IR76b-expressing neurons in Drosophila melanogaster are necessary for associative reward learning of an amino acid mixture.

Learning where to find nutrients while at the same time avoiding toxic food is essential for survival of any animal. Using Drosophila melanogaster larvae as a study case, we investigate the role of gustatory sensory neurons expressing IR76b for associative learning of amino acids, the building blocks of proteins. We found surprising complexity in the neuronal underpinnings of sensing amino acids, and a functional division of sensory neurons. We found that the IR76b receptor is dispensable for amino acid learning, whereas the neurons expressing IR76b are specifically required for the rewarding but not the punishing effect of amino acids. This unexpected dissociation in neuronal processing of amino acids for different behavioural functions provides a study case for functional divisions of labour in gustatory systems.

Betulinic Acid Increases the Lifespan of Drosophila melanogaster via Sir2 and FoxO Activation.

Betulinic acid (BetA), a triterpenoid derivative found abundantly in the plant kingdom, has emerged as a promising candidate for promoting longevity. Many research studies have shown its antioxidant, anti-inflammatory, antiviral, and anticancer activities, making it an interesting subject for investigating its potential influence on lifespan. This study aimed to investigate the effects of BetA on longevity and the mechanisms associated with it using the fruit fly Drosophila melanogaster as the organism model. The results showed that 50 µM BetA supplementation extended the mean lifespan of fruit flies by 13% in males and 6% in females without any adverse effects on their physiology, such as fecundity, feeding rate, or locomotion ability reduction. However, 50 µM BetA supplementation failed to increase the lifespan in mutants lacking functional silent information regulator 2 (Sir2) and Forkhead box O (FoxO)-null, implying that the longevity effect of BetA is related to Sir2 and FoxO activation. Our study contributes to the knowledge in the field of anti-aging research and inspires further investigations into natural compounds such as BetA to enhance organismal healthspan.

Protective effect of agar oligosaccharide on male Drosophila melanogaster suffering from oxidative stress via intestinal microflora activating the Keap1-Nrf2 signaling pathway.

Agar oligosaccharide (AOS) is a new kind of marine functional oligosaccharide with generous biological activities. To investigate the antioxidative effects of AOS in vivo, 3 % aqueous hydrogen peroxide (H2O2) was used to induce oxidative stress in male Drosophila melanogaster (D. melanogaster) fed 5 % sucrose (SUC). AOS (0.125 %) in the medium extended the lifespan of D. melanogaster suffering from oxidative stress by improving antioxidant capacity and intestinal function. Electron microscopic observation of epithelial cells showed that AOS alleviated the damage caused by H2O2 challenge in the intestine of D. melanogaster, including a reduction of gut leakage and maintenance of intestinal length and cell ultrastructure. The Keap1-Nrf2 (analogues of CncC gene in D. melanogaster) signaling pathway was significantly activated based on gene expression levels and a reduction in ROS content in the intestine of D. melanogaster suffering from oxidative stress. The improvement of antioxidant capacity may be related to the regulation of intestinal microflora with AOS supplementation for D. melanogaster. Nrf2-RNAi, sterile and gnotobiotic D. melanogaster were used to validate the hypothesis that AOS activated the Keap1-Nrf2 signaling pathway to achieve antioxidant effects by regulating intestinal microflora. The above results contribute to our understanding of the antioxidative mechanism of AOS and promote its application in the food industry.

Drosophila Free-Flight Odor Tracking is Altered in a Sex-Specific Manner By Preimaginal Sensory Exposure.

In insects such as Drosophila melanogaster, flight guidance is based on converging sensory information provided by several modalities, including chemoperception. Drosophila flies are particularly attracted by complex odors constituting volatile molecules from yeast, pheromones and microbe-metabolized food. Based on a recent study revealing that adult male courtship behavior can be affected by early preimaginal exposure to maternally transmitted egg factors, we wondered whether a similar exposure could affect free-flight odor tracking in flies of both sexes. Our main experiment consisted of testing flies differently conditioned during preimaginal development in a wind tunnel. Each fly was presented with a dual choice of food labeled by groups of each sex of D. melanogaster or D. simulans flies. The combined effect of food with the cis-vaccenyl acetate pheromone (cVA), which is involved in aggregation behavior, was also measured. Moreover, we used the headspace method to determine the "odorant" identity of the different labeled foods tested. We also measured the antennal electrophysiological response to cVA in females and males resulting from the different preimaginal conditioning procedures. Our data indicate that flies differentially modulated their flight response (take off, flight duration, food landing and preference) according to sex, conditioning and food choice. Our headspace analysis revealed that many food-derived volatile molecules diverged between sexes and species. Antennal responses to cVA showed clear sex-specific variation for conditioned flies but not for control flies. In summary, our study indicates that preimaginal conditioning can affect Drosophila free flight behavior in a sex-specific manner.

Deciphering the role of Hippo pathway in lung cancer.

Hippo pathway has been initially recognized as a regulatory mechanism for modulation of organ size in fruitfly. Subsequently, its involvement in the regulation of homeostasis and tumorigenesis has been identified. This pathway contains some tumor suppressor genes such as hippo (hpo) and warts (wts), as well as a number of oncogenic ones such as yorkie (yki). Recent studies have shown participation of Hippo pathway in the lung carcinogenesis. This pathway can affect lung cancer via different mechanisms. The interaction between some miRNAs and Hippo pathway is a possible mechanism for carcinogenic processes. Moreover, some other types of non-coding RNAs including PVT1, SFTA1P, NSCLCAT1 and circ_0067741 are implicated in this process. Besides, anti-cancer effects of gallic acid, icotinib hydrochloride, curcumin, ginsenoside Rg3, cryptotanshinone, nitidine chloride, cucurbitacin E, erlotinib, verteporfin, sophoridine, cisplatin and verteporfin in lung cancer are mediated through modulation of Hippo pathway. Here, we summarize the results of recent studies that investigated the role of Hippo signaling in the progression of lung cancer, the impact of non-coding RNAs on this pathway and the effects of anti-cancer agents on Hippo signaling in the context of lung cancer.

Neuroprotective Effects of Lycium Barbarum Fruit Extract on Pink1B9Drosophila Melanogaster Genetic Model of Parkinson's Disease.

Lycium barbarum (LB) is a famous traditional Chinese medicinal plant as well as food supplement possessing various pharmacological functions such as anti-aging and antioxidant effects. The Parkinson's disease (PD)-related kinase Pink1 plays vital role in maintaining the neuron cell homeostasis, having been recognized as a potential target for the development of anti-PD drugs. In this work, the neuroprotective effects of methanol extract of LB fruit (LBFE) were investigated using a Drosophila PD model (PINK1B9) and a human neuroblastoma SH-SY5Y cell line. We found that when LBFE was supplied to the PINK1B9 flies at 6, 12, and 18 days of age, it raised the ATP and dopamine levels at all ages, extended life span, improved motor behavior, and rescued olfactory deficits of the PINK1B9 flies. In addition, histopathological examinations indicated that muscle atrophy in thoraces of the mutant flies was significantly repaired. Finally, LBFE was able to rescue the SH-SY5Y cells against MPP+-induced neurotoxicity. This work reports for the first time the anti-PD potential of L. barbarum fruit extract in PINK1 mutant fruit flies, presenting a new viewpoint for studing the mechanism of action of LBFE.

Caffeine improves mitochondrial function in PINK1B9-null mutant Drosophila melanogaster.

Mitochondrial dysfunction plays a central role in Parkinson's disease (PD) and can be triggered by xenobiotics and mutations in mitochondrial quality control genes, such as the PINK1 gene. Caffeine has been proposed as a secondary treatment to relieve PD symptoms mainly by its antagonistic effects on adenosine receptors (ARs). Nonetheless, the potential protective effects of caffeine on mitochondrial dysfunction could be a strategy in PD treatment but need further investigation. In this study, we used high-resolution respirometry (HRR) to test caffeine's effects on mitochondrial dysfunction in PINK1B9-null mutants of Drosophila melanogaster. PINK1 loss-of-function induced mitochondrial dysfunction in PINK1B9-null flies observed by a decrease in O2 flux related to oxidative phosphorylation (OXPHOS) and electron transfer system (ETS), respiratory control ratio (RCR) and ATP synthesis compared to control flies. Caffeine treatment improved OXPHOS and ETS in PINKB9-null mutant flies, increasing the mitochondrial O2 flux compared to untreated PINKB9-null mutant flies. Moreover, caffeine treatment increased O2 flux coupled to ATP synthesis and mitochondrial respiratory control ratio (RCR) in PINK 1B9-null mutant flies. The effects of caffeine on respiratory parameters were abolished by rotenone co-treatment, suggesting that caffeine exerts its beneficial effects mainly by stimulating the mitochondrial complex I (CI). In conclusion, we demonstrate that caffeine may improve mitochondrial function by increasing mitochondrial OXPHOS and ETS respiration in the PD model using PINK1 loss-of-function mutant flies.

The Drosophila Baramicin polypeptide gene protects against fungal infection.

The fruit fly Drosophila melanogaster combats microbial infection by producing a battery of effector peptides that are secreted into the haemolymph. Technical difficulties prevented the investigation of these short effector genes until the recent advent of the CRISPR/CAS era. As a consequence, many putative immune effectors remain to be formally described, and exactly how each of these effectors contribute to survival is not well characterized. Here we describe a novel Drosophila antifungal peptide gene that we name Baramicin A. We show that BaraA encodes a precursor protein cleaved into multiple peptides via furin cleavage sites. BaraA is strongly immune-induced in the fat body downstream of the Toll pathway, but also exhibits expression in other tissues. Importantly, we show that flies lacking BaraA are viable but susceptible to the entomopathogenic fungus Beauveria bassiana. Consistent with BaraA being directly antimicrobial, overexpression of BaraA promotes resistance to fungi and the IM10-like peptides produced by BaraA synergistically inhibit growth of fungi in vitro when combined with a membrane-disrupting antifungal. Surprisingly, BaraA mutant males but not females display an erect wing phenotype upon infection. Here, we characterize a new antifungal immune effector downstream of Toll signalling, and show it is a key contributor to the Drosophila antimicrobial response.

The role of innate immunity in the protection conferred by a bacterial infection against cancer: study of an invertebrate model.

All multicellular organisms are exposed to a diversity of infectious agents and to the emergence and proliferation of malignant cells. The protection conferred by some infections against cancer has been recently linked to the production of acquired immunity effectors such as antibodies. However, the evolution of innate immunity as a mechanism to prevent cancer and how it is jeopardized by infections remain poorly investigated. Here, we explored this question by performing experimental infections in two genetically modified invertebrate models (Drosophila melanogaster) that develop invasive or non-invasive neoplastic brain tumors. After quantifying tumor size and antimicrobial peptide gene expression, we found that Drosophila larvae infected with a naturally occurring bacterium had smaller tumors compared to controls and to fungus-infected larvae. This was associated with the upregulation of genes encoding two antimicrobial peptides-diptericin and drosomycin-that are known to be important mediators of tumor cell death. We further confirmed that tumor regression upon infection was associated with an increase in tumor cell death. Thus, our study suggests that infection could have a protective role through the production of antimicrobial peptides that increase tumor cell death. Finally, our study highlights the need to understand the role of innate immune effectors in the complex interactions between infections and cancer cell communities in order to develop innovative cancer treatment strategies.

Antimicrobial peptides: Application informed by evolution.

Antimicrobial peptides (AMPs) are essential components of immune defenses of multicellular organisms and are currently in development as anti-infective drugs. AMPs have been classically assumed to have broad-spectrum activity and simple kinetics, but recent evidence suggests an unexpected degree of specificity and a high capacity for synergies. Deeper evaluation of the molecular evolution and population genetics of AMP genes reveals more evidence for adaptive maintenance of polymorphism in AMP genes than has previously been appreciated, as well as adaptive loss of AMP activity. AMPs exhibit pharmacodynamic properties that reduce the evolution of resistance in target microbes, and AMPs may synergize with one another and with conventional antibiotics. Both of these properties make AMPs attractive for translational applications. However, if AMPs are to be used clinically, it is crucial to understand their natural biology in order to lessen the risk of collateral harm and avoid the crisis of resistance now facing conventional antibiotics.

Hemocyte-targeted gene expression in the female malaria mosquito using the hemolectin promoter from Drosophila.

Hemocytes, the immune cells in mosquitoes, participate in immune defenses against pathogens including malaria parasites. Mosquito hemocytes can also be infected by arthropod-borne viruses but the pro- or anti-viral nature of this interaction is unknown. Although there has been progress on hemocyte characterization during pathogen infection in mosquitoes, the specific contribution of hemocytes to immune responses and the hemocyte-specific functions of immune genes and pathways remain unresolved due to the lack of genetic tools to manipulate gene expression in these cells specifically. Here, we used the Gal4-UAS system to characterize the activity of the Drosophila hemocyte-specific hemolectin promoter in the adults of Anopheles gambiae, the malaria mosquito. We established an hml-Gal4 driver line that we further crossed to a fluorescent UAS responder line, and examined the expression pattern in the adult progeny driven by the hml promoter. We show that the hml regulatory region drives hemocyte-specific transgene expression in a subset of hemocytes, and that transgene expression is triggered after a blood meal. The hml promoter drives transgene expression in differentiating prohemocytes as well as in differentiated granulocytes. Analysis of different immune markers in hemocytes in which the hml promoter drives transgene expression revealed that this regulatory region could be used to study phagocytosis as well as melanization. Finally, the hml promoter drives transgene expression in hemocytes in which o'nyong-nyong virus replicates. Altogether, the Drosophila hml promoter constitutes a good tool to drive transgene expression in hemocyte only and to analyze the function of these cells and the genes they express during pathogen infection in Anopheles gambiae.

The Gypsy Endogenous Retrovirus Drives Non-Cell-Autonomous Propagation in a Drosophila TDP-43 Model of Neurodegeneration.

A hallmark of neurodegenerative disease is focal onset of pathological protein aggregation, followed by progressive spread of pathology to connected brain regions. In amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), pathology is often associated with aggregation of TAR DNA-binding protein 43 (TDP-43). Although aggregated TDP-43 protein moves between cells, it is not clear whether and how this movement propagates the degeneration. Here, we have established a Drosophila model of human TDP-43 in which we initiated toxic expression of human TDP-43 focally within small groups of glial cells. We found that this focal onset kills adjacent neurons. Surprisingly, we show that this spreading death is caused by an endogenous retrovirus within the glia, which leads to DNA damage and death in adjacent neurons. These findings suggest a possible mechanism by which human retroviruses such as HERV-K might contribute to TDP-43-mediated propagation of neurodegeneration.

The Drosophila melanogaster antimicrobial peptides Mtk-1 and Mtk-2 are active against the malarial parasite Plasmodium falciparum.

Antimicrobial peptides (AMPs) are important components of the vertebrate and invertebrate innate immune systems. Although AMPs are widely recognized for their broad-spectrum activity against bacteria, fungi, and viruses, their activity against protozoan parasites has not been investigated in detail. In this study, we tested 10 AMPs from three different insect species: the greater wax moth Galleria mellonella (cecropin A-D), the fruit fly Drosophila melanogaster (drosocin, Mtk-1 and Mtk-2), and the blow fly Lucilia sericata (LSerPRP-2, LSerPRP-3 and stomoxyn). We tested each AMP against the protozoan parasite Plasmodium falciparum which is responsible for the most severe form of malaria in humans. We also evaluated the impact of these insect AMPs on mouse and pig erythrocytes. Whereas all AMPs showed low hemolytic effects towards mouse and pig erythrocytes, only D. melanogaster Mtk-1 and Mtk-2 significantly inhibited the growth of P. falciparum at low concentrations. Mtk-1 and Mtk-2 could therefore be considered as leads for the development of antiparasitic drugs targeting the clinically important asexual blood stage of P. falciparum.

Antioxidant Effect of Barley Sprout Extract via Enhancement of Nuclear Factor-Erythroid 2 Related Factor 2 Activity and Glutathione Synthesis.

We previously showed that barley sprout extract (BSE) prevents chronic alcohol intake-induced liver injury in mice. BSE notably inhibited glutathione (GSH) depletion and increased inflammatory responses, revealing its mechanism of preventing alcohol-induced liver injury. In the present study we investigated whether the antioxidant effect of BSE involves enhancing nuclear factor-erythroid 2 related factor 2 (Nrf2) activity and GSH synthesis to inhibit alcohol-induced oxidative liver injury. Mice fed alcohol for four weeks exhibited significantly increased oxidative stress, evidenced by increased malondialdehyde (MDA) level and 4-hydroxynonenal (4-HNE) immunostaining in the liver, whereas treatment with BSE (100 mg/kg) prevented these effects. Similarly, exposure to BSE (0.1-1 mg/mL) significantly reduced oxidative cell death induced by t-butyl hydroperoxide (t-BHP, 300 µM) and stabilized the mitochondrial membrane potential (∆ψ). BSE dose-dependently increased the activity of Nrf2, a potential transcriptional regulator of antioxidant genes, in HepG2 cells. Therefore, increased expression of its target genes, heme oxygenase-1 (HO-1), NADPH quinone oxidoreductase 1 (NQO1), and glutamate-cysteine ligase catalytic subunit (GCLC) was observed. Since GCLC is involved in the rate-limiting step of GSH synthesis, BSE increased the GSH level and decreased both cysteine dioxygenase (CDO) expression and taurine level. Because cysteine is a substrate for both taurine and GSH synthesis, a decrease in CDO expression would further contribute to increased cysteine availability for GSH synthesis. In conclusion, BSE protected the liver cells from oxidative stress by activating Nrf2 and increasing GSH synthesis.

[Some insulins to orchestrate growth]. / Des insulines pour orchestrer la croissance.

Body size is an intrinsic property of living organisms that is intimately linked to the developmental program to produce fit individuals with proper proportions. Final size is the result of both genetic determinants and sophisticated mechanisms adapting size to available resources. Even though organs grow according to autonomous programs, some coordination mechanisms ensure that the different body parts adjust their growth with the rest of the body. In Drosophila, Dilp8, a hormone of the Insulin/Relaxin family is a key player in this inter-organs coordination and is required together with its receptor Lgr3 to limit developmental variability. Recently, the transcriptional co-activator Yki (homologue of YAP/TAZ factors in mammals) was shown to regulate dilp8 expression and contribute to the coordination of organ growth in Drosophila.

The selective antifungal activity of Drosophila melanogaster metchnikowin reflects the species-dependent inhibition of succinate-coenzyme Q reductase.

Insect-derived antifungal peptides have a significant economic potential, particularly for the engineering of pathogen-resistant crops. However, the nonspecific antifungal activity of such peptides could result in detrimental effects against beneficial fungi, whose interactions with plants promote growth or increase resistance against biotic and abiotic stress. The antifungal peptide metchnikowin (Mtk) from Drosophila melanogaster acts selectively against pathogenic Ascomycota, including Fusarium graminearum, without affecting Basidiomycota such as the beneficial symbiont Piriformospora indica. Here we investigated the mechanism responsible for the selective antifungal activity of Mtk by using the peptide to probe a yeast two-hybrid library of F. graminearum cDNAs. We found that Mtk specifically targets the iron-sulfur subunit (SdhB) of succinate-coenzyme Q reductase (SQR). A functional assay based on the succinate dehydrogenase (SDH) activity of mitochondrial complex II clearly demonstrated that Mtk inhibited the SDH activity of F. graminearum mitochondrial SQR by up to 52%, but that the equivalent enzyme in P. indica was unaffected. A phylogenetic analysis of the SdhB family revealed a significant divergence between the Ascomycota and Basidiomycota. SQR is one of the key targets of antifungal agents and we therefore propose Mtk as an environmentally sustainable and more selective alternative to chemical fungicides.

Inhibition of HMGB1 protects the retina from ischemia-reperfusion, as well as reduces insulin resistance proteins.

The role of inflammation in diabetic retinal amage is well accepted. While a number of cytokines and inflammatory mediators are responsible for these changes, upstream regulators are less well studied. Additionally, the role for these upstream mediators in retinal health is unclear. In this study, we hypothesized that inhibition of high mobility group box 1 (HMGB1) could restore normal insulin signaling in retinal endothelial cells (REC) grown in high glucose, as well as protect the retina against ischemia/reperfusion (I/R)-induced retinal damage. REC were grown in normal (5mM) or high glucose (25mM) and treated with Box A or glycyrrhizin, two different HMGB1 inhibitors. Western blotting was done for HMGB1, toll-like receptor 4 (TLR4), insulin receptor, insulin receptor substrate-1 (IRS-1), and Akt. ELISA analyses were done for tumor necrosis factor alpha (TNFα) and cleaved caspase 3. In addition, C57/B6 mice were treated with glycyrrhizin, both before and after ocular I/R. Two days following I/R, retinal sections were processed for neuronal changes, while vascular damage was measured at 10 days post-I/R. Results demonstrate that both Box A and glycyrrhizin reduced HMGB1, TLR4, and TNFα levels in REC grown in high glucose. This led to reduced cleavage of caspase 3 and IRS-1Ser307 phosphorylation, and increased insulin receptor and Akt phosphorylation. Glycyrrhizin treatment significantly reduced loss of retinal thickness and degenerate capillary numbers in mice exposed to I/R. Taken together, these results suggest that inhibition of HMGB1 can reduce retinal insulin resistance, as well as protect the retina against I/R-induced damage.

The insect-derived antimicrobial peptide metchnikowin targets Fusarium graminearum ß(1,3)glucanosyltransferase Gel1, which is required for the maintenance of cell wall integrity.

Antimicrobial peptides (AMPs) are essential components of the insect innate immune system. Their diversity provides protection against a broad spectrum of microbes and they have several distinct modes of action. Insect-derived AMPs are currently being developed for both medical and agricultural applications, and their expression in transgenic crops confers resistance against numerous plant pathogens. The antifungal peptide metchnikowin (Mtk), which was originally discovered in the fruit fly Drosophila melanogaster, is of particular interest because it has potent activity against economically important phytopathogenic fungi of the phylum Ascomycota, such as Fusarium graminearum, but it does not harm beneficial fungi such as the mycorrhizal basidiomycete Piriformospora indica. To investigate the specificity of Mtk, we used the peptide to screen a F. graminearum yeast two-hybrid library. This revealed that Mtk interacts with the fungal enzyme ß(1,3)-glucanosyltransferase Gel1 (FgBGT), which is one of the enzymes responsible for fungal cell wall synthesis. The interaction was independently confirmed in a second interaction screen using mammalian cells. FgBGT is required for the viability of filamentous fungi by maintaining cell wall integrity. Our study therefore paves the way for further applications of Mtk in formulation of bio fungicides or as a supplement in food preservation.

Kinesin-1 Expressed in Insect Cells Improves Microtubule in Vitro Gliding Performance, Long-Term Stability and Guiding Efficiency in Nanostructures.

The cytoskeletal motor protein kinesin-1 has been successfully used for many nanotechnological applications. Most commonly, these applications use a gliding assay geometry where substrate-attached motor proteins propel microtubules along the surface. So far, this assay has only been shown to run undisturbed for up to 8 h. Longer run times cause problems like microtubule shrinkage, microtubules getting stuck and slowing down. This is particularly problematic in nanofabricated structures where the total number of microtubules is limited and detachment at the structure walls causes additional microtubule loss. We found that many of the observed problems are caused by the bacterial expression system, which has so far been used for nanotechnological applications of kinesin-1. We strive to enable the use of this motor system for more challenging nanotechnological applications where long-term stability and/or reliable guiding in nanostructures is required. Therefore, we established the expression and purification of kinesin-1 in insect cells which results in improved purity and--more importantly--long-term stability > 24 h and guiding efficiencies of > 90% in lithographically defined nanostructures.

Spindle Assembly and Chromosome Segregation Requires Central Spindle Proteins in Drosophila Oocytes.

Oocytes segregate chromosomes in the absence of centrosomes. In this situation, the chromosomes direct spindle assembly. It is still unclear in this system which factors are required for homologous chromosome bi-orientation and spindle assembly. The Drosophila kinesin-6 protein Subito, although nonessential for mitotic spindle assembly, is required to organize a bipolar meiotic spindle and chromosome bi-orientation in oocytes. Along with the chromosomal passenger complex (CPC), Subito is an important part of the metaphase I central spindle. In this study we have conducted genetic screens to identify genes that interact with subito or the CPC component Incenp. In addition, the meiotic mutant phenotype for some of the genes identified in these screens were characterized. We show, in part through the use of a heat-shock-inducible system, that the Centralspindlin component RacGAP50C and downstream regulators of cytokinesis Rho1, Sticky, and RhoGEF2 are required for homologous chromosome bi-orientation in metaphase I oocytes. This suggests a novel function for proteins normally involved in mitotic cell division in the regulation of microtubule-chromosome interactions. We also show that the kinetochore protein, Polo kinase, is required for maintaining chromosome alignment and spindle organization in metaphase I oocytes. In combination our results support a model where the meiotic central spindle and associated proteins are essential for acentrosomal chromosome segregation.