IRX1 and congenital heart disease: In humans, mutations in 25 different homeobox transcription factors have been found in patients with congenital heart disease (McCulley and Black 2012); expression of 14 of these (Cited2, Ets1, Foxh1, Gata4, Gata6, Hand1, Hand2, Hoxa1, Irx1, Nkx2-5, Nkx2-6, Pitx2, and Tbx1) was disrupted by TCDD in our mouse ES cell differentiation experiments.