2 NOVEL MEMBERS OF THE PROLACTIN GROWTH-HORMONE FAMILY ARE EXPRESSED IN THE MOUSE PLACENTA

Two novel members of the mouse PRL/GH family have been identified thro ugh a search of an expressed sequence tag database. The encoded protei ns do not appear to be homologs of other known members of this hormone family. One of these proteins, designated PRL-like protein E (PLP-E), is predicted to be synthesized as a precursor of 265 amino acids, mod ified by N-linked glycosylation, and secreted as a mature glycoprotein of 236 residues. The second clone encodes a protein of 253 residues w ith consensus sites for N-linked glycosylation; the secreted form of t he protein, designated PRL-like protein F (PLP-F), is predicted to be 223 amino acids in length. Both of these messenger RNAs are expressed specifically in the placenta, with peak levels of PLP-E on days 10-12 and of PLP-F on days 14-16. Expression of PLP-E is restricted to the t rophoblast giant cells, whereas PLP-F is synthesized only in the spong iotrophoblasts. The genes for both of these proteins map to a 700-kilo base region of mouse chromosome 13 that includes other members of the PRL/GH family.