EXPRESSION AND FUNCTION OF AMPHIREGULIN DURING MURINE PREIMPLANTATIONDEVELOPMENT

Amphiregulin (Ar) is an EGF receptor ligand that functions to modulate the growth of both normal and malignant epithelial cells. We asked wh ether mouse preimplantation embryos express Ar, and if so, what the fu nction of Ar is during preimplantation development. We used RT-PCR to show expression of Ar mRNA in mouse blastocysts, and using a polyclona l anti-Ar antibody and indirect immunofluorescence, we detected the pr esence of Ar protein in morula- and blastocyst-stage embryos. Ar prote in was present in both the cytoplasm and nucleus in both morulae- and blastocyst-stage embryos, which is similar to Ar distribution in other cell types. Embryos cultured in Ar developed into blastocysts move qu ickly and also exhibited increased cell numbers compared to control em bryos. in addition, 4-cell stage embryos cultured in an antisense Ar p hosphorothioate-modified oligodeoxynucleotide (S-oligo) for 48 hr exhi bited slower rates of blastocyst formation and reduced embryo cell num bers compared to embryos exposed to a random control S-oligo. TGF-alph a significantly improved blastocyst formation, but not cell numbers, f or embryos cultured in the antisense Ar S-oligo. From these observatio ns, we propose that Ar may function as an autocrine growth factor for mouse preimplantation embryos by promoting blastocyst formation and em bryo cell number. We also propose that blastocyst formation is stimula ted by Ar and TGF-alpha, while Ar appears to exert a greater stimulato ry effect on cell proliferation than does TGF-alpha in these embryos. (C) 1997 Wiiey-Liss, Inc.