Ontogenic gene expression profiling during pig hepatogenesis and effects of intrauterine growth retardation on liver development

To better understand hepatogenesis, comprehensive ontogenic gene expression profiling was performed to determine baseline expression patterns associated with liver development. Liver was collected from the greatest weight fetus of four distinct unilaterally hysterectomized:ovariectimized gilts at prenatal day (PND) 37, 50, 70, and 110. In addition, liver from smallest weight fetuses (runts) were collected to investigate effects of intra-uterine growth retardation (IUGR) on liver development. Total RNA was isolated, mRNA amplified and subjected to microarray analysis (Agilent). Three comparisons were performed: PND50 vs. PND37, PND70 vs. PND50 and PND110 vs. PND70; only genes whose expression, between at least two time points, was ± 1.5 fold with P < 0.05 were characterized further. A total of 6061 annotated genes exhibited altered expression: 648 down- and 341 up-regulated at PND37 vs. PND50; 666 down- and 1399 up-regulated at PND70 vs. PND50; and 1564 down- and 1443 up-regulated at PND110 vs. PND70. Thirty-five transcripts were selected for validation by absolute quantitative PCR; they clustered into five functional categories: i) hematopoietic and early liver function, ii) extracellular matrix, iii) hepatocyte function, iv) biliary function, and v) transcription factors. Another four comparisons were made to elucidate effects of IUGR: greatest weight (control) vs. smallest weights (runt) on PND 37, 50, 70 and 110. A total of 412 were differentially exp[ressed. 29 down and 25 up-regulated at PND37, 72 down and 52 up-regulated at PND50, 20 down and 33 up-regulated at PND70 and 48 dwon and 45 up-regulated at PND110. 6 genes were further analyzed by qPCR. They all clustered into serum proteins category. Overall design: Gene expression in pig fetal liver was analyzed on prenatal days: 37, 50, 70 and 110. Four liver samples from four independent pregnancies were collected at each time point.