We still continue to screen mouse genomic DNA by PCR and mouse mRNA from several tissues by RT-PCR with various fish primers to pull out the mammalian homolog. We continue to design primers and to sequence degenerate PCR products. After 2 years of effort differential display efforts have been abandoned by us because of irreproducibility. In every case, estradiol also regulates them, but to my great surprise this novel set of five genes is not inhibited by the ER and ER antagonist, ICI182,780. This suggests there are four ERs.
Life becomes very complicated if there are four ERs, but the data are compelling.
Comparison of in vivo ligand-binding and transactivation properties of human ERa and ERb.