Multicellular organisms generate tissues of diverse shapes and functions from cells and extracellular matrices. Their adhesion molecules mediate cell-cell and cell-matrix interactions, which not only play crucial roles in maintaining tissue integrity but also serve as key regulators of tissue morphogenesis. Cells constantly probe their environment to make decisions: They integrate chemical and mechanical information from the environment via diffusible ligand- or adhesion-based signaling to decide whether to release specific signaling molecules or enzymes, to divide or differentiate, to move away or stay, or even whether to live or die. These decisions in turn modify their environment, including the chemical nature and mechanical properties of the extracellular matrix. Tissue morphology is the physical manifestation of the remodeling of cells and matrices by their historical biochemical and biophysical landscapes. We review our understanding of matrix and adhesion molecules in tissue morphogenesis, with an emphasis on key physical interactions that drive morphogenesis. Expected final online publication date for the , Volume 39 is October 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

We show that the germline specificity of P element transposition is controlled at the level of mRNA splicing and not at the level of transcription. In the major P element RNA transcript, isolated from somatic cells, the first three open reading frames are joined by the removal of two introns. Using in vitro mutagenesis and genetic analysis we demonstrate the existence of a third intron whose removal is required for transposase production. We propose that this intron is only removed in the germline and that its removal is the sole basis for the germline restriction of P element transposition.

Understanding sensory systems that perceive environmental inputs and neural circuits that select appropriate motor outputs is essential for studying how organisms modulate behavior and make decisions necessary for survival. Drosophila melanogaster oviposition is one such important behavior, in which females evaluate their environment and choose to lay eggs on substrates they may find aversive in other contexts. We employed neurogenetic techniques to characterize neurons that influence the choice between repulsive positional and attractive egg-laying responses toward the bitter-tasting compound lobeline. Surprisingly, we found that neurons expressing Gr66a, a gustatory receptor normally involved in avoidance behaviors, receive input for both attractive and aversive preferences. We hypothesized that these opposing responses may result from activation of distinct Gr66a-expressing neurons. Using tissue-specific rescue experiments, we found that Gr66a-expressing neurons on the legs mediate positional aversion. In contrast, pharyngeal taste cells mediate the egg-laying attraction to lobeline, as determined by analysis of mosaic flies in which subsets of Gr66a neurons were silenced. Finally, inactivating mushroom body neurons disrupted both aversive and attractive responses, suggesting that this brain structure is a candidate integration center for decision-making during Drosophila oviposition. We thus define sensory and central neurons critical to the process by which flies decide where to lay an egg. Furthermore, our findings provide insights into the complex nature of gustatory perception in Drosophila. We show that tissue-specific activation of bitter-sensing Gr66a neurons provides one mechanism by which the gustatory system differentially encodes aversive and attractive responses, allowing the female fly to modulate her behavior in a context-dependent manner.

BACKGROUND: The insecticides spinosad and imidacloprid are neurotoxins with distinct modes of action. Both target nicotinic acetylcholine receptors (nAChRs), albeit different subunits. Spinosad is an allosteric modulator, that upon binding initiates endocytosis of its target, nAChRα6. Imidacloprid binding triggers excessive neuronal ion influx. Despite these differences, low-dose effects converge downstream in the precipitation of oxidative stress and neurodegeneration.

RESULTS: Using RNA-Seq, we compared the transcriptional signatures of spinosad and imidacloprid, at low-dose exposures. Both insecticides cause upregulation of Glutathione S-transferase and Cytochrome P450 genes in the brain and downregulation in the fat body, whereas reduced expression of immune-related genes is observed in both tissues. Spinosad shows unique impacts on genes involved in lysosomal function, protein folding, and reproduction. Co-expression analyses revealed little to no correlation between genes affected by spinosad and nAChRα6 expressing neurons, but a positive correlation with glial cell markers. We also detected and experimentally confirmed nAChRα6 expression in fat body cells and male germline cells. This led us to uncover lysosomal dysfunction in the fat body following spinosad exposure, and a fitness cost in spinosad-resistant (nAChRα6 null) males - oxidative stress in testes, and reduced fertility.

CONCLUSION: Spinosad and imidacloprid share transcriptional perturbations in immunity-, energy homeostasis-, and oxidative stress-related genes. Low doses of other neurotoxic insecticides should be investigated for similar impacts. While target-site spinosad resistance mutation has evolved in the field, this may have a fitness cost. Our findings demonstrate the power of tissue-specific transcriptomics approach and the use of single-cell transcriptome data. This article is protected by copyright. All rights reserved.

The revolution in neuroscientific data acquisition is creating an analysis challenge. We propose leveraging cloud-computing technologies to enable large-scale neurodata storing, exploring, analyzing, and modeling. This utility will empower scientists globally to generate and test theories of brain function and dysfunction.

Starvation induces a protective process of self-cannibalization called autophagy that is thought to mediate nonselective degradation of cytoplasmic material. We recently reported that mitochondria escape autophagosomal degradation through extensive fusion into mitochondrial networks upon certain starvation conditions. The extent of mitochondrial elongation is dependent on the type of nutrient deprivation, with amino acid depletion having a particularly strong effect. Downregulation of the mitochondrial fission protein Drp1 was determined to be important in bringing about starvation-induced mitochondrial fusion. The formation of mitochondrial networks during nutrient depletion selectively blocked their autophagic degradation, presumably allowing cells to sustain efficient ATP production and thereby survive starvation.

One of the key morphogenetic processes used during development is the controlled intercalation of cells between their neighbors. This process has been co-opted into a range of developmental events, and it also underlies an event that occurs in each major group of bilaterians: elongation of the embryo along the anterior-posterior axis [1]. In Drosophila, a novel component of this process was recently discovered by Paré et al., who showed that three Toll genes function together to drive cell intercalation during germband extension [2]. This finding raises the question of whether this role of Toll genes is an evolutionary novelty of flies or a general mechanism of embryonic morphogenesis. Here we show that the Toll gene function in axis elongation is, in fact, widely conserved among arthropods. First, we functionally demonstrate that two Toll genes are required for cell intercalation in the beetle Tribolium castaneum. We then show that these genes belong to a previously undescribed Toll subfamily and that members of this subfamily exhibit striped expression (as seen in Tribolium and previously reported in Drosophila [3-5]) in embryos of six other arthropod species spanning the entire phylum. Last, we show that two of these Toll genes are required for normal morphogenesis during anterior-posterior embryo elongation in the spider Parasteatoda tepidariorum, a member of the most basally branching arthropod lineage. From our findings, we hypothesize that Toll genes had a morphogenetic function in embryo elongation in the last common ancestor of all arthropods, which existed over 550 million years ago.

In mammals, fat store levels are regulated by brain centers that control food intake and metabolism. A new study by Al-Anzi and colleagues in this issue of Neuron identifies neurons with similar functions in Drosophila, further establishing the fly as a legitimate model to study obesity.

We demonstrate the feasibility of generating thousands of transgenic Drosophila melanogaster lines in which the expression of an exogenous gene is reproducibly directed to distinct small subsets of cells in the adult brain. We expect the expression patterns produced by the collection of 5,000 lines that we are currently generating to encompass all neurons in the brain in a variety of intersecting patterns. Overlapping 3-kb DNA fragments from the flanking noncoding and intronic regions of genes thought to have patterned expression in the adult brain were inserted into a defined genomic location by site-specific recombination. These fragments were then assayed for their ability to function as transcriptional enhancers in conjunction with a synthetic core promoter designed to work with a wide variety of enhancer types. An analysis of 44 fragments from four genes found that >80% drive expression patterns in the brain; the observed patterns were, on average, comprised of <100 cells. Our results suggest that the D. melanogaster genome contains >50,000 enhancers and that multiple enhancers drive distinct subsets of expression of a gene in each tissue and developmental stage. We expect that these lines will be valuable tools for neuroanatomy as well as for the elucidation of neuronal circuits and information flow in the fly brain.

Sparse manipulation of neuron excitability during free behavior is critical for identifying neural substrates of behavior. Genetic tools for precise neuronal manipulation exist in the fruit fly, Drosophila melanogaster, but behavioral tools are still lacking to identify potentially subtle phenotypes only detectible using high-throughput and high spatiotemporal resolution. We developed three assay components that can be used modularly to study natural and optogenetically induced behaviors. FlyGate automatically releases flies one at a time into an assay. FlyDetect tracks flies in real time, is robust to severe occlusions, and can be used to track appendages, such as the head. GlobeDisplay is a spherical projection system covering the fly's visual receptive field with a single projector. We demonstrate the utility of these components in an integrated system, FlyPEZ, by comprehensively modeling the input-output function for directional looming-evoked escape takeoffs and describing a millisecond-timescale phenotype from genetic silencing of a single visual projection neuron type.