Biology subjects

Cox, R. D.

Publications and source records attributed to Cox, R. D..

7 recordsLinked to original sources

bioRxiv2024

TBX15 regulates a network of immune response genes in adipose tissue and alters fat mass and depot weight in heterozygous knockout mice

Adipose tissue distribution in the body is an indicator of metabolic disease risk, independent of body mass index (BMI), and is indirectly measured by waist-hip-ratio (WHR). T-Box transcription factor-15 (TBX15) has been implicated in regulation of adipose distribution in multiple human and mouse studies, and the TBX15-WARS2 genome-wide association study locus has been associated with BMI-adjusted-WHR signals in multiple investigations. As a potential mediator of this signal, we investigated the role of Tbx15 using heterozygous and homozygous mouse knockout models to determine if loss of this gene alters adipose physiology, and to identify the transcriptional network regulated by Tbx15 in adipose tissue and preadipocyte cells. In a metabolic phenotyping experiment we provided either low fat diet (LFD) or high fat diet (HFD) to male and female heterozygous Tbx15+/- and wildtype Tbx15+/+mice from weaning and maintained for 24 weeks. Only Tbx15+/-mice maintained on LFD weighed less than wildtype LFD controls, and female LFD Tbx15+/- mice had lower fat mass overall. We found that in LFD Tbx15+/- mice, multiple visceral fat depots weighed less than wildtype controls, and this was maintained when corrected for body mass for both gonadal and mesenteric visceral adipose depots. When comparing adipocyte size in multiple adipose depots, some reduction in number of larger adipocytes was detected in the perirenal adipose tissue of female HFD Tbx15+/- vs Tbx15+/+ mice, mesenteric adipose tissue from female LFD Tbx15+/- vs Tbx15+/+ mice and male HFD Tbx15+/- vs Tbx15+/+mice. RNA-sequencing of subcutaneous (inguinal) adipose tissues from 12-week old male and female knockout Tbx15-/-, Tbx15+/- and Tbx15+/+ mice raised on a standard chow diet identified 897 upregulated genes and 2328 downregulated genes in female Tbx15-/- mice compared to Tbx15+/+mice. We then combined this dataset with TBX15 ChIP-sequencing data from mouse preadipocyte 3T3-L1 cells overexpressing TBX15 to identify a credible set of genes directly regulated by TBX15. These 52 genes were enriched for B- and T-cell receptor signalling, JAK-STAT signalling and haematopoietic cell lineage pathways; suggesting a direct regulatory role for TBX15 in these pathways in adipose tissue. Together, these data highlight a role for TBX15 in regulation of differential adipose tissue expansion, particularly under low caloric conditions. Further, we identify a potentially important role for TBX15 in the well described adipocyte-immune cell crosstalk associated with obesity and type 2 diabetes mellitus.

physiology↗

bioRxiv2024

Loss of RREB1 reduces adipogenesis and improves insulin sensitivity in mouse and human adipocytes

There are multiple independent genetic signals at the Ras-responsive element binding protein 1 (RREB1) locus associated with type 2 diabetes risk, fasting glucose, ectopic fat, height, and bone mineral density. We have previously shown that loss of RREB1 in pancreatic beta cells reduces insulin content and impairs islet cell development and function. However, RREB1 is a widely expressed transcription factor and the metabolic impact of RREB1 loss in vivo remains unknown. Here, we show that male and female global heterozygous knockout (Rreb1+/-) mice have reduced body length, weight, and fat mass on high-fat diet. Rreb1+/- mice have sex- and diet-specific decreases in adipose tissue and adipocyte size; male mice on high-fat diet had larger gonadal adipocytes, while males on standard chow and females on high-fat diet had smaller, more insulin sensitive subcutaneous adipocytes. Mouse and human precursor cells lacking RREB1 have decreased adipogenic gene expression and activated transcription of genes associated with osteoblast differentiation, which was associated with Rreb1+/- mice having increased bone mineral density in vivo. Finally, human carriers of RREB1 T2D protective alleles have smaller adipocytes, consistent with RREB1 loss-of-function reducing diabetes risk.

physiology↗

bioRxiv2023

Mechanisms of the FTO locus association with obesity: Irx3 controls a sumoylation-dependent switch between adipogenesis and osteogenesis

BackgroundIRX3 is implicated in genetic predisposition to obesity via the FTO variant locus. IRX3 shows FTO risk allele-dependent upregulation specifically during early adipogenesis, leading to a shift from energy-dissipation to fat storage in mature adipocytes. However, how changes in IRX3 expression at one developmental stage affect cellular phenotype at a later stage remains unclear. We here hypothesize that IRX3 regulates adipocyte development via transcriptional modulation of epigenetic reprogramming factors. MethodsWe combined ChIP-, ATAC- and RNA-sequencing to map direct Irx3 target genes in regions of open chromatin during early adipogenesis of wild-type and Irx3-KO preadipocytes. Gene ontology analyses was performed to identify significantly enriched biological pathways. Denaturing western blotting was used to assess sumoylation levels, and the inhibitor ML-792 was used to specifically block sumoylation. Luciferase assays were performed to estimate effects of ML-792 on Ppar{gamma} activity. Bodipy lipid staining, immunofluorescence and qPCR were employed to assess adipogenic differentiation in 3D culture. Alkaline phosphatase and Alizarine Red S staining, as well as immunofluorescence and qPCR were used to assess osteogenic differentiation in 3D culture. ResultsWe identified more than 300 Irx3 binding sites in preadipocytes, and these were almost exclusively restricted to promoter regions, with a strong enrichment of genes related to sumoylation, histone modifications and chromatin remodeling. Genes from every step of the sumoylation cycle were bound by Irx3 and differentially expressed in response to Irx3-KO, leading to increased global sumoylation levels in the KO cells. Irx3 ablation and elevated sumoylation inhibited Ppar{gamma} activity and adipogenic differentiation in preadipocytes, both of which could be restored by pharmacological inhibition of sumoylation. The Irx3-KO cells demonstrated reduced epigenetic suppression against osteogenesis, resulting in increased osteogenesis in 3D culture. Finally, osteogenesis induced by Irx3 ablation could partially be reversed by inhibition of sumoylation. ConclusionsOur study has uncovered IRX3 as a novel upstream regulator of sumoylation, and a potent controller of epigenetic regulators, both directly and indirectly via suppressing global sumoylation levels. This study indicates that the FTO locus promotes obesity via IRX3-mediated suppression of sumoylation, which promotes adipogenic commitment and differentiation through epigenetic programming. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=61 SRC="FIGDIR/small/562662v1_figu1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@115feaborg.highwire.dtl.DTLVardef@102a6c0org.highwire.dtl.DTLVardef@111bd1corg.highwire.dtl.DTLVardef@1969061_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2022

Including Phylogenetic Conservatism of Shortgrass Prairie Restoration Desired Species Does Not Improve Species Germination Prediction

PREMISEWe investigated whether phylogenetic conservatism can improve the performance of seed germinability prediction models. Previous studies in tallgrass prairie and alpine meadow revealed that seed morphological traits demonstrate phylogenetic conservatism. We hypothesized that phylogenetic conservatism in seed traits could help predict the seed germinability, under the assumption that seed traits contain phylogenetic signals. METHODSWe measured seed germination percentage and seed morphological traits (seed mass, seed height, and seed surface area) on 34 native species from shortgrass prairie in North America. We supplemented these data with similar data from the literature on 11 more species. We calculated the robustness of the phylogenetic signal of each trait to the number of species sampled. We also compressed the phylogenetic distance matrix to a two-dimensional space, and applied the Akaike information criterion to evaluate the effects of phylogeny on seed germinability prediction models. KEY RESULTSWe found weak but significant phylogenetic signals in seed mass and seed height in the full data set. These phylogenetic signals were not able to improve seed germinability prediction model performance among shortgrass prairie species. Our robustness tests of phylogenetic signals using random sub-sampling showed that the detection rate of phylogenetic signals in seed mass was increased along with the expansion of species pool, and nearly 100% at 40 species. However, the detection rate of phylogenetic signals in seed height was constantly low, around 20%. CONCLUSIONSWhen the phylogenetic signals are weak, the phylogenetic position does not improve germinability prediction model performance. Therefore, phylogenetic signals detected during a single species pool calculation may not accurately reflect the phylogenetic conservatism of the trait in a plant community. We suggest testing for robustness of phylogenetic signals using random sub-sampling tests.

ecology↗

bioRxiv2022

A Wars2 mutant mouse shows a sex and diet specific change in fat distribution, reduced food intake and depot-specific upregulation of WAT browning

1.BackgroundIncreased waist-to-hip ratio (WHR) is associated with increased mortality and risk of type 2 diabetes and cardiovascular disease. The TBX15-WARS2 locus has consistently been associated with increased WHR. Previous study of the hypomorphic Wars2V117L/V117L mouse model found phenotypes including severely reduced fat mass, and white adipose tissue (WAT) browning, suggesting Wars2 could be a potential modulator of fat distribution and WAT browning. MethodsTo test for differences in browning induction across different adipose depots of Wars2V117L/V117L mice, we measured multiple browning markers of a 4-month old chow-fed cohort in subcutaneous and visceral WAT and brown adipose tissue (BAT). To explain previously observed fat mass loss, we also tested for the upregulation of plasma mitokines FGF21 and GDF15 and for differences in food intake in the same cohort. Finally, to test for diet-associated differences in fat distribution, we placed Wars2V117L/V117L mice on low-fat or high-fat diet (LFD, HFD) and assessed their body composition by Echo-MRI and compared terminal adipose depot weights at 6 months of age. ResultsThe chow-fed Wars2V117L/V117L mice showed more changes in WAT browning marker gene expression in the subcutaneous inguinal WAT depot (iWAT) than in the visceral gonadal WAT depot (gWAT). These mice also demonstrated reduced food intake and elevated plasma FGF21 and GDF15, and mRNA from heart and BAT. When exposed to HFD, the Wars2V117L/V117L mice showed resistance to diet-induced obesity and a male and HFD-specific reduction of gWAT : iWAT ratio. ConclusionSevere reduction of Wars2 gene function causes a systemic phenotype which leads to upregulation of FGF21 and GDF15, resulting in reduced food intake and depot-specific changes in browning and fat mass.

physiology↗

bioRxiv2021

Phenotyping of Klf14 mouse white adipose tissue enabled by whole slide segmentation with deep neural networks

White adipose tissue (WAT) plays a central role in metabolism, with multiple diseases and genetic mutations causing its remodeling. Quantitative analysis of white adipocyte size is of great interest to understand physiology and disease, but previous studies of H&E histology have been limited to a subsample of whole depot cross-sections. In this paper, we present the deep learning pipeline DeepCytometer, that can segment mouse and human whole slides ([~=]40,000 cells per mouse slide on average) using an adaptive tiling method, correct for cell overlap and reject non-white adipocytes from the segmentation. Using quantile colour maps we show intra- and inter-depot cell size heterogeneity with local correlation; quantile estimates also suggest significant differences in population estimates from 75 whole slides compared to smaller data sets. We propose three linked levels (body weight BW, depot weight DW and cell area quartiles) for exploratory analysis of mouse Klf14 phenotypes in gonadal and subcutaneous depots. We find a rich set of phenotypes when stratifying by sex, depot and three genotype strata: (1) WTs/Hets with a Het father (Controls), (2) WTs with a Het mother, and (3) Hets with a Het mother (functional KOs or FKOs). Namely, at BW level, mean difference testing suggests that female FKOs are similar to Controls, but WTs with a Het mother are significantly larger. At DW and cell levels, linear models with interaction terms and BW or DW covariates, respectively, reveal phenotypes not shown by difference of means tests. For example, at DW level, gonadal and subcutaneous models are similar, and female FKOs have lower fat percentage than Controls due to both an offset and the DW/BW slope in the linear model. Meanwhile, female WTs with a Het mother have on average similar fat percentage to Controls, but as their slopes are close to zero, their DWs are uncorrelated to BW, suggesting that larger female WTs with a Het mother have lower fat percentage than smaller ones. In contrast to depot level, at cell level female gonadal phenotypes diverge from subcutaneous ones. Furthermore, male Controls and FKOs have similar average area values in subcutaneous depots, but area~DW slope flattening in FKOs suggests that larger DWs could be caused by cell size increase in Controls and by cell count increase in FKOs. Thus, DeepCytometer and associated exploratory analysis reveal new insights into adipocyte heterogeneity and phenotyping.

bioinformatics↗

bioRxiv2021

Akr1d1-/- mice have a sexually dimorphic metabolic phenotype with reduced fat mass, increased insulin sensitivity and hypertriglyceridemia in males

BackgroundSteroid 5{beta}-reductase (AKR1D1) plays important roles in hepatic glucocorticoid clearance and bile acid synthesis. Glucocorticoids and bile acids are potent metabolic regulators, but whether AKR1D1 controls metabolic phenotype in vivo is unknown. MethodsAkr1d1-/-mice were generated on a C57BL/6 background. Liquid chromatography / mass spectrometry, metabolomic and transcriptomic approaches were used to determine effects on glucocorticoid and bile acid homeostasis. Metabolic phenotypes including body weight and composition, lipid homeostasis, glucose tolerance and insulin sensitivity were evaluated. Molecular changes were assessed by RNASeq and western blotting. Male Akr1d1-/-mice were challenged with a 60% high fat diet. ResultsAkr1d1-/-mice had a sex specific metabolic phenotype. At 30-weeks of age male, but not female, Akr1d1-/-mice were more insulin sensitive and had reduced lipid accumulation in the liver and adipose tissue, concomitant with hypertriglyceridemia and increased intramuscular triacylglycerol. This phenotype was underpinned by sexually dimorphic changes in bile acid metabolism and composition, but without overt effects on glucocorticoid action. Male Akr1d1-/-mice were not protected against diet induced obesity and insulin resistance. ConclusionThis study shows that AKR1D1 controls bile acid homeostasis in vivo and that altering its activity can affect insulin sensitivity and lipid homeostasis in a sex dependent manner.

physiology↗