Proteolytic cleavage of versican during cardiac cushion morphogenesis.
The proteoglycan versican is essential to the formation of endocardial cushion mesenchyme by epithelial-mesenchymal transformation (EMT). A potentially important factor in the regulation of versican activity during cushion EMT is proteolysis by ADAMTS metalloproteinases. Using antibodies to the DPEAAE neoepitope created by ADAMTS proteolysis of versican, we detected the amino terminal 70-kDa versican cleavage fragment in cardiac cushions. Initially (i.e., 9.5 days post coitum [dpc]), the fragment is associated with endocardial cells undergoing EMT and with newly derived mesenchymal cells. ADAMTS-1 and its cofactor fibulin-1 were also associated with these cells. As cushions become increasingly populated with mesenchymal cells (10.5-12.5 dpc), the fragment remains asymmetrically distributed compared with the pattern of total versican. Highest levels of the fragment are present in regions immediately subjacent to the endocardium characterized as having densely packed, rounded cells, lacking cellular protrusions. With further development (i.e., 12.5-14.5 dpc), the pattern of fragment distribution within cushions broadens to include the ECM surrounding loosely packed mesenchymal cells in the cushion core. Together, the findings reveal that versican proteolysis leading to the production of the 70-kDa fragment is integral to the formation and differentiation of endocardial cushion mesenchyme.
Kern
Christine B
CB
Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Twal
Waleed O
WO
Mjaatvedt
Corey H
CH
Fairey
Sarah E
SE
Toole
Bryan P
BP
Iruela-Arispe
M Luisa
ML
Argraves
W Scott
WS
D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D019521:Body Patterning; D002135:Calcium-Binding Proteins / Q000235:genetics; D002457:Cell Extracts; D011508:Chondroitin Sulfate Proteoglycans / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology*; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D020257:Ventricular Remodeling; D053675:Versicans
D002135:Calcium-Binding Proteins; D002457:Cell Extracts; D011508:Chondroitin Sulfate Proteoglycans; D037181:Lectins, C-Type; D020033:Protein Isoforms; C508323:Vcan protein, mouse; C060820:fibulin; D053675:Versicans; D051722:ADAM Proteins