Glypicans are a group of membrane-bound heparan sulfate proteoglycans
(HSPG) that are tissue specific and developmentally regulated. Transcr
ipts for avian glypican are found in endocardial cushions, limb buds,
somites and forebrain of early chick embryos. Since avian glypican is
not well characterized, the cellular localization. regulation of expre
ssion, and possible function during cardiac development have been stud
ied. A polyclonal antibody was raised against a 20-amino acid peptide
corresponding to an antigenic sequence within avian glypican core prot
ein. The antibody recognized the expressed core protein in bacterial l
ysates and the endogenous HSPG in the proteoglycan fraction from chick
forebrain. Immunolocalization studies indicated that the core protein
is associated with cell membranes. The level of mRNA for avian glypic
an in MEQC (myc embryonic quail cardiomyocytes) grown in medium contai
ning 10% fetal calf serum was compared to the message levels in cells
grown without serum for 3 days. By Northern analysis, glypican transcr
ipts were increased markedly after serum starvation. Up-regulation of
glypican transcripts by serum withdrawal was partially prevented by ad
dition of TGF beta-1 and bFGF, suggesting that these growth factors ma
y regulate its expression. MEQC cells deprived of serum migrated into
clumps that could be blocked by an antisense OND (oligodeoxynucleotide
) to the mRNA encoding the avian glypican. The same antisense OND inhi
bited the migration of endothelial cells from chick tubular heart expl
ants over the surface of collagen gels. These results indicate that av
ian glypican may play a role in cell migration during development of e
ndocardial cushions. (C) 1998 Academic Press Limited.