Pervasive Behavioral Effects of MicroRNA Regulation in Drosophila

On growth and form of animal behavior

In this study we propose an architecture (bauplan) for the growth and form of behavior in vertebrates and arthropods. We show in what sense behavior is an extension of anatomy. Then we show that movement-based behavior shares linearity and modularity with the skeletal body plan, and with the Hox genes; that it mirrors the geometry of the physical environment; and that it reveals the animal's understanding of the animate and physical situation, with implications for perception, attention, emotion, and primordial cognition. First we define the primitives of movement in relational terms, as in comparative anatomy, yielding homological primitives. Then we define modules, generative rules and the architectural plan of behavior in terms of these primitives. In this way we expose the homology of behaviors, and establish a rigorous trans-phyletic comparative discipline of the morphogenesis of movement-based behavior. In morphogenesis, behavior builds up and narrows incessantly according to strict geometric rules. The same rules apply in moment-to-moment behavior, in ontogenesis, and partly also in phylogenesis. We demonstrate these rules in development, in neurological recovery, with drugs (dopamine-stimulated striatal modulation), in stressful situations, in locomotor behavior, and partly also in human pathology. The buildup of movement culminates in free, undistracted, exuberant behavior. It is observed in play, in superior animals during agonistic interactions, and in humans in higher states of functioning. Geometrization promotes the study of genetics, anatomy, and behavior within one and the same discipline. The geometrical bauplan portrays both already evolved dimensions, and prospective dimensional constraints on evolutionary behavioral innovations.

Identification of miRNAs Involved in Olfactory Regulation in Antennae of Beet Webworm, Loxostege sticticalis (Lepidoptera: Pyralidae)

The beet webworm, Loxostege sticticalis, is a typical migratory pest. Although miRNAs participate in many physiological functions, little is known about the functions of miRNAs in olfactory regulation. In this study, 1120 (869 known and 251 novel) miRNAs were identified in the antennae of L. sticticalis by using high-throughput sequencing technology. Among the known miRNAs, 189 from 49 families were insect-specific, indicating that these miRNAs might play unique roles in insects. Furthermore, based on the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, we found that 3647 and 1393 miRNAs were associated with localization and the regulation of localization, respectively, and 80 miRNAs were enriched in the neuroactive ligand-receptor interaction pathway. These miRNAs might be involved in the olfactory system of L. sticticalis. Notably, qRT-PCR showed that most of the tested miRNAs presented similar expression patterns compared with the RNA-seq data and that miR-87-3, novel-miR-78, and novel-miR-142 were significantly differentially expressed in the antennae of males and females. In addition, 21 miRNAs were predicted to target 23 olfactory genes, including 10 odorant-binding proteins (OBPs), 3 chemosensory proteins (CSPs), 4 odorant receptors (ORs), 1 ionotropic receptor (IR), and 5 gustatory receptors (GRs). The olfactory-related miRNAs exhibited low-abundance transcripts, except undef-miR-55 and undef-miR-523, and gender-biased expression was not observed for olfactory-related miRNAs. Our findings provide an overview of the potential miRNAs involved in olfactory regulation, which may provide important information on the function of miRNAs in the insect olfactory system.

A microRNA that controls the emergence of embryonic movement

Movement is a key feature of animal systems, yet its embryonic origins are not fully understood. Here, we investigate the genetic basis underlying the embryonic onset of movement in Drosophila focusing on the role played by small non-coding RNAs (microRNAs, miRNAs). To this end, we first develop a quantitative behavioural pipeline capable of tracking embryonic movement in large populations of fly embryos, and using this system, discover that the Drosophila miRNA miR-2b-1 plays a role in the emergence of movement. Through the combination of spectral analysis of embryonic motor patterns, cell sorting and RNA in situs, genetic reconstitution tests, and neural optical imaging we define that miR-2b-1 influences the emergence of embryonic movement by exerting actions in the developing nervous system. Furthermore, through the combination of bioinformatics coupled to genetic manipulation of miRNA expression and phenocopy tests we identify a previously uncharacterised (but evolutionarily conserved) chloride channel encoding gene - which we term Movement Modulator (Motor) - as a genetic target that mechanistically links miR-2b-1 to the onset of movement. Cell-specific genetic reconstitution of miR-2b-1 expression in a null miRNA mutant background, followed by behavioural assays and target gene analyses, suggest that miR-2b-1 affects the emergence of movement through effects in sensory elements of the embryonic circuitry, rather than in the motor domain. Our work thus reports the first miRNA system capable of regulating embryonic movement, suggesting that other miRNAs are likely to play a role in this key developmental process in Drosophila as well as in other species.

Glutamate-GABA imbalance mediated by miR-8-5p and its STTM regulates phase-related behavior of locusts

The aggregation of locusts from solitary to gregarious phases is crucial for the formation of devastating locust plagues. Locust management requires research on the prevention of aggregation or alternative and greener solutions to replace insecticide use, and insect-derived microRNAs (miRNAs) show the potential for application in pest control. Here, we performed a genome-wide screen of the differential expression of miRNAs between solitary and gregarious locusts and showed that miR-8-5p controls the γ-aminobutyric acid (GABA)/glutamate functional balance by directly targeting glutamate decarboxylase (Gad). Blocking glutamate-GABA neurotransmission by miR-8-5p overexpression or Gad RNAi in solitary locusts decreased GABA production, resulting in locust aggregation behavior. Conversely, activating this pathway by miR-8-5p knockdown in gregarious locusts induced GABA production to eliminate aggregation behavior. Further results demonstrated that ionotropic glutamate/GABA receptors tuned glutamate/GABA to trigger/hamper the aggregation behavior of locusts. Finally, we successfully established a transgenic rice line expressing the miR-8-5p inhibitor by short tandem target mimic (STTM). When locusts fed on transgenic rice plants, Gad transcript levels in the brain increased greatly, and aggregation behavior was lost. This study provided insights into different regulatory pathways in the phase change of locusts and a potential control approach through behavioral regulation in insect pests.

A novel post-developmental role of the Hox genes underlies normal adult behavior

The molecular mechanisms underlying the stability of mature neurons and neural circuits are poorly understood. Here we explore this problem and discover that the Hox genes are a component of the genetic program that maintains normal neural function in adult Drosophila. We show that post-developmental downregulation of the Hox gene Ultrabithorax (Ubx) in adult neurons leads to substantial anomalies in flight. Mapping the cellular basis of these effects reveals that Ubx is required within a subset of dopaminergic neurons, and cell circuitry analyses in combination with optogenetics allow us to link these dopaminergic neurons to flight control. Functional imaging experiments show that Ubx is necessary for normal dopaminergic activity, and neuron-specific RNA-sequencing defines two previously uncharacterized ion channel-encoding genes as potential mediators of Ubx behavioral roles. Our study thus reveals a novel role of the Hox system in controlling adult behavior and neural function. Based on the broad evolutionary conservation of the Hox system across distantly related animal phyla, we predict that the Hox genes might play neurophysiological roles in adult forms of other species, including humans.

The Reversible Carnitine Palmitoyltransferase 1 Inhibitor (Teglicar) Ameliorates the Neurodegenerative Phenotype in a Drosophila Huntington’s Disease Model by Acting on the Expression of Carnitine-Related Genes

Huntington’s disease (HD) is a dramatic neurodegenerative disorder caused by the abnormal expansion of a CAG triplet in the huntingtin gene, producing an abnormal protein. As it leads to the death of neurons in the cerebral cortex, the patients primarily present with neurological symptoms, but recently metabolic changes resulting from mitochondrial dysfunction have been identified as novel pathological features. The carnitine shuttle is a complex consisting of three enzymes whose function is to transport the long-chain fatty acids into the mitochondria. Here, its pharmacological modification was used to test the hypothesis that shifting metabolism to lipid oxidation exacerbates the HD symptoms. Behavioural and transcriptional analyses were carried out on HD Drosophila model, to evaluate the involvement of the carnitine cycle in this pathogenesis. Pharmacological inhibition of CPT1, the rate-limiting enzyme of the carnitine cycle, ameliorates the HD symptoms in Drosophila, likely acting on the expression of carnitine-related genes.

Roles of Drosophila Hox Genes in the Assembly of Neuromuscular Networks and Behavior

Hox genes have been known for specifying the anterior-posterior axis (AP) in bilaterian body plans. Studies in vertebrates have shown their importance in developing region-specific neural circuitry and diversifying motor neuron pools. In Drosophila, they are instrumental for segment-specific neurogenesis and myogenesis early in development. Their robust expression in differentiated neurons implied their role in assembling region-specific neuromuscular networks. In the last decade, studies in Drosophila have unequivocally established that Hox genes go beyond their conventional functions of generating cellular diversity along the AP axis of the developing central nervous system. These roles range from establishing and maintaining the neuromuscular networks to controlling their function by regulating the motor neuron morphology and neurophysiology, thereby directly impacting the behavior. Here we summarize the limited knowledge on the role of Drosophila Hox genes in the assembly of region-specific neuromuscular networks and their effect on associated behavior.

Resources and Methods for the Analysis of MicroRNA Function in Drosophila

Since the widespread discovery of microRNAs (miRNAs) 20 years ago, the Drosophila melanogaster model system has made important contributions to understanding the biology of this class of noncoding RNAs. These contributions are based on the amenability of this model system not only for biochemical analysis but molecular, genetic, and cell biological analyses as well. Nevertheless, while the Drosophila genome is now known to encode 258 miRNA precursors, the function of only a small minority of these have been well characterized. In this review, we summarize the current resources and methods that are available to study miRNA function in Drosophila with a particular focus on the large-scale resources that enable systematic analysis. Application of these methods will accelerate the discovery of ways that miRNAs are embedded into genetic networks that control basic features of metazoan cells.

MicroRNA-Dependent Control of Sensory Neuron Function Regulates Posture Behavior in Drosophila

All what we see, touch, hear, taste, or smell must first be detected by the sensory elements of our nervous system. Sensory neurons, therefore, represent a critical component in all neural circuits and their correct function is essential for the generation of behavior and adaptation to the environment. Here, we report that the evolutionarily-conserved microRNA (miRNA) miR-263b plays a key behavioral role in Drosophila melanogaster through effects on the function of larval sensory neurons. Several independent experiments (in 50:50 male:female populations) support this finding: first, miRNA expression analysis, via reporter expression and fluorescent-activated cell sorting (FACS)-quantitative PCR (qPCR) analysis, demonstrate miR-263b expression in larval sensory neurons. Second, behavioral tests in miR-263b null mutants show defects in self-righting, an innate and evolutionarily conserved posture-control behavior that allows larvae to rectify their position if turned upside-down. Third, competitive inhibition of miR-263b in sensory neurons using a miR-263b "sponge" leads to self-righting defects. Fourth, systematic analysis of sensory neurons in miR-263b mutants shows no detectable morphologic defects in their stereotypic pattern, while genetically-encoded calcium sensors expressed in the sensory domain reveal a reduction in neural activity in miR-263b mutants. Fifth, miR-263b null mutants show reduced "touch-response" behavior and a compromised response to sound, both characteristic of larval sensory deficits. Furthermore, bioinformatic miRNA target analysis, gene expression assays, and behavioral phenocopy experiments suggest that miR-263b might exert its effects, at least in part, through repression of the basic helix-loop-helix (bHLH) transcription factor Atonal Altogether, our study suggests a model in which miRNA-dependent control of transcription factor expression affects sensory function and behavior.SIGNIFICANCE STATEMENT Sensory neurons are key to neural circuit function, but how these neurons acquire their specific properties is not well understood. Here, we examine this problem, focusing on the roles played by microRNAs (miRNAs). Using Drosophila, we demonstrate that the evolutionarily-conserved miRNA miR-263b controls sensory neuron function allowing the animal to perform an adaptive, elaborate three-dimensional movement. Our work thus shows that microRNAs can control complex motor behaviors by modulating sensory neuron physiology, and suggests that similar miRNA-dependent mechanisms may operate in other species. The work contributes to advance the understanding of the molecular basis of behavior and the biological roles of microRNAs within the nervous system.

Dynamic neurotransmitter specific transcription factor expression profiles during Drosophila development

The remarkable diversity of neurons in the nervous system is generated during development, when properties such as cell morphology, receptor profiles and neurotransmitter identities are specified. In order to gain a greater understanding of neurotransmitter specification we profiled the transcription state of cholinergic, GABAergic and glutamatergic neurons in vivo at three developmental time points. We identified 86 differentially expressed transcription factors that are uniquely enriched, or uniquely depleted, in a specific neurotransmitter type. Some transcription factors show a similar profile across development, others only show enrichment or depletion at specific developmental stages. Profiling of Acj6 (cholinergic enriched) and Ets65A (cholinergic depleted) binding sites in vivo reveals that they both directly bind the ChAT locus, in addition to a wide spectrum of other key neuronal differentiation genes. We also show that cholinergic enriched transcription factors are expressed in mostly non-overlapping populations in the adult brain, implying the absence of combinatorial regulation of neurotransmitter fate in this context. Furthermore, our data underlines that, similar to Caenorhabditis elegans, there are no simple transcription factor codes for neurotransmitter type specification.

This article has an associated First Person interview with the first author of the paper.

Summary: Transcriptome profiling of cholinergic, GABAergic and glutamatergic neurons in Drosophila identified multiple transcription factors as potential regulators of neurotransmitter fate.

MicroRNAs Regulate Multiple Aspects of Locomotor Behavior in Drosophila

Locomotion is an ancient and fundamental output of the nervous system required for animals to perform many other complex behaviors. Although the formation of motor circuits is known to be under developmental control of transcriptional mechanisms that define the fates and connectivity of the many neurons, glia and muscle constituents of these circuits, relatively little is known about the role of post-transcriptional regulation of locomotor behavior. MicroRNAs have emerged as a potentially rich source of modulators for neural development and function. In order to define the microRNAs required for normal locomotion in Drosophila melanogaster, we utilized a set of transgenic Gal4-dependent competitive inhibitors (microRNA sponges, or miR-SPs) to functionally assess ca. 140 high-confidence Drosophila microRNAs using automated quantitative movement tracking systems followed by multiparametric analysis. Using ubiquitous expression of miR-SP constructs, we identified a large number of microRNAs that modulate aspects of normal baseline adult locomotion. Addition of temperature-dependent Gal80 to identify microRNAs that act during adulthood revealed that the majority of these microRNAs play developmental roles. Comparison of ubiquitous and neural-specific miR-SP expression suggests that most of these microRNAs function within the nervous system. Parallel analyses of spontaneous locomotion in adults and in larvae also reveal that very few of the microRNAs required in the adult overlap with those that control the behavior of larval motor circuits. These screens suggest that a rich regulatory landscape underlies the formation and function of motor circuits and that many of these mechanisms are stage and/or parameter-specific.

Emergence of consistent intra-individual locomotor patterns during zebrafish development

The analysis of larval zebrafish locomotor behavior has emerged as a powerful indicator of perturbations in the nervous system and is used in many fields of research, including neuroscience, toxicology and drug discovery. The behavior of larval zebrafish however, is highly variable, resulting in the use of large numbers of animals and the inability to detect small effects. In this study, we analyzed whether individual locomotor behavior is stable over development and whether behavioral parameters correlate with physiological and morphological features, with the aim of better understanding the variability and predictability of larval locomotor behavior. Our results reveal that locomotor activity of an individual larva remains consistent throughout a given day and is predictable throughout larval development, especially during dark phases, under which larvae demonstrate light-searching behaviors and increased activity. The larvae’s response to startle-stimuli was found to be unpredictable, with no correlation found between response strength and locomotor activity. Furthermore, locomotor activity was not associated with physiological or morphological features of a larva (resting heart rate, body length, size of the swim bladder). Overall, our findings highlight the areas of intra-individual consistency, which could be used to improve the sensitivity of assays using zebrafish locomotor activity as an endpoint.

A Single MicroRNA-Hox Gene Module Controls Equivalent Movements in Biomechanically Distinct Forms of Drosophila

Movement is the main output of the nervous system. It emerges during development to become a highly coordinated physiological process essential to survival and adaptation of the organism to the environment. Similar movements can be observed in morphologically distinct developmental stages of an organism, but it is currently unclear whether or not these movements have a common molecular cellular basis. Here we explore this problem in Drosophila, focusing on the roles played by the microRNA (miRNA) locus miR-iab4/8, which we previously showed to be essential for the normal corrective response displayed by the fruit fly larva when turned upside down (self-righting). Our study shows that miR-iab4 is required for normal self-righting across all three Drosophila larval stages. Unexpectedly, we also discover that this miRNA is essential for normal self-righting behavior in the adult fly, an organism with different morphology, neural constitution, and biomechanics. Through the combination of gene expression, optical imaging, and quantitative behavioral approaches, we provide evidence that miR-iab4 exerts its effects on adult self-righting behavior in part through repression of the Hox gene Ultrabithorax (Ubx) in a specific set of adult motor neurons, the NB2-3/lin15 neurons. Our results show that miRNA controls the function, rather than the morphology, of these neurons and demonstrate that post-developmental changes in Hox gene expression can modulate behavior in the adult. Our work reveals that a common miRNA-Hox genetic module can be re-deployed in different neurons to control functionally equivalent movements in biomechanically distinct organisms and describes a novel post-developmental role of the Hox genes in adult neural function.

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The fruit fly miRNA gene miR-iab4 controls the same behavior in the larva and adult

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miR-iab4 exerts its behavioral roles via repression of the Hox gene Ultrabithorax

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miRNA/Hox inputs affect the physiology and not the anatomy of specific motor neurons

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Conditional expression shows a novel role of the Hox genes in adult neural function

Global identification of functional microRNA-mRNA interactions in Drosophila

MicroRNAs (miRNAs) are key mediators of post-transcriptional gene expression silencing. So far, no comprehensive experimental annotation of functional miRNA target sites exists in Drosophila. Here, we generated a transcriptome-wide in vivo map of miRNA-mRNA interactions in Drosophila melanogaster, making use of single nucleotide resolution in Argonaute1 (AGO1) crosslinking and immunoprecipitation (CLIP) data. Absolute quantification of cellular miRNA levels presents the miRNA pool in Drosophila cell lines to be more diverse than previously reported. Benchmarking two CLIP approaches, we identify a similar predictive potential to unambiguously assign thousands of miRNA-mRNA pairs from AGO1 interaction data at unprecedented depth, achieving higher signal-to-noise ratios than with computational methods alone. Quantitative RNA-seq and sub-codon resolution ribosomal footprinting data upon AGO1 depletion enabled the determination of miRNA-mediated effects on target expression and translation. We thus provide the first comprehensive resource of miRNA target sites and their quantitative functional impact in Drosophila.

A gene expression atlas of embryonic neurogenesis in Drosophila reveals complex spatiotemporal regulation of lncRNAs

Cell type specification during early nervous system development in Drosophila melanogaster requires precise regulation of gene expression in time and space. Resolving the programs driving neurogenesis has been a major challenge owing to the complexity and rapidity with which distinct cell populations arise. To resolve the cell type-specific gene expression dynamics in early nervous system development, we have sequenced the transcriptomes of purified neurogenic cell types across consecutive time points covering crucial events in neurogenesis. The resulting gene expression atlas comprises a detailed resource of global transcriptome dynamics that permits systematic analysis of how cells in the nervous system acquire distinct fates. We resolve known gene expression dynamics and uncover novel expression signatures for hundreds of genes among diverse neurogenic cell types, most of which remain unstudied. We also identified a set of conserved long noncoding RNAs (lncRNAs) that are regulated in a tissue-specific manner and exhibit spatiotemporal expression during neurogenesis with exquisite specificity. lncRNA expression is highly dynamic and demarcates specific subpopulations within neurogenic cell types. Our spatiotemporal transcriptome atlas provides a comprehensive resource for investigating the function of coding genes and noncoding RNAs during crucial stages of early neurogenesis.

Summary: DIV-MARIS, an adapted technique for examining stage- and cell type-specific gene expression, reveals a complex network of mRNAs and lncRNAs expressed in specific cell types during early Drosophila embryonic nervous system development.

The Role of miRNAs in Drosophila melanogaster Male Courtship Behavior

Drosophila melanogaster courtship, although stereotypical, continually changes based on cues received from the courtship subject. Such adaptive responses are mediated via rapid and widespread transcriptomic reprogramming, a characteristic now widely attributed to microRNAs (miRNAs), along with other players. Here, we conducted a large-scale miRNA knockout screen to identify miRNAs that affect various parameters of male courtship behavior. Apart from identifying miRNAs that impact male-female courtship, we observed that miR-957 mutants performed significantly increased male-male courtship and "chaining" behavior, whereby groups of males court one another. We tested the effect of miR-957 reduction in specific neuronal cell clusters, identifying miR-957 activity in Doublesex (DSX)-expressing and mushroom body clusters as an important regulator of male-male courtship interactions. We further characterized the behavior of miR-957 mutants and found that these males court male subjects vigorously, but do not elicit courtship. Moreover, they fail to lower courtship efforts toward females with higher levels of antiaphrodisiac pheromones. At the level of individual pheromones, miR-957 males show a reduced inhibitory response to both 7-Tricosene (7-T) and cis-vaccenyl acetate, with the effect being more pronounced in the case of 7-T. Overall, our results indicate that a single miRNA can contribute to the regulation of complex behaviors, including detection or processing of chemicals that control important survival strategies such as chemical mate-guarding, and the maintenance of sex- and species-specific courtship barriers.

Epigenetics in Insects: Genome Regulation and the Generation of Phenotypic Diversity

Epigenetic inheritance is fundamentally important to cellular differentiation and developmental plasticity. In this review, we provide an introduction to the field of molecular epigenetics in insects. Epigenetic information is passed across cell divisions through the methylation of DNA, the modification of histone proteins, and the activity of noncoding RNAs. Much of our knowledge of insect epigenetics has been gleaned from a few model species. However, more studies of epigenetic information in traditionally nonmodel taxa will help advance our understanding of the developmental and evolutionary significance of epigenetic inheritance in insects. To this end, we also provide a brief overview of techniques for profiling and perturbing individual facets of the epigenome. Doing so in diverse cellular, developmental, and taxonomic contexts will collectively help shed new light on how genome regulation results in the generation of diversity in insect form and function.

Regulation of Circadian Behavior by Astroglial MicroRNAs in Drosophila

We describe a genome-wide microRNA (miRNA)-based screen to identify brain glial cell functions required for circadian behavior. To identify glial miRNAs that regulate circadian rhythmicity, we employed a collection of "miR-sponges" to inhibit miRNA function in a glia-specific manner. Our initial screen identified 20 glial miRNAs that regulate circadian behavior. We studied two miRNAs, miR-263b and miR-274, in detail and found that both function in adult astrocytes to regulate behavior. Astrocyte-specific inhibition of miR-263b or miR-274 in adults acutely impairs circadian locomotor activity rhythms with no effect on glial or clock neuronal cell viability. To identify potential RNA targets of miR-263b and miR-274, we screened 35 predicted miRNA targets, employing RNA interference-based approaches. Glial knockdown of two putative miR-274 targets, CG4328 and MESK2, resulted in significantly decreased rhythmicity. Homology of the miR-274 targets to mammalian counterparts suggests mechanisms that might be relevant for the glial regulation of rhythmicity.

The lncRNA male-specific abdominal plays a critical role in Drosophila accessory gland development and male fertility

Although thousands of long non-coding RNAs (lncRNA) have been identified in the genomes of higher eukaryotes, the precise function of most of them is still unclear. Here, we show that a >65 kb, male-specific, lncRNA, called male-specific abdominal (msa) is required for the development of the secondary cells of the Drosophila male accessory gland (AG). msa is transcribed from within the Drosophila bithorax complex and shares much of its sequence with another lncRNA, the iab-8 lncRNA, which is involved in the development of the central nervous system (CNS). Both lncRNAs perform much of their functions via a shared miRNA embedded within their sequences. Loss of msa, or of the miRNA it contains, causes defects in secondary cell morphology and reduces male fertility. Although both lncRNAs express the same miRNA, the phenotype in the secondary cells and the CNS seem to reflect misregulation of different targets in the two tissues.

In many animals, the male seminal fluid induces physiology changes in the mated female that increase a male’s reproductive success. These changes are often referred to as the post-mating response (PMR). In Drosophila, the seminal fluid proteins responsible for generating the PMR are made in a specialized gland, analogous to the mammalian seminal vesicle and prostate, called the accessory gland (AG). In this work, we show that a male-specific, long, non-coding RNA (lncRNA), called msa, plays a critical role in the development and function of this gland, primarily through a microRNA (miRNA) encoded within its sequence. This same miRNA had previously been shown to be expressed in the central nervous system (CNS) via an alternative promoter, where its ability to repress homeotic genes is required for both male and female fertility. Here, we present evidence that the targets of this miRNA in the AG are likely different from those found in the CNS. Thus, the same miRNA seems to have been selected to affect Drosophila fertility through two different mechanisms. Although many non-coding RNAs have now been identified, very few can be shown to have function. Our work highlights a lncRNA that has multiple biological functions, affecting cellular morphology and fertility.

Epigenetics in teleost fish: From molecular mechanisms to physiological phenotypes

While the field of epigenetics is increasingly recognized to contribute to the emergence of phenotypes in mammalian research models across different developmental and generational timescales, the comparative biology of epigenetics in the large and physiologically diverse vertebrate infraclass of teleost fish remains comparatively understudied. The cypriniform zebrafish and the salmoniform rainbow trout and Atlantic salmon represent two especially important teleost orders, because they offer the unique possibility to comparatively investigate the role of epigenetic regulation in 3R and 4R duplicated genomes. In addition to their sequenced genomes, these teleost species are well-characterized model species for development and physiology, and therefore allow for an investigation of the role of epigenetic modifications in the emergence of physiological phenotypes during an organism's lifespan and in subsequent generations. This review aims firstly to describe the evolution of the repertoire of genes involved in key molecular epigenetic pathways including histone modifications, DNA methylation and microRNAs in zebrafish, rainbow trout, and Atlantic salmon, and secondly, to discuss recent advances in research highlighting a role for molecular epigenetics in shaping physiological phenotypes in these and other teleost models. Finally, by discussing themes and current limitations of the emerging field of teleost epigenetics from both theoretical and technical points of view, we will highlight future research needs and discuss how epigenetics will not only help address basic research questions in comparative teleost physiology, but also inform translational research including aquaculture, aquatic toxicology, and human disease.