Coagulation Factor Iii B In Zebrafish Embryos

Tissue factor (coagulation factorâ…¢) is a cell surface receptor binding to coagulation factorâ…¦/â…¦a and was initially recognized as an initiator of the extrinsic coagulation path way.The human TF gene has been cloned and is localized to chromosome 1 (p21-p22). The 6 exons are translated into a 263 amino acid protein with a 219 amino acid extracellular domain, a 23 amino acid transmembrane region, and a 21 amino acid intracellular domain.Tissue factor is also involved in thrombosis and inflammation associated with sepsis, atherosclerosis, tumor progression, and embryogenesis. It has been reported that humans can not survive without TF, and homozygous knockout of tissue factor in mouse embryos resulted in approximately 90% embryonic lethality by E10.5. Therefore, TF is essential for embryonic development but its specific functions are unknown.The study of zebrafish embryogenesis has yielded many insights into the development of the embryonic vasculature. Zebrafish embryos develop externally, are nearly transparent, and are thin enough for diffusion mediated oxygenation from the medium. In fact, zebrafish can survive the first week of development without a functional vasculature or heart beat, allowing a detailed analysis even in animals with severe cardiovascular defects. By contrast, avian and mammalian embryos die rapidly in the absence of a functional cardiovascular system.Recently, the zebrafish Tissue Factor gene (TF) has been cloned. Paralogs encode coagulation factorsâ…¢a andâ…¢b both show remarkable sequence identity to the human and mouse coagulation factor III gene. Here we turn to zebrafish to pursue the role of TF. We examined the role of coagulation factorâ…¢b (fib) during zebrafish embryonic development. Expression analysis revealed that endogenous fib was chronologically expressed in the pectoral fins and in the vicinity of the pharynx. Knockdown of fib by injection of a. f3b morpholino at the 1-2 cell stage caused distinct morphological defects in embryos, including edema in the fourth brain ventricle at early embryonic stages and occasional bleeding at later stages. Injection of TFb morpholino reduced expression of an oligodendrocyte marker gene (olig2) but had no effect on a neuronal marker gene (huc). Furthermore, f3b morphants displayed abnormal vascular patterning.In conclusion, zebrafish f3b is required for the development of the brain and vasculature during embryogenesis.