Disruption of Gpr45 causes reduced hypothalamic POMC expression and obesity

Maternal immune cell gene expression associates with maternal gut microbiome, milk composition and infant gut microbiome

BACKGROUND

Pre-pregnancy overweight and obesity promote deleterious health impacts on both mothers during pregnancy and the offspring. Significant changes in the maternal peripheral blood mononuclear cells (PBMCs) gene expression due to obesity are well-known. However, the impact of pre-pregnancy overweight on immune cell gene expression during pregnancy and its association with maternal and infant outcomes is not well explored.

METHODS

Blood samples were collected from healthy normal weight (NW, pre-pregnancy BMI 18.5-24.9) or overweight (OW, pre-pregnancy BMI 25-29.9) 2nd parity pregnant women at 12, 24 and 36 weeks of pregnancy. PBMCs were isolated from the blood and subjected to mRNA sequencing. Maternal and infant microbiota were analyzed by 16S rRNA gene sequencing. Integrative multi-omics data analysis was performed to evaluate the association of gene expression with maternal diet, gut microbiota, milk composition, and infant gut microbiota.

RESULTS

Gene expression analysis revealed that 453 genes were differentially expressed in the OW women compared to NW women at 12 weeks of pregnancy, out of which 354 were upregulated and 99 were downregulated. Several up-regulated genes in the OW group were enriched in inflammatory, chemokine-mediated signaling and regulation of interleukin-8 production-related pathways. At 36 weeks of pregnancy healthy eating index score was positively associated with several genes that include, DTD1, ELOC, GALNT8, ITGA6-AS1, KRT17P2, NPW, POT1-AS1 and RPL26. In addition, at 36 weeks of pregnancy, genes involved in adipocyte functions, such as NG2 and SMTNL1, were negatively correlated to human milk 2'FL and total fucosylated oligosaccharides content collected at 1 month postnatally. Furthermore, infant Akkermansia was positively associated with maternal PBMC anti-inflammatory genes that include CPS1 and RAB7B, at 12 and 36 weeks of pregnancy.

CONCLUSIONS

These findings suggest that prepregnancy overweight impacts the immune cell gene expression profile, particularly at 12 weeks of pregnancy. Furthermore, deciphering the complex association of PBMC's gene expression levels with maternal gut microbiome and milk composition and infant gut microbiome may aid in developing strategies to mitigate obesity-mediated effects.

Rare coding variant analysis for human diseases across biobanks and ancestries

Large-scale sequencing has enabled unparalleled opportunities to investigate the role of rare coding variation in human phenotypic variability. Here, we present a pan-ancestry analysis of sequencing data from three large biobanks, including the All of Us research program. Using mixed-effects models, we performed gene-based rare variant testing for 601 diseases across 748,879 individuals, including 155,236 with ancestry dissimilar to European. We identified 363 significant associations, which highlighted core genes for the human disease phenome and identified potential novel associations, including UBR3 for cardiometabolic disease and YLPM1 for psychiatric disease. Pan-ancestry burden testing represented an inclusive and useful approach for discovery in diverse datasets, although we also highlight the importance of ancestry-specific sensitivity analyses in this setting. Finally, we found that effect sizes for rare protein-disrupting variants were concordant between samples similar to European ancestry and other genetic ancestries (βDeming = 0.7-1.0). Our results have implications for multi-ancestry and cross-biobank approaches in sequencing association studies for human disease.

Embryonic Lethal Phenotyping to Identify Candidate Genes Related with Birth Defects

Congenital birth defects contribute significantly to preterm birth, stillbirth, perinatal death, infant mortality, and adult disability. As a first step to exploring the mechanisms underlying this major clinical challenge, we analyzed the embryonic phenotypes of lethal strains generated by random mutagenesis. In this study, we report the gross embryonic and perinatal phenotypes of 55 lethal strains randomly picked from a collection of mutants that carry piggyBac (PB) transposon inserts. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggested most of the analyzed mutations hit genes involved in heart and nervous development, or in Notch and Wnt signaling. Among them, 12 loci are known to be associated with human diseases. We confirmed 53 strains as embryonic or perinatal lethal, while others were subviable. Gross morphological phenotypes such as body size abnormality (29/55, 52.73%), growth or developmental delay (35/55, 63.64%), brain defects (9/55, 16.36%), vascular/heart development (31/55, 56.36%), and other structural defects (9/55, 16.36%) could be easily observed in the mutants, while three strains showed phenotypes similar to those of human patients. Furthermore, we detected body weight or body composition alterations in the heterozygotes of eight strains. One of them was the TGF-β signaling gene Smad2. The heterozygotes showed increased energy expenditure and a lower fat-to-body weight ratio compared to wild-type mice. This study provided new insights into mammalian embryonic development and will help understand the pathology of congenital birth defects in humans. In addition, it expanded our understanding of the etiology of obesity.

IL-17A produced by POMC neurons regulates diet-induced obesity

Overeating leads to obesity, a low-grade inflammatory condition involving interleukin-17A (IL-17A). While pro-opiomelanocortin (POMC) neurons regulate feeding, their connection with IL-17A is not well understood. To impair IL-17A signaling in POMC neurons, IL-17A receptor (Il17ra) was deleted by crossing IL17ra-flox and Pomc-Cre mice. Despite effective deletion, these mice showed no differences in body weight or adiposity compared to control mice, challenging the idea that IL-17A induces obesity through POMC neuron regulation. However, both groups exhibited reduced weight gain and adiposity upon high-fat diet compared to mice carrying only the floxed alleles, suggesting independent effects of Pomc-Cre transgene on body weight. Further analysis reveals that POMC neurons express IL-17A, and reduction in number of POMC neurons in Pomc-Cre mice could be linked to decreased IL-17A expression, which correlates with reduced adipocyte gene expression associated with obesity. Our data underscore an unexpected crosstalk between IL-17A-producing POMC neurons and the endocrine system in obesity regulation.

Exploring the Impacts of Age at Menarche on Cognitive Aging in Late Adulthood: Evidence from a Mendelian Randomization Study on the Taiwanese Population

INTRODUCTION

The potential influence of age at menarche (AM) on cognitive aging remains inadequate, partly because of the difficulties presented by multiple confounders. To address this issue, Mendelian randomization (MR) analysis was used to explore the causal impacts of AM on cognitive aging.

METHODS

Using the publicly accessible Taiwan Biobank, we identified single nucleotide polymorphisms (SNPs) significantly associated with AM as instrumental variables to estimate the effects of instruments on cognitive function assessed with the Mini-Mental State Examination (MMSE). We employed several MR methods, including two-stage least squares, inverse variance weighting (IVW), MR-Egger, weighted median, weighted mode, and constrained maximum likelihood (cML) MR methods, to ensure the stability and reliability of the results.

RESULTS

MR analyses indicated no significant causal relationship between genetically determined AMs and total and subdomain MMSE scores, except the G5 subdomain (βIVW = 0.156, 95% confidence interval [CI]: 0.005, 0.307; βcML = 0.161, 95% CI: 0.014, 0.309). However, in a leave-one-out sensitivity analysis, we found a significant relationship between AM and cognitive aging after eliminating rs157863 and rs6758290, thus demonstrating the potential pleiotropic effects of these two SNPs. After these two SNPs were eliminated, we found a significant causal relationship between AM and overall MMSE scores (βIVW = 0.425, 95% CI: 0.011, 0.839), though.

CONCLUSION

Evidence from the present MR study did not fully support a causal relationship between AM and cognitive function decline in later life. Potential pleiotropic effects of the genes underlying these two traits are worthy of further investigation.

Orphan G protein-coupled receptors: the ongoing search for a home

G protein-coupled receptors (GPCRs) make up the largest receptor superfamily, accounting for 4% of protein-coding genes. Despite the prevalence of such transmembrane receptors, a significant number remain orphans, lacking identified endogenous ligands. Since their conception, the reverse pharmacology approach has been used to characterize such receptors. However, the multifaceted and nuanced nature of GPCR signaling poses a great challenge to their pharmacological elucidation. Considering their therapeutic relevance, the search for native orphan GPCR ligands continues. Despite limited structural input in terms of 3D crystallized structures, with advances in machine-learning approaches, there has been great progress with respect to accurate ligand prediction. Though such an approach proves valuable given that ligand scarcity is the greatest hurdle to orphan GPCR deorphanization, the future pairings of the remaining orphan GPCRs may not necessarily take a one-size-fits-all approach but should be more comprehensive in accounting for numerous nuanced possibilities to cover the full spectrum of GPCR signaling.

Advances in transposable elements: from mechanisms to applications in mammalian genomics

It has been 70 years since Barbara McClintock discovered transposable elements (TE), and the mechanistic studies and functional applications of transposable elements have been at the forefront of life science research. As an essential part of the genome, TEs have been discovered in most species of prokaryotes and eukaryotes, and the relative proportion of the total genetic sequence they comprise gradually increases with the expansion of the genome. In humans, TEs account for about 40% of the genome and are deeply involved in gene regulation, chromosome structure maintenance, inflammatory response, and the etiology of genetic and non-genetic diseases. In-depth functional studies of TEs in mammalian cells and the human body have led to a greater understanding of these fundamental biological processes. At the same time, as a potent mutagen and efficient genome editing tool, TEs have been transformed into biological tools critical for developing new techniques. By controlling the random insertion of TEs into the genome to change the phenotype in cells and model organisms, critical proteins of many diseases have been systematically identified. Exploiting the TE's highly efficient in vitro insertion activity has driven the development of cutting-edge sequencing technologies. Recently, a new technology combining CRISPR with TEs was reported, which provides a novel targeted insertion system to both academia and industry. We suggest that interrogating biological processes that generally depend on the actions of TEs with TEs-derived genetic tools is a very efficient strategy. For example, excessive activation of TEs is an essential factor in the occurrence of cancer in humans. As potent mutagens, TEs have also been used to unravel the key regulatory elements and mechanisms of carcinogenesis. Through this review, we aim to effectively combine the traditional views of TEs with recent research progress, systematically link the mechanistic discoveries of TEs with the technological developments of TE-based tools, and provide a comprehensive approach and understanding for researchers in different fields.

Neurolysin Knockout Mice in a Diet-Induced Obesity Model

Neurolysin oligopeptidase (E.C.3.4.24.16; Nln), a member of the zinc metallopeptidase M3 family, was first identified in rat brain synaptic membranes hydrolyzing neurotensin at the Pro-Tyr peptide bond. The previous development of C57BL6/N mice with suppression of Nln gene expression (Nln-/-), demonstrated the biological relevance of this oligopeptidase for insulin signaling and glucose uptake. Here, several metabolic parameters were investigated in Nln-/- and wild-type C57BL6/N animals (WT; n = 5-8), male and female, fed either a standard (SD) or a hypercaloric diet (HD), for seven weeks. Higher food intake and body mass gain was observed for Nln-/- animals fed HD, compared to both male and female WT control animals fed HD. Leptin gene expression was higher in Nln-/- male and female animals fed HD, compared to WT controls. Both WT and Nln-/- females fed HD showed similar gene expression increase of dipeptidyl peptidase 4 (DPP4), a peptidase related to glucagon-like peptide-1 (GLP-1) metabolism. The present data suggest that Nln participates in the physiological mechanisms related to diet-induced obesity. Further studies will be necessary to better understand the molecular mechanism responsible for the higher body mass gain observed in Nln-/- animals fed HD.

A protein-coding gene expression atlas from the brain of pregnant and non-pregnant goats

Background: The brain is an extraordinarily complex organ with multiple anatomical structures involved in highly specialized functions related with behavior and physiological homeostasis. Our goal was to build an atlas of protein-coding gene expression in the goat brain by sequencing the transcriptomes of 12 brain regions in seven female Murciano-Granadina goats, from which three of them were 1-month pregnant. Results: Between 14,889 (cerebellar hemisphere) and 15,592 (pineal gland) protein-coding genes were expressed in goat brain regions, and most of them displayed ubiquitous or broad patterns of expression across tissues. Principal component analysis and hierarchical clustering based on the patterns of mRNA expression revealed that samples from certain brain regions tend to group according to their position in the anterior-posterior axis of the neural tube, i.e., hindbrain (pons and medulla oblongata), midbrain (rostral colliculus) and forebrain (frontal neocortex, olfactory bulb, hypothalamus, and hippocampus). Exceptions to this observation were cerebellum and glandular tissues (pineal gland and hypophysis), which showed highly divergent mRNA expression profiles. Differential expression analysis between pregnant and non-pregnant goats revealed moderate changes of mRNA expression in the frontal neocortex, hippocampus, adenohypophysis and pons, and very dramatic changes in the olfactory bulb. Many genes showing differential expression in this organ are related to olfactory function and behavior in humans. Conclusion: With the exception of cerebellum and glandular tissues, there is a relationship between the cellular origin of sampled regions along the anterior-posterior axis of the neural tube and their mRNA expression patterns in the goat adult brain. Gestation induces substantial changes in the mRNA expression of the olfactory bulb, a finding consistent with the key role of this anatomical structure on the development of maternal behavior.

High-Throughput Screening of Mouse Gene Knockouts Identifies Established and Novel High Body Fat Phenotypes

PURPOSE

Obesity is a major public health problem. Understanding which genes contribute to obesity may better predict individual risk and allow development of new therapies. Because obesity of a mouse gene knockout (KO) line predicts an association of the orthologous human gene with obesity, we reviewed data from the Lexicon Genome5000TM high throughput phenotypic screen (HTS) of mouse gene KOs to identify KO lines with high body fat.

MATERIALS AND METHODS

KO lines were generated using homologous recombination or gene trapping technologies. HTS body composition analyses were performed on adult wild-type and homozygous KO littermate mice from 3758 druggable mouse genes having a human ortholog. Body composition was measured by either DXA or QMR on chow-fed cohorts from all 3758 KO lines and was measured by QMR on independent high fat diet-fed cohorts from 2488 of these KO lines. Where possible, comparisons were made to HTS data from the International Mouse Phenotyping Consortium (IMPC).

RESULTS

Body fat data are presented for 75 KO lines. Of 46 KO lines where independent external published and/or IMPC KO lines are reported as obese, 43 had increased body fat. For the remaining 29 novel high body fat KO lines, Ksr2 and G2e3 are supported by data from additional independent KO cohorts, 6 (Asnsd1, Srpk2, Dpp8, Cxxc4, Tenm3 and Kiss1) are supported by data from additional internal cohorts, and the remaining 21 including Tle4, Ak5, Ntm, Tusc3, Ankk1, Mfap3l, Prok2 and Prokr2 were studied with HTS cohorts only.

CONCLUSION

These data support the finding of high body fat in 43 independent external published and/or IMPC KO lines. A novel obese phenotype was identified in 29 additional KO lines, with 27 still lacking the external confirmation now provided for Ksr2 and G2e3 KO mice. Undoubtedly, many mammalian obesity genes remain to be identified and characterized.

Codonopsis Radix modulates water and electrolytes homeostasis in mice

Codonopsis Radix is a traditional Chinese medicine best known for its effects in treating digestive, cardiovascular, immunological and hematopoitic diseases. It also appears in the traditional Chinese medical prescriptions against ascites. However, the physiological effect and molecular mechanism of Codonopsis Radix in water and electrolytes homeostasis have not been well studied. We found that Codonopsis Radix decoction increased water intake and the urine volume, but decreased food intake in mice. The treatment significantly reduced angiotensin II receptor (AT1R) transcription and serum aldosterone level in animals, suggested perturbed function of renin-angiotensin system. RNAseq analysis of Codonopsis Radix treated NCI–H295R cells detected suppressed AT1R, SP1, and TEF transcription as well. Thus, Codonopsis Radix may regulate water and electrolytes homeostasis by affecting AT1R expression and aldosterone biosynthesis, possibly through downregulating SP1 and TEF transcription.

LKB1 up-regulation inhibits hypothalamic inflammation and attenuates diet-induced obesity in mice

BACKGROUND

Diet-induced obesity (DIO) is associated with chronic, low-grade inflammation in the hypothalamus. The inflammatory pathway of the hypothalamus is activated during obesity, and inhibition of activation of the inflammatory pathway can partially reverse obesity. Therefore, exploring new targets for inhibiting hypothalamic inflammation will provide new ideas for the prevention and treatment of obesity. Liver kinase B1 (LKB1), a serine/threonine kinase, is a tumor suppressor and metabolic regulator. Recent studies have shown that LKB1 has a certain anti-inflammatory effect. However, a role of LKB1 in the regulation of hypothalamic inflammation remains unclear. Therefore, we examined whether LKB1 overexpression in the hypothalamus could weaken the hypothalamic inflammation and inhibit the development of obesity.

METHODS

LKB1 overexpressing adeno-associated virus (AAV) particles were injected stereotactically into the third ventricle (3 V) of C57BL/6 mice fed with HFD. We assessed changes in body mass and adiposity, food intake, hypothalamic inflammatory markers, and energy and glucose metabolism.

RESULTS

LKB1 up-regulation in hypothalamus attenuated diet-induced hypothalamic inflammation, reduced food intake and body weight gain. In addition, the overexpression of hypothalamic LKB1 increased the insulin sensitivity and improved whole-body lipid metabolism, which attenuated hepatic fat accumulation and serum lipid levels.

CONCLUSION

Hypothalamic LKB1 up-regulation attenuates hypothalamic inflammation, and protects against hypothalamic inflammation induced damage to melanocortin system, resulting in lower food intake and lower fat mass accumulation, which consequently protects mice from the development of obesity. Our data suggest LKB1 as a novel negative regulator of hypothalamic inflammation, and also a potentially important target for treating other inflammatory diseases.

Aging-related modifications to G protein-coupled receptor signaling diversity

Aging is a highly complex molecular process, affecting nearly all tissue systems in humans and is the highest risk factor in developing neurodegenerative disorders such as Alzheimer's and Parkinson's disease, cardiovascular disease and Type 2 diabetes mellitus. The intense complexity of the aging process creates an incentive to develop more specific drugs that attenuate or even reverse some of the features of premature aging. As our current pharmacopeia is dominated by therapeutics that target members of the G protein-coupled receptor (GPCR) superfamily it may be prudent to search for effective anti-aging therapeutics in this fertile domain. Since the first demonstration of GPCR-based β-arrestin signaling, it has become clear that an enhanced appreciation of GPCR signaling diversity may facilitate the creation of therapeutics with selective signaling activities. Such 'biased' ligand signaling profiles can be effectively investigated using both standard molecular biological techniques as well as high-dimensionality data analyses. Through a more nuanced appreciation of the quantitative nature across the multiple dimensions of signaling bias that drugs possess, researchers may be able to further refine the efficacy of GPCR modulators to impact the complex aberrations that constitute the aging process. Identifying novel effector profiles could expand the effective pharmacopeia and assist in the design of precision medicines. This review discusses potential non-G protein effectors, and specifically their potential therapeutic suitability in aging and age-related disorders.

Deletion of liver kinase B1 in POMC neurons predisposes to diet-induced obesity

AIMS

Liver kinase B1 (LKB1) is a serine/threonine kinase. Although many biological functions of LKB1 have been identified, the role of hypothalamic LKB1 in the regulation of central energy metabolism and susceptibility to obesity is unknown. Therefore, we constructed POMC neuron-specific LKB1 knockout mice (PomcLkb1 KO) and studied it at the physiological, morphological, and molecular biology levels.

MAIN METHODS

Eight-week-old male PomcLkb1 KO mice and their littermates were fed a standard chow fat diet (CFD) or a high-fat diet (HFD) for 3 months. Body weight and food intake were monitored. Dual-energy X-ray absorptiometry was used to measure the fat mass and lean mass. Glucose and insulin tolerance tests and serum biochemical markers were evaluated in the experimental mice. In addition, the levels of peripheral lipogenesis genes and central energy metabolism were measured.

KEY FINDINGS

PomcLkb1 KO mice did not exhibit impairments under normal physiological conditions. After HFD intervention, the metabolic phenotype of the PomcLkb1 KO mice changed, manifesting as increased food intake and an enhanced obesity phenotype. More seriously, PomcLkb1 KO mice showed increased leptin resistance, worsened hypothalamic inflammation and reduced POMC neuronal expression.

SIGNIFICANCE

We provide evidence that LKB1 in POMC neurons plays a significant role in regulating energy homeostasis. LKB1 in POMC neurons emerges as a target for therapeutic intervention against HFD-induced obesity and metabolic diseases.

Targeting hypoxia downstream signaling protein, CAIX, for CAR T-cell therapy against glioblastoma

BACKGROUND

Glioblastoma survival remains unchanged despite continuing therapeutic innovation. Herein, we aim to (i) develop chimeric antigen receptor (CAR) T cells with a specificity to a unique antigen, carbonic anhydrase IX (CAIX), which is expressed in the hypoxic microenvironment characteristic of glioblastoma, and (ii) demonstrate its efficacy with limited off-target effects.

METHODS

First we demonstrated expression of CAIX in patient-derived glioblastoma samples and available databases. CAR T cells were generated against CAIX and efficacy was assessed in 4 glioblastoma cell lines and 2 glioblastoma stem cell lines. Cytotoxicity of anti-CAIX CAR T cells was assessed via interferon gamma, tumor necrosis factor alpha, and interleukin-2 levels when co-cultured with tumor cells. Finally, we assessed efficacy of direct intratumoral injection of the anti-CAIX CAR T cells on an in vivo xenograft mouse model using the U251 luciferase cell line. Tumor infiltrating lymphocyte analyses were performed.

RESULTS

We confirm that CAIX is highly expressed in glioblastoma from patients. We demonstrate that CAIX is a suitable target for CAR T-cell therapy using anti-CAIX CAR T cells against glioblastoma in vitro and in vivo. In our mouse model, a 20% cure rate was observed without detectable systemic effects.

CONCLUSIONS

By establishing the specificity of CAIX under hypoxic conditions in glioblastoma and highlighting its efficacy as a target for CAR T-cell therapy, our data suggest that anti-CAIX CAR T may be a promising strategy to treat glioblastoma. Direct intratumoral injection increases anti-CAIX CAR T-cell potency while limiting its off-target effects.

MicroRNA-188 regulates aging-associated metabolic phenotype

With the increasing aging population, aging-associated diseases are becoming epidemic worldwide, including aging-associated metabolic dysfunction. However, the underlying mechanisms are poorly understood. In the present study, we aimed to investigate the role of microRNA miR-188 in the aging-associated metabolic phenotype. The results showed that the expression of miR-188 increased gradually in brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT) of mice during aging. MiR-188 knockout mice were resistant to the aging-associated metabolic phenotype and had higher energy expenditure. Meanwhile, adipose tissue-specific miR-188 transgenic mice displayed the opposite phenotype. Mechanistically, we identified the thermogenic-related gene Prdm16 (encoding PR domain containing 16) as the direct target of miR-188. Notably, inhibition of miR-188 expression in BAT and iWAT of aged mice by tail vein injection of antagomiR-188 ameliorated aging-associated metabolic dysfunction significantly. Taken together, our findings suggested that miR-188 plays an important role in the regulation of the aging-associated metabolic phenotype, and targeting miR-188 could be an effective strategy to prevent aging-associated metabolic dysfunction.

Increased Reticulon 3 (RTN3) Leads to Obesity and Hypertriglyceridemia by Interacting With Heat Shock Protein Family A (Hsp70) Member 5 (HSPA5)

BACKGROUND

Reticulon 3 (RTN3) is an endoplasmic reticulum protein that has previously been shown to play a role in neurodegenerative diseases, but little is known about its role in lipid metabolism.

METHODS

Obese patients (n=149), hypertriglyceridemic patients (n=343), and healthy control subjects (n=84) were enrolled to assess their levels of RTN3. To explore the pathophysiological roles of RTN3 in the control of lipid metabolism, we used transgenic mice overexpressing the wild-type human RTN3 gene, the RTN3-null transgenic mouse model, and multiple Caenorhabditis legans strains for molecular characterization. The underlying mechanisms were studied with 3T3L1 cell cultures in vitro.

RESULTS

We report that overexpressed RTN3 in mice induces obesity and higher accumulation of triglycerides. Increased RTN3 expression is also found in patients with obesity and hypertriglyceridemia. We reveal that RTN3 plays critical roles in regulating the biosynthesis and storage of triglycerides and in controlling lipid droplet expansion. Mechanistically, RTN3 regulates these events through its interactions with heat shock protein family A (Hsp70) member 5, and this enhanced interaction increases sterol regulatory element-binding protein 1c and AMP-activated kinase activity.

CONCLUSIONS

This study provides evidence for a role of RTN3 in inducing obesity and triglyceride accumulation and suggests that inhibiting the expression of RTN3 in fat tissue may be a novel therapeutic approach to treat obesity and hypertriglyceridemia.

GDF5 Promotes White Adipose Tissue Thermogenesis via p38 MAPK Signaling Pathway

Growth differentiation factor 5 (GDF5) was reported to regulate brown adipogenesis; however, its effects on insulin sensitivity, full metabolic syndrome spectrum, and the thermogenesis in subcutaneous white adipose tissue (sWAT) have not been elucidated yet. We thus generated fatty acid-binding protein 4 (Fabp4)-GDF5 transgenic (TG) mice and showed that GDF5 TG mice developed a relative lean phenotype on a high-fat diet (HFD) and showed increased insulin sensitivity. Over expression of GDF5 in adipose tissues greatly promoted the thermogenic process in sWAT after cold or β3-agonist treatment. In TG mice, sWAT showed an important thermogenic effect as the thermogenic gene expression was markedly increased, which was consistent with the typical features of beige adipocytes. Moreover, knockdown of the protein GDF5 impaired browning program in sWAT after thermogenic stimuli. Enhanced mitogen-activated protein kinase (MAPK)/activating transcription factor 2 (ATF2) signaling was also identified in sWAT of HFD-fed GDF5 mice, and thermogenesis in mature adipocytes induced by GDF5 protein could be partly blocked by a p38 MAPK inhibitor. Taken together, our data suggest that GDF5 could improve insulin sensitivity and prevent metabolic syndrome, the adaptive thermogenesis in sWAT could mediate the obesity resistance effects of GDF5 in mice and partially resulted in the activation of the p38 MAPK signaling pathway.

Efficient genome-wide first-generation phenotypic screening system in mice using the piggyBac transposon

Genome-wide phenotypic screens provide an unbiased way to identify genes involved in particular biological traits, and have been widely used in lower model organisms. However, cost and time have limited the utility of such screens to address biological and disease questions in mammals. Here we report a highly efficient piggyBac (PB) transposon-based first-generation (F1) dominant screening system in mice that enables an individual investigator to conduct a genome-wide phenotypic screen within a year with fewer than 300 cages. The PB screening system uses visually trackable transposons to induce both gain- and loss-of-function mutations and generates genome-wide distributed new insertions in more than 55% of F1 progeny. Using this system, we successfully conducted a pilot F1 screen and identified 5 growth retardation mutations. One of these mutants, a Six1/4 ^PB/+ mutant, revealed a role in milk intake behavior. The mutant animals exhibit abnormalities in nipple recognition and milk ingestion, as well as developmental defects in cranial nerves V, IX, and X. This PB F1 screening system offers individual laboratories unprecedented opportunities to conduct affordable genome-wide phenotypic screens for deciphering the genetic basis of mammalian biology and disease pathogenesis.

Demethylation of G-Protein-Coupled Receptor 151 Promoter Facilitates the Binding of Krüppel-Like Factor 5 and Enhances Neuropathic Pain after Nerve Injury in Mice

G-protein-coupled receptors are considered to be cell-surface sensors of extracellular signals, thereby having a crucial role in signal transduction and being the most fruitful targets for drug discovery. G-protein-coupled receptor 151 (GPR151) was reported to be expressed specifically in the habenular area. Here we report the expression and the epigenetic regulation of GRP151 in the spinal cord after spinal nerve ligation (SNL) and the contribution of GPR151 to neuropathic pain in male mice. SNL dramatically increased GPR151 expression in spinal neurons. GPR151 mutation or spinal inhibition by shRNA alleviated SNL-induced mechanical allodynia and heat hyperalgesia. Interestingly, the CpG island in the GPR151 gene promoter region was demethylated, the expression of DNA methyltransferase 3b (DNMT3b) was decreased, and the binding of DNMT3b with GPR151 promoter was reduced after SNL. Overexpression of DNMT3b in the spinal cord decreased GPR151 expression and attenuated SNL-induced neuropathic pain. Furthermore, Krüppel-like factor 5 (KLF5), a transcriptional factor of the KLF family, was upregulated in spinal neurons, and the binding affinity of KLF5 with GPR151 promoter was increased after SNL. Inhibition of KLF5 reduced GPR151 expression and attenuated SNL-induced pain hypersensitivity. Further mRNA microarray analysis revealed that mutation of GPR151 reduced the expression of a variety of pain-related genes in response to SNL, especially mitogen-activated protein kinase (MAPK) signaling pathway-associated genes. This study reveals that GPR151, increased by DNA demethylation and the enhanced interaction with KLF5, contributes to the maintenance of neuropathic pain via increasing MAPK pathway-related gene expression.SIGNIFICANCE STATEMENT G-protein-coupled receptors (GPCRs) are targets of various clinically approved drugs. Here we report that SNL increased GPR151 expression in the spinal cord, and mutation or inhibition of GPR151 alleviated SNL-induced neuropathic pain. In addition, SNL downregulated the expression of DNMT3b, which caused demethylation of GPR151 gene promoter, facilitated the binding of transcriptional factor KLF5 with the GPR151 promoter, and further increased GPR151 expression in spinal neurons. The increased GPR151 may contribute to the pathogenesis of neuropathic pain via activating MAPK signaling and increasing pain-related gene expression. Our study reveals an epigenetic mechanism underlying GPR151 expression and suggests that targeting GPR151 may offer a new strategy for the treatment of neuropathic pain.

MicroRNA-27a controls the intracellular survival of Mycobacterium tuberculosis by regulating calcium-associated autophagy

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) kills millions every year, and there is urgent need to develop novel anti-TB agents due to the fast-growing of drug-resistant TB. Although autophagy regulates the intracellular survival of Mtb, the role of calcium (Ca²⁺) signaling in modulating autophagy during Mtb infection remains largely unknown. Here, we show that microRNA miR-27a is abundantly expressed in active TB patients, Mtb-infected mice and macrophages. The target of miR-27a is the ER-located Ca²⁺ transporter CACNA2D3. Targeting of this transporter leads to the downregulation of Ca²⁺ signaling, thus inhibiting autophagosome formation and promoting the intracellular survival of Mtb. Mice lacking of miR-27a and mice treated with an antagomir to miR-27a are more resistant to Mtb infection. Our findings reveal a strategy for Mtb to increase intracellular survival by manipulating the Ca²⁺-associated autophagy, and may also support the development of host-directed anti-TB therapeutic approaches.

How Mycobacterium tuberculosis (Mtb) escapes autophagy-mediated clearance is poorly understood. Here, Liu et al. show that Mtb-induced MicroRNA-27a targets the ER-associated calcium transporter CACNA2D3, leading to suppression of antimicrobial autophagy and to enhanced intracellular survival of Mtb.

The Vitamin K Epoxide Reductase Vkorc1l1 Promotes Preadipocyte Differentiation in Mice

OBJECTIVE

Identification of novel regulators involved in adipose development is important to understand the molecular mechanism underlying obesity and associated metabolic disorders. Through isolation and analysis of a vitamin K epoxide reductase Vkorc1l1 mutant, this study aimed to disclose its function and underlying mechanism in adipose development and to obtain valuable insights regarding the mechanism of obesity.

METHODS

A Vkorc1l1 mutation recovered from a forward genetic screen for obesity-related loci in mice was characterized to explore its effects in gene expression, animal metabolism, and adipose development. Adipogenesis was evaluated in both Vkorc1l1 mutant stromal vascular fraction and Vkorc1l1 knockdown preadipocytes. Intracellular vitamin K₂ level and the effect of vitamin K₂ on adipogenesis were tested in primary preadipocytes.

RESULTS

Vkorc1l1 mutants displayed a considerably lower fat to body weight ratio, substantially decreased plasma leptin, and significantly underdeveloped white adipose tissue. Adipogenic defects related with Vkorc1l1 deficiency were observed both in vivo and in vitro. Vitamin K₂ could inhibit adipogenesis in stromal vascular fraction. Increased intracellular vitamin K₂ level was detected in Vkorc1l1 mutant preadipocytes.

CONCLUSIONS

Vkorc1l1 promotes adipogenesis and possibly obesity. Downregulation of Vkorc1l1 increases intracellular vitamin K₂ level and impedes preadipocyte differentiation.

Disruption of Ssp411 causes impaired sperm head formation and male sterility in mice

BACKGROUND

We previously cloned the Ssp411 gene. We found that the Ssp411 protein is predominantly expressed in elongated spermatids in the rat testis in a stage-dependent manner. Although our findings strongly suggested that Ssp411 might play an important role in mammalian spermatogenesis, this hypothesis has not been studied.

METHODS

We first used real-time PCR, Western blotting and immunohistochemistry to confirm that the expression pattern of Ssp411 in several murine tissues is similar to its expression pattern in corresponding rat tissues. To better understand the roles of Ssp411 in male reproduction in vivo, we identified and characterized an Ssp411 expression-disrupted murine strain (Ssp411^PB/PB) that was generated by piggyBac (PB) transposon insertion. We studied Ssp411-interacting proteins using proteome microarray, co-IP and GST pull-down assay.

RESULTS

Both Ssp411 mRNA and protein were detected exclusively in spermatids after step 9 during spermiogenesis in testis. Phenotypic analysis suggested that only Ssp411^PB/PB males are sterile. These males have smaller testes, reduced sperm counts, decreased sperm motility and deformed spermatozoa. Microscopy analysis indicated that the manchette, a structurally reshaped sperm head, is aberrant in Ssp411^PB/PB spermatids. The results of proteome microarray analysis and GST pull-down assays suggested that Ssp411 participates the ubiquitin-proteasome system by interacting with PSMC3. This has been reported to be manchette-associated and important for the head shaping of spermatids.

CONCLUSIONS

Our study suggested that Ssp411 is required for spermiogenesis. It seems to play a role in sperm head shaping. The lack of Ssp411 causes sperm deformation and results in male infertility.

GENERAL SIGNIFICANCE

Ssp411^PB/PB mouse strain is an animal model of idiopathic oligoasthenoteratozoospermia (iOAT), and the gene may represent a therapeutic target for iOAT patients.

Glucose Intake Alters Expression of Neuropeptides Derived from Proopiomelanocortin in the Lateral Hypothalamus and the Nucleus Accumbens in Fructose Preference Rats

To study the neuroendocrine mechanism of sugar preference, we investigated the role of glucose feeding in the regulation of expression levels of neuropeptides derived from proopiomelanocortin (POMC) in the lateral hypothalamus (LH) and nucleus accumbens (NAc) in fructose preference rats. Fructose preference rats were induced by using the lithium chloride backward conditioning procedure. The fructose preference was confirmed by the two-bottle test. The drinking behavior of rats was assessed by the fructose concentration gradient test. The preference of 10% glucose or 0.1% saccharine was assessed, and the expression levels of neuropeptides derived from POMC in the LH and the NAc in fructose preference rats were measured by Western blot analysis. Fructose preference rats displayed a greater fructose preference than control rats. Furthermore, fructose preference rats preferred glucose solution rather than saccharine solution, while control rats preferred saccharine solution rather than glucose solution. The expression levels of neuropeptides derived from POMC in the LH and the NAc were changed by glucose but not saccharine intake. In summary, the data suggests that glucose intake increases the expression of neuropeptides derived from POMC in the LH and the NAc in fructose preference rats.

Rasal2 deficiency reduces adipogenesis and occurrence of obesity-related disorders

Objective

Identification of additional regulatory factors involved in the onset of obesity is important to understand the mechanisms underlying this prevailing disease and its associated metabolic disorders and to develop therapeutic strategies. Through isolation and analysis of a mutant, we aimed to uncover the function of a Ras-GAP gene, Rasal2 (Ras protein activator like 2), in the development of obesity and related metabolic disorders and to obtain valuable insights regarding the mechanism underlying the function.

Methods

An obesity-based genetic screen was performed to identify an insertional mutation that disrupts the expression of Rasal2 (Rasal2^PB/PB mice). Important metabolic parameters, such as fat mass and glucose tolerance, were measured in Rasal2^PB/PB mice. The impact of Rasal2 on adipogenesis was evaluated in the mutant mice and in 3T3-L1 preadipocytes treated with Rasal2 siRNA. Ras and ERK activities were then evaluated in Rasal2-deficient preadipocytes or mice, and their functional relationships with Rasal2 on adipogenesis were investigated by employing Ras and MEK inhibitors.

Results

Rasal2^PB/PB mice showed drastic decrease in Rasal2 expression and a lean phenotype. The mutant mice displayed decreased adiposity and resistance to high-fat diet induced metabolic disorders. Further analysis indicated that Rasal2 deficiency leads to impaired adipogenesis in vivo and in vitro. Moreover, while Rasal2 deficiency resulted in increased activity of both Ras and ERK in preadipocytes, reducing Ras, but not ERK, suppressed the impaired adipogenesis.

Conclusions

Rasal2 promotes adipogenesis, which may critically contribute to its role in the development of obesity and related metabolic disorders and may do so by repressing Ras activity in an ERK-independent manner.

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Rasal2-deficient mice show decreased adiposity fed on either high-fat or normal-chow diet.

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Rasal2-deficient mice are resistant to high-fat diet-induced obesity and related metabolic disorders.

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Rasal2 deficiency causes a decrease in adipogenesis in vivo and in vitro.

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Rasal2 likely regulates adipogenesis by repressing Ras activity through an ERK-independent mechanism.