The diversity and direction of the nerve cells responsible for muscle movements are controlled by a protein called FoxP1, according to research published this year.
Such neurons are known as motor neurons. In the spine, motor neurons that control muscles in different regions of the body segregate into columns. Jeremy Dasen and Thomas Jessell of Columbia University in New York and their colleagues found that the amount of FoxP1 present alters the proportions of the different column types that neurons form. Increasing the expression of FoxP1 in embryonic mouse and chick motor neurons, for example, led to more neurons in the columns that innervate muscles in limbs.
Meanwhile, removing the FoxP1 gene not only affected column diversity but also altered the connections among motor neurons in limbs, and the patterns of axons that project into individual muscles.