The use of proteomic analysis to study trafficking defects in axons

Mutations in microtubule subunits and microtubule-associated proteins are the causes of many neurological disorders. These human conditions are usually associated with axonal tract defects or degeneration. The molecular mechanisms of these axonal dysfunction are still largely unknown. Conventional methods may not yield a complete analysis of downstream molecules related to axonal dysfunctions. Therefore, we devised a simple unbiased method to screen molecular motors and axonal molecules, which might be involved in axonal defects. We performed our analysis in the mouse with a targeted deletion in the doublecortin (Dcx) gene. Dcx is a microtubule-associated protein with direct effects on microtubule motors. Furthermore, the knockout of Dcx and its functionally redundant structurally similar paralog, doublecortin-like kinase 1 (Dclk1), in mouse results in thinner or absent axon tracts, including the corpus callosum and anterior commissures. We compared protein profiles of corpus callosum from Dcx knockout and wild-type mouse of P0-P2 using mass spectrometry. This strategy allowed us to identify novel candidates downstream of Dcx involved in axon transport.