Positional Cloning of C. elegans Suppressor Mutations of an Alpha-tubulin Defect
Olivia Arreola and Lester Laddaran
Project Advisor:  Renee Baran

     The Baran lab uses Caenorhabditis elegans to study molecular mechanisms that regulate synapse formation and stabilization. We focus on tba-1, a gene that codes for the alpha-tubulin subunit of microtubules. Dimers of alpha-tubulin and beta-tubulin are the building blocks of microtubules, and the assembly and disassembly of the dimers and microtubule polymers are highly regulated. Microtubules likely play more than one function during neuron development because mutations in several types of microtubule-associated proteins (MAPs) in vertebrates result in synapse loss and motor neuron degeneration. We are using a molecular genetic approach to identify genes that promote synapse stability. We work with ju89, a missense mutation of tba-1 that alters the exterior of tubulin polymers. We hypothesize that this mutation disrupts critical residues to which structural MAPs or motor proteins attach. Structural MAPs, such as human tau, may act to bundle microtubules or link microtubules to other components of the cytoskeleton. Motor proteins, such as dynein and kinesin, also have multiple functions, including transport of proteins along microtubule networks in cells.
     Unlinked mutations, called suppressor mutations, were isolated that compensate for the ju89 defect. We are cloning two of these genes. This process entails identifying the locations of the suppressor genes, the molecules they encode, and their functions. We use a high-throughput SNP (single nucleotide polymorphism) mapping strategy and PCR (polymerase chain reaction) on DNA from the scored progeny to locate the genes.

Support provided by:  Howard Hughes Medical Institute Undergraduate Science Education Grant to Ms. Arreola and the Corey Raffel Fellowship to Mr. Laddaran