Activation of Male Liver Chromatin Accessibility and STAT5-Dependent Gene Transcription by Plasma Growth Hormone Pulses

Abstract

Sex differences in pituitary growth hormone (GH) secretion (pulsatile in males vs near continuous/persistent in females) impart sex-dependent expression to hundreds of genes in adult mouse liver. Signal transducer and activator of transcription (STAT) 5, a GH-activated transcription factor that is essential for liver sexual dimorphism, is dynamically activated in direct response to each male plasma GH pulse. However, the impact of GH-induced STAT5 pulses on liver chromatin accessibility and downstream transcriptional events is unknown. In this study, we investigated the impact of a single pulse of GH given to hypophysectomized mice on local liver chromatin accessibility (DNase hypersensitive site analysis), transcription rates (heterogeneous nuclear RNA analysis), and gene expression (quantitative polymerase chain reaction and RNA sequencing) determined 30, 90, or 240 minutes later. The STAT5-dependent but sex-independent early GH response genes Igf1 and Cish showed rapid, GH pulse-induced increases in chromatin accessibility and gene transcription, reversing the effects of hypophysectomy. Rapid increases in liver chromatin accessibility and transcriptional activity were also induced in hypophysectomized male mice for some (Ces2b, Ugt2b38) but not for other liver STAT5-dependent male-biased genes (Cyp7b1). Moreover, in pituitary-intact male mice, Igf1, Cish, Ces2b, and Ugt2b38 all showed remarkable cycles of chromatin opening and closing, as well as associated cycles of induced gene transcription, which closely followed each endogenous pulse of liver STAT5 activity. Thus, the endogenous rhythms of male plasma GH pulsation dynamically open and then close liver chromatin at discrete, localized regulatory sites in temporal association with transcriptional activation of Igf1, Cish, and a subset of STAT5-dependent male-biased genes.

Will the real bile acid sulfotransferase please stand up? Identification of Sult2a8 as a major hepatic bile acid sulfonating enzyme in mice

“…Although Sult2a1 may be important for LCA sulfonation in mice, the results suggest that Sult2a8 plays a prominent role, particularly in males. Indeed, interrogation of publically available RNA-SEQ data (Gene Expression Omnibus GSE93380) (22) for livers of chow-fed adult male and female CD-1 mice reveals a striking difference in the hepatic mRNA expression of Sult2a8 versus other Sult2a family members (Fig. 1B).…”

Long non-coding RNA Gm15441 attenuates hepatic inflammasome activation in response to metabolic stress

“…Data were analyzed using a custom RNA-seq analysis pipeline (Connerney et al, 2017) as described elsewhere (Lodato et al, 2017). Briefly, sequence reads were mapped to the mouse genome (release mm9) using TopHat2 (v2.1.1) (Kim et al, 2013).…”

“…Briefly, sequence reads were mapped to the mouse genome (release mm9) using TopHat2 (v2.1.1) (Kim et al, 2013). Genomic regions that contain exonic sequence in at least one isoform of a gene (exon collapsed regions; (Connerney et al, 2017)) were defined for each RefSeq gene and for each lncRNA gene. HTSeq (0.6.1p1) was then used to obtain read counts for exon collapsed regions of RefSeq genes, and featureCounts (1.4.6-p5) was used to obtain read counts for exon collapsed regions of lncRNA genes.…”

Sex-biased long non-coding RNAs negatively correlated with sex-opposite protein coding gene co-expression networks in Diversity Outbred mouse liver

“…Sex-specific liver gene expression does not, however, become widespread until puberty [30,31]. Surgical removal of the pituitary gland by hypophysectomy (hypox) in mice, and rats, identifies two major classes of sexbiased genes in each sex, based on their responses to the loss of GH and other pituitary hormones [32,33]. Male class 1 and female class 1 liver sex-specific genes are activated by the GH secretion pattern of the sex where they are more highly expressed, whereas, male class 2 and female class 2 liver sexspecific genes are repressed by the GH secretion pattern of the sex where they are less highly expressed ( Fig.…”

“…S1). Consequently, following hypox, class 1 genes are down regulated and class 2 Melia and Waxman, Page 3 2/25/18 genes are de-repressed (up regulated) in mouse liver, which leads to a near global loss of sex-specific gene expression [32,33]. The molecular basis for these distinct hypox response phenotypes is poorly understood.Gene clustering has been used to identify groups of genes (gene modules/gene clusters) whose expression is strongly associated with different molecular phenotypes (gene signatures), including cancer subtypes [34][35][36][37] and various cellular processes [38][39][40].…”