Krüppel-like Factor 9 Is a Feed-forward Regulator of Glucocorticoid Signaling

Epidemiological studies show that children of chronically stressed mothers are at higher risk for adverse health outcomes throughout life, but the pathological mechanisms underlying this increased risk remain poorly understood. Using zebrafish as a model system, the Coffman Lab at the MDI Biological Laboratory showed in 2016 that larvae exposed to chronically elevated levels of the glucocorticoid (GC) stress hormone cortisol exhibit elevated pro-inflammatory gene expression. Further, the Coffman Lab showed that immune gene response to injury or infection was blunted in adult fish raised from cortisol treated larvae, presenting a novel paradigm for the investigation of disease mechanisms involving chronic GC exposure during development. The two most consistently overexpressed GC targets in the 2016 study and follow-up experiments were fkbp5, a well-known regulator of the receptor for cortisol (the glucocorticoid receptor, or GR, a nuclear hormone receptor), and the transcription factor Krüppel-Like Factor 9 (Klf9). The Krüppel-Like family of transcription factors is known to include effectors of nuclear receptor signaling, but less is known about the role of Klf9 in GC signaling. Thus, I used CRISPR to generate a mutant zebrafish line lacking functional Klf9. Using this knockout line we discovered that klf9 mediates aspects of the physiological response to GC signaling by 1) facilitating immune gene response to cortisol, 2) repressing the expression of GR regulator fkbp5, and 3) regulating metabolism downstream of hormone signal. These results are described in detail in the following chapters