Restricted spatiotemporal expression of lactoferrin during murine embryogenesis

Lactoferrin is a member of the transferrin family of iron-binding proteins to which several physiological functions have been ascribed. While there is a wealth of evidence about the distribution and function of this protein in the adult, the expression and function, if any, of lactoferrin during embryogenesis has not been investigated. In the current study, the spatiotemporal distribution of lactoferrin was analyzed during normal murine embryonic development. This analysis demonstrated that lactoferrin is expressed in three distinct patterns during embryogenesis. First, lactoferrin is expressed at the 2-cell stage in the preimplantation embryo where it continues to be expressed until the blastocyst stage when expression ceases. The second phase of lactoferrin expression is not detected until the latter half of gestation when the protein is detected in the myeloid cells, beginning in the fetal liver at embryonic day 11 and later in the spleen and bone marrow coinciding with the onset and diversification of myelopoiesis in these organs during embryogenesis. Finally, lactoferrin is detected in a variety of glandular epithelial cells and/or their secretions, including respiratory and oral epithelia which is consistent with the expression pattern observed for this protein in the adult where it plays an important role in host defense at the mucosal surface. Taken together, these analyses indicate that the role of lactoferrin in the developing embryo is restricted to the preimplantation stage and development of first and second line host defense systems.