Interferon-related developmental regulator (IFRD1) is the human homologue of the <taxon tax_id="10116">Rattus norvegicus</taxon> early response protein PC4 and its murine homologue TIS7 [<cite idref="PUB00010173"/>]. The exact function of IFRD1 is unknown but it has been shown that PC4 is necessary for muscle differentiation and that it might have a role in signal transduction. This entry also contains IFRD2 and its murine equivalent SKMc15, which are highly expressed soon after gastrulation and in the hepatic primordium, suggesting an involvement in early hematopoiesis [<cite idref="PUB00008660"/>].