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 en codes an 86-amino acid precursor protein containing a 26-amino acid si gnal 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 PEG-60 peptide isolated from pig intestine. In the gut of adult mice, an increasing rostrocaud al gradient in MPGC60 mRNA levels was observed by Northern analysis. I n situ hybridization analysis demonstrated strong Mpgc60 expression in Paneth cells and in a subset of goblet cells in the differentiated gu t. During postnatal differentiation of the gut, a strong increase in M pgc60 expression was detected in both small and large intestine. Howev er, in small intestine activation of the Mpgc60 gene occurred earlier than in the large intestine. Apart from the intestinal tract, MPGC60 m RNA was also detectable in the mesenchyme surrounding the uterine epit helium and in endothelia of some blood vessels. However, in contrast t o the situation observed in pig, no Mpgc60 expression was detectable b y Northern, in situ and reverse transcriptase polymerase chain reactio n (RT-PCR) analysis in cells of the immune system, that is, in monocyt es, macrophages, peripheral blood and in spleen. Northern blot analysi s on mRNA isolated from porcine and murine intestine showed a single t ranscript in mouse, but several transcripts in pig. Southern blot and fluorescent in situ hybridisation (FISH) analysis demonstrated the pre sence 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 res ponsible for human hereditary mixed polyposis syndrome has been locali zed to human 6q. This raises the possibility that Mpgc60 is a candidat e gene for this human disorder.