When motor nerve cells, or neurons, from chickens and mice make more of a certain protein, the cells act like fast motor neurons, sending signals to muscles more quickly in short bursts good for jumping and running. Switching off the protein-making gene makes the motor neurons act slow, firing fewer times over a longer period, which helps with standing and staying upright.
The protein, Delta-like homolog 1, or Dlk1, is made in 30 percent of motor neurons. It helps to determine at which speed the cells work, and it may determine how the motor nerve cells develop to control different movements, scientists report March 13 in Science. Additional experiments showed that mice with motor neurons completely lacking the protein could walk, stand and swim as well as normal mice, but they had trouble stopping their movements and created a bit less force with their legs.