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-34, Pro-36, Pro-38 and Pro-40. O-glycosylated on hydroxyprolines; noncontiguous hydroxylproline residues are glycosylated with arabinogalactan. Belongs to the AG-peptide AGP family.