Characterization Of A Novel Delayed Hatching Phenotype In Caenorhabditis Elegans PDF Download

Nicotinamide adenine dinucleotide (NAD+) is a crucial molecule used for many important cellular processes, including respiration, longevity, and DNA repair. Synthesis and maintenance of NAD+ levels are necessary for health on an individual-cell and whole-organism level. Caenorhabditis elegans maintains its NAD+ levels through three biosynthetic pathways. Deficiencies in these pathways result in a variety of developmental and reproductive phenotypes, which lead to the discovery of additional roles of NAD+. Recently, a delayed hatching phenotype was observed in a mutant strain lacking the NMRK-1 enzyme, which functions in the synthesis of NAD+ from nicotinamide riboside. I characterized this phenotype in an effort to elucidate its molecular mechanism. I determined that the phenotype was unlike a previously described delayed hatching phenotype, and that it was associated with deficiency in only one of the three NAD+ biosynthetic pathways. By observing the rate at which the mutants progressed through embryogenesis, I showed that the embryogenesis of animals that fail to hatch within the normal time frame is not affected. Using classical genetic methods, I found that the phenotype was a maternal effect phenotype, drawing the focus to the mother animal for further study. Using RNA interference, I determined that the hexosamine pathway was required for the phenotype to occur. My conclusions led me to develop a model for the mechanism behind the delayed hatching of the nmrk-1 mutants. These findings are important for determining currently unknown roles of NAD+ in C. elegans hatching and development.