APRES: electronically managed student feedback via peer review

Students maximise learning when they receive timely and detailed feedback on their performance from teachers as well as peers. Yet in many subjects taught at university level, feedback consists only of grades and written commentary from teachers, on a final version of submitted work. This form of feedback provides little incentive or opportunity for improvement and places considerable demands on staff in subjects with high enrolments. In 2004 we addressed these problems in our subject Experimental Animal Behaviour, by involving other students (peers) in the feedback process, and designing a web-based software platform APRES to manage the administratively complex task of exchanging submitted work and reviews between students in an anonymous context. We evaluated the success of our innovation by means of written student evaluations, changes in Quality of Teaching survey scores, and changes in the quality of submitted work. All three areas indicate that the project was highly successful. We believe that there is considerable promise for widespread application of this form of feedback and the software platform that enabled us to implement it

<i>Plasmodium </i>Condensin Core Subunits SMC2/SMC4 Mediate Atypical Mitosis and Are Essential for Parasite Proliferation and Transmission

Condensin is a multi-subunit protein complex regulating chromosome condensation and segregation during cell division. In Plasmodium spp., the causative agent of malaria, cell division is atypical and the role of condensin is unclear. Here we examine the role of SMC2 and SMC4, the core subunits of condensin, during endomitosis in schizogony and endoreduplication in male gametogenesis. During early schizogony, SMC2/SMC4 localize to a distinct focus, identified as the centromeres by NDC80 fluorescence and chromatin immunoprecipitation sequencing (ChIP-seq) analyses, but do not form condensin I or II complexes. In mature schizonts and during male gametogenesis, there is a diffuse SMC2/SMC4 distribution on chromosomes and in the nucleus, and both condensin I and condensin II complexes form at these stages. Knockdown of smc2 and smc4 gene expression reveals essential roles in parasite proliferation and transmission. The condensin core subunits (SMC2/SMC4) form different complexes and may have distinct functions at various stages of the parasite life cycle

Systematic analysis of Plasmodium myosins reveals differential expression, localisation, and function in invasive and proliferative parasite stages

The myosin superfamily comprises of actin‐dependent eukaryotic molecular motors important in a variety of cellular functions. Although well studied in many systems, knowledge of their functions in Plasmodium, the causative agent of malaria, is restricted. Previously, six myosins were identified in this genus, including three Class XIV myosins found only in Apicomplexa and some Ciliates. The well characterized MyoA is a Class XIV myosin essential for gliding motility and invasion. Here, we characterize all other Plasmodium myosins throughout the parasite life cycle and show that they have very diverse patterns of expression and cellular location. MyoB and MyoE, the other two Class XIV myosins, are expressed in all invasive stages, with apical and basal locations, respectively. Gene deletion revealed that MyoE is involved in sporozoite traversal, MyoF and MyoK are likely essential in the asexual blood stages, and MyoJ and MyoB are not essential. Both MyoB and its essential light chain (MCL‐B) are localised at the apical end of ookinetes but expressed at completely different time points. This work provides a better understanding of the role of actomyosin motors in Apicomplexan parasites, particularly in the motile and invasive stages of Plasmodium during sexual and asexual development within the mosquito

Plasmodium SAS4: basal body component of male cell which is dispensable for parasite transmission.

The centriole/basal body (CBB) is an evolutionarily conserved organelle acting as a microtubule organising centre (MTOC) to nucleate cilia, flagella, and the centrosome. SAS4/CPAP is a conserved component associated with BB biogenesis in many model flagellated cells. Plasmodium, a divergent unicellular eukaryote and causative agent of malaria, displays an atypical, closed mitosis with an MTOC (or centriolar plaque), reminiscent of an acentriolar MTOC, embedded in the nuclear membrane. Mitosis during male gamete formation is accompanied by flagella formation. There are two MTOCs in male gametocytes: the acentriolar nuclear envelope MTOC for the mitotic spindle and an outer centriolar MTOC (the basal body) that organises flagella assembly in the cytoplasm. We show the coordinated location, association and assembly of SAS4 with the BB component, kinesin-8B, but no association with the kinetochore protein, NDC80, indicating that SAS4 is part of the BB and outer centriolar MTOC in the cytoplasm. Deletion of the SAS4 gene produced no phenotype, indicating that it is not essential for either male gamete formation or parasite transmission

Plasmodium SAS4: basal body component of male cell which is dispensable for parasite transmission

The centriole/basal body (CBB) is an evolutionarily conserved organelle acting as a microtubule organising centre (MTOC) to nucleate cilia, flagella, and the centrosome. SAS4/CPAP is a conserved component associated with BB biogenesis in many model flagellated cells. Plasmodium, a divergent unicellular eukaryote and causative agent of malaria, displays an atypical, closed mitosis with an MTOC (or centriolar plaque), reminiscent of an acentriolar MTOC, embedded in the nuclear membrane. Mitosis during male gamete formation is accompanied by flagella formation. There are two MTOCs in male gametocytes: the acentriolar nuclear envelope MTOC for the mitotic spindle and an outer centriolar MTOC (the basal body) that organises flagella assembly in the cytoplasm. We show the coordinated location, association and assembly of SAS4 with the BB component, kinesin8B, but no association with the kinetochore protein, NDC80, indicating that SAS4 is part of the BB and outer centriolar MTOC in the cytoplasm. Deletion of the SAS4 gene produced no phenotype, indicating that it is not essential for either male gamete formation or parasite transmission

MRE11 Is Crucial for Malaria Parasite Transmission and Its Absence Affects Expression of Interconnected Networks of Key Genes Essential for Life

The meiotic recombination 11 protein (MRE11) plays a key role in DNA damage response and maintenance of genome stability. However, little is known about its function during development of the malaria parasite Plasmodium. Here, we present a functional, ultrastructural and transcriptomic analysis of Plasmodium parasites lacking MRE11 during its life cycle in both mammalian and mosquito vector hosts. Genetic disruption of Plasmodium berghei mre11 (PbMRE11) results in significant retardation of oocyst development in the mosquito midgut associated with cytoplasmic and nuclear degeneration, along with concomitant ablation of sporogony and subsequent parasite transmission. Further, absence of PbMRE11 results in significant transcriptional downregulation of genes involved in key interconnected biological processes that are fundamental to all eukaryotic life including ribonucleoprotein biogenesis, spliceosome function and iron-sulfur cluster assembly. Overall, our study provides a comprehensive functional analysis of MRE11's role in Plasmodium development during the mosquito stages and offers a potential target for therapeutic intervention during malaria parasite transmission

Plasmodium ARK2 and EB1 drive unconventional spindle dynamics, during chromosome segregation in sexual transmission stages

The Aurora family of kinases orchestrates chromosome segregation and cytokinesis during cell division, with precise spatiotemporal regulation of its catalytic activities by distinct protein scaffolds. Plasmodium spp., the causative agents of malaria, are unicellular eukaryotes with three unique and highly divergent aurora-related kinases (ARK1-3) that are essential for asexual cellular proliferation but lack most canonical scaffolds/activators. Here we investigate the role of ARK2 during sexual proliferation of the rodent malaria Plasmodium berghei, using a combination of super-resolution microscopy, mass spectrometry, and live-cell fluorescence imaging. We find that ARK2 is primarily located at spindle microtubules in the vicinity of kinetochores during both mitosis and meiosis. Interactomic and co-localisation studies reveal several putative ARK2-associated interactors including the microtubule-interacting protein EB1, together with MISFIT and Myosin-K, but no conserved eukaryotic scaffold proteins. Gene function studies indicate that ARK2 and EB1 are complementary in driving endomitotic division and thereby parasite transmission through the mosquito. This discovery underlines the flexibility of molecular networks to rewire and drive unconventional mechanisms of chromosome segregation in the malaria parasite.</p

Plasmodium P-type cyclin CYC3 modulates endomitotic growth during oocyst development in mosquitoes

Cell-cycle progression and cell division in eukaryotes are governed in part by the cyclin family and their regulation of cyclin-dependent kinases (CDKs). Cyclins are very well characterised in model systems such as yeast and human cells, but surprisingly little is known about their number and role in Plasmodium, the unicellular protozoan parasite that causes malaria. Malaria parasite cell division and proliferation differs from that of many eukaryotes. During its life cycle it undergoes two types of mitosis: endomitosis in asexual stages and an extremely rapid mitotic process during male gametogenesis. Both schizogony (producing merozoites) in host liver and red blood cells, and sporogony (producing sporozoites) in the mosquito vector, are endomitotic with repeated nuclear replication, without chromosome condensation, before cell division. The role of specific cyclins during Plasmodium cell proliferation was unknown. We show here that the Plasmodium genome contains only three cyclin genes, representing an unusual repertoire of cyclin classes. Expression and reverse genetic analyses of the single Plant (P)-type cyclin, CYC3, in the rodent malaria parasite, Plasmodium berghei, revealed a cytoplasmic and nuclear location of the GFP-tagged protein throughout the lifecycle. Deletion of cyc3 resulted in defects in size, number and growth of oocysts, with abnormalities in budding and sporozoite formation. Furthermore, global transcript analysis of the cyc3-deleted and wild type parasites at gametocyte and ookinete stages identified differentially expressed genes required for signalling, invasion and oocyst development. Collectively these data suggest that cyc3 modulates oocyst endomitotic development in Plasmodium berghei

Compositional and expression analyses of the glideosome during the Plasmodium life cycle reveal an additional myosin light chain required for maximum motility

Myosin A (MyoA) is a Class XIV myosin implicated in gliding motility and host cell and tissue invasion by malaria parasites. MyoA is part of a membrane-associated protein complex called the glideosome, which is essential for parasite motility and includes the MyoA light chain MTIP, and several glideosome-associated proteins (GAPs). However, most studies of MyoA have focused on single stages of the parasite life cycle. We examined MyoA expression throughout the Plasmodium berghei life cycle in both mammalian and insect hosts. In extracellular ookinetes, sporozoites and merozoites, MyoA was located at the parasite periphery. In the sexual stages, zygote formation and initial ookinete differentiation precede MyoA synthesis and deposition, which occurred only in the developing protuberance. In developing intracellular asexual blood stages, MyoA was synthesized in mature schizonts and was located at the periphery of segmenting merozoites, where it remained throughout maturation, merozoite egress and host cell invasion. Besides the known GAPs in the malaria parasite, the complex included GAP40, an additional myosin light chain designated essential light chain (ELC) and several other candidate components. This ELC bound the MyoA neck region adjacent to the MTIP binding site, and both myosin light chains co-located to the glideosome. Co-expression of MyoA with its two light chains revealed that the presence of both light chains enhances MyoA-dependent actin motility. In conclusion, we have established a system to study the interplay and function of the three glideosome components, enabling the assessment of inhibitors that target this motor complex to block host cell invasion