Recent CIG publications Archive

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PLoS One.: co-auth.: group Fajas

 2018 Feb 14;13(2):e0192314. doi: 10.1371/journal.pone.0192314. eCollection 2018.

Chromatin immunoprecipitation improvements for the processing of small frozen pieces of adipose tissue.

Abstract

Chromatin immunoprecipitation (ChIP) has gained importance to identify links between the genome and the proteome. Adipose tissue has emerged as an active tissue, which secretes a wide range of molecules that have been related to metabolic and obesity-related disorders, such as diabetes, cardiovascular failure, metabolic syndrome, or cancer. In turn, epigenetics has raised the importance in discerning the possible relationship between metabolic disorders, lifestyle and environment. However, ChIP application in human adipose tissue is limited by several factors, such as sample size, frozen sample availability, high lipid content and cellular composition of the tissue. Here, we optimize the standard protocol of ChIP for small pieces of frozen human adipose tissue. In addition, we test ChIP for the histone mark H3K4m3, which is related to active promoters, and validate the performance of the ChIP by analyzing gene promoters for factors usually studied in adipose tissue using qPCR. Our improvements result in a higher performance in chromatin shearing and DNA recovery of adipocytes from the tissue, which may be useful for ChIP-qPCR or ChIP-seq analysis.

PMID: 29444131

 

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Nat Commun.: auth.: group Thorens

 2018 Feb 7;9(1):546. doi: 10.1038/s41467-018-03034-0.

α-cell glucokinase suppresses glucose-regulated glucagon secretion.

Abstract

Glucagon secretion by pancreatic α-cells is triggered by hypoglycemia and suppressed by high glucose levels; impaired suppression of glucagon secretion is a hallmark of both type 1 and type 2 diabetes. Here, we show that α-cell glucokinase (Gck) plays a role in the control of glucagon secretion. Using mice with α-cell-specific inactivation of Gck (αGckKO mice), we find that glucokinase is required for the glucose-dependent increase in intracellular ATP/ADP ratio and the closure of KATP channels in α-cells and the suppression of glucagon secretion at euglycemic and hyperglycemic levels. αGckKO mice display hyperglucagonemia in the fed state, which is associated with increased hepatic gluconeogenic gene expression and hepatic glucose output capacity. In adult mice, fed hyperglucagonemia is further increased and glucose intolerance develops. Thus, glucokinase governs an α-cell metabolic pathway that suppresses secretion at or above normoglycemic levels; abnormal suppression of glucagon secretion deregulates hepatic glucose metabolism and, over time, induces a pre-diabetic phenotype.

PMID: 29416045

 

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J Clin Invest.: co-auth.: PAF

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Oncogene.: co-auth.: W.Wahli

 2018 Jan 25. doi: 10.1038/s41388-017-0109-8. [Epub ahead of print]

ROS release by PPARβ/δ-null fibroblasts reduces tumor load through epithelial antioxidant response.

Tan EHP1Sng MK2,3How ISB2Chan JSK2Chen J3Tan CK3Wahli W3,4,5Tan NS6,7,8,9.

Abstract

Tumor stroma has an active role in the initiation, growth, and propagation of many tumor types by secreting growth factors and modulating redox status of the microenvironment. Although PPARβ/δ in fibroblasts was shown to modulate oxidative stress in the wound microenvironment, there has been no evidence of a similar effect in the tumor stroma. Here, we present evidence of oxidative stress modulation by intestinal stromal PPARβ/δ, using a FSPCre-Pparb/d-/- mouse model and validated it with immortalized cell lines. The FSPCre-Pparb/d-/- mice developed fewer intestinal polyps and survived longer when compared with Pparb/dfl/fl mice. The pre-treatment of FSPCre-Pparb/d-/- and Pparb/dfl/fl with antioxidant N-acetyl-cysteine prior DSS-induced tumorigenesis resulted in lower tumor load. Gene expression analyses implicated an altered oxidative stress processes. Indeed, the FSPCre-Pparb/d-/- intestinal tumors have reduced oxidative stress than Pparb/dfl/fl tumors. Similarly, the colorectal cancer cells and human colon epithelial cells also experienced lower oxidative stress when co-cultured with fibroblasts depleted of PPARβ/δ expression. Therefore, our results establish a role for fibroblast PPARβ/δ in epithelial-mesenchymal communication for ROS homeostasis.

PMID: 29367760

 

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Mol Ecol.: co-auth.: GTF

 2017 Jan;26(1):259-276. doi: 10.1111/mec.13861. Epub 2016 Oct 14.

MC1R variants affect the expression of melanocortin and melanogenic genes and the association between melanocortin genes and coloration.

Abstract

The melanocortin-1 receptor (MC1R) gene influences coloration by altering the expression of genes acting downstream in the melanin synthesis. MC1R belongs to the melanocortin system, a genetic network coding for the ligands that regulate MC1R and other melanocortin receptors controlling different physiological and behavioural traits. The impact of MC1R variants on these regulatory melanocortin genes was never considered, even though MC1R mutations could alter the influence of these genes on coloration (e.g. by decreasing MC1R response to melanocortin ligands). Using barn owl growing feathers, we investigated the differences between MC1R genotypes in the (co)expression of six melanocortin and nine melanogenic-related genes and in the association between melanocortin gene expression and phenotype (feather pheomelanin content). Compared to the MC1R rufous allele, responsible for reddish coloration, the white allele was not only associated with an expected lower expression of melanogenic-related genes (TYR, TYRP1, OCA2, SLC45A2, KIT, DCT) but also with a lower MC1R expression and a higher expression of ASIP, the MC1R antagonist. More importantly, the expression of PCSK2, responsible for the maturation of the MC1R agonist, α-melanocyte-stimulating hormone, was positively related to pheomelanin content in MC1R white homozygotes but not in individuals carrying the MC1R rufous allele. These findings indicate that MC1R mutations not only alter the expression of melanogenic-related genes but also the association between coloration and the expression of melanocortin genes upstream of MC1R. This suggests that MC1R mutations can modulate the regulation of coloration by the pleiotropic melanocortin genes, potentially decoupling the often-observed associations between coloration and other phenotypes.

KEYWORDS:

barn owl; colour genetics; colour polymorphism; gene expression; melanin; pleiotropy

PMID: 27664794

 

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Clin Genet.: co-auth.: group Reymond

 2018 Jan 25. doi: 10.1111/cge.13194. [Epub ahead of print]

Intellectual developmental disorder with cardiac arrhythmia syndrome in a child with compound heterozygous GNB5 variants.

Abstract

Identification of a novel compound heterozygous of GNB5 in a patient with intellectual developmental disorder with cardiac arrhytmia (IDDCA), from non-consaguineous family. Three-dimensional modelling and in silico predictions suggest that GNB5 variants are causative of the phenotype, extending the number of IDDCA patients so far identified.

KEYWORDS:

GNB5; ID; IDDCA; LADCI; cardiac arrhythmia

PMID: 29368331