Prolactin (PRL)-like protein J, a novel member of the PRL/growth hormone family, is exclusively expressed in maternal decidua

A search of a nonmouse, nonhuman, expressed sequence tag database for messe nger RNAs in the PRL/GH family has identified a novel rat complementary DNA clone. The encoded protein, designated PRL-like protein J (PLP-J), is pred icted to be synthesized as a precursor of 211 amino acids, modified by N-li nked glycosylation, and secreted as a mature glycoprotein of 182 residues. PLP-J messenger RNA synthesis is limited to early pregnancy with abundant e xpression on day 7, slightly declining expression on day 9, and no detectab le expression by day II. Unlike most other PRL family members, PLP-J does n ot appear to be synthesized by placental trophoblasts but, rather, by decid ual cells surrounding the implantation site. By sequence similarity to rat PLP-J, a murine done was identified in a mouse expressed sequence tag datab ase. Mouse PLP-J was used to map the gene to a 700-kb region of mouse chrom osome 18 that includes other members of the PRL/GH family.