Defining CLS-2 and SPD-1 Function in Central Spindle Assembly during C. elegans Sperm Meiosis
By: Cuc Huynh and Sebastian Gomez
Department: Cellular & Molecular Biology
Faculty Advisor: Dr. Diana Chu
Male infertility is a serious concern for many Americans. To elucidate how infertility arises, meiosis is an important facet where chromosomes must be properly segregated. One model organism that has been helpful in studying the mechanisms behind cell division is the Caenorhabditis elegans nematode. To ensure proper chromosome segregation, a central spindle structure forms with the aid of the kinetochore protein, CLS-2, at the midzone region of the segregating chromosomes in mitosis and oocyte meiosis. CLS-2 then recruits SPD-1, a microtubule bundler protein, to elongate the spindle. Interestingly, this pattern has not been detected in sperm meiosis thus questioning whether sperm meiosis has a distinctive mechanism of chromosome segregation. In the case of C. elegans sperm meiosis, few microtubules are present in the midzone except those tied to the lagging unpaired X chromosome. We hypothesize that CLS-2 and SPD-1 do not play a significant role in central spindle assembly in sperm meiosis. Instead, sperm meiosis relies on the pulling forces of the kinetochore-connected microtubules rather than the central spindle. We will deplete CLS-2 and SPD-1 in young adult C. elegans males using the auxin-inducible degradation system and apply immunostaining techniques to observe our proteins of interest. Stained samples will be examined under a confocal microscope. We will also use live imaging to observe any differences in DNA localization patterns before and after live worms are treated with auxin. In both immunostaining and live imaging experiments, CLS-2 and SPD-1 fail to localize to the midzone except to the location of the lagging unpaired X chromosome. In males depleted of CLS-2 or SPD-1, we expect the spatial and temporal characteristics of segregating chromosomes to be similar to wild-type. Understanding SPD-1 and CLS-2 localization dynamics can elucidate the molecular mechanisms that drive male meiotic chromosome segregation required for efficiently forming healthy sperm.