|Description||Nicotine dependence is the single largest cause of preventable death in the world, claiming 480,000 lives each year in the US alone, including those caused by secondhand smoke. In this study, we investigated the biological effect of nicotine on germ cell fate specification using the nematode C. elegans germline as a model system.
Wild-type hermaphrodites produce both sperm and oocytes. They are therefore self-fertile. However, a mutant lacking PUF-8 (Pumilio RNA binding protein) and LIP-1 (ERK phosphatase) produce only sperm, resulting in sterility (Mog phenotype) at a permissive temperature (20°C). Remarkably, this puf-8; lip-1 mutant develops germline tumors via the dedifferentiation of spermatocytes at a restrictive temperature (25°C). Using this mutant, we investigate the effect of nicotine on germ cell fate specification. First, we treated puf-8; lip-1 homozygotes with different concentrations of nicotine at 25°C and analyzed the germline phenotypes by germline staining. Interestingly, puf-8; lip-1 mutants exposed to 200 μM or less nicotine developed germline tumors via dedifferentiation as seen in control. However, exposure to doses ranging from 500 to 2000 μM significantly reduced germline tumor frequency in a dose-dependent manner, instead showing the Mog phenotype. Moreover, the same doses in unc-32 glp-1(ar202) gain-of-function mutants at 20oC similarly decreased tumor frequency from 17% to 5%. These results hypothesize that high nicotine doses reprogram germ cells with germline tumor or oogenic potential into germ cell with sperm fate. Gene expression of several cell fate regulators was significantly increased following exposure of wild-type worms to 500 and 2000 μM dosing solutions. Our results and future plan hopes to address the potential effect of nicotine on the regulatory network controlling cell fate specification in C. elegans as well as other model systems.||en_US