Isolation and characterization of a novel trophoblast-specific cDNA in the mouse

A novel trophoblast-specific cDNA has been isolated by differential screening of a 13.5-day mouse placental cDNA library. The 755-bp cDNA, which is almost full length, encodes a polypeptide of 124 amino acids with an 18-amino-acid hydrophobic leader sequence. No significant homology with any known gene or protein has been detected. Northern blot analysis has shown that the gene is expressed abundantly in the placenta and is not detected in any other tissues. In situ hybridization revealed that the gene is expressed first in a subgroup of ectoplacental cone cells at 7.5 days of development and its later expression is confined to the spongiotrophoblast cells of the mature placenta. The role of the gene is not currently known, but the presence of a signal peptide suggests that it may be a secreted protein.