Zhong, Z., Ohnmacht, J., Reimer, M.M., Bach, I., Becker, T., and Becker, C.G. (2012) Chondrolectin mediates growth cone interactions of motor axons with an intermediate target. The Journal of neuroscience : the official journal of the Society for Neuroscience. 32(13):4426-4439.
The C-type lectin chondrolectin (chodl) represents one of the major gene products dysregulated in spinal muscular atrophy models in mice. However, to date, no function
has been determined for the gene. We have identified chodl and other novel genes potentially involved in motor axon differentiation, by expression profiling of transgenically labeled
motor neurons in embryonic zebrafish. To enrich the profile for genes involved in differentiation of peripheral motor axons,
we inhibited the function of LIM-HDs (LIM homeodomain factors) by overexpression of a dominant-negative cofactor, thereby
rendering labeled axons unable to grow out of the spinal cord. Importantly, labeled cells still exhibited axon growth and
most cells retained markers of motor neuron identity. Functional tests of chodl, by overexpression and knockdown, confirm crucial functions of this gene for motor axon growth in vivo. Indeed, knockdown of chodl induces arrest or stalling of motor axon growth at the horizontal myoseptum, an intermediate target and navigational choice
point, and reduced muscle innervation at later developmental stages. This phenotype is rescued by chodl overexpression, suggesting that correct expression levels of chodl are important for interactions of growth cones of motor axons with the horizontal myoseptum. Combined, these results identify
upstream regulators and downstream functions of chodl during motor axon growth.