TBX5 and embryonal carcinoma: In addition, both Ifi204 and Ifi205 were negatively correlated with Gata4. It has been reported that p204 (the protein product of Ifi204) is required for differentiation of P19 murine embryonal carcinoma cells to beating cardiac myocytes: its expression is activated by cardiac Gata4 and two other proteins, Nkx2.5 and Tbx5 [32].