A subset of SBA lectin-binding proteins isolated from myocardial-conditioned media transforms cardiac endothelium into mesenchyme.
It has been shown that the inductively active proteins for cardiac mesenchyme formation are localized to a particulate form of extracellular matrix that resembles adheron-like complexes. These complexes are extractable from the embryonic heart using EDTA and can be visualized with the lectin SBA (Glycine max). In addition, the growth medium obtained from embryonic myocardial cell cultures has also been shown to support mesenchyme formation. However, except for the identification of EDTA extract and conditioned media, all previous experiments analyzing this system have relied on negative type results (i.e. the loss of biological activity) to show a relationship between the particulate matrix and the transformation process. We report here that SBA affinity chromatography can be used to partially purify a subset of proteins from myocardial conditioned medium which elicits the transformation of endothelial cells into mesenchyme. In addition, a polyclonal antibody made against this subset of proteins is specific for the in situ particulate matrix and recognizes several proteins in conditioned medium and EDTA extracts. This antibody is also specific for matrix particulates in other areas of the embryo that undergo an epithelial/mesenchymal interaction. These results provide the most direct evidence to date that conditioned medium is equivalent to the hypothesized inductively active particulate matrix. In addition, the data provides evidence that conditioned medium can be used to identify the functional role of the components of the particulate matrix in mesenchyme formation.
Sinning
A R
AR
Department of Anatomy, University of Mississippi Medical Center, Jackson 39216, USA.
Hewitt
C C
CC
Markwald
R R
RR
D000818:Animals; D000906:Antibodies / Q000032:analysis; D015153:Blotting, Western; D002478:Cells, Cultured; D002642:Chick Embryo; D002846:Chromatography, Affinity; D017077:Culture Media, Conditioned / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004627:Embryonic Induction / Q000502:physiology*; D004727:Endothelium / Q000502:physiology; D005109:Extracellular Matrix; D006321:Heart / Q000196:embryology*; D037102:Lectins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D008648:Mesoderm / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D037121:Plant Lectins; D011485:Protein Binding; D030262:Soybean Proteins; D013025:Glycine max; D010835:Phytohemagglutinins
D000906:Antibodies; D017077:Culture Media, Conditioned; D037102:Lectins; D037121:Plant Lectins; D030262:Soybean Proteins; C028824:soybean lectin; D010835:Phytohemagglutinins