Identification and Functional Characterization of The Neuronal Pathway Regulating Insect Steroid Hormone Biosynthesis
Bibliographic record
Abstract
Steroid hormones are key players for many aspects of development, growth, and reproduction in multicellular organisms.In insects, the principal steroid hormones, ecdysteroids, coordinate growth and maturation.In Drosophila, a peak in ecdysteroid concentration triggers developmental transitions culminating with molting and metamorphosis.Moreover, recent studies shed light on the basal levels of ecdysteroids, which negatively affect body growth prior to maturation.Ecdysteroid biosynthesis in the prothoracic gland (PG) is affected by several signals, especially neuronal signals, and controls the proper timing of growth and maturation.The prothoracicotropic hormone (PTTH)-producing neurons and serotonergic SE0PG neurons innervate the PG, regulating ecdysteroid biosynthesis.However, only these two types of neurons may not account for the precise timing of basal and peak of ecdysteroid biosynthesis in response to the complex combination of environmental stimuli.Consequently, I hypothesized that other neuronal regulatory systems must exist in the PG.Based on this hypothesis, I aimed to identify and characterize novel PG-innervating neurons.Using the FlyLight database, I found several types of PG-innervating neurons that have not yet been fully characterized.Among these neurons, I focused on three pairs of Corazonin (Crz)-producing neurons, which contact PTTH neurons and PG cells.Inhibition of Crz neuronal activity increased pupal size, whereas it had little effect on pupariation timing.This phenotype resulted from enhanced growth and a delay in basal ecdysteroid elevation during the mid-third instar larval (L3) stage.Silencing of Crz in Crz neurons resulted in increased levels of bantam microRNA, which represses basal ecdysteroid biosynthesis.To examine whether PG cells receive Crz, I visualized the expression of CrzR.Unexpectedly, CrzR was expressed in PTTH neurons rather than PG cells.Silencing of CrzR in PTTH neurons exhibited increased pupal size, phenocopying the inhibition of Crz neurons.Interestingly, Crz receptor (CrzR) expression in PTTH neurons was higher during the mid-L3 stage than during the late-L3 stage.When Crz neurons were optogenetically activated, a strong calcium response was observed in PTTH neurons in the mid-, but not the late-L3 stage larvae brains.These data suggest that the Crz-PTTH neuronal axis modulates basal, but not peak ecdysteroid biosynthesis.Most significantly, this study uncovered a regulatory neuronal system affecting ecdysteroid biosynthesis in a developmental stage-specific manner.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".