Figure 7

Summary of developmental events during liver vasculogenesis and growth. (A) Timing of liver morphogenesis in zebrafish. According to Field et al. [5], the liver morphogenesis in zebrafish consists of two phases, budding and growth. Our current study showed the formation of three liver lobs during the growth phase. (B) Timing of liver vasculogenesis. Detailed analysis of liver vasculogenesis and precise determination of blood flow initiation in liver sinusoids of live embryonic zebrafish have led us to define three phases of liver vasculogenesis: contact of ECs and hepatocytes, formation of nascent sinusoids, initiation of blood circulation and formation of the vascular network in the liver. (C) Stages of liver growth. Based on our analyses of liver vasculogenesis and growth in wild type as well as in cloche mutant and Tnnt2 morphant larvae, we propose three stages of liver growth: avascular growth as a transition to the growth phase, where ECs are not required; endothelium-dependent, and circulation-dependent growth stage. Approximate periods of the stages of liver vasculogenesis and growth are represented along the time line in hpf or dpf. The green time lines represent the period of liver vasculogenesis.