Suppression of tba-1(ju89) neural defects by zer-1
Mentor:Renee Baran, Associate Professor, Biology, Occidental College
Microtubules are dynamic cytoskeleton structures essential for axon outgrowth and axonal transport in neurons. Microtubules are constructed from alpha and beta tubulin dimers. Previous research in our lab showed the ju89 allele of alpha-tubulin tba-1 causes defects in C. elegans motor neuron development and function. Multiple suppressors of tba-1(ju89) were isolated in a genetic screen and mapped to specific chromosome regions. Our goal was to identify genes that interact with microtubules and regulate their function in neurons. Whole genome sequencing of one suppressor strain identified a mutation in the zer-1 gene. zer-1 encodes a conserved substrate recognition subunit of an ubiquitin-mediated protein degradation complex. Ubiquitination is a post-translational modification found in all eukaryotic organisms where ubiquitin attaches to a target substrate protein to signal for its degradation or recycling. In our current study, our goal was to confirm that decreasing ZER-1 protein function can suppress tba-1(ju89). Conversely, providing wild type ZER-1 should rescue the suppressor phenotype. We crossed tba-1(ju89) worms to a zer-1 deletion strain, zer-1(tm3414). tba-1(ju89) worms that are heterozygous zer-1(tm3414) were rescued for both the movement and synaptic phenotypes, but homozygous zer-1(tm3414) were not. This suggests that concentration levels of the substrate(s) of ZER-1 are fine-tuned by the cell. ZER-1 may regulate microtubule stability directly or modulate expression of other microtubule-associated proteins in neurons. Experiments are in process to sub-clone genomic DNA for zer-1 into a plasmid vector for further experiments. The zer-1 genomic sub-clone will be injected into tba-1(ju89) worms to confirm that wild type zer-1 is able to rescue the suppressor phenotype. The zer-1 genomic construct will also be used to construct a ZER-1-GFP transgene for future studies of ZER-1 expression in neurons.