Genetic analysis of Eclosion hormone action during Drosophila larval ecdysis

Abstract

Insect growth is punctuated by molts, during which the animal produces a new exoskeleton. The molt culminates in ecdysis, an ordered sequence of behaviors that causes the old cuticle to be shed. This sequence is activated by Ecdysis triggering hormone (ETH), which acts on the CNS to activate neurons that produce neuropeptides implicated in ecdysis, including Eclosion hormone (EH), Crustacean cardioactive peptide (CCAP) and Bursicon. Despite more than 40 years of research on ecdysis, our understanding of the precise roles of these neurohormones remains rudimentary. Of particular interest is EH; although it is known to upregulate ETH release, other roles for EH have remained elusive. We isolated an Eh null mutant in Drosophila and used it to investigate the role of EH in larval ecdysis. We found that null mutant animals invariably died at around the time of ecdysis, revealing an essential role in its control. Further analyses showed that these animals failed to express the preparatory behavior of pre-ecdysis while directly expressing the motor program of ecdysis. Although ETH release could not be detected, the lack of pre-ecdysis could not be rescued by injections of ETH, suggesting that EH is required within the CNS for ETH to trigger the normal ecdysial sequence. Using a genetically encoded calcium probe, we showed that EH configured the response of the CNS to ETH. These findings show that EH plays an essential role in the Drosophila CNS in the control of ecdysis, in addition to its known role in the periphery of triggering ETH release.

Stereotyped responses of Drosophila peptidergic neuronal ensemble depend on downstream neuromodulators

“…By targeting a calcium-sensitive GFP (GCaMP) to different peptidergic ensembles, Kim et al (2006) showed that each of these sets of peptidergic neurons is activated at a particular time and for a specific duration following a challenge by ETH in vitro. By correlating these times with the expression of the different behavioral phases of ecdysis, each set was assigned a role in the control of particular ecdysial subroutine, which was also broadly consistent with functional and genetic evidence (Diao et al, 2016; Kim et al, 2006, 2015; Krüger et al, 2015; Lahr et al, 2012; Park et al, 2003). Nevertheless, the mechanisms by which the direct targets of ETH would be activated at different times after an ETH challenge remained unanswered.…”

“…Eclosion hormone (EH) is a key neuropeptide in the control of ecdysis (Ewer and Reynolds, 2002; Gammie and Truman, 1999; Krüger et al, 2015). It is involved in potentiating and accelerating the release of ETH that causes the sudden onset of ecdysis behaviors (Ewer et al, 1997; Kingan et al, 1997); in addition, it plays a critical role within the CNS for the expression of ecdysis behaviors.…”

“…It is involved in potentiating and accelerating the release of ETH that causes the sudden onset of ecdysis behaviors (Ewer et al, 1997; Kingan et al, 1997); in addition, it plays a critical role within the CNS for the expression of ecdysis behaviors. In Drosophila larvae, for instance, mutants lacking EH do not express pre-ecdysis, transitioning directly into a prolonged ecdysis-like phase, which is, nevertheless, generally ineffective in causing the shedding of the old cuticle (Krüger et al, 2015). Eh mutant animals also expressed specific behavioral defects at pupal ecdysis, which, interestingly, differed from those expressed in the larva.…”

“…Drosophila EH neurons are direct targets of ETH (Diao et al, 2016; Kim et al, 2006) and respond to ETH with a shorter latency than do CCAP neurons (Kim et al, 2006); in addition, the response of larval CCAP neurons to ETH is severely weakened in the absence of EH (Krüger et al, 2015). These results suggest that EH neurons are an ETH target that is upstream of CCAP neurons.…”

Ecdysis-related pleiotropic neuropeptides expression during Anopheles albimanus development

“…17 ETH is a peptide that activates neurons that produce the eclosion hormone (EH), CCAP and bursicon. 18 Other important neuropeptides involved in growth and development are the insulin like peptides (ILP´s), orcokinins and allatostatins. ILP´s seem to be involved in development, regulation of carbohydrate and lipid metabolism, 19 diapause induction, 20 stress resistance, 21 regulation of sexual behaviors, 22 regulation of life span 23 and regulation of sleep.…”