Abstract Body: Allogeneic heart transplantation is limited due to the lack of a sufficient number of donor organs. Exogenic organ production is one alternative strategy to engineer human hearts for transplantation. This strategy requires disabling the development of an organ and complementing the mutant host embryo with pluripotent stem cells from the same or different species. In the present study, we used gene editing and somatic cell nuclear transfer technology (SCNT) to engineer a NKX2-5 null porcine embryo. Using morphological, molecular and bulk RNA-seq techniques we determined that the NKX2-5 null porcine embryo was lethal by E18, growth arrested and had structural perturbations. Bulk RNA-seq analysis confirmed perturbed cardiogenesis and together with ChIP-seq datasets revealed downstream targets for NKX2-5 including GLI2 and SOX11. These analyses support the critical role for NKX2-5 directed gene regulatory networks (GRNs) in the developing heart. We then used SCNT and blastocyst complementation with GFP-labeled pig stem cells to rescue the NKX2-5 null lethality and phenotype. Collectively, these studies provide an important platform for future studies focused on engineering a human heart in a gene edited pig that could be a source of donor hearts for transplantation.