Austin P. Dreyer, PhD

Research

Bottle of Flies
Bottle of developing Drosophila pupae

The core theme of my research is understanding how organisms obtain and then utilize nutrients. To study aspects of feeding and metabolism, I use the model organism, Drosophila melanogaster, and the range of genetic manipulations uniquely possible in the easy to care for fruit fly. The overlap in genetic and physiological controls between mammals and fruit flies also makes Drosophila an attractive system to address fundamental questions about how all animals function (and you don't have to take my word for it!).

Currently, I am working on several projects studying feeding behaviors and metabolism in a circadian context at Loyola University of Chicago (LUC) while keeping one foot firmly rooted in the evolutionary-developmental research of my PhD studying morphological evolution at Michigan State University (MSU).

Regulation of Circadian Feeding Rhythms

Circadian patterns of behavioral and physiological activity are ubiquitous across nearly all biological life, from single-celled cyanobacteria, up through plants, fungi, and animals. The synchronization of activity patterns to the 24 hour cycles of a day on Earth is the result of endogenous molecular clocks that track time using feedback loops of specific proteins rather than hands on an actual clock. By tapping into that molecular machinery, organisms are able to properly time when to move, eat, sleep, reproduce, etc.

For decades, Drosophila locomotion has been used to study circadian control of rest:activity patterns, uncovering the core molecular clock present across taxa in the process. As technology continues to advance additional behaviors have become tractable, including the ability to automatically record feeding in flies over the course of a week or more. The Fly Liquidfood Interaction Counter (FLIC) uses electrical charges to measure when a fly feeds from a liquid food source while standing on a charged metal disc. Using this newly-developed system one major component of my research is understanding molecular and genetic regulation of circadian feeding rhythms.

FLIC monitors in incubator
Fly Liquidfood Interaction Counter (FLIC) monitors in action

Entrainment of Circadian Clocks by Food Availability

It is well established that a host of taxa posses an internal clock that helps align activity to the 24 hour period of a day. It is also true that the exact period of an organisms internal clock deviates slightly from 24 hours, representative of the adaptability of the clock to accommodate environmental variation, such as seasonal changes in day length. To keep the endogenous clock aligned with prevailing environmental conditions, certain stimuli have the capacity to "carry along" the clock in alignment with the environment in a process called entrainment. Light exposure is the most obvious of entrainment signals, also called zeitgebers (= "time givers" in German), an environmental signal that enables organisms to be in exact alignment with the rest of their surroundings.

Feeding entrainment apparatus v3.0
Using 3D printed plastics, a Drosophila Activity Monitor (DAM), Legos©, and an Arduino microcontroller to study feeding entrainment!

Food availability is another zeitgeber that has been demonstrated in several vertebrate systems, but how food entrainment works is unclear, partially due to the complexity of the animals being studied. Understanding the mechanisms by which consumption of nutrition coordinates behavioral and physiological cycles of activity is a promising avenue of research that may be able to address the continued epidemic of metabolic disorders across the world. Given the homologies between fruit flies and mammals, I am working to use Drosophila to unravel the pathways of food entrainment in a less complex system, the findings of which can then be applied to vertebrates. To investigate food entrainment in flies, I have collaborated with the engineering department at LUC to 3D print a custom food well-plate that allows me to control when flies are able to eat while simultaneously recording their activity patterns via a Drosophila Activity Monitor (DAM).

Morphological Evolution and the Regulation of Trait Size

The evolution of morphological variation across taxa is largely a question of changes in the proportional size between the same or similar sets of traits rather than the evolution of novel features. To study the proportional size of traits in relation to one another, also called allometries, I focused on the growth and development of male Drosophila melanogaster genitalia which exhibit a particular scaling relationship with overall body size that is distinct from most other traits. I also developed a mathematical model of proportional trait development to probe the theoretical ability of traits to evolve in covariation with one another within a single body plan. The results of my dissertation indicated that the regulation of trait development plays a key role in the evolutionary trajectories of those same traits. Allometries were the focus of my dissertation work at MSU, and are an area of research that I hope to continue exploring throughout my scientific career.