Genetic Identification of Spinal Interneurons that Coordinate Left-Right Locomotor Activity Necessary for Walking Movements. 2004.
what already known
ventromedial spinal cord (termed lamina VIII), a region abundant in commissural interneurons that project to the vicinity of contralateral motor neurons.
Some lamina VIII commissural interneurons form monosynaptic connections with motor neurons and are rhythmically active during locomotion, suggesting they have roles in coordinating bilateral flexor and extensor locomotor activity.
severing the ventral commissure results in a loss in coordinated motor neuron activity in the left and right halves of the spinal cord
Recent genetic studies have shown that inactivation of the receptor tyrosine kinase EphA4 results in defects in spinal locomotor function.
Within the developing spinal cord, several distinct classes of commissural inteneurons settle in lamina VIII.
Two of these interneuron classes, which we term V0V and V0D neurons, differentiate from a discrete progenitor domain, which is marked by expression of the homeodomain transcription factor Dbx1.
V0V interneurons derive from the ventral half of the Dbx1 progenitor domain and transiently express the homeodomain protein Evx1 (Moran-Rivard et al., 2001), whereas V0D interneurons, which lack Evx1 expression, derive from the dorsal Dbx1 domain (Pierani et al., 2001; G.M.L. and S.G., unpublished data).
Both sets of Dbx1-derived interneurons exhibit strikingly similar migratory patterns and initial commissural axonal trajectories Pierani et al. 2001 and Moran-Rivard et al. 2001, suggesting that they are closely related both by provenance and function.
what even unknown
Evx1 mutant mice exhibit normal locomotor activity, whereas Dbx1 mutant mice exhibit profound changes in locomotor coordination.