Characterization of a Neuroendocrine Network That Coordinates Sugar and Water Ingestion in Drosophila melanogaster

Consumption of food and water is tightly regulated by the nervous system to maintain internal nutrient homeostasis. Although generally considered independently, interactions between hunger and thirst drives are important to coordinate competing needs. In chapter 1, I provide a review of hunger regulation and thirst regulation in mammals and Drosophila melanogaster. I then discuss the neural and hormonal coordination of hunger and thirst in both mammals and D. melanogaster.In Drosophila, four neurons called the Interoceptive Subesophageal zone Neurons (ISNs) respond to intrinsic hunger and thirst signals to oppositely regulate sucrose and water ingestion. In chapter 2, I characterize the neural circuit downstream of the ISNs. This work is presented in the form of a preprint first author manuscript. Using the fly brain connectome, genetic tools, behavioral assays, and functional imaging, I show, together with co-authors Gina Pontes, Nicholas Jourjine and Alexander Del Toro, that the ISNs modulate a peptidergic network of neurons. These include a novel cell type Bilateral T shaped neuron (BiT), insulin producing cells (IPC), crustacean cardioactive peptide (CCAP) neurons, and CCHamide-2 receptor isoform RA (CCHa2R-RA) neurons. These neurons contribute differentially to ingestion of sugar and water, with BiT, IPCs and CCAP neurons oppositely regulating sugar and water ingestion, and CCHa2R-RA neurons modulating only water ingestion. Thus, the decision to consume sugar or water occurs via regulation of a broad peptidergic network that integrates internal signals of nutritional state to generate nutrient-specific ingestion.In chapter 3, I characterize other neurons that are involved in sugar and/or water ingestion. Using a computational approach to identify neurons in close proximity, genetic manipulation, behavioral assays, and in vivo functional imaging, I characterized several neurons involved in sugar and/or water ingestion regulation. Aster, bidirectionally regulates sugar and water ingestion just as the ISNs, Horseshoe, decreases both sugar and water ingestion, and Cowboy likely promotes sugar ingestion. In vivo functional connectivity experiments revealed that they were not downstream of the ISNs, however, Aster, possibly Horseshoe, and another cell type Gallinule are downstream of sensory neurons. Thus, I have identified another cell type that bidirectionally regulates sugar and water ingestion, two cell types that modulate feeding, and a cell type that likely conveys gustatory information to memory centers in the fly brain.In chapter 4, I describe with co-authors Zoila Alvarez-Aponte, Rachel Brem, Diana Bautista and Denzil Streete, the development and implementation of the Inclusive Excellence in Quals Prep (IEQP) program. This program was designed to provide mentorship, community, and academic support for students from diverse backgrounds as they prepared for their QE. The main components for IEQP program included pairing students with graduate student mentors, academic and wellness workshops, and community building events. This program was first implemented on a pilot cohort of 11 graduate students. After program evaluation, the most significant component of the program was peer mentorship. After program completion, students’ perception of their preparedness, QE-related skills, the support received from their advisors, and the agency they felt over their proposed work increased.In the final part of this dissertation, chapter 5, I summarize the main findings of this dissertation and propose future directions for exploration

Hunger- and thirst-sensing neurons modulate a neuroendocrine network to coordinate sugar and water ingestion

Consumption of food and water is tightly regulated by the nervous system to maintain internal nutrient homeostasis. Although generally considered independently, interactions between hunger and thirst drives are important to coordinate competing needs. In Drosophila, four neurons called the interoceptive subesophageal zone neurons (ISNs) respond to intrinsic hunger and thirst signals to oppositely regulate sucrose and water ingestion. Here, we investigate the neural circuit downstream of the ISNs to examine how ingestion is regulated based on internal needs. Utilizing the recently available fly brain connectome, we find that the ISNs synapse with a novel cell-type bilateral T-shaped neuron (BiT) that projects to neuroendocrine centers. In vivo neural manipulations revealed that BiT oppositely regulates sugar and water ingestion. Neuroendocrine cells downstream of ISNs include several peptide-releasing and peptide-sensing neurons, including insulin producing cells (IPCs), crustacean cardioactive peptide (CCAP) neurons, and CCHamide-2 receptor isoform RA (CCHa2R-RA) neurons. These neurons contribute differentially to ingestion of sugar and water, with IPCs and CCAP neurons oppositely regulating sugar and water ingestion, and CCHa2R-RA neurons modulating only water ingestion. Thus, the decision to consume sugar or water occurs via regulation of a broad peptidergic network that integrates internal signals of nutritional state to generate nutrient-specific ingestion

Fly Cell Atlas: A single-nucleus transcriptomic atlas of the adult fruit fly.

For more than 100 years, the fruit fly Drosophila melanogaster has been one of the most studied model organisms. Here, we present a single-cell atlas of the adult fly, Tabula Drosophilae, that includes 580,000 nuclei from 15 individually dissected sexed tissues as well as the entire head and body, annotated to >250 distinct cell types. We provide an in-depth analysis of cell type-related gene signatures and transcription factor markers, as well as sexual dimorphism, across the whole animal. Analysis of common cell types between tissues, such as blood and muscle cells, reveals rare cell types and tissue-specific subtypes. This atlas provides a valuable resource for the Drosophila community and serves as a reference to study genetic perturbations and disease models at single-cell resolution

Fly Cell Atlas: A single-nucleus transcriptomic atlas of the adult fruit fly

For more than 100 years, the fruit fly Drosophila melanogaster has been one of the most studied model organisms. Here, we present a single-cell atlas of the adult fly, Tabula Drosophilae , that includes 580,000 nuclei from 15 individually dissected sexed tissues as well as the entire head and body, annotated to >250 distinct cell types. We provide an in-depth analysis of cell type–related gene signatures and transcription factor markers, as well as sexual dimorphism, across the whole animal. Analysis of common cell types between tissues, such as blood and muscle cells, reveals rare cell types and tissue-specific subtypes. This atlas provides a valuable resource for the Drosophila community and serves as a reference to study genetic perturbations and disease models at single-cell resolution