and endochondral ossification in rat mandibular condylar cartilage Arch Oral Biol 49, 1009-1118, IHC, rat temporomandibular joints,