Immunogen sequence: LDMPVVPGLG GPGESRHEPL GLPMESYQPW ALPNGWNGQM YCPKEQAQPP HLWKSTLPDV VSHPSDASSY RRGRKKRVPY TKVQLKELER EYATNKFITK D. HoxA13 and HoxD13 also bind to other BMP and TGF-beta/Activin-regulated Smad proteins including Smad1 and Smad2, but not