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A complete developmental sequence of a Drosophila neuronal lineage as revealed by twin-spot MARCM.

Yu HH, Kao CF, He Y, Ding P, Kao JC, Lee T - PLoS Biol. (2010)

Bottom Line: By identifying the sequentially derived neurons, we found that the neuroblast serially makes 40 types of AL projection neurons (PNs).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.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Janelia Farm Research Campus, Ashburn, Virginia, United States of America.

ABSTRACT
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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Twelve types of early-larval-derived GH146-positive uniglomerular adPNs.Twin-spot MARCM clones of adPNs labeled with GAL4-GH146 (A-M) or acj6-GAL4 (N). Top panels: composite confocal images of sister clones in the AL; middle panels: single focal sections of the AL covering the glomerular targets of GMC progeny (magenta); bottom panels: axon projections of GMC progeny (magenta); islets in bottom panels: axon projections of both GMC progeny (magenta) and its paired NB clone (green). Note each adPN type (magenta) consistently pairs with adPN NB clones (green) of specific compositions. Analysis of NB clones revealed the 12 types of GH146-positive adPNs are made in an invariant sequence from (A) to (M). And all the lone, unpaired NB clones (H), whose preceding GMC progeny probably die prematurely, were induced in the interval between VA1d and 1 adPNs. The sequence of early-larval adPN neurogenesis is summarized in the bottom. In addition, there are multiple neurons per type, as evidenced in middle panels that the glomerular target of GMC progeny can be co-labeled by its accompanying NB clone. For the lineage after VA1lm PNs, one can visualize GH146-negative adPNs with acj6-GAL4 as revealed in (N) where the last VA1lm adPN pairs with a 32-neuron-containing NB clone.
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pbio-1000461-g002: Twelve types of early-larval-derived GH146-positive uniglomerular adPNs.Twin-spot MARCM clones of adPNs labeled with GAL4-GH146 (A-M) or acj6-GAL4 (N). Top panels: composite confocal images of sister clones in the AL; middle panels: single focal sections of the AL covering the glomerular targets of GMC progeny (magenta); bottom panels: axon projections of GMC progeny (magenta); islets in bottom panels: axon projections of both GMC progeny (magenta) and its paired NB clone (green). Note each adPN type (magenta) consistently pairs with adPN NB clones (green) of specific compositions. Analysis of NB clones revealed the 12 types of GH146-positive adPNs are made in an invariant sequence from (A) to (M). And all the lone, unpaired NB clones (H), whose preceding GMC progeny probably die prematurely, were induced in the interval between VA1d and 1 adPNs. The sequence of early-larval adPN neurogenesis is summarized in the bottom. In addition, there are multiple neurons per type, as evidenced in middle panels that the glomerular target of GMC progeny can be co-labeled by its accompanying NB clone. For the lineage after VA1lm PNs, one can visualize GH146-negative adPNs with acj6-GAL4 as revealed in (N) where the last VA1lm adPN pairs with a 32-neuron-containing NB clone.

Mentions: We supposed that use of GAL4-GH146 alone should allow us to identify the majority of adPNs born prior to the mid-larval stage. We therefore reserved acj6-GAL4, which has much more non-PN expression, for the elucidation of the late larval development of the adPN lineage and filling any gap present in the sequence of GH146-positive adPNs. As described below, we first resolved the GH146 part of the larval adPN lineage (Figure 2). We then determined the later-derived GH146-negative adPNs using acj6-GAL4 (Figure 3). Finally, we identified the embryonic-born adPNs with GAL4-GH146, followed by acj6-GAL4 (Figure 4).


A complete developmental sequence of a Drosophila neuronal lineage as revealed by twin-spot MARCM.

Yu HH, Kao CF, He Y, Ding P, Kao JC, Lee T - PLoS Biol. (2010)

Twelve types of early-larval-derived GH146-positive uniglomerular adPNs.Twin-spot MARCM clones of adPNs labeled with GAL4-GH146 (A-M) or acj6-GAL4 (N). Top panels: composite confocal images of sister clones in the AL; middle panels: single focal sections of the AL covering the glomerular targets of GMC progeny (magenta); bottom panels: axon projections of GMC progeny (magenta); islets in bottom panels: axon projections of both GMC progeny (magenta) and its paired NB clone (green). Note each adPN type (magenta) consistently pairs with adPN NB clones (green) of specific compositions. Analysis of NB clones revealed the 12 types of GH146-positive adPNs are made in an invariant sequence from (A) to (M). And all the lone, unpaired NB clones (H), whose preceding GMC progeny probably die prematurely, were induced in the interval between VA1d and 1 adPNs. The sequence of early-larval adPN neurogenesis is summarized in the bottom. In addition, there are multiple neurons per type, as evidenced in middle panels that the glomerular target of GMC progeny can be co-labeled by its accompanying NB clone. For the lineage after VA1lm PNs, one can visualize GH146-negative adPNs with acj6-GAL4 as revealed in (N) where the last VA1lm adPN pairs with a 32-neuron-containing NB clone.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2927434&req=5

pbio-1000461-g002: Twelve types of early-larval-derived GH146-positive uniglomerular adPNs.Twin-spot MARCM clones of adPNs labeled with GAL4-GH146 (A-M) or acj6-GAL4 (N). Top panels: composite confocal images of sister clones in the AL; middle panels: single focal sections of the AL covering the glomerular targets of GMC progeny (magenta); bottom panels: axon projections of GMC progeny (magenta); islets in bottom panels: axon projections of both GMC progeny (magenta) and its paired NB clone (green). Note each adPN type (magenta) consistently pairs with adPN NB clones (green) of specific compositions. Analysis of NB clones revealed the 12 types of GH146-positive adPNs are made in an invariant sequence from (A) to (M). And all the lone, unpaired NB clones (H), whose preceding GMC progeny probably die prematurely, were induced in the interval between VA1d and 1 adPNs. The sequence of early-larval adPN neurogenesis is summarized in the bottom. In addition, there are multiple neurons per type, as evidenced in middle panels that the glomerular target of GMC progeny can be co-labeled by its accompanying NB clone. For the lineage after VA1lm PNs, one can visualize GH146-negative adPNs with acj6-GAL4 as revealed in (N) where the last VA1lm adPN pairs with a 32-neuron-containing NB clone.
Mentions: We supposed that use of GAL4-GH146 alone should allow us to identify the majority of adPNs born prior to the mid-larval stage. We therefore reserved acj6-GAL4, which has much more non-PN expression, for the elucidation of the late larval development of the adPN lineage and filling any gap present in the sequence of GH146-positive adPNs. As described below, we first resolved the GH146 part of the larval adPN lineage (Figure 2). We then determined the later-derived GH146-negative adPNs using acj6-GAL4 (Figure 3). Finally, we identified the embryonic-born adPNs with GAL4-GH146, followed by acj6-GAL4 (Figure 4).

Bottom Line: By identifying the sequentially derived neurons, we found that the neuroblast serially makes 40 types of AL projection neurons (PNs).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.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Janelia Farm Research Campus, Ashburn, Virginia, United States of America.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus