Rebecca Lyczak et al. (2005) International Worm Meeting "Uncovering the paternal and maternal roles for the scu-1 gene in meiotic progression in sperm and early embryos of Caenorhabditis elegans"

Jeffrey Olimpo, Anna Mazor, Arianna Brewer, Christine Snyder, Lauren Washam, Thomas Group, Rebecca Lyczak, Vicky Appleman, Kristen Smith, Mary Ann Murrow

[International Worm Meeting, 2005]

Shortly after fertilization in the nematode Caenorhabditis elegans, the oocyte chromosomes complete their meiotic divisions, resulting in the release of two polar bodies. During meiotic exit, the chromosomes donated by both the egg and sperm decondense and pronuclear envelopes form as the cells readies for the first cleavage. Around the same time, the sperm donated centrosome plays a role in polarizing the anterior-posterior axis. Little is known about the regulation of meiotic exit and the potential link to the establishment of embryonic polarity. To study this, we are analyzing a mutant in C. elegans, called scu-1 (sperm cue abnormal) which has defects in both meiotic exit and anterior-posterior axis formation in the one-cell embryo. Our current research focuses on phenotypic characterization of the meiotic exit defect in the early scu-1 embryo, analysis of meiosis during spermatogenesis in scu-1 mutant males, and study of the maternal and paternal contributions of the scu-1 gene product. To analyze the meiotic defect in early embryos, we are looking in detail at molecular markers of meiosis through antibody staining, and time-lapse gfp movies to evaluate when in the meiotic cell-cycle, scu-1 mutant embryos show discrete defects. We are exploring persistence of phospho-histone on oocyte chromosomes, and analysis of tubulin and histone::gfp as ways to monitor this. From this analysis we have discovered that there is a delay in chromosome decondensation following meiosis. We have also begun to look closely at spermatogenesis, using chromosome and microtubule staining. Our preliminary analysis has uncovered chromosome segregation defects in spermatocyte divisions, and chromosome condensation problems in mature spermatids. In an attempt to better understand the maternal and paternal requirements for the scu-1 gene product in meiotic exit and polarity, we are performing mel and pel crosses and examining the resulting embryos via time-lapse imaging under DIC optics. Initial crosses indicate that maternal or paternal contribution is sufficient for normal meiotic progression and embryo viability. It is our hope that these studies will result in a clearer picture of the role for scu-1 during oocyte and sperm meiosis and the role of maternal and paternal SCU-1 during early development.