Identification of homeobox genes expressed during the process of rat liver regeneration after partial hepatectomy.

Homeobox (HBox) genes are well-known to be involved in development and differentiation. To ascertain a role of HBox genes in the process of liver regeneration, we identified HBox genes expressed at various times after partial hepatectomy in rats (at 0 hr, 1 hr, 2 days, and 4 days) by using reverse transcription-polymerase chain reaction (RT-PCR), cloning, and sequencing techniques. By the competitive RT-PCR method using generic primers, expression levels of HBox genes in regenerating livers were estimated at as low as only 0.4-2% of that in 14-day embryonic liver; however, we identified multiple HBox genes at different stages. Comparing sets of HBox genes identified at different stages, we could find two candidates of stage specifically expressed HBox genes (one rat caudal-related gene, RCdx-3, stimulated at 1 hr, and one rat Hox gene, RHoxB5, repressed after hepatectomy) and continuous expression of five Hox genes (RHoxA1, A4, A5, B2, and B3) before and after hepatectomy. These HBox genes are considered to correlate with the process of liver regeneration.