Targeted ablation of CCAP neuropeptide-containing neurons ofDrosophilacauses specific defects in execution and circadian timing of ecdysis behavior

Abstract

Insect growth and metamorphosis is punctuated by molts, during which a new cuticle is produced. Every molt culminates in ecdysis, the shedding of the remains of the old cuticle. Both the timing of ecdysis relative to the molt and the actual execution of this vital insect behavior are under peptidergic neuronal control. Based on studies in the moth, Manduca sexta, it has been postulated that the neuropeptide Crustacean cardioactive peptide (CCAP)plays a key role in the initiation of the ecdysis motor program. We have used Drosophila bearing targeted ablations of CCAP neurons (CCAP KO animals) to investigate the role of CCAP in the execution and circadian regulation of ecdysis. CCAP KO animals showed specific defects at ecdysis, yet the severity and nature of the defects varied at different developmental stages. The majority of CCAP KO animals died at the pupal stage from the failure of pupal ecdysis, whereas larval ecdysis and adult eclosion behaviors showed only subtle defects. Interestingly, the most severe failure seen at eclosion appeared to be in a function required for abdominal inflation, which could be cardioactive in nature. Although CCAP KO populations exhibited circadian eclosion rhythms, the daily distribution of eclosion events (i.e.,gating) was abnormal. Effects on the execution of ecdysis and its circadian regulation indicate that CCAP is a key regulator of the behavior. Nevertheless, an unexpected finding of this work is that the primary functions of CCAP as well as its importance in the control of ecdysis behaviors may change during the postembryonic development of Drosophila.

Functional Dissection of a Neuronal Network Required for Cuticle Tanning and Wing Expansion inDrosophila

“…Kir2.1 thus appears to be a more effective suppressor of N CCAP function than reaper, which had a pupal mortality rate of 79% (283 of 357 animals) in parallel crosses. The survival of adults expressing reaper likely results from incomplete killing of N CCAP neurons in some animals, as reported previously by Park et al (2003). However, we observed no loss of N CCAP neurons in pharate adults expressing 3ϫ EKO (Fig.…”

“…The temperature sensitivity of Shi ts1 allows dynamin function to be acutely inhibited by shifting flies to the restricted temperature. Park et al (2003) have reported previously that expression of UAS-Shi ts1 within N CCAP yields flies with the juvenile phenotype. However, because suppression of dynamin function in these experiments was constitutive rather than acute, with flies raised at the restricted temperature, the observed phenotypes may have derived from pleiotropic developmental defects distinct from suppression of synaptic transmission (Kitamoto, 2001).…”

“…The restriction of bursicon expression to N CCAP in late-stage pharate adults implies that the mechanisms of bursicon release can be studied by targeted manipulation of N CCAP physiology using the CCAP-Gal4 driver introduced by Park et al (2003) in conjunction with appropriate UASeffector constructs. Previously, we have demonstrated the efficacy of targeted suppression of neuronal excitability in analyzing neuronal function (White et al, 2001;Nitabach et al, 2002).…”

The unfulfilled/DHR51 gene of Drosophila melanogaster modulates wing expansion and fertility

“…Two pathways participate in wing expansion; a neuroendocrine cascade (McNabb et al, 1997;Park et al, 2003;Dewey et al, 2004;Luan et al, 2006) and tissue remodeling of the wing itself (Kiger et al, 2007). Given the neural localization of unf transcripts, the three sets of peptidergic neurons that comprise the neuroendocrine cascade that regulates wing expansion behaviors are candidates that may be responsible for the wing expansion defects of unf mutants.…”

Huntingtin Aggregation Kinetics and Their Pathological Role in aDrosophilaHuntington’s Disease Model

“…We expressed mRFPHttQ138 using CCAP-GAL4 that expresses in a single neuron per hemisegment (Park et al 2003;Vomel and Wegener 2007). This driver allows single-cell resolution for assaying how soluble HttQ138 interacts with larger aggregates.…”