Identification and embryonic expression of a new AP‐2 transcription factor, AP‐2ϵ

AP‐2 proteins comprise a family of highly related transcription factors, which are expressed during mouse embryogenesis in a variety of ectodermal, neuroectodermal, and mesenchymal tissues. AP‐2 transcription factors were shown to be involved in morphogenesis of craniofacial, urogenital, neural crest‐derived, and placental tissues. By means of a partial cDNA fragment identified during an expressed sequence tag search for AP‐2 genes, we identified a fifth, previously unknown AP‐2–related gene, AP‐2ϵ. AP‐2ϵ encodes an open reading frame of 434 amino acids, which reveals the typical modular structure of AP‐2 transcription factors with highly conserved C‐terminal DNA binding and dimerization domains. Although the N‐terminally localized activation domain is less homologous, position and identity of amino acids essential for transcriptional transactivation are conserved. Reverse transcriptase‐polymerase chain reaction analyses of murine embryos revealed AP‐2ϵ expression from gestational stage embryonic day 7.5 throughout all later embryonic stages until birth. Whole‐mount in situ hybridization using a specific AP‐2ϵ cDNA fragment demonstrated that during embryogenesis, expression of AP‐2ϵ is mainly restricted to neural tissue, especially the midbrain, hindbrain, and olfactory bulb. This expression pattern was confirmed by immunohistochemistry with an AP‐2ϵ–specific antiserum. By using this antiserum, we could further localize AP‐2ϵ expression in a hypothalamic nucleus and the neuroepithelium of the vomeronasal organ, suggesting an important function of AP‐2ϵ for the development of the olfactory system. Developmental Dynamics 231:128–135, 2004. © 2004 Wiley‐Liss, Inc.