Developmental organization of central neurons in the adult <i>Drosophila</i> ventral nervous system

Shepherd, David; Sahota, Virender K.; Court, Robert; Williams, Darren W.; Truman, James W.

doi:10.1002/cne.24690

Cited by 36 publications

(119 citation statements)

References 47 publications

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“…This principle provides a useful framework for understanding the organization and function of motor circuits that flexibly control a wide range of fly behaviors, from walking to aggression to courtship. Studies of motor control in the fly VNC are now possible thanks to an increasing catalog of genetically-identified cell types (Lacin et al, 2019;Shepherd et al, 2019, Namiki et al, 2018, connectomic reconstruction with serial-section EM and the ability to image from VNC neurons in walking flies (Chen et al, 2018). We anticipate that Drosophila will provide a useful complement to other model organisms in understanding the neural basis of flexible motor control.…”

Section: Discussionmentioning

confidence: 99%

A size principle for leg motor control inDrosophila

Azevedo

Dickinson

Gurung

et al. 2019

Preprint

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To move the body, the brain must precisely coordinate patterns of activity among diverse populations of motor neurons. In many species, including vertebrates, the motor neurons innervating a given muscle fire in a specific order that is determined by a gradient of cellular size and electrical excitability. This hierarchy allows premotor circuits to recruit motor neurons of increasing force capacity in a task-dependent manner. However, it remains unclear whether such a size principle also applies to species with more compact motor systems, such as the fruit fly, Drosophila melanogaster, which has just 53 motor neurons per leg. Using in vivo calcium imaging and electrophysiology, we found that genetically-identified motor neurons controlling flexion of the fly tibia exhibit a gradient of anatomical, physiological, and functional properties consistent with the size principle. Large, fast motor neurons control high force, ballistic movements while small, slow motor neurons control low force, postural movements. Intermediate neurons fall between these two extremes. In behaving flies, motor neurons are recruited in order from slow to fast. This hierarchical organization suggests that slow and fast motor neurons control distinct motor regimes. Indeed, we find that optogenetic manipulation of each motor neuron type has distinct effects on the behavior of walking flies.

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Section: Discussionmentioning

confidence: 99%

A size principle for leg motor control inDrosophila

Azevedo

Dickinson

Gurung

et al. 2019

Preprint

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“…Finally, our method incorporates an important advance in being able to preserve both parts of the CNS intact while these still remain connected, and thus make it possible to image pathways between the supraesophageal and subesophageal ganglia of the brain and the cells that arborize in both. Preserving the continuity of pathways through the connectives ensures retention of the integrity of descending inputs to the many lineages of subesophageal neurons (Shepherd et al, 2019), as well as complementary ascending pathways. Only by retaining both halves of the brain can cells with neurite arbors in both be preserved complete, which as far as we are aware has not previously been reported for EM.…”

Section: Discussionmentioning

confidence: 99%

En bloc preparation of Drosophila brains enables high-throughput FIB-SEM connectomics

Lǚ

Hayworth

et al. 2019

Preprint

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Deriving the detailed synaptic connections of the entire nervous system has been a long term but unrealized goal of the nascent field of connectomics. For Drosophila, in particular, three sample preparation problems must be solved before the requisite imaging and analysis can even begin. The first is dissecting the brain, connectives, and ventral nerve cord (roughly comparable to the brain, neck, and spinal cord of vertebrates) as a single contiguous unit. Second is fixing and staining the resulting specimen, too large for previous techniques such as flash freezing, so as to permit the necessary automated segmentation of neuron membranes. Finally the contrast must be sufficient to support synapse detection at imaging speeds that enable the entire connectome to be collected. To address these issues, we report three major novel methods to dissect, fix, dehydrate and stain this tiny but complex nervous system in its entirety; together they enable us to uncover a Focused Ion-Beam Scanning Electron Microscopy (FIB-SEM) connectome of the entire Drosophila brain. They reliably recover fixed neurons as round profiles with darkly stained synapses, suitable for machine segmentation and automatic synapse detection, for which only minimal human intervention is required. Our advanced procedures use: a custom-made jig to microdissect both regions of the central nervous system, dorsal and ventral, with their connectives; fixation and Durcupan embedment, followed by a special hot-knife slicing protocol to reduce the brain to dimensions suited to FIB; contrast enhancement by heavy metals; together with a progressive lowering of temperature protocol for dehydration. Collectively these optimize the brain's morphological preservation, imaging it at a usual resolution of 8nm per voxel while simultaneously speeding the formerly slow rate of FIB-SEM. With these methods we could recently obtain a FIB-SEM image stack of the Drosophila brain eight times faster than hitherto, at approximately the same rate as, but without the requirement to cut, nor imperfections in, EM serial sections.

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“…Cell body positions are not a reliable indicator of the segmental organization of the VNS. There are many examples of cell bodies being passively displaced during neuropil expansion at metamorphosis resulting in somata being drawn across the midline or pulled into adjacent neuromeres (Shepherd et al, 2019).…”

Section: Definition Of the Vnsmentioning

confidence: 99%

“…(IntNp) because it occupies most of the central third of the dorsoventral area in transverse section (IntNp, Figures 4 and 5). The leg neuropil contains the dendritic branches of the leg motorneurons as well premotor interneurons (Shepherd et al, 2019) and sensory afferent terminals from leg campaniform sensilla, hair plates and the "hook" and "claw" projection types from the FCO (Mamiya et al, 2018). Like the tectulum, the leg neuropils exhibit clear functional segregation: Motor neurons are located dorsally and the sensory modalities are partitioned into layers, with proprioception in intermediate neuropil, and a somatotopic representation of tactile information in the ventral-most zone (Murphey et al, 1989;Tsubouchi et al, 2017).…”

Section: The Leg Neuropilmentioning

confidence: 99%