May specifically influence certain angiogenesis process (PubMed:19874420). Expressed from the late gastrulation/early segmentation stage in the midbrain/hindbrain boundary (MHB) and in the posterior trunk region. Subsequently, its expression is restricted in the tail bud region and notochord. At 22 hrs after fertilization (hpf), high level expression is observed in the notochord and MHB. The tail bud expression declined by 30 hpf. Notochord expression declines at 48 hpf and disappears by 72 hpf although low level MHB expression remains until 72 hpf (PubMed:19874420). Up-regulated by Wnt signaling. Morpholino knockdown of the protein causes disorganized intersegmental vessels in the trunk. Belongs to the isthmin family.