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The development of any organism is directed by sequential gene expression that provides a basis for differentiation and specialization of cells. Our lab is interested in the genes that control organogenesis, specifically, the development of the C. elegans pharynx. The microscopic nematode Caenorhabditis elegans is a model organism that provides many advantages for this study, including a completely sequenced genome, a known cell lineage and a transparency that makes observation very simple. We selected two strains from a previous mutagenesis screen to investigate, M136 and M138, which are characterized by extreme deformation of the pharynx resulting from possible failure of pharyngeal muscle cells to undergo normal morphogenesis. We hypothesized that the phenotype may be a result of abnormal adhesion of cells and resulting in L1 larval lethality. We addressed the basis of this lethality using multiple methods, immunocytochemistry to reveal the structure of the abnormal pharynx, fluorescent bead feeding assays to determine if the pharynx has function, genetic mapping to reveal the identity of the gene involved, and a genetic cross to determine the presence of the correct number of cells. Single nucleotide polymorphism mapping revealed the mutation to be located on chromosome I between map units one and eight. A complementation analysis showed M136 and M138 are caused by a mutation to the same gene. Immunocytochemistry demonstrated the mutation caused defects to multiple cell types and but the genetic cross indicated all pharynx muscle cells are present in mutant worms. Future research will entail complementation with deletion strains to determine the exact location of the mutation, followed by the use of transgenic rescue microinjections to confirm the identity of the gene.


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