A team of researchers at the University of Southern California, led by stem cell researcher Lindsey Barske, have identified the molecular signals that control the development of the vertebrate face. They studied the early development in zebrafish using hi-tech genetic, genomic and imaging tools to understand how facial patterns form. It was found that\u00a0Jagged-Notch and Endothelin1, two types of molecular signals, play a critical role in shaping the upper and lower parts of the face, respectively. These two signals work together and control the timing of when stem cells develop into facial cartilage. While Endothelin1 was found to trigger the cartilage formation in the lower face at an early stage, Jagged-Notch stalled the cartilage development till the later development, which is the reason behind the distinct difference between the upper and lower portions of the face. According to the researchers, these variations in molecular signals have been responsible throughout evolution for the different skulls in animals as well as the variations in human faces.<\/p>\n