Especially, T-box factors such as Tbx1, Tbx2, Tbx3, Tbx5, Tbx18 and Tbx20 are described to be involved in virtually all steps of cardiogenesis and mutations are associated with developmental syndromes and cardiac abnormalities like DiGeorge syndrome (Tbx1) or Holt-Oram syndrome (Tbx5) [10–12]. The gene discussed is TBX5; the disease is Holt-Oram syndrome.