The conserved KMN network is required for KT-MT attachments in vivo and is composed of three groups of proteins: SPC105/KNL1, the MIS12 complex and the NDC80 complex.  NDC80 is required for end-on MT attachments, which are important for moving the chromosomes towards the poles at anaphase. We have identified several activities that depend on SPC105R, kinetochore assembly (NDC80 recruitment), lateral microtubule attachments, and sister centromere fusion.  The latter is important for coorientation, the mechanism that promotes attachment of sister kinetochores in meiosis I to microtubules from the same pole. 

• Read more about Investigate the structure and function of the meiotic centromere and kinetochore

Prior to meiosis, the DNA replicates. Cohesin is the protein complex that holds these sister chromatids together until meiosis I and II. Cohesin regulation is complex because it must be protected from destruction prior to these stages, and then released in stages. First the chromosomes arms during meiosis I, and then the centromeres and the pericentromeric regions in meiosis II. regulate sister centromere fusion. The analysis of kinetochore proteins SPC105R/KNL1 and Protein Phosphatase 1 (PP1-87B) has shown that two independent mechanisms maintain sister centromere cohesion in Drosophila oocytes. Maintenance of sister centromere cohesion by SPC105R involves protection against Separase, the enzyme that’s destroys cohesin proteins. In contrast, maintenance of sister centromere cohesion by PP1-87B does not involve Separase. Instead, PP1-87B maintains sister centromere cohesion by inhibiting stable KT-MT attachments. In a recent paper describing this work, we propose two mechanisms regulate co-orientation in Drosophila oocytes. First, SPC105R protects cohesins at sister centromeres to maintain fusion.  Second, separation of sister centromeres in meiosis II occurs without degrading cohesins, depends on end-on microtubule attachments, and during meiosis I is prevented by PP1-87B mediated destabilization of these attachments.

• Read more about Characterize the relationship between the CPC and phosphatases

A key player in Drosophila meiosis is the four-protein chromosomal passenger complex (CPC). INCENP (Figure 2A) targets the complex to specific structures and recruits Aurora B, a kinase and the catalytic component of the CPC. In females expressing RNAi to Incenp or Aurora B, no meiotic spindle forms, showing that the CPC is required for chromosomes mediated spindle formation in oocytes.

• Read more about Characterize the relationship between CPC localization and bi-orientation

Pairs of meiotic chromosomes, or homologs, are brought together in an elaborate pairing process which culminates with synapsis, where bivalents are held together along their entire length by the synaptonemal complex (SC).   Formation of the SC between homologs is essential for crossing over and chromosome segregation but how the homologs are paired and SC assembly initiates is poorly understood.   We investigated the requirements for SC assembly in Drosophila oocytes and found that there are three temporally and genetically distinct stages of synapsis initiation (Figure 1).  First, early zygotene cells have one or two patches of SC that colocalizes with a cluster of centromeres, suggesting synapsis initiates first at the centromeres.  Second, oocytes at mid-zygotene contain the centromere SC plus several euchromatic sites.  The centromeric and first euchromatic SC initiation sites depend on the cohesin protein ORD.  Third, late zygotene contains many more sites of SC initiation and these depend on the Kleisin-like protein C(2)M.  Surprisingly, the synapsis initiation events in late zygotene are independent of the earlier mid-zygotene events but all synapsis depend on the cohesin subunit SMC3.  Our results show that cohesin proteins have an important role in SC initiation.

• Read more about A pathway for synapsis initiation during zygotene in Drosophila oocytes

Meiotic recombination occurs during prophase I when homologous chromosomes are synapsed along their entire length. Synapsis is defined as the close and stable association of homologous chromosomes through a proteinaceous structure called the synaptonemal complex (SC). In most organisms, this complex is composed of two main parts: lateral elements that attach along the axis of each homologous chromosome and transverse elements that span the central region of the SC and function to tether the homologs [1,2]. At the leptotene/zygotene stages of meiotic prophase, these structural proteins begin to load onto the chromosome axes, and are completely assembled at pachytene, when homologous chromosomes are synapsed along their entire length. Recombination between the homologous chromosomes initiates with DNA double-strand breaks (DSBs) that are repaired as either crossovers or noncrossovers [3–5]. Crossovers establish chromatin linkages called chiasmata, which, along with sister chromatid cohesion, hold homologs together after recombination has been completed and chromosomes have dissociated their SC proteins. Chiasmata help orient the homologous chromosomes on the metaphase I spindle and ensure their proper segregation at anaphase I. The failure to establish a crossover/chiasma can result in the nondisjunction of homologs and lead to aneuploid gametes.

• Read more about Chromosome axis defects induce a checkpoint-mediated delay and interchromosomal effect on crossing over during Drosophila meiosis