Proteoglycan that seems to be implicated in diverse developmental roles such as differentiation, cell-cell recognition, embryogenesis and programmed cell death. Contains 4-hydroxyproline; hydroxylated on Pro-30, Pro-32 and Pro-34. O-glycosylated on hydroxyprolines; noncontiguous hydroxylproline residues are glycosylated with arabinogalactan. Belongs to the AG-peptide AGP family.