Identification of expressed genes in regenerating rat liver in 0-4-8-12 h short interval successive partial hepatectomy

Cloning and prokaryotic expression of rat homolog of Serpina3n and its expression change during liver regeneration

A strikingly upregulated expressed sequence tag was screened from regenerating rat liver at 8 h in a 0-4-8-12 h short-interval successive partial hepatectomy model from a previous study. In the present study, a full-length open reading frame (ORF) corresponding to this expressed sequence tag was predicted through electronic cloning and was subsequently cloned from an 8-h rat regenerating liver and deposited in GenBank (accession No. HM448398). Sequence analysis of HM448398 and the predicted ORF revealed that the two ORFs may be different transcripts of a gene. The sequence of HM448398 was highly homologous to that of rat Serpina3n, suggesting that it may be a homolog of Serpina3n. The pGEX-2TK prokaryotic expression vector for this ORF was constructed, and the result of sodium dodecyl sulfate polyacrylamide gel electrophoresis manifested that the recombinant expression vector could express the glutathione-S-transferase-fused rat homolog of Serpina3n in an insoluble form in BL21. The target fusion protein was purified with affinity chromatography and was used as antigen to immunize rabbits for the production of polyclonal antibodies. Immunohistochemistry and real-time reverse transcription polymerase chain reaction analysis revealed that the gene was highly expressed in the priming and termination phases of liver regeneration. These findings lay a solid foundation for further study of roles of HM448398 using knock-in and RNA interference methods during liver regeneration.

Variability of sequence surrounding the Xist gene in rodents suggests taxon-specific regulation of X chromosome inactivation

One of the two X chromosomes in female mammalian cells is subject to inactivation (XCI) initiated by the Xist gene. In this study, we examined in rodents (voles and rat) the conservation of the microsatellite region DXPas34, the Tsix gene (antisense counterpart of Xist), and enhancer Xite that have been shown to flank Xist and regulate XCI in mouse. We have found that mouse regions of the Tsix gene major promoter and minisatellite repeat DXPas34 are conserved among rodents. We have also shown that in voles and rat the region homologous to the mouse Tsix major promoter, initiates antisense to Xist transcription and terminates around the Xist gene start site as is observed with mouse Tsix. A conservation of Tsix expression pattern in voles, rat and mice suggests a crucial role of the antisense transcription in regulation of Xist and XIC in rodents. Most surprisingly, we have found that voles lack the regions homologous to the regulatory element Xite, which is instead replaced with the Slc7a3 gene that is unassociated with the X-inactivation centre in any other eutherians studied. Furthermore, we have not identified any transcription that could have the same functions as murine Xite in voles. Overall, our data show that not all the functional elements surrounding Xist in mice are well conserved even within rodents, thereby suggesting that the regulation of XCI may be at least partially taxon-specific.

Dissimilar hepatic protein expression profiles during the acute and flow phases following experimental thermal injury

The liver plays a major role in the early hypometabolic and later hypermetabolic phases after severe burn injury. Proteomic analysis was used to identify altered proteins in liver during these two phases. Sprague-Dawley rats were subjected to a full-thickness dorsal burn injury covering 40% of the total body surface area. Controls consisted of sham-treated animals. Liver tissues were collected on postburn days 1 and 7. The proteomic data show greater production of positive acute phase proteins on day 1 than on day 7. Many antioxidant enzymes were coordinately downregulated on day 1, including the potent biliverdin reductase. These antioxidants were restored and in some cases upregulated on day 7. This opposite trend in the change of antioxidant proteins corroborated our finding of more pronounced oxidative stress on day 1 than on day 7 as measured via protein carbonyl content. The changes of metabolic enzymes on days 1 and 7 were consistent with hypo- and hyper-metabolic states, respectively. Furthermore, a previously unreported decrease in ornithine aminotransferase on day 7 may be a key contributor to the observed increased urinary urea excretion during the hypermetabolic phase. Overall, the many differences in protein expression observed on postburn days 1 and 7 reflect the dissimilar hepatic metabolic patterns during the acute and flow phases following burn injury.