Secreted growth factor that mediates its signal through cell-surface proteoglycan and non-proteoglycan receptors (By similarity). Binds cell-surface proteoglycan receptor via their chondroitin sulfate (CS) groups (By similarity). Thereby regulates many processes like cell proliferation, cell survival, cell growth, cell differentiation and cell migration (By similarity). Has antibacterial activity against both Gram-positive and Gram-negative bacteria (PubMed:20308059). Expressed in high levels in brain and eye. Lower levels in bone. In the tailbud embryo stage, it is expressed exclusively in the central nervous system, especially in the hind region of the brain. Belongs to the pleiotrophin family.