The aim of this study is to discover the molecular mechanism of the 22-week gestated human fetal liver( HFL ) which rarely displays both hematopoietic and hepatic functions. Based on large-scale cDNA library sequencing and bioinformatic analysis, the largest gene expression profile of human fetal liver in the world was successfully established. A set of gene clusters functionally related to the liver development, hepatocarcinogenesis and hematopoiesis have been identified. This is for the first time that we could panoramically understand the molecular mechanism of the dual functions of human fetal liver. Moreover, 201 unrecorded human homologous genes and 609 novel genes have been identified and annotated, which accounting for more than 7% of the known human genes in 2001. In the recent human genome annotation map (human genome build 35.1 ), 45 genes were nominated based on this study.In addition, we have characterized a set of gene families represented by hepatopoietin (HPO), Semaphorin,LSECtin and ARFGAP. Two distinctive novel pathways,"extracellular HPO→ HPO receptor→ EGF receptor→Raf→ MEK→ MAPK" for autocrine and "intracellular HPO→ JAB1→c-JUN (AP-1 )" for intracrine of HPO, an unusual cytokine functioned in the regeneration of liver,has been reported for the first time, which have shed new lights on the study of the signal transduction of the entire HPO family. We have also demonstrated that HPO could act as a FAD thioloxidase and that only its intracrine pathway is dependent on the enzymatic activity. It is also known for the first time that the enzyme activity is critically important for the cytokine HPO. Regarding the regulation of the gene expression of HPO, it was demonstrated that HPO promoter includes a negative regulatory element and a core promoter (comprises an initiator and its flanking three tandem IFE elements).Furthermore, two novel members of Semaphorin family,SEMA6C and SEMA6D, were cloned and shown to be able to determine the orientation of the cell growth. We have aisc discovered and characterized a novel lectin family including LSECtin, CD23, DC-SIGN and DCSIGNR. The function of LSECtin was also defined to be important in adhesion of the cells. In addition, the first human member of ARFGAP family was cloned and shown to regulate protein secretion. The publications based on this study have been cited for 145 times by SCI journals before 2005. This study has provided important original data for the annotation of human genome and establishment of human transcriptome. It also played an important role in Chinese national achievement of cloning and annotation of the 10% human cDNAs project and set up the corner-stone for the leading role of China in the international "Human Liver Protecme Project".