Ready-to-use ELISA kits are available for the detection of E(spI), an alias of the protein, TLE family member 4, transcriptional corepressor. The official gene symbol is TLE4. The protein, with a mass of 83.8 kDa and length of 773 residues, is reported to be nuclear. It is a member of the WD repeat Groucho/TLE family and may be known by other names, including: transducin-like enhancer of split 4 homolog of Drosophila E(sp1), groucho-related protein 4, enhancer of split groucho 4, B lymphocyte gene 1, and transducin-like enhancer protein 4, and BCE1.