Current Biology
Volume 32, Issue 10, 23 May 2022, Pages 2341-2348.e3
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Hormone-controlled changes in the differentiation state of post-mitotic neurons

https://doi.org/10.1016/j.cub.2022.04.027Get rights and content
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Highlights

  • Drosophila mushroom body γ neurons undergo two rounds of terminal differentiation

  • Ecdysone signaling via EcR-B1 partially de-differentiates larval γ neurons

  • Mamo is necessary to respecify the adult γ-neuron molecular identity

  • Mamo can promote γ-neuron identity even if the initial fating step was deficient

Summary

While we think of neurons as having a fixed identity, many show spectacular plasticity.1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Metamorphosis drives massive changes in the fly brain;11,12 neurons that persist into adulthood often change in response to the steroid hormone ecdysone.13,14 Besides driving remodeling,11, 12, 13, 14 ecdysone signaling can also alter the differentiation status of neurons.7,15 The three sequentially born subtypes of mushroom body (MB) Kenyon cells (γ, followed by α′/β′, and finally α/β)16 serve as a model of temporal fating.17, 18, 19, 20, 21 γ neurons are also used as a model of remodeling during metamorphosis. As γ neurons are the only functional Kenyon cells in the larval brain, they serve the function of all three adult subtypes. Correspondingly, larval γ neurons have a similar morphology to α′/β′ and α/β neurons—their axons project dorsally and medially. During metamorphosis, γ neurons remodel to form a single medial projection. Both temporal fate changes and defects in remodeling therefore alter γ-neuron morphology in similar ways. Mamo, a broad-complex, tramtrack, and bric-à-brac/poxvirus and zinc finger (BTB/POZ) transcription factor critical for temporal specification of α′/β′ neurons,18,19 was recently described as essential for γ remodeling.22 In a previous study, we noticed a change in the number of adult Kenyon cells expressing γ-specific markers when mamo was manipulated.18 These data implied a role for Mamo in γ-neuron fate specification, yet mamo is not expressed in γ neurons until pupariation,18,22 well past γ specification. This indicates that mamo has a later role in ensuring that γ neurons express the correct Kenyon cell subtype-specific genes in the adult brain.

Keywords

de-differentiation
specification
remodeling
plasticity
metamorphosis
ecdysone
mamo
γ neuron
mushroom body
neuronal identity

Data and code availability

  • Microscopy data reported in this paper will be deposited to: Mendeley Data: https://doi.org/10.17632/z2py7h2tfx.1.

  • This paper does not report original code.

  • Any additional information required to reanalyze the data reported in this paper is available from the lead contact upon request.

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