Islet beta-cell regeneration and reg genes.

In this paper, we show that the reg gene is expressed in experimentally induced regenerating or hyperplastic islets. We have previously reported that ectopic expression of the reg gene occurs in some human colonic and rectal tumors, suggesting that enhanced reg expression may be related to the proliferative state of tumor cells. Reg protein has also been shown to have significant sequence homology with plant and animal lectins, a class of compounds that has been shown to be a growth promoter. At present, any direct relationship between reg protein and beta-cell replication remains to be established. However, since the reg protein is a secretory protein and reg can be expressed at an early stage of pancreatic cell differentiation, the reg protein may act on the stem cells of beta-cells in an autocrine or paracrine manner. In normal mature exocrine cells, the reg gene is expressed and the gene product may be necessary to maintain adequate exocrine pancreatic function. The physiological reasons for the maintenance of two functional reg genes encoding proteins of slightly different sequence in mice are still unclear. The cloning of additional rat and human non-allelic reg genes could provide additional clues.