| Biglycan is a new extracellular component of the Chordin BMP 4 signaling pathway . ^^^ In this study , we identified Biglycan ( Bgn ) , a member of the small leucine rich proteoglycan family , as a new extracellular modulator of BMP 4 signaling . ^^^ Microinjection of Bgn mRNA induced secondary axes , dorsalized the mesoderm and inhibited BMP 4 activity in Xenopus embryos . ^^^ Biochemical experiments showed that Bgn binds BMP 4 and Chordin , interaction that increased binding of BMP 4 to Chordin . ^^^ Bgn was also able to improve the efficiency of Chordin Tsg complexes to block BMP 4 activity . ^^^ |