UNLABELLED: Sensorimotor delays decouple behaviors from the events that drive them. The brain compensates for these delays with predictive mechanisms, but the efficacy and timescale over which these mechanisms operate remain poorly understood. Here, we assess how prediction is used to compensate for prey movement that occurs during visuomotor processing. We obtained high-speed video records of freely moving, tongue-projecting salamanders catching walking prey, emulating natural foraging conditions. We found that tongue projections were preceded by a rapid head turn lasting ∼130 ms. This motor lag, combined with the ∼100 ms phototransduction delay at photopic light levels, gave a ∼230 ms visuomotor response delay during which prey typically moved approximately one body length. Tongue projections, however, did not significantly lag prey position but were highly accurate instead. Angular errors in tongue projection accuracy were consistent with a linear extrapolation model that predicted prey position at the time of tongue contact using the average prey motion during a ∼175 ms period one visual latency before the head movement. The model explained successful strikes where the tongue hit the fly, and unsuccessful strikes where the fly turned and the tongue hit a phantom location consistent with the fly's earlier trajectory. The model parameters, obtained from the data, agree with the temporal integration and latency of retinal responses proposed to contribute to motion extrapolation. These results show that the salamander predicts future prey position and that prediction significantly improves prey capture success over a broad range of prey speeds and light levels.

SIGNIFICANCE STATEMENT: Neural processing delays cause actions to lag behind the events that elicit them. To cope with these delays, the brain predicts what will happen in the future. While neural circuits in the retina and beyond have been suggested to participate in such predictions, few behaviors have been explored sufficiently to constrain circuit function. Here we show that salamanders aim their tongues by using extrapolation to estimate future prey position, thereby compensating for internal delays from both visual and motor processing. Predictions made just before a prey turn resulted in the tongue being projected to a position consistent with the prey's pre-turn trajectory. These results define the computations and operating regimen for neural circuits that predict target motion.

The timely onset of metamorphosis in holometabolous insects depends on their reaching the appropriate size known as critical weight. Once critical weight is reached, juvenile hormone (JH) titers decline, resulting in the release of prothoracicotropic hormone (PTTH) at the next photoperiod gate and thereby inducing metamorphosis. How individuals determine when they have reached critical weight is unknown. We present evidence that in Drosophila, a component of the ring gland, the prothoracic gland (PG), assesses growth to determine when critical weight has been achieved.

Metamorphosis is one of the most common, yet dramatic of life history strategies. In insects, complete metamorphosis with morphologically distinct larval stages arose from hemimetabolous ancestors that were more direct developing. Over the past century, several ideas have emerged that suggest the holometabolous pupa is developmentally homologous to the embryonic stages of the hemimetabolous ancestor. Other theories consider the pupal stage to be a modification of a hemimetabolous nymph. To address this question, we have isolated an ortholog of the pupal determinant, broad (br), from the hemimetabolous milkweed bug and examined its role during embryonic development. We show that Oncopeltus fasciatus br (Of’br) is expressed in two phases. The first occurs during germ band invagination and segmentation when Of’br is expressed ubiquitously in the embryonic tissues. The second phase of Of’br expression appears during the pronymphal phase of embryogenesis and persists through nymphal differentiation to decline just before hatching. Knock-down of Of’br transcripts results in defects that range from posterior truncations in the least-affected phenotypes to completely fragmented embryonic tissues in the most severe cases. Analysis of the patterning genes engrailed and hunchback reveal loss of segments and a failure in neural differentiation after Of’br depletion. Finally, we show that br is constitutively expressed during embyrogenesis of the ametabolous firebrat, Thermobia domestica. This suggests that br expression is prominent during embryonic development of ametabolous and hemimetabolous insects but was lost with the emergence of the completely metamorphosing insects.

The serotonergic system in the vertebrate brain is implicated in various behaviors and diseases. Its involvement in motor control has been studied for over half a century, but efforts to build a unified model of its functions have been hampered due to the complexity of serotonergic neuromodulation. This review summarizes the anatomical structure of the serotonergic system, its afferent and efferent connections to other brain regions, and recent insights into the sensorimotor computations in the serotonergic system, and considers future research directions into the roles of serotonergic system in motor control.

The generation of coordinated body movements relies on sensory feedback from mechanosensitive proprioceptors. We have found that the proper function of NompC, a putative mechanosensitive TRP channel, is not only required for fly locomotion, but also crucial for larval crawling. Calcium imaging revealed that NompC is required for the activation of two subtypes of sensory neurons during peristaltic muscle contractions. Having isolated a full-length nompC cDNA with a protein coding sequence larger than previously predicted, we demonstrate its function by rescuing locomotion defects in nompC mutants, and further show that antibodies against the extended C terminus recognize NompC in chordotonal ciliary tips. Moreover, we show that the ankyrin repeats in NompC are required for proper localization and function of NompC in vivo and are required for association of NompC with microtubules. Taken together, our findings suggest that NompC mediates proprioception in locomotion and support its role as a mechanosensitive channel.

It has long been known that many flying insects use visual cues to orient with respect to the wind and to control their groundspeed in the face of varying wind conditions. Much less explored has been the role of mechanosensory cues in orienting insects relative to the ambient air. Here we show that Drosophila melanogaster, magnetically tethered so as to be able to rotate about their yaw axis, are able to detect and orient into a wind, as would be experienced during forward flight. Further, this behavior is velocity dependent and is likely subserved, at least in part, by the Johnston’s organs, chordotonal organs in the antennae also involved in near-field sound detection. These wind-mediated responses may help to explain how flies are able to fly forward despite visual responses that might otherwise inhibit this behavior. Expanding visual stimuli, such as are encountered during forward flight, are the most potent aversive visual cues known for D. melanogaster flying in a tethered paradigm. Accordingly, tethered flies strongly orient towards a focus of contraction, a problematic situation for any animal attempting to fly forward. We show in this study that wind stimuli, transduced via mechanosensory means, can compensate for the aversion to visual expansion and thus may help to explain how these animals are indeed able to maintain forward flight.

The steroid hormone 20-hydroxyecdysone (20E) initiates metamorphosis in insects by signaling through the ecdysone receptor complex, a heterodimer of the ecdysone receptor (EcR) and ultraspiracle (USP). Analysis of usp mutant clones in the wing disc of Drosophila shows that in the absence of USP, early hormone responsive genes such as EcR, DHR3 and E75B fail to up-regulate in response to 20E, but other genes that are normally expressed later, such as (&bgr;)-Ftz-F1 and the Z1 isoform of the Broad-Complex (BRC-Z1), are expressed precociously. Sensory neuron formation and axonal outgrowth, two early metamorphic events, also occur prematurely. In vitro experiments with cultured wing discs showed that BRC-Z1 expression and early metamorphic development are rendered steroid-independent in the usp mutant clones. These results are consistent with a model in which these latter processes are induced by a signal arising during the middle of the last larval stage but suppressed by the unliganded EcR/USP complex. Our observations suggest that silencing by the unliganded EcR/USP receptor and the subsequent release of silencing by moderate steroid levels may play an important role in coordinating early phases of steroid driven development.

The autonomic nervous system regulates the function of internal organs such as the gut. The parasympathetic and sympathetic arms of this system tend to operate antagonistically. Espinosa-Medina et al. used anatomical and molecular analyses to reevaluate the assignment of neurons in the sacral autonomic nervous system (see the Perspective by Adameyko). Previously categorized as parasympathetic, these neurons are now identified as sympathetic. The results resolve a persistent confusion about how the two systems developed and open the avenue to more predictable outcomes in developing treatments targeted to the pelvic autonomic nervous system. Science, this issue p. 893; see also p. 833 Contrary to a century-old dogma, the pelvic nerves and ganglia do not belong to the parasympathetic nervous system but to the sympathetic one. A kinship between cranial and pelvic visceral nerves of vertebrates has been accepted for a century. Accordingly, sacral preganglionic neurons are considered parasympathetic, as are their targets in the pelvic ganglia that prominently control rectal, bladder, and genital functions. Here, we uncover 15 phenotypic and ontogenetic features that distinguish pre- and postganglionic neurons of the cranial parasympathetic outflow from those of the thoracolumbar sympathetic outflow in mice. By every single one, the sacral outflow is indistinguishable from the thoracolumbar outflow. Thus, the parasympathetic nervous system receives input from cranial nerves exclusively and the sympathetic nervous system from spinal nerves, thoracic to sacral inclusively. This simplified, bipartite architecture offers a new framework to understand pelvic neurophysiology as well as development and evolution of the autonomic nervous system.

The severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) and SARS-CoV-1 accessory protein Orf3a colocalizes with markers of the plasma membrane, endocytic pathway, and Golgi apparatus. Some reports have led to annotation of both Orf3a proteins as a viroporin. Here we show that neither SARS-CoV-2 nor SARS-CoV-1 form functional ion conducting pores and that the conductances measured are common contaminants in overexpression and with high levels of protein in reconstitution studies. Cryo-EM structures of both SARS-CoV-2 and SARS-CoV-1 Orf3a display a narrow constriction and the presence of a basic aqueous vestibule, which would not favor cation permeation. We observe enrichment of the late endosomal marker Rab7 upon SARS-CoV-2 Orf3a overexpression, and co-immunoprecipitation with VPS39. Interestingly, SARS-CoV-1 Orf3a does not cause the same cellular phenotype as SARS-CoV-2 Orf3a and does not interact with VPS39. To explain this difference, we find that a divergent, unstructured loop of SARS-CoV-2 Orf3a facilitates its binding with VPS39, a HOPS complex tethering protein involved in late endosome and autophagosome fusion with lysosomes. We suggest that the added loop enhances SARS-CoV-2 Orf3a ability to co-opt host cellular trafficking mechanisms for viral exit or host immune evasion.

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.