Isthmin, also known as Isthmin-1, is a secreted protein initially identified in the Xenopus midbrain-hindbrain organizer (MHB) or isthmus organizer, where it is highly expressed. Mouse Isthmin is a 454 amino acid protein containing a TSR (thrombospondin type 1 repeat) domain in the central region, and an AMOP (adhesion-associated domain in MUC4 and other proteins) domain at the C-terminus. The TSR domain is highly conserved with 98% identity between mouse and human, and 87-88% identity between mouse and Xenopus. The C-terminus AMOP domain is also highly conserved with 99% identity between mouse and human, and 91% identity between mouse and Xenopus. Recently, it has been suggested that Isthmin has angiostatic activity in vitro and in vivo. Isthmin inhibits endothelial cell (EC) capillary network formation mainly by interfering with the early stages of in vitro angiogenesis on Matrigel. Isthmin inhibits VEGF-induced EC proliferation and induces apoptosis in the presence of VEGF. Overexpression of Isthmin in B16 melanoma inhibits tumor growth and tumor angiogenesis in mice. Knockdown of Isthmin in zebrafish embryos leads to abnormal intersegmental vessel (ISV) formation in the trunk.BioLegend's LEGEND MAX(TM) Mouse Isthmin ELISA Kit is a Sandwich Enzyme-Linked Immunosorbent Assay (ELISA) with a 96-well strip plate that is pre-coated with a capture antibody. This kit is specifically designed for the accurate quantitation of mouse Isthmin from cell culture supernatant, serum, plasma, and other biological fluids. This kit is analytically validated with ready-to-use reagents.