Identification of differentially expressed mRNAs in human fetal liver across gestation

Differential gene expression, with its precise start and stop times, is bel ieved to be critical for the programmed development of new cells and tissue s. Within the developing fetus, one tissue of particular interest is fetal liver. This organ undergoes rapid changes in the pathway toward fiver devel opment in utero since it is also the major site of hematopoiesis, until bon e marrow hematopoiesis predominates. Believing that patterns would emerge f rom the bi-weekly large-scale inspection of expressed genes in the fetal li ver, we employed differential display reverse transcription-polymerase chai n reaction (DDRT-PCR) as our primary inspection tool. Using DDRT-PCR, we is olated cDNAs differentially expressed throughout fetal liver development an d in adult liver. We displayed similar to 25 000 cDNAs from 10 and 24 week fetal liver and adult liver. From this initial screen, we determined that s imilar to 0.1-1% of the mRNA population undergoes expression changes. We ex tracted, purified and sequenced 25 differentially displayed cDNA bands. Fou rteen cDNAs had similarities to known genes, while 11 cDNAs were not simila r to any characterized gene. The differentially expressed cDNAs from known genes present in fetal liver include a-fetoprotein, stem cell factor, eryth roid a-spectrin, 2,3-bisphosphoglycerate mutase, insulin-like growth factor -2, porphobilinogen deaminase and Mac30. The differentially expressed cDNAs present in adult liver but not in 10 week fetal liver were nicotinamide de aminase, human fibrinogen-related protein and a-acid glycoprotein. The majo rity of differentially expressed genes found during this effort appear to b e turned on during organogenesis, however, some genes were found that are a pparently turned off completely.