Expression of human intestinal mRNA transcripts during development: analysis by a semiquantitative RNA polymerase chain reaction method.

To study the relative expression of lactase, sucrase-isomaltase, dipeptidyl peptidase IV, and the Na(+)-dependent glucose transporter mRNA transcripts in small samples of human tissue, we have developed and validated a very simple semiquantitative RNA polymerase chain reaction method that can be used on as little as 5-10 mg of tissue. Here we report the use of this method to study the expression of these genes at different stages of development, in different tissues and in different parts of the intestine, in comparison with another intestinal marker, the colon-specific transcript of carbonic anhydrase 1. Lactase, sucrase-isomaltase, and the Na(+)-dependent glucose transporter mRNA are expressed predominantly in the small intestine, although lactase mRNA is expressed at a very low level in fetuses. Dipeptidyl peptidase IV mRNA shows a much wider tissue distribution. Sucrase-isomaltase and dipeptidyl peptidase IV mRNA are present at high levels in fetal colon and also at surprisingly high levels in adult colon. Lactase mRNA, on the other hand, is present at very low levels in fetal colon and is not detectable at all in adult colon. The Na(+)-dependent glucose transporter mRNA in contrast is expressed at higher levels in the adult colon than in the fetal colon. This is also the case for the carbonic anhydrase 1 transcript, although this transcript is not expressed in the small intestine. Thus, each of these genes shows different developmental and cell-specific regulation.