Birth defects are now the major cause of infant death in the US and Europe. Despite their tremendous impact, we know very little about the causes of most birth defects. Prior research has focused on environmental causes, especially nutrition (such as folate). However, recent evidence indicates that genetics is important too. Our goal is to analyze the gene sequences (“exome”) of birth defect patients in order to find a gene that might explain their disease. Deciphering the genes that cause birth defects is particularly difficult, however. In order to tackle this problem, we combine patient driven gene discovery with developmental mechanism discovery in disease model systems, especially the frog model, Xenopus. This model organism is particularly well-suited for studying birth defect genes because experiments are fast and easy to perform, and as a tetrapod, Xenopus has many similarities to human development. Once we have identified a candidate gene from our patient, we test it in frog to see if it also causes a similar phenotype. If it does, then we try to understand the underlying developmental mechanisms. We try to figure out “how” the gene directs embryonic development.