Chicken ovalbumin upstream promoter transcription factor (COUP-TF) belongs to the NR2 subfamily of the nuclear hormone receptor family. COUP-TFI and COUP-TFII are two of the well-characterized members in the NR2 subfamily. These two members are highly conserved in their two zinc-finger DNA binding domains (DBD) and the ligand binding domain (LBD), and function as repressors or activators of downstream target genes to regulate different biological processes . COUP-TFI and II bind to 5'-AGGTCA-3' motif palindromes, either directly or indirectly, through heterodimer formation with other proteins (e.g. RXRs) to regulate downstream target gene expression. COUP-TFI is involved in neuronal development, tissue patterning, and differentiation . COUP-TFII has been shown to be involved in angiogenesis, glucose homeostasis, and mesenchymal cell commitment.