A library of lineage-specific driver lines connects developing neuronal circuits to behavior in the Ventral Nerve Cord.

Understanding the developmental trajectories of neuronal lineages is crucial for elucidating how they are assembled into functional neural networks. Studies investigating the nervous system development in model animals have focused only on a few regions of the Central Nervous System due to the limited availability of genetic drivers to target these regions throughout development and adult life. This hindered our understanding of how distinct neuronal lineages come together to form neuronal circuits during development.

Mint/X11 PDZ domains from non-bilaterian animals recognize and bind Ca2 calcium channel C-termini in vitro.

PDZ domain mediated interactions with voltage-gated calcium (Ca) channel C-termini play important roles in localizing membrane Ca signaling. The first such interaction was described between the scaffolding protein Mint-1 and Ca2.2 in mammals.

Mint/X11 PDZ domains from non-bilaterian animals recognize and bind Ca 2 calcium channel C-termini .

PDZ domain mediated interactions with voltage-gated calcium (Ca ) channel C-termini play important roles in localizing membrane Ca signaling. The first such interaction was described between the scaffolding protein Mint-1 and Ca 2.2 in mammals.

High-throughput identification of the spatial origins of optic lobe neurons using single-cell mRNA-sequencing.

The medulla is the largest neuropil of the optic lobe. It contains about 100 neuronal types that have been comprehensively characterized morphologically and molecularly. These neuronal types are specified from a larval neuroepithelium called the Outer Proliferation Center (OPC) via the integration of temporal, spatial, and Notch-driven mechanisms.

Using single-cell RNA sequencing to generate predictive cell-type-specific split-GAL4 reagents throughout development.

Cell-type-specific tools facilitate the identification and functional characterization of the distinct cell types that form the complexity of neuronal circuits. A large collection of existing genetic tools in relies on enhancer activity to label different subsets of cells and has been extremely useful in analyzing functional circuits in adults. However, these enhancer-based GAL4 lines often do not reflect the expression of nearby gene(s) as they only represent a small portion of the full gene regulatory elements.

Using single-cell RNA sequencing to generate cell-type-specific split-GAL4 reagents throughout development.

Unlabelled: Cell-type-specific tools facilitate the identification and functional characterization of distinct cell types, which underly the complexity of neuronal circuits. A large collection of existing genetic tools in Drosophila relies on enhancer activity to label different subsets of cells. These enhancer-based GAL4 lines often fail to show a predicable expression pattern to reflect the expression of nearby gene(s), partly due to an incomplete capture of the full gene regulatory elements.

Spalt and disco define the dorsal-ventral neuroepithelial compartments of the developing Drosophila medulla.

Spatial patterning of neural stem cell populations is a powerful mechanism by which to generate neuronal diversity. In the developing Drosophila medulla, the symmetrically dividing neuroepithelial cells of the outer proliferation center crescent are spatially patterned by the nonoverlapping expression of 3 transcription factors: Vsx1 in the center, Optix in the adjacent arms, and Rx in the tips. These spatial genes compartmentalize the outer proliferation center and, together with the temporal patterning of neuroblasts, act to diversify medulla neuronal fates.

Imp and Syp mediated temporal patterning of neural stem cells in the developing Drosophila CNS.

The assembly of complex neural circuits requires that stem cells generate diverse types of neurons in the correct temporal order. Pioneering work in the Drosophila embryonic ventral nerve cord has shown that neural stem cells are temporally patterned by the sequential expression of rapidly changing transcription factors to generate diversity in their progeny. In recent years, a second temporal patterning mechanism, driven by the opposing gradients of the Imp and Syp RNA-binding proteins, has emerged as a powerful way to generate neural diversity.

Dissection, Immunohistochemistry and Mounting of Larval and Adult Drosophila Brains for Optic Lobe Visualization.

The Drosophila optic lobe, comprised of four neuropils: the lamina, medulla, lobula and lobula plate, is an excellent model system for exploring the developmental mechanisms that generate neural diversity and drive circuit assembly. Given its complex three-dimensional organization, analysis of the optic lobe requires that one understand how its adult neuropils and larval progenitors are positioned relative to each other and the central brain. Here, we describe a protocol for the dissection, immunostaining and mounting of larval and adult brains for optic lobe imaging.

Identification of enhancers that drive the spatially restricted expression of and in the outer proliferation center of the developing optic lobe.

Combinatorial spatial and temporal patterning of stem cells is a powerful mechanism for the generation of neural diversity in insect and vertebrate nervous systems. In the developing medulla, the neural stem cells of the outer proliferation center (OPC) are spatially patterned by the mutually exclusive expression of three homeobox transcription factors: Vsx1 in the center of the OPC crescent (cOPC), Optix in the main arms (mOPC), and Rx in the posterior tips (pOPC). These spatial factors act together with a temporal cascade of transcription factors in OPC neuroblasts to specify the greater than 80 medulla cell types.

Integration of temporal and spatial patterning generates neural diversity.

In the Drosophila optic lobes, 800 retinotopically organized columns in the medulla act as functional units for processing visual information. The medulla contains over 80 types of neuron, which belong to two classes: uni-columnar neurons have a stoichiometry of one per column, while multi-columnar neurons contact multiple columns. Here we show that combinatorial inputs from temporal and spatial axes generate this neuronal diversity: all neuroblasts switch fates over time to produce different neurons; the neuroepithelium that generates neuroblasts is also subdivided into six compartments by the expression of specific factors.

A Unique Class of Neural Progenitors in the Drosophila Optic Lobe Generates Both Migrating Neurons and Glia.

How neuronal and glial fates are specified from neural precursor cells is an important question for developmental neurobiologists. We address this question in the Drosophila optic lobe, composed of the lamina, medulla, and lobula complex. We show that two gliogenic regions posterior to the prospective lamina also produce lamina wide-field (Lawf) neurons, which share common progenitors with lamina glia.

Temporal patterning of neuroblasts controls Notch-mediated cell survival through regulation of Hid or Reaper.

Temporal patterning of neural progenitors is one of the core mechanisms generating neuronal diversity in the central nervous system. Here, we show that, in the tips of the outer proliferation center (tOPC) of the developing Drosophila optic lobes, a unique temporal series of transcription factors not only governs the sequential production of distinct neuronal subtypes but also controls the mode of progenitor division, as well as the selective apoptosis of Notch(OFF) or Notch(ON) neurons during binary cell fate decisions. Within a single lineage, intermediate precursors initially do not divide and generate only one neuron; subsequently, precursors divide, but their Notch(ON) progeny systematically die through Reaper activity, whereas later, their Notch(OFF) progeny die through Hid activity.

Temporal patterning of Drosophila medulla neuroblasts controls neural fates.

In the Drosophila optic lobes, the medulla processes visual information coming from inner photoreceptors R7 and R8 and from lamina neurons. It contains approximately 40,000 neurons belonging to more than 70 different types. Here we describe how precise temporal patterning of neural progenitors generates these different neural types.

Cell migration in Drosophila optic lobe neurons is controlled by eyeless/Pax6.

In the developing Drosophila optic lobe, eyeless, apterous and distal-less, three genes that encode transcription factors with important functions during development, are expressed in broad subsets of medulla neurons. Medulla cortex cells follow two patterns of cell movements to acquire their final position: first, neurons are arranged in columns below each neuroblast. Then, during pupation, they migrate laterally, intermingling with each other to reach their retinotopic position in the adult optic lobe.

Eye evolution at high resolution: the neuron as a unit of homology.

Based on differences in morphology, photoreceptor-type usage and lens composition it has been proposed that complex eyes have evolved independently many times. The remarkable observation that different eye types rely on a conserved network of genes (including Pax6/eyeless) for their formation has led to the revised proposal that disparate complex eye types have evolved from a shared and simpler prototype. Did this ancestral eye already contain the neural circuitry required for image processing? And what were the evolutionary events that led to the formation of complex visual systems, such as those found in vertebrates and insects? The recent identification of unexpected cell-type homologies between neurons in the vertebrate and Drosophila visual systems has led to two proposed models for the evolution of complex visual systems from a simple prototype.

Conserved role of the Vsx genes supports a monophyletic origin for bilaterian visual systems.

Background: Components of the genetic network specifying eye development are conserved from flies to humans, but homologies between individual neuronal cell types have been difficult to identify. In the vertebrate retina, the homeodomain-containing transcription factor Chx10 is required for both progenitor cell proliferation and the development of the bipolar interneurons, which transmit visual signals from photoreceptors to ganglion cells.

Results: We show that dVsx1 and dVsx2, the two Drosophila homologs of Chx10, play a conserved role in visual-system development.

Specification and development of the pars intercerebralis and pars lateralis, neuroendocrine command centers in the Drosophila brain.

The central neuroendocrine system in the Drosophila brain includes two centers, the pars intercerebralis (PI) and pars lateralis (PL). The PI and PL contain neurosecretory cells (NSCs) which project their axons to the ring gland, a complex of peripheral endocrine glands flanking the aorta. We present here a developmental and genetic study of the PI and PL.