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DEB – Developmental timing, Environment, and Behaviors

Our interest focuses on understanding how does the environment interact with the genes to times the Juvenile-to-adult DevelopmentalTransition (JDT) and its associated behaviors. The JDT  (Metamorphosis/ puberty) determines the reproductive ability for a given species. Therefore, uncovering the mechanism timing this developmental transition is essential to improve pest management efficiency but also, in the case of human, to battle against adverse health consequences caused by earlier puberty.

 Background:

Environmental modulation of the Neuroendocrine Circuitry: Development and Behaviors. In insects and mammals, the juvenile-to-adult transition is trigger by a burst of steroid hormones production instructed by the brain neuroendocrine circuitry. The precise timing of hormonal burst is defined in the brain by a dynamic interplay between genes and the environment, which take place from the embryo till the juvenile ages. During this interplay, the brain is the final tissue, which integrates internal and environmental signals to triggers the onset of JDT. Due to this long-term back-and-forth between internal and external milieu, our knowledge of the regulation of the neurohormonal circuitry activity is incomplete. Therefore, our main interest focuses on understanding how do the environmental and internal cues modulate the activity of the neuroendocrine circuitry during the developmental period to times JDT and coordinates its associated behaviors.

Biological Model:

We use Drosophila melanogaster as our favorite model due to its ease use for genetic modifications that enabled the identification of novel conserved genes. The life cycle of Drosophila can be classified in four distinct phases: the embryonic developmental phase, juvenile growth phase, prepupa and pupa maturation phase (metamorphosis) and adult stage. Sexual maturation in Drosophila and other holometabolous insects occurs during pupariation stages through a process named metamorphosis.

Scientific originality of the team:

Despite the physiological divergence between insects and mammals, studies have shown that insect metamorphosis and mammalian puberty exhibit similar neuroendocrine design principles and pathways, suggesting the existence of common regulatory signals controlling JDT onset between them. Indeed, we just identified a conserved brain circuitry regulating steroid hormones production and the timing of JDT in both mammals and Drosophila melanogaster. This, in combination with the genetic amenability of flies, has made Drosophila a top-choice model for our team to study the instructive role of the brain on timing juvenile-to-adult developmental transition.

Research topics and objectives:

(i) Define the environmental signals timing JDT: 

By performing unbiased genetic RNAi screens, we will identify the environmental signals involved in the activation of the neuroendocrine circuit at the onset of JDT. Besides, D. melanogaster shows a close relation with D. suzukii, suggesting that genes identified in this project could be conserved between those species, offering possible new targets for the development of bio-pesticides. 

(ii) Assess the communication between the neurons and the gland cells: 

The neuroendocrine circuit projects its axon into the prothoracic gland, where it secretes a neuropeptide to stimulate the production of steroid hormones. We take advantage of this simple brain-gland model to assess how do neuropeptides stimulate glands; and whether adverse environmental conditions could strengthen or weaken this communication to define JDT timing.

(iii) Determine the coordination between the developmental and behavioral programs. We are currently developing different strategies to test how does the behavioral program is set up and coordinated with the developmental program. Indeed, in most animals, JDT is accompanied by multiple behavioral changes leading towards exploring and engaging in social complexities.

Scientific and social issues

Understanding the mechanism timing the onset of this transition is essential for public health but also agriculture. For instance, slow-down of the exponential insect population growth is crucial to improve pest management strategies, and this also impacts medical research if the insect is a vector for dangerous diseases like dengue. Moreover, knowledge about the JDT timing mechanism is indispensable to battle against a current trend for earlier initiation of puberty, which causes several adverse health consequences.