THE MOUSE ONE P-DOMAIN (PS2) AND 2 P-DOMAIN (MSP) GENES EXHIBIT DISTINCT PATTERNS OF EXPRESSION

We have previously shown that the human pS2 gene, which codes for a se creted peptide of 60 amino acids, is expressed in a number of human ca rcinomas, including carcinomas of the breast, the pancreas, and the la rge bowel. Strong pS2 gene expression was also observed in the normal gastric mucosa and in the regenerative tissues surrounding ulcerous le sions of the gastrointestinal tract. A number of pS2 similar peptides, designated as P-domain peptides, have been described, notably the por cine (PSP), murine (mSP), and human (hSP) spasmolytic polypeptides, wh ich correspond to duplicated pS2 proteins. We have now cloned a mouse homolog of the human pS2 cDNA to dispose of an animal model to study t he pS2 protein function, which remains unknown at the present time. We show that the mouse putative pS2 protein sequence and the physiologic al pattern of expression of the mouse pS2 gene are well conserved. The mouse pS2 gene is highly expressed in the stomach mucosa cells, where as no pS2 gene expression could be detected in the mouse mammary gland , even during postnatal development processes dependent on growth fact ors or hormones. Using in situ hybridization, we show that although co expressed in the fundus, the antrum and the antrum-pyloric regions of the stomach, the mouse pS2 and mSP genes exhibit distinct and compleme ntary cellular patterns of expression.