The studies also raise the possibility that the combinatorial code contains additional information, beyond the regulation of motor neuron wiring. "This is still conjecture, but the sheer number of Hox proteins, and their capacity to direct neuronal differentiation, suggests that they may also impart identity to the interneurons that enable them to connect selectively with motor neurons. And, aspects of the code could also give identity to sensory neurons, enabling their connections with motor neurons," said Jessell. Deciphering the entire Hox code could provide crucial insights into the organization of the complex circuitry that the spinal cord uses to control muscle action.
Speculation aside, Jessell is optimistic that there will eventually be clinical value in deciphering the Hox code. "In developing ways to recover from spinal cord injuries, much attention has focused on getting the axons of cortical neurons to grow past the lesion site and innervate target neurons in distant parts of the spinal cord," he said. "Now, it may be that the spinal cord circuit is still intact -- and there is some evidence to believe this -- so all you need to do is get regenerating axons to grow past the site of the lesion.
"Or, it could be that injury causes subtle alterations in the wiring of spinal circuits, and these alterations may constrain the capacity for full recovery of motor function. So, the more that is understood about the basic workings of this locomotor cir
Source:Howard Hughes Medical Institute