PHOSPHOREGULATION OF SPERM MEIOTIC CHROMOSOME SEGREGATION
Luis Quintanilla, Vanessa Cota, Thais Godoy-Cintra, Diana S. Chu.
San Francisco State University, San Francisco, CA.
Phosphoregulation, a significant process that regulates key cellular activities, relies on a fine balance between kinases and phosphatases. Serine/threonine kinases and phosphatases are responsible for mediating key chromosome segregation events: the interaction with microtubules and kinetochores which help pull chromosomes apart, and the removal of cohesion between chromosomes before they separate. A group of key meiotic serine/threonine PP1 phosphatases found only in C. elegans sperm, called GSP-3 and GSP-4 (GSP-3/4), are required for proper chromosome segregation specifically in male meiosis. Chromosome segregation fails when GSP-3/4 are absent in sperm and result in infertility. Although GSP-3/4 are essential for proper sperm meiotic chromosome segregation, their phosphoregulatory relationship at the kinetochore and cohesion remains largely unknown. Thus, we hypothesize that GSP-3/4 are dually responsible for regulating kinetochore and cohesion regions by opposing kinase activities at these sites. Here, we show that GSP-3/4 are essential for proper localization of BUB-1, a kinase located at the outer kinetochore during sperm meiosis. Furthermore, we show that GSP-3/4 are not required for proper localization of AIR-2, a microtubule and cohesion destabilizing kinase, during sperm formation, suggesting that removal of cohesion should be unimpaired, yet sister chromatids fail to separate during meiosis II. Lastly, preliminary results suggest that PLK-1, a kinase that acts at the kinetochore and cohesion regions as sperm develop, is not affected by GSP-3/4, suggesting that GSP-3/4 activity is restricted around kinetochore and cohesion during sperm meiosis. Together, these results elucidate the phosphoregulatory relationships at the kinetochore and cohesion during the male meiotic event.