Abstract Studies in rodents have fundamentally advanced our understanding of pancreatic islet cell development and function, but limitations of rodent models for understanding human pancreas formation and disease have intensified interest in experimental systems that more closely reflect human pancreas development and islet function. Our studies have revealed advantages for investigating islet development in pigs, including evidence for multiple conserved features of islet development in pigs and humans, not observed in mice. This includes expression of transcription factors like SIX2 and SIX3 which govern hallmark features of human islet β cell fate and function. We have developed a reliable framework for procuring pig pancreata and islets from any developmental stage, and described molecular, cellular, signaling and genetic features of developing pig α, β, and δ cells from fetal to neo-natal stages, including the first detailed developmental transcriptome of these cells. In addition, our team has generated some of the first gene-edited pigs using CRISPR/Cas9 targeting. These advances motivate the following Aims: Aim 1. Elucidate the genetic architecture of pig islet cell development and functional maturation Aim 2. Identify native regulators of pig islet SIX2 and SIX3 expression Aim 3. Investigate phenotypes of HNF1A heterozygous mutation in pigs To achieve our aims, we assembled a superb team of collaborating investigators with complementary expertise in developmental biology, pig genetics, islet biology, genomics and diabetes research. This work should allow previously unattainable investigation of genetic and physiological mechanisms regulating pig islet cells. This includes identification of regulatory features that connect chromatin dynamics and gene transcription to control islet α, β and δ cell fate and function, and creation of new models of MODY that better recapitulate human disease genetics, pathogenesis and therapeutics. Our work should create new flexible experimental paradigms to investigate development and functional maturation of islet cells from physiological and pathological stages, a striking advantage that broadens the impact of our proposal on human health.