A group of rare diseases called ciliopathies — polycystic kidney disease notable among them — emerge from defects in cilia. These are the tiny hairlike structures on the surface of almost every cell type. Scientists experimentally ‘knocked out,’ or genetically deleted, the cilia in a population of otherwise normal human pluripotent stem cells. Subsequently, human tissues and mini-organ structures (organoids) derived from these cilia-free stem cells manifested ciliopathy-like symptoms, such those seen in polycystic kidney disease or in certain problems in brain development.
