Embryo

Increased Messenger RNA for Allograft Inflammatory Factor-1, LERK-5, and a Novel Gene in 17.5-Day Relative to 15.5-DAY Bovine Embryos

Abstract

Considerable embryonic loss occurs between Days 15 and 18 of gestation in cattle, when critical cellular and molecular events occur, including maternal recognition of pregnancy. To gain insight into these events, mRNA differential display analysis was used to identify 8 unique cDNA fragments present in greater abundance in 17.5-day than in 15.5-day bovine embryos. Four cDNA fragments, confirmed to be up-regulated in 17.5-day embryos using Northern analysis, were cloned and sequenced. Three cDNA fragments shared sequence identities with known homologs: human allograft inflammatory factor-1 (AIF-1), human LERK-5, and bovine interferon-. One novel cDNA fragment did not share sequence identity to previously reported genes, except for a similar DNA sequence in the human genome. AIF-1 mRNA was present in developing placenta through day 36 of gestation, and abundant levels were observed in adult bovine spleen and lung. The novel gene, which we have named peri-attachment factor (PAF), was not detected in adult tissues using Northern analysis, nor in conceptuses between days-30 and 36 of pregnancy. Additional sequence information for bPAF was obtained from a cDNA library constructed from a 25-day bovine embryo. The protein corresponding to the open reading frame has four protein kinase C phosphorylation sites, two casein kinase II phosphorylation sites, a nuclear targeting sequence, but no obvious DNA or RNA binding motifs. Abundant expression of this gene during a narrow but critical window of embryonic development makes it worthy of further study.