Required for bone modeling during late embryogenesis. Regulates type I collagen synthesis in osteoblasts during their postnatal maturation. Present in chondrocytes, osteoblasts, osteoclasts and osteocytes (at protein level). Expressed at 9.5 dpc and 13.5 dpc. N-glycosylated. O-glycosylated. O-mannosylated by POMT1 and POMT2 and elongated by POMGNT1. Most mice die neonatally from respiratory distress (50% on a mixed C57BL6/CD1 background and 100% on an inbred C57BL6/129Ola background). Surviving mice fail to thrive and show significantly reduced body weight, skeletal deformities and spontaneous fractures. More than 80% die by postnatal day 10, and none survives to weaning.