Molecular cloning and characterization of murine Mpgc60, a gene predominantly expressed in the intestinal tract.
We have isolated from mouse intestine a full-length cDNA clone that encodes an 86-amino acid precursor protein containing a 26-amino acid signal sequence. As deduced from its sequence, the mature 60-aa protein named MPGC60 belongs to the Kazal type of secreted trypsin inhibitors. The MPGC60 peptide has 58% homology with the PEC-60 peptide isolated from pig intestine. In the gut of adult mice, an increasing rostrocaudal gradient in MPGC60 mRNA levels was observed by Northern analysis. In situ hybridization analysis demonstrated strong Mpgc60 expression in Paneth cells and in a subset of goblet cells in the differentiated gut. During postnatal differentiation of the gut, a strong increase in Mpgc60 expression was detected in both small and large intestine. However, in small intestine activation of the Mpgc60 gene occurred earlier than in the large intestine. Apart from the intestinal tract, MPGC60 mRNA was also detectable in the mesenchyme surrounding the uterine epithelium and in endothelia of some blood vessels. However, in contrast to the situation observed in pig, no Mpgc60 expression was detectable by Northern, in situ and reverse transcriptase polymerase chain reaction (RT-PCR) analysis in cells of the immune system, that is, in monocytes, macrophages, peripheral blood and in spleen. Northern blot analysis on mRNA isolated from porcine and murine intestine showed a single transcript in mouse, but several transcripts in pig. Southern blot and fluorescent in situ hybridisation (FISH) analysis demonstrated the presence of a single gene situated in band A of chromosome 4. This region is syntenic with human chromosome regions 6q, 8q and 9p. The gene responsible for human hereditary mixed polyposis syndrome has been localized to human 6q. This raises the possibility that Mpgc60 is a candidate gene for this human disorder.