A Complete Developmental Sequence of a Drosophila Neuronal Lineage as Revealed by Twin-Spot MARCM

Howard Hughes Medical Institute, Janelia Farm Research Campus, Ashburn, Virginia, United States of America.
PLoS Biology (Impact Factor: 9.34). 08/2010; 8(8). DOI: 10.1371/journal.pbio.1000461
Source: PubMed


Drosophila brains contain numerous neurons that form complex circuits. These neurons are derived in stereotyped patterns from a fixed number of progenitors, called neuroblasts, and identifying individual neurons made by a neuroblast facilitates the reconstruction of neural circuits. An improved MARCM (mosaic analysis with a repressible cell marker) technique, called twin-spot MARCM, allows one to label the sister clones derived from a common progenitor simultaneously in different colors. It enables identification of every single neuron in an extended neuronal lineage based on the order of neuron birth. Here we report the first example, to our knowledge, of complete lineage analysis among neurons derived from a common neuroblast that relay olfactory information from the antennal lobe (AL) to higher brain centers. By identifying the sequentially derived neurons, we found that the neuroblast serially makes 40 types of AL projection neurons (PNs). During embryogenesis, one PN with multi-glomerular innervation and 18 uniglomerular PNs targeting 17 glomeruli of the adult AL are born. Many more PNs of 22 additional types, including four types of polyglomerular PNs, derive after the neuroblast resumes dividing in early larvae. Although different offspring are generated in a rather arbitrary sequence, the birth order strictly dictates the fate of each post-mitotic neuron, including the fate of programmed cell death. Notably, the embryonic progenitor has an altered temporal identity following each self-renewing asymmetric cell division. After larval hatching, the same progenitor produces multiple neurons for each cell type, but the number of neurons for each type is tightly regulated. These observations substantiate the origin-dependent specification of neuron types. Sequencing neuronal lineages will not only unravel how a complex brain develops but also permit systematic identification of neuron types for detailed structure and function analysis of the brain.

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    • "PNs that innervate the adult AL are produced both at embryonic and larval stages (Marin et al., 2005; Jefferis et al., 2001). From a complete lineage analysis among neurons derived from the ad-neuroblast, it was revealed that the ad-neuroblast serially generates 40 types of PNs (Fig. 1D) (Yu et al., 2010). Eighteen types of PNs are born during the embryonic stage, and 22 additional types of PNs are generated in the early larval stage. "
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    ABSTRACT: The antennal lobe (AL) of Drosophila is the first olfactory processing center in which olfactory input and output are spatially organized into distinct channels via glomeruli to form a discrete neural map. In each glomerulus, the axons of a single type of olfactory receptor neurons (ORNs) synapse with the dendrites of a single type of projection neurons (PNs). The AL is an ideal place to study how the wiring specificity between specific types of ORNs and PNs is established during development. During the past two decades, the involvement of diverse molecules in the specification and patterning of ORNs and PNs has been reported. Furthermore, local interneurons-another component of glomeruli-have been recently catalogued and their functions have been gradually dissected. Although there is accumulating knowledge about the involvement of these three cell types in the wiring specificity of the olfactory system, in this review, we focus especially on the development of PN dendrites.
    Genes & Genetic Systems 05/2014; 89(1):17-26. DOI:10.1266/ggs.89.17 · 0.93 Impact Factor
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    • "In most cases, all neurons of a given lineage extend their axons as one or two coherent fiber bundles along invariant trajectories in the brain neuropil and innervate a specific set of neuropil compartments (Hartenstein et al., 2008; Ito and Awasaki, 2008). Well-described examples are the four mushroom body lineages (Crittenden et al., 1998; Ito et al., 1997) and the four lineages that interconnect the antennal lobe (olfactory center) with the mushroom body input domain, the calyx (Das et al., 2008, 2013; Lai et al., 2008; Stocker et al., 1990; Yu et al., 2010). The development and anatomical projection of most lineages remains largely unknown; ascertaining this knowledge and using it to generate an accurate map of Drosophila brain circuitry at the level of neuron populations ( " macro-circuitry " ) is an important project followed by us and others over the past several years. "
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    ABSTRACT: Neurons of the Drosophila central brain fall into approximately 100 paired groups, termed lineages. Each lineage is derived from a single asymmetrically-dividing neuroblast. Embryonic neuroblasts produce 1,500 primary neurons (per hemisphere) that make up the larval CNS followed by a second mitotic period in the larva that generates approximately 10,000 secondary, adult-specific neurons. Clonal analyses based on previous works using lineage-specific Gal4 drivers have established that such lineages form highly invariant morphological units. All neurons of a lineage project as one or a few axon tracts (secondary axon tracts, SATs) with characteristic trajectories, thereby representing unique hallmarks. In the neuropil, SATs assemble into larger fiber bundles (fascicles) which interconnect different neuropil compartments. We have analyzed the SATs and fascicles formed by lineages during larval, pupal, and adult stages using antibodies against membrane molecules (Neurotactin/Neuroglian) and synaptic proteins (Bruchpilot/N-Cadherin). The use of these markers allows one to identify fiber bundles of the adult brain and associate them with SATs and fascicles of the larval brain. This work lays the foundation for assigning the lineage identity of GFP-labeled MARCM clones on the basis of their close association with specific SATs and neuropil fascicles, as described in the accompanying paper (Wong et al., 2013).
    Developmental Biology 07/2013; 384(2). DOI:10.1016/j.ydbio.2013.07.008 · 3.55 Impact Factor
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    • "For example, the neurons produced by MB1-4 in the late embryo/early larva fill the γ-lobe; they are followed by neurons forming the α'/β' lobes, and finally by neurons of the α/β lobes (Ito et al., 1997; Kunz et al., 2012). In the case of dNB/BAmv3, most neurons innervate a single glomerulus of the antennal lobe and project to discrete regions within the calyx and lateral horn (Jefferis et al., 2001; Yu et al., 2010). It is reasonable to assume that the projection envelope of a lineage, which is shared by all neurons of that lineage, is determined to some extent by transcription factors expressed earlier in development and are common to the neuroblast of that lineage. "
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    ABSTRACT: The Drosophila central brain is largely composed of lineages, units of sibling neurons derived from a single progenitor cell or neuroblast. During the early embryonic period neuroblast generate the primary neurons that constitute the larval brain. Neuroblasts reactivate in the larva, adding to their lineages a large number of secondary neurons which, according to previous studies in which selected lineages were labeled by stably expressed markers, differentiate during metamorphosis, sending terminal axonal and dendritic branches into defined volumes of the brain neuropil. We call the overall projection pattern of neurons forming a given lineage the "projection envelope" of that lineage. By inducing MARCM clones at the early larval stage, we labeled the secondary progeny of each neuroblast. For the supraesophageal ganglion excluding mushroom body (the part of the brain investigated in the present work) we obtained 81 different types of clones, Based on the trajectory of their secondary axon tracts (described in the accompanying paper), we assigned these clones to specific lineages defined in the larva. Since a labeled clone reveals all aspects (cell bodies, axon tracts, terminal arborization) of a lineage, we were able to describe projection envelopes for all secondary lineages of the supraesophageal ganglion. This work provides a framework by which the secondary neurons (forming the vast majority of adult brain neurons) can be assigned to genetically and developmentally defined groups. It also represents a step towards the goal to establish, for each lineage, the link between its mature anatomical and functional phenotype, and the genetic make-up of the neuroblast it descends from.
    Developmental Biology 07/2013; 384(2). DOI:10.1016/j.ydbio.2013.07.009 · 3.55 Impact Factor
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