In Science this week, a University of California, Los Angeles-led team publishes a study showing the genetic basis for loss of flight in the Galapagos cormorant, the only bird of its species to have lost the ability to fly. The researchers studied wing and pectoral skeleton reduction in these cormorants, then sequenced the genomes of four cormorant species to identify candidate genes that may have contributed to the evolution of flightlessness. They pinpoint genes associated with human developmental disorders, including ones that affect limb development. One of these genes affects bone growth when edited into in mice and another affects cilia formation when introduced into roundworms. The authors suggest that these genes may have been positively selected, giving Galapagos cormorants advantages such as decreased buoyancy when diving via shorter wings.
Also in Science, an international research team reports the discovery of a cluster of microRNAs involved in fine-tuning normal and chronic pain responses. Specifically, they found that the miR-183 cluster in mice is responsible for setting pain threshold in nociceptors — a neuron type that controls more than 80 percent of chronic pain-regulated genes. They also found that mice lacking miR-183 were hypersensitive to mechanical stimuli but responded normally to other stimuli such as cold, heat, and pinpricks, indicating that the miRNA cluster scales down neuron excitability. Profiling of 214 human neuron samples showed that a similar mechanism might exist in other mammals.