Endoglin is a 90kD type I transmembrane glycoprotein of the zona pellucida (ZP) family of proteins. Endoglin and TGF-b RIII/betaglycan are type III receptors for TGF-b superfamily ligands, sharing 71% aa sequence identity within the transmembrane (TM) and cytoplasmic domains. Mouse endoglin cDNA encodes 653aa including a 26aa signal sequence, a 555aa extracellular domain with a two-part ZP domain, a TM domain, and a 47aa cytoplasmic domain. A mouse isoform with a 35aa cytoplasmic domain (S-endoglin) can oppose effects of long (L) endoglin. Endoglin is highly expressed on proliferating vascular endothelial cells, chondrocytes, and syncytiotrophoblasts of term placenta, with lower amounts on hematopoietic, mesenchymal and neural crest stem cells, activated monocytes, and lymphoid and myeloid leukemic cells. Endoglin expression can be increased by TGF-b, senescence (S-endoglin in endothelium), stress-induced S100B (in placenta or amnion), or hypoxia. The mouse endoglin ECD shares 69%, 84%, 62%, 63%, and 66% aa sequence identity with human, rat, bovine, porcine, and canine endoglin, respectively. In complexes with type II receptors (TGF-b RII), endoglin homodimers can interact with TGF-b1 and TGF-b3 but not TGF-b2. Similarly, they interact with activin A and BMP-7 via activin type IIA or B receptors, and with BMP-2 via BMPR-IA/ALK-3 or BMPR-IB/ALK-6. BMP-9, however, is reported to bind endoglin directly. Endoglin modification of ligand-induced signaling can vary according to conditions. For example, expression of endoglin can inhibit TGF-b1 signals but enhance BMP-7 signals in the same myoblast cell line. Many studies find that endoglin-deficient endothelial cells show inhibited signaling in response to TGF-b. Deletion of mouse endoglin causes lethal vascular and cardiovascular defects. Human endoglin haploinsufficiency, which reduces both transmembrane and soluble endoglin, can cause the vascular disorder, hereditary hemorrhagic telangiectasia type I. These abnormalities confirm the essential function of endoglin in differentiation of vascular smooth muscle, angiogenesis, and neovascularization. Myocardial infarction is associated with low circulating endoglin, with lowest values correlating with poor prognosis. In preeclampsia of pregnancy, high levels of proteolytically generated soluble endoglin and VEGF R1 (sFlt-1), along with low placental growth factor (PlGF), are pathogenic due to angiogenic activity. The elevated soluble endoglin can be detected in either blood or urine. Soluble endoglin can also be elevated in knee osteoarthritis (both in plasma and synovial fluid), sickle cell disease, severe malaria, and metastatic colorectal cancer. Endoglin has been proposed as a therapeutic target for cancer due to its high expression in tumor vasculature.
Sample Type:Cell culture supernates, cell lysates, serum, plasma, and urine.
Intended Use:For the quantitative determination of mouse Endoglin concentrations in cell culture supernates, cell lysates, serum, plasma, and urine.
Sensitivity:Seventy-four assays were evaluated and the minimum detectable dose (MDD) of Endoglin ranged from 1.28-13.6pg/ml. The mean MDD was 4.17pg/ml. The MDD was determined by adding two standard deviations to the mean optical density value of twenty zero standard replicates and calculating the corresponding concentration.
Specificity:This assay recognizes both recombinant and natural mouse Endoglin.
Test Principle:This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for mouse Endoglin has been pre-coated onto a microplate. Standards, Control, and samples are pipetted into the wells and any Endoglin present is bound by the immobilized antibody. After washing away any unbound substances, an enzyme-linked polyclonal antibody specific for mouse Endoglin is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells. The enzyme reaction yields a blue product that turns yellow when the Stop Solution is added. The intensity of the color measured is in proportion to the amount of Endoglin bound in the initial step. The sample values are then read off the standard curve.
Kit Components:Mouse Endoglin Microplate: 12 stripsx8 wellsMouse Endoglin conjugated to HRP: 1x12mlMouse Endoglin Standard (lyophilized): 1x20ngMouse Endoglin Control (lyophilized.): 1 vialAssay Diluent RD1S: 1x12mlCalibrator Diluent RD5-4: 2x21mlWash Buffer Concentrate: 1x50mlColor Reagent A (hydrogen peroxide): 1x12mlColor Reagent B (tetramethylbenzidine): 1x12mlStop Solution: 1x23mlPlate Covers: 4 adhesive strips
Storage and Stability:See Kit Protocol for detailed storage instructions.
