MOUSE FETAL ANTIGEN-1 (MFA1), THE CIRCULATING GENE-PRODUCT OF MDLK, PREF-1 AND SCP-1 - ISOLATION, CHARACTERIZATION AND BIOLOGY

The mouse homologue to human fetal antigen I (hFA1) was purified from mouse amniotic fluid by cation exchange chromatography and immunospeci fic affinity chromatography. Mouse FA1 (mFA1) is a single chain glycop rotein with an M(r) of 42-50 kDa (SDS-PAGE). The N-terminal amino acid sequence (39 residues) revealed 74% identity to hFA1 and 100% identit y to the translated cDNAs referred to as mouse dlk, pref-1 and SCP-1. mFA1 is the secreted processed molecule encoded by the mRNA defined by these identical mouse cDNAs. Monospecific rabbit anti-mFA1 antibodies , purified by ammonium sulfate precipitation and immunospecific affini ty chromatography, were used for immunohistochemical and quantitative ELISA techniques. The indirect immunoperoxidase technique demonstrated mFA1 within the endocrine structures of adult mouse pancreas, whereas the exocrine tissue remained unstained. FA1-positive staining was als o seen in the pituitary gland and the mouse adrenal gland. The concent ration of mFA1 in a pool of amniotic fluid was assessed at 25 mu g ml( -1) and the serum concentration in normal nonpregnant adult mice (n = 28) was 11.3 +/- 5.0 ng ml(-1) (2 so). During pregnancy the concentrat ion of mFA1 in maternal serum increased above the nonpregnant referenc e value at midpregnancy, reaching a maximum concentration (> 0.35 mu g ml(-1)) 2 days prepartum. The maternal serum concentration was positi vely correlated with the number of fetuses. After delivery the rate of disappearance of mFA1 in maternal serum was very fast with a f(1/2) < 1 h. The concentration of mFA1 in newborn mice was about 15 mu g ml(- 1) and did not reach normal adult values until the age of > 50 days.