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Review
. 2021 Feb:43:39-45.
doi: 10.1016/j.cois.2020.09.015. Epub 2020 Oct 14.

Programmed cell death reshapes the central nervous system during metamorphosis in insects

Gyunghee Lee  1 , Jae H Park  2
Affiliations
Review

Programmed cell death reshapes the central nervous system during metamorphosis in insects

Gyunghee Lee et al. Curr Opin Insect Sci. 2021 Feb.

Abstract

Metamorphosis is fascinating and dramatic stage of postembryonic development in insects [1]. The most prominent metamorphic changes seen in holometabolous insects involve destruction of most larval structures and concomitant generation of adult ones. Such diverse cellular events are orchestrated by ecdysone. The central nervous system (CNS) is also extensively remodeled to process new sensory inputs; to coordinate new types of locomotion; and to perform higher-order decision making [2]. Programmed cell death (PCD) is an integral part of the metamorphic development. It eliminates obsolete larval tissues and extra cells that are generated from the morphogenesis of adult tissues. In the CNS, PCD of selected neurons and glial cells as well as reshaping of persistent larval cells are essential for establishing the adult CNS. In this review, we summarize the ecdysone signaling, and then molecular and cellular events associated with PCD primarily in the metamorphosing CNS of Drosophila melanogaster.

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Conflict of interest statement

Declarations of interest: none

Figures

Figure 1.
Figure 1.
Diverse modes of ecdysone-dependent PCD during metamorphosis. Factor ‘X’ could be an exogenous signal that might act cooperatively or epistatically with ecdysone signaling to regulate timely induction of PCD. EcR may inhibit PCD as a transcriptional repressor to prevent premature death of certain tissues or cells before their normal death. Potential cross-talk between autophagy and apoptosis is indicated by a double-pointed arrow. In particular, PCD of the salivary glands is mediated cooperatively by both autophagic and apoptotic mechanisms. In contrast, midgut cell death is primarily induced by autophagy, although ecdysone signal induces expression of the apoptotic genes. Inhibitory pathways are indicated by blunted arrows. (abbr. PM, plasma membrane; EcI, ecdysone importer; TF, transcription factor)
Figure 2.
Figure 2.
A summary of diverse cell death events during metamorphosis in D. melanogaster. Each horizontal bar indicates a timeline of designated cells dying after puparium formation. Non-neuronal cells are shown by green bars and neuronal cells by blue. Orange-coded areas indicate changes of the ecdysone titers (color strength and height correlate with the titer, which is reconstructed based on ref. 79). Vertical positions of each bar is nothing to do with the ecdysone titers. As addressed in the text, PCD of some cells does not involve ecdysone signal. A broken line indicates unclear timeline.
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