UNDERSTANDING THE NOVEL ROLE OF CHECKPOINT PROTEIN ROUGH DEAL IN HOMOLOG ORIENTATION AND CENTROMERIC COHESION IN DROSOPHILA MALE MEIOSIS

Meiosis is a central mechanism in sexual reproduction, through which the diploid precursor cells in the germline produce haploid gametes. After fertilization, a new set of diploid genome forms in the offspring with the characteristics of mother and father. The faithful transmission of genetic material to next generation relies on the fidelity of chromosome segregation during meiosis. A variety of mechanisms regulate the chromosome segregations in meiosis, including homolog interaction, chromosome cohesion, and sister-chromatid orientation. In most eukaryotic organisms, homolog interactions are built by the formation of chiasmata resulted from crossovers, but it is absent in male Drosophila in which an alternative conjunction complex is obligate to stabilize homologous chromosome. In addition, Drosophila also deploys a three-member complex, called SOS consisting of SOLO, ORD and SUNN, to establish and maintain the sister-chromatid cohesion in meiosis, while this responsibility is executed by a well-known cohesin complex composed of four subunits (SMC1, SMC3, REC8 and SA) in other eukaryotes. A conserved meiosis-specific sister-chromatid mono-orientation is evident in Drosophila, as in the meiosis I of other eukaryotes, but the regulatory pathway has been elusive until now in both sexes of Drosophila.

In this investigation, we used conventional genetic and advanced fluorescence microscopy to investigate the role of checkpoint Rough Deal (ROD) in Drosophila male meiosis by using trans-heterozygous rod mutants. Based on our results, ROD protein is required for the maintenance, but not the establishment, of centromere cohesion by prohibiting the redistribution of Shugoshin protein MEI-S332. More importantly, ROD modulates the orientation of sister chromatid in meiosis I, might through the regulation and coordination of microtubule attachments on kinetochores. Therefore, dysfunction of ROD causes a high frequency of chromosome mis-segregation, which gives rise to premature equational segregation and 4/O chromosome nondisjunction in the first meiotic division. To get more insights into the ROD function in meiosis, we further generate a conditional ROD-depleted line in which we expect to induce the degradation of ROD protein in Drosophila spermatocytes, which could help us to fully understand the role of ROD in a null-like background.