Gene duplication and the evolution of the higher diptera

Gene duplication is an important source of evolutionary innovation. Using the publicly available genomic information, I studied lineage-specific gene duplications in Drosophila melanogaster (fruit fly), Anopheles gambiae (mosquito), Tribolium castaneum (red flour beetle), and Apis mellifera (honey bee) at three scales: eye-specific genes, developmental genes, and genome-wide. All three studies consistently show that the Drosophila genome contains an exceptionally high number of lineage-specific yet ancient gene duplicates, the majority of which must have originated during the early diversification of the higher Diptera (Brachycera) at least 100 million years ago. Genetic data suggest that gene duplication played an important role in the evolution of visual performance in the fast flying higher Diptera by spatial or intracellular subfunctionalization. Developmental gene duplications, by contrast, in many cases retained overlapping expression patterns and preserved partial to complete redundancy consistent with a role in boosting developmental robustness. Genes involved in metabolic process constantly occupy approximately 50% of all the conserved protein-coding gene families in the insect genomes, both in different species and at various evolutionary time periods, suggesting that the fraction of metabolic genes is maintained over the long term. Further, gene ontology analysis suggests that energy metabolism-related genes are significantly enriched in Brachycera-specific duplicates. My work leads to the conclusion that the early evolution of the higher Diptera was exceptionally impacted by gene duplication. This mutational mechanism apparently fueled the genetic underpinnings of energy metabolism related pathways coinciding with the emergence of the exceptionally fast flight capacities, which characterize most members of the Brachycera clade. I further propose that the retention of duplicated genes spiked during the early diversification of the higher Diptera due to an extended period of effective population size reduction

The Pax gene eyegone facilitates repression of eye development in Tribolium

<p>Abstract</p> <p>Background</p> <p>The <it>Pax </it>transcription factor gene <it>eyegone </it>(<it>eyg</it>) participates in many developmental processes in <it>Drosophila</it>, including the Notch signaling activated postembryonic growth of the eye primordium, global development of the adult head and the development of the antenna. In contrast to other <it>Pax </it>genes, the functional conservation of <it>eyg </it>in species other than <it>Drosophila </it>has not yet been explored.</p> <p>Results</p> <p>We investigated the role of <it>eyg </it>during the postembryonic development of the red flour beetle <it>Tribolium castaneum</it>. Our results indicate conserved roles in antennal but not in eye development. Besides segmentation defects in the antenna, <it>Tribolium eyg </it>knockdown animals were characterized by eye enlargement due to the formation of surplus ommatidia at the central anterior edge of the compound eye. This effect resulted from the failure of the developing gena to locally repress retinal differentiation, which underlies the formation of the characteristic anterior notch in the <it>Tribolium </it>eye. Neither varying the induction time point of <it>eyg </it>knockdown nor knocking down components of the <it>Janus kinase</it>/<it>Signal Transducer and Activators of Transcription </it>signaling pathway in combination with <it>eyg </it>reduced eye size like in <it>Drosophila</it>.</p> <p>Conclusions</p> <p>Taken together, expression and knockdown data suggest that <it>Tribolium eyg </it>serves as a competence factor that facilitates the repression of retinal differentiation in response to an unknown signal produced in the developing gena. At the comparative level, our findings reveal diverged roles of <it>eyg </it>associated with the evolution of different modes of postembryonic head development in endopterygote insects as well as diversified head morphologies in darkling beetles.</p

Genomic and gene regulatory signatures of cryptozoic adaptation: Loss of blue sensitive photoreceptors through expansion of long wavelength-opsin expression in the red flour beetle Tribolium castaneum

Abstract Background Recent genome sequence analysis in the red flour beetle Tribolium castaneum indicated that this highly crepuscular animal encodes only two single opsin paralogs: a UV-opsin and a long wavelength (LW)-opsin; however, these animals do not encode a blue (B)-opsin as most other insects. Here, we studied the spatial regulation of the Tribolium single LW- and UV-opsin gene paralogs in comparison to that of the five opsin paralogs in the retina of Drosophila melanogaster. Results In situ hybridization analysis reveals that the Tribolium retina, in contrast with other insect retinas, constitutes a homogenous field of ommatidia that have seven LW-opsin expressing photoreceptors and one UV-/LW-opsin co-expressing photoreceptor per eye unit. This pattern is consistent with the loss of photoreceptors sensitive to blue wavelengths. It also identifies Tribolium as the first example of a species in insects that co-expresses two different opsins across the entire retina in violation of the widely observed one receptor rule of sensory cells. Conclusion Broader studies of opsin evolution in darkling beetles and other coleopteran groups have the potential to pinpoint the permissive and adaptive forces that played a role in the evolution of vision in Tribolium castaneum

Genome sequencing and transcriptome analyses of the Siberian hamster hypothalamus identify mechanisms for seasonal energy balance

We thank the manuscript reviewers for constructive feedback; David G. Hazlerigg, Cristina Saenz de Miera, and Valerie Simonneaux for genome sequence contributions; Nicolas Scrutton and Lindsey Duguid for expert technical assistance; and Michael Jarsulic for technical assistance on the high-performance computing clusters. This project was supported by a project research grant from The British Society for Neuroendocrinology (to T.J.S.); Grants BB/M021629/1 and BB/M001555/1 (to F.J.P.E.) from the Biotechnology and Biological Sciences Research Council, and Grants UL1-TR000430 (to T.J.S. and B.J.P.) and R01-AI067406 (to B.J.P.) from the National Institutes of Health. T.J.S. is funded by The Leverhulme Trust. The Center for Research Informatics was supported by the Biological Sciences Division at the University of Chicago with additional support provided by the Institute for Translational Medicine/Clinical and Translational award (NIH 5UL1TR002389-02) and the University of Chicago Comprehensive Cancer Center Support Grant (NIH Grant P30CA014599). The bioinformatics analysis was performed on high-performance computing clusters at the Center for Research Informatics, Biological Sciences Division. P.B. was funded by the Scottish Government Rural and Environment Science and Analytical Services Division grant to the Rowett Institute.Peer reviewedPublisher PD

Genome sequencing and transcriptome analyses of the Siberian hamster hypothalamus identify mechanisms for seasonal energy balance

Synthesis of triiodothyronine (T3) in the hypothalamus induces marked seasonal neuromorphology changes across taxa. How species-specific responses to T3 signaling in the CNS drive annual changes in body weight and energy balance remains uncharacterized. These experiments sequenced and annotated the Siberian hamster (Phodopus sungorus) genome, a model organism for seasonal physiology research, to facilitate the dissection of T3-dependent molecular mechanisms that govern predictable, robust, and long-term changes in body weight. Examination of the Phodopus genome, in combination with transcriptome sequencing of the hamster diencephalon under winter and summer conditions, and in vivo-targeted expression analyses confirmed that proopiomelanocortin (pomc) is a primary genomic target for the long-term T3-dependent regulation of body weight. Further in silico analyses of pomc promoter sequences revealed that thyroid hormone receptor 1β-binding motif insertions have evolved in several genera of the Cricetidae family of rodents. Finally, experimental manipulation of food availability confirmed that hypothalamic pomc mRNA expression is dependent on longer-term photoperiod cues and is unresponsive to acute, short-term food availability. These observations suggest that species-specific responses to hypothalamic T3, driven in part by the receptor-binding motif insertions in some cricetid genomes, contribute critically to the long-term regulation of energy balance and the underlying physiological and behavioral adaptations associated with the seasonal organization of behavior. © 2019 National Academy of Sciences. All rights reserved

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Genomic signatures of globally enhanced gene duplicate accumulation in the megadiverse higher Diptera fueling intralocus sexual conflict resolution

Gene duplication is an important source of evolutionary innovation. To explore the relative impact of gene duplication during the diversification of major insect model system lineages, we performed a comparative analysis of lineage-specific gene duplications in the fruit fly Drosophila melanogaster (Diptera: Brachycera), the mosquito Anopheles gambiae (Diptera: Culicomorpha), the red flour beetle Tribolium castaneum (Coleoptera), and the honeybee Apis mellifera (Hymenoptera). Focusing on close to 6,000 insect core gene families containing maximally six paralogs, we detected a conspicuously higher number of lineage-specific duplications in Drosophila (689) compared to Anopheles (315), Tribolium (386), and Apis (223). Based on analyses of sequence divergence, phylogenetic distribution, and gene ontology information, we present evidence that an increased background rate of gene duplicate accumulation played an exceptional role during the diversification of the higher Diptera (Brachycera), in part by providing enriched opportunities for intralocus sexual conflict resolution, which may have boosted speciation rates during the early radiation of the megadiverse brachyceran subclade Schizophora