PROJECT SUMMARY / ABSTRACT
Arsenic exposure from well water and food is a major public health concern. Early life (e.g., prenatal) exposure
to low level arsenic increases risk of developing psychiatric disorders such as depression and anxiety in
adulthood. Arsenic is an endocrine disruptor and available evidence suggests that its psychopathological effects
stem from interference with glucocorticoid receptor (GR) signaling; however, gaps remain in our understanding
of the underlying mechanisms. Krüppel-like factor 9 (Klf9) is a transcription factor important for neurogenesis
and metabolic regulation and is a regulatory hub at the junction of multiple endocrine and cellular stress signaling
pathways. KLF9 has been implicated in stress-induced psychopathology and neurodegeneration. We and others
have shown that Klf9 is a feedforward regulator of GR signaling. We have obtained preliminary data indicating
that the GR-Klf9 gene regulatory pathway is perturbed in zebrafish embryos exposed to low-level arsenic, This
exploratory/developmental research project will use zebrafish as a model system to test the hypothesis that
chronic early life exposure to low levels of arsenic increases risk of depression and/or other psychiatric disorders
by developmentally altering homeostatic setpoints to persistently impede GR- and/or Klf9-dependent stress
responsivity, resulting in long-term loss of plasticity and dysfunction. Zebrafish are an ideal model system for the
proposed studies as they share all the relevant genes and neuroendocrine signaling pathways with humans, and
are social, diurnal animals with complex behaviors that can be measured and related to human psychology and
stress-responsive behavior. Moreover, the larvae provide unsurpassed access for experimental manipulation
and observation, and transgenic reporter lines for monitoring GR and brain activity by fluorescence microscopy.
The proposed research will use those tools, as well as a klf9 and GR-knockout lines that we recently created
using CRISPR, to accomplish two specific aims. The first is to determine if chronic exposure to arsenic results
in long-term glucocorticoid resistance and increased neuroinflammation. To that end we will assess the effects
of chronic arsenic exposure during early development on basal and stress-induced activity of GR target genes
and inflammation markers in larvae and adult brain tissue, as well as on larval and adult cortisol levels. The
second specific aim is to determine if chronic developmental exposure to low level arsenic results in aberrant
brain activity and behaviors. To accomplish this, we will use fluorescence microscopy and automated movement
tracking to ask how chronic developmental exposure to low-level arsenic affect brain development, basal and
stress-responsive neuronal activity in parts of the larval brain that regulate neuroendocrine stress signaling, and
behavior of the exposed larvae across the lifespan. The project will open a new avenue for future research
focused on the mechanisms underlying the the pathophysiological effects of early life arsenic exposure on the
neuroendocrine stress system.
