Biglycan is a small leucine-rich repeat proteoglycan (SLRP) which is found in a variety of extracellular matrix tissues, including bone, cartilage and tendon. In humans, biglycan is encoded by the BGN gene[5] which is located on the X chromosome. Biglycan is believed to play a role in the mineralization of bone. Knock-out mice that have had the gene for biglycan suppressed (Bgn -/-) have an osteoporosis-like phenotype with reduced growth rate and lower bone mass than mice that can express biglycan. Biglycan core protein binds to the growth factors BMP-4 and influences its bioactivity. It has also been reported that the presence of biglycan is necessary for BMP-4 to exert its effects on osteoblasts. There is also evidence that biglycan binds to TGF-beta 1.