For example, congenital dysfibrinogenemia (OMIM:616004) is a blood clotting disorder caused by defective fibrinogen genes FGB, FGG and FGA. Circulating factors affecting blood clotting are synthesized by hepatocytes, and indeed, our data show that fibrinogen genes are highly and exclusively expressed in the liver (Supplementary Fig. S3a). This evidence concerns the gene FGB and familial hypodysfibrinogenemia.