Circadian Disruption in Genes, Brain, and Behavior
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Authors
Hui, Cassandra
Issue Date
2024
Type
Dissertation
Language
Keywords
Alternative Title
Abstract
Escalating urbanization and the ensuing proliferation of artificial light at night (ALAN) are profoundly altering the natural cycles of light and darkness that have long governed the behavior and biochemical processes of organisms. This disruption to circadian rhythms, our intrinsic biological clocks, poses significant health risks, including sleep disorders, metabolic dysfunctions, and increased susceptibility to chronic diseases. Understanding the mechanisms of circadian disruption and its broad implications is crucial, particularly as the modern world becomes increasingly illuminated. My dissertation delves into the effects of ALAN on circadian rhythms, employing Drosophila melanogaster (fruit flies) and Taeniopygia guttata (zebra finches) as model organisms to explore these impacts at molecular, neuronal, and behavioral levels. Chapter 1 introduces the conserved protein YIPPEE, likely involved in immune function, in Drosophila and shows downregulation of Yippee expression lengthens the circadian period and influences key clock genes. This suggests potential links between circadian systems and immune-related processes. Chapter 2 maps neuronal activation responses to ALAN in zebra finches through immediate early genes (IEGs) expression across 24 brain regions. These results uncover the differential activation of brain regions involved in vision, movement, learning, memory, pain processing, and hormone regulation under ALAN exposure. Chapter 3 shows that social interactions exacerbate ALAN-induced circadian disruptions. Birds housed together under ALAN experience increased desynchronization of brain and liver timing and advanced activity onset, the first demonstration of social dynamics modulating the molecular clock in vertebrates.