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-31, Pro-33 and Pro-35. O-glycosylated on hydroxyprolines; noncontiguous hydroxylproline residues are glycosylated with arabinogalactan. Belongs to the AG-peptide AGP family.