Zebrafish Mutant Lines Reveal the Interplay between nr3c1 and nr3c2 in the GC-Dependent Regulation of Gene Transcription

Abstract

Glucocorticoids mainly exert their biological functions through their cognate receptor, encoded by the nr3c1 gene. Here, we analysed the glucocorticoids mechanism of action taking advantage of the availability of different zebrafish mutant lines for their receptor. The differences in gene expression patterns between the zebrafish gr knock-out and the grs357 mutant line, in which a point mutation prevents binding of the receptor to the hormone-responsive elements, reveal an intricate network of GC-dependent transcription. Particularly, we show that Stat3 transcriptional activity mainly relies on glucocorticoid receptor GR tethering activity: several Stat3 target genes are induced upon glucocorticoid GC exposure both in wild type and in grs357/s357 larvae, but not in gr knock-out zebrafish. To understand the interplay between GC, their receptor, and the mineralocorticoid receptor, which is evolutionarily and structurally related to the GR, we generated an mr knock-out line and observed that several GC-target genes also need a functional mineralocorticoid receptor MR to be correctly transcribed. All in all, zebrafish mutants and transgenic models allow in vivo analysis of GR transcriptional activities and interactions with other transcription factors such as MR and Stat3 in an in-depth and rapid way.

STAT3 and HIF1α cooperatively mediate the transcriptional and physiological responses to hypoxia

“…Zebrafish is an in vivo model in which the pathophysiological roles of HIF1α and JAK/STAT signalling have been extensively studied (Santhakumar et al ., 2012; Gerri et al, 2017; Gerri et al ., 2018; Vettori et al ., 2017; Marchi et al ., 2020; Liu et al, 2017; Peron et al ., 2020; Peron et al ., 2021; Dinarello et al ., 2022). Thus, it appeared as a valid platform to analyze the STAT3-HIF1α crosstalk.…”

Dexamethasone and OLT1177 Cooperate in the Reduction of Melanoma Growth by Inhibiting STAT3 Functions

“…Additionally, STAT3 can be phosphorylated at the level of S727, which mainly regulates mitochondrial functions of STAT3 [56,57]. Although STAT3 is also regulated by glucocorticoids, these hormones can positively or negatively affect the activity of STAT3 [58,59]. As shown in Figure 1D,E, phosphorylation of S727 and Y705 in the tumors are significantly reduced by the combination of OLT1177 and dexamethasone compared to mice treated with the vehicle, whereas total STAT3 is unaffected.…”

Glucocorticoid Signaling Pathway: From Bench to Bedside

“…Using zebrafish as an animal model, Dinarello et al compared the GR-mediated gene expression profile among different zebrafish lines, including the wild-type, the gr knock-out, and a mutant line harboring a point mutation that prevented the DNA binding of the receptor [ 18 ]. They also investigated the role of the zebrafish mineralocorticoid receptor (MR) in regulating GR-mediated transcriptional activity.…”

“…Independently of the molecular mechanism, MR seems to play a fundamental role in the expression of GR target genes. Finally, the authors highlighted the validity of zebrafish as an in vivo model to study the transcriptional activity of GR [ 18 ].…”