Characterization of Axon Outgrowth and Morphology Defects in Acetyltransferase and Doublecortin-like Kinase Double Mutants
Mentor:Renee Baran, Associate professor, Biology, Occidental College
Microtubules are heteropolymers that comprise the mitotic spindle and function in cellular transport, axonal outgrowth, and synaptic development in neurons. Microtubules localize, assemble, and degrade in a dynamic fashion that meets the needs of the cell at any given instant. Polymerization entails precise regulation, which is accomplished by the activity of microtubule-associated proteins (MAPs) and enzymes that perform post-translational modifications. Previous work showed that mutations in the C. elegans doublecortin-like kinase (zyg-8) produced defects in axonal morphology in GABAergic motor neurons and touch receptor neurons (TRNs). Other work implicates acetylation at the Lysine 40 residue of microtubules as a determinant of a characteristic fifteen protofilament configuration in the TRNs. One model is that microtubule structure and function necessitates proper ZYG-8 binding to the microtubule’s exterior as well as the coordinated action of acetyltransferases in the lumen; their simultaneous failure may exaggerate the microtubule defects seen in zyg-8 and acetyltransferase single mutants. We constructed double mutants between zyg-8 mutants expressing a GFP reporter transgene – or484;mec-4::GFP and or490;mec-4::GFP – and two acetyltransferase mutants – mec-17 and atat-2. Microscopy results suggest that ALM and PLM neurons of mec-17;or484 and atat-2;or484 experience a modest increase in axonal abnormalities, oversized cell somas, and axonal targeting errors than zyg-8 mutants alone. Evaluation of double mutants containing the or490 allele is underway. Ultimately, this research intends to clarify the mechanism by which ZYG-8 interacts with other modifying enzymes to regulate microtubule structure and activity.