We are interested in identifying genes that (1) regulate development of the urethral tube, and (2) control outgrowth and three-dimensional patterning of the genital tubercle. We have discovered a new organizer that is essential for early outgrowth of the genital tubercle. The activity of this organizing tissue is mediated by a secreted signaling molecule called Sonic hedgehog. We have also identified a growth factor receptor that plays an essential role in urethral tube closure. This work has opened a new area of investigation, providing the opportunity to study how environmental factors influence the genetic circuitry that regulates embryonic development. The lab also has a strong interest in the evolution of external genitalia. We are addressing questions aimed at identifying the mechanisms responsible for this major morphological innovation, and understanding how genitourinary structures have diversified during tetrapod evolution.