Arcuate nucleus transcriptome profiling identifies ankyrin repeat and suppressor of cytokine signalling box-containing protein 4 as a gene regulated by fasting in central nervous system feeding circuits

The Roles of Obesity and ASB4 in Preeclampsia Pathogenesis

Preeclampsia is a complex pregnancy-related hypertensive disorder which poses significant risks for both maternal and fetal health. Preeclampsia affects 5-8% of pregnancies in the United States, causing a significant public health and economic burden. Despite extensive research, the etiology and pathogenesis of preeclampsia remain elusive, but have been correlated with maternal conditions such as obesity. In recent decades, the incidence of preeclampsia increased along with the prevalence of obesity among women of reproductive age. Maternal obesity has been shown to negatively affect pregnancy in almost all aspects. However, the precise mechanisms by which obesity influences preeclampsia are unclear. Ankyrin repeat and SOCS Box Containing protein 4 (ASB4) is an E3 ubiquitin ligase that can promote the degradation of a wide range of target proteins. ASB4-null mice display a full spectrum of preeclampsia-like phenotypes during pregnancy including hypertension, proteinuria, and decreased litter size. Furthermore, maternal obesity induced by a high-fat diet aggravates preeclampsia-like phenotypes in pregnant mice lacking ASB4. Variants in the ASB4 gene have been associated with obesity in humans, and a functional connection between the ASB4 gene and obesity has been established in mice. This review discusses the connections between preeclampsia, obesity, and ASB4.

Whole Transcriptome Analysis of Hypothalamus in Mice during Short-Term Starvation

Molecular profiling of the hypothalamus in response to metabolic shifts is a critical cue to better understand the principle of the central control of whole-body energy metabolism. The transcriptional responses of the rodent hypothalamus to short-term calorie restriction have been documented. However, studies on the identification of hypothalamic secretory factors that potentially contribute to the control of appetite are lacking. In this study, we analyzed the differential expression of hypothalamic genes and compared the selected secretory factors from the fasted mice with those of fed control mice using bulk RNA-sequencing. We verified seven secretory genes that were significantly altered in the hypothalamus of fasted mice. In addition, we determined the response of secretory genes in cultured hypothalamic cells to treatment with ghrelin and leptin. The current study provides further insights into the neuronal response to food restriction at the molecular level and may be useful for understanding the hypothalamic control of appetite.

ASB4 modulates central melanocortinergic neurons and calcitonin signaling to control satiety and glucose homeostasis

Variants in the gene encoding ankyrin repeat and SOCS box-containing 4 (ASB4) are linked to human obesity. Here, we characterized the pathways underlying the metabolic functions of ASB4. Hypothalamic Asb4 expression was suppressed by fasting in wild-type mice but not in mice deficient in AgRP, which encodes Agouti-related protein (AgRP), an appetite-stimulating hormone, suggesting that ASB4 is a negative target of AgRP. Many ASB4 neurons in the brain were adjacent to AgRP terminals, and feeding induced by AgRP neuronal activation was disrupted in Asb4-deficient mice. Acute knockdown of Asb4 in the brain caused marked hyperphagia due to increased meal size, and Asb4 deficiency led to increased meal size and food intake at the onset of refeeding, when very large meals were consumed. Asb4-deficient mice were resistant to the meal-terminating effects of exogenously administered calcitonin and showed decreased neuronal expression of Calcr, which encodes the calcitonin receptor. Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus in mice are involved in glucose homeostasis, and Asb4 deficiency specifically in POMC neurons resulted in glucose intolerance that was independent of obesity. Furthermore, individuals with type 2 diabetes showed reduced ASB4 abundance in the infundibular nuclei, the human equivalent of the arcuate nucleus. Together, our results indicate that ASB4 acts in the brain to improve glucose homeostasis and to induce satiety after substantial meals, particularly those after food deprivation.

Using machine intelligence to uncover Alzheimer’s disease progression heterogeneity

Aim: Research suggests that Alzheimer’s disease (AD) is heterogeneous with numerous subtypes. Through a proprietary interactive ML system, several underlying biological mechanisms associated with AD pathology were uncovered. This paper is an introduction to emerging analytic efforts that can more precisely elucidate the heterogeneity of AD. Methods: A public AD data set (GSE84422) consisting of transcriptomic data of postmortem brain samples from healthy controls (n = 121) and AD (n = 380) subjects was analyzed. Data were processed by an artificial intelligence platform designed to discover potential drug repurposing candidates, followed by an interactive augmented intelligence program. Results: Using perspective analytics, six perspective classes were identified: Class I is defined by TUBB1, ASB4, and PDE5A; Class II by NRG2 and ZNF3; Class III by IGF1, ASB4, and GTSE1; Class IV is defined by cDNA FLJ39269, ITGA1, and CPM; Class V is defined by PDE5A, PSEN1, and NDUFS8; and Class VI is defined by DCAF17, cDNA FLJ75819, and SLC33A1. It is hypothesized that these classes represent biological mechanisms that may act alone or in any combination to manifest an Alzheimer’s pathology. Conclusions: Using a limited transcriptomic public database, six different classes that drive AD were uncovered, supporting the premise that AD is a heterogeneously complex disorder. The perspective classes highlighted genetic pathways associated with vasculogenesis, cellular signaling and differentiation, metabolic function, mitochondrial function, nitric oxide, and metal ion metabolism. The interplay among these genetic factors reveals a more profound underlying complexity of AD that may be responsible for the confluence of several biological factors. These results are not exhaustive; instead, they demonstrate that even within a relatively small study sample, next-generation machine intelligence can uncover multiple genetically driven subtypes. The models and the underlying hypotheses generated using novel analytic methods may translate into potential treatment pathways.

Bile acid toxicity in Paneth cells contributes to gut dysbiosis induced by high-fat feeding

High-fat feeding (HFF) leads to gut dysbiosis through unclear mechanisms. We hypothesize that bile acids secreted in response to high-fat diets (HFDs) may act on intestinal Paneth cells, leading to gut dysbiosis. We found that HFF resulted in widespread taxonomic shifts in the bacteria of the ileal mucosa, characterized by depletion of Lactobacillus and enrichment of Akkermansia muciniphila, Clostridium XIVa, Ruminococcaceae, and Lachnospiraceae, which were prevented by the bile acid binder cholestyramine. Immunohistochemistry and in situ hybridization studies showed that G protein-coupled bile acid receptor (TGR5) expressed in Paneth cells was upregulated in the rats fed HFD or normal chow supplemented with cholic acid. This was accompanied by decreased lysozyme+ Paneth cells and α-defensin 5 and 6 and increased expression of XBP-1. Pretreatment with ER stress inhibitor 4PBA or with cholestyramine prevented these changes. Ileal explants incubated with deoxycholic acid or cholic acid caused a decrease in α-defensin 5 and 6 and an increase in XBP-1, which was prevented by TGR5 antibody or 4PBA. In conclusion, this is the first demonstration to our knowledge that TGR5 is expressed in Paneth cells. HFF resulted in increased bile acid secretion and upregulation of TGR5 expression in Paneth cells. Bile acid toxicity in Paneth cells contributes to gut dysbiosis induced by HFF.

Mapping Molecular Datasets Back to the Brain Regions They are Extracted from: Remembering the Native Countries of Hypothalamic Expatriates and Refugees

This article focuses on approaches to link transcriptomic, proteomic, and peptidomic datasets mined from brain tissue to the original locations within the brain that they are derived from using digital atlas mapping techniques. We use, as an example, the transcriptomic, proteomic and peptidomic analyses conducted in the mammalian hypothalamus. Following a brief historical overview, we highlight studies that have mined biochemical and molecular information from the hypothalamus and then lay out a strategy for how these data can be linked spatially to the mapped locations in a canonical brain atlas where the data come from, thereby allowing researchers to integrate these data with other datasets across multiple scales. A key methodology that enables atlas-based mapping of extracted datasets-laser-capture microdissection-is discussed in detail, with a view of how this technology is a bridge between systems biology and systems neuroscience.

Global analysis of gene expression mediated by OX1 orexin receptor signaling in a hypothalamic cell line

The orexins and their cognate G-protein coupled receptors have been widely studied due to their associations with various behaviors and cellular processes. However, the detailed downstream signaling cascades that mediate these effects are not completely understood. We report the generation of a neuronal model cell line that stably expresses the OX1 orexin receptor (OX1) and an RNA-Seq analysis of changes in gene expression seen upon receptor activation. Upon treatment with orexin, several families of related transcription factors are transcriptionally regulated, including the early growth response genes (Egr), the Kruppel-like factors (Klf), and the Nr4a subgroup of nuclear hormone receptors. Furthermore, some of the transcriptional effects observed have also been seen in data from in vivo sleep deprivation microarray studies, supporting the physiological relevance of the data set. Additionally, inhibition of one of the most highly regulated genes, serum and glucocorticoid-regulated kinase 1 (Sgk1), resulted in the diminished orexin-dependent induction of a subset of genes. These results provide new insight into the molecular signaling events that occur during OX1 signaling and support a role for orexin signaling in the stimulation of wakefulness during sleep deprivation studies.

New Perspectives on Genomic Imprinting, an Essential and Multifaceted Mode of Epigenetic Control in the Developing and Adult Brain

Mammalian evolution entailed multiple innovations in gene regulation, including the emergence of genomic imprinting, an epigenetic regulation leading to the preferential expression of a gene from its maternal or paternal allele. Genomic imprinting is highly prevalent in the brain, yet, until recently, its central roles in neural processes have not been fully appreciated. Here, we provide a comprehensive survey of adult and developmental brain functions influenced by imprinted genes, from neural development and wiring to synaptic function and plasticity, energy balance, social behaviors, emotions, and cognition. We further review the widespread identification of parental biases alongside monoallelic expression in brain tissues, discuss their potential roles in dosage regulation of key neural pathways, and suggest possible mechanisms underlying the dynamic regulation of imprinting in the brain. This review should help provide a better understanding of the significance of genomic imprinting in the normal and pathological brain of mammals including humans.

Cell type-specific transcriptomics of hypothalamic energy-sensing neuron responses to weight-loss

Molecular and cellular processes in neurons are critical for sensing and responding to energy deficit states, such as during weight-loss. Agouti related protein (AGRP)-expressing neurons are a key hypothalamic population that is activated during energy deficit and increases appetite and weight-gain. Cell type-specific transcriptomics can be used to identify pathways that counteract weight-loss, and here we report high-quality gene expression profiles of AGRP neurons from well-fed and food-deprived young adult mice. For comparison, we also analyzed Proopiomelanocortin (POMC)-expressing neurons, an intermingled population that suppresses appetite and body weight. We find that AGRP neurons are considerably more sensitive to energy deficit than POMC neurons. Furthermore, we identify cell type-specific pathways involving endoplasmic reticulum-stress, circadian signaling, ion channels, neuropeptides, and receptors. Combined with methods to validate and manipulate these pathways, this resource greatly expands molecular insight into neuronal regulation of body weight, and may be useful for devising therapeutic strategies for obesity and eating disorders.

DOI:http://dx.doi.org/10.7554/eLife.09800.001

Humans and other animals must get adequate nutrition in order to survive. As a result, the body has several systems that work side by side to maintain a healthy body weight and ensure that enough food gets eaten to provide the energy that the body needs. Problems with these systems can contribute towards obesity and other eating disorders.

Certain types of cells in the brain play important roles in controlling weight and appetite, although the genes and cellular mechanisms that underlie these abilities are not well understood. When an animal is deprived of food, so-called AGRP neurons produce molecules that increase appetite and make it easier to gain weight. These neurons also go through structural changes and increase their electrical activity during weight loss. Another group of cells, called the POMC neurons, becomes less active when an animal is deprived of energy.

Using a technique called cell type-specific transcriptomics, Henry, Sugino et al. have now revealed that the expression of hundreds of genes in AGRP and POMC neurons changes depending on whether mice are well fed or food deprived. Food deprivation also affects more genes in AGRP neurons than has been seen in other types of brain cell, and the AGRP neurons are also more sensitive to a change in food intake than POMC neurons.

In the future, this gene expression data and knowledge of the pathways affected by the genes could help researchers to develop new treatments for obesity and other disorders that affect appetite. Henry, Sugino et al. then mapped how these changes in gene expression trigger molecular “pathways” in the neurons that alter how the cells work. These affect many parts of the cells, including ion channels, transcription factors, receptors, and secreted proteins. In addition, food deprivation activated pathways in AGRP neurons that protect the cells from damage and death caused by elevated neuron activity and also triggered signaling pathways that increase body weight.

In the future, this gene expression data and knowledge of the pathways affected by the genes could help researchers to develop new treatments for obesity and other disorders that affect appetite.

DOI:http://dx.doi.org/10.7554/eLife.09800.002

Effect of photoperiod on the feline adipose transcriptome as assessed by RNA sequencing

Background

Photoperiod is known to cause physiological changes in seasonal mammals, including changes in body weight, physical activity, reproductive status, and adipose tissue gene expression in several species. The objective of this study was to determine the effects of day length on the adipose transcriptome of cats as assessed by RNA sequencing. Ten healthy adult neutered male domestic shorthair cats were used in a randomized crossover design study. During two 12-wk periods, cats were exposed to either short days (8 hr light:16 hr dark) or long days (16 hr light:8 hr dark). Cats were fed a commercial diet to maintain baseline body weight to avoid weight-related bias. Subcutaneous adipose biopsies were collected at wk 12 of each period for RNA isolation and sequencing.

Results

A total of 578 million sequences (28.9 million/sample) were generated by Illumina sequencing. A total of 170 mRNA transcripts were differentially expressed between short day- and long day-housed cats. 89 annotated transcripts were up-regulated by short days, while 24 annotated transcripts were down-regulated by short days. Another 57 un-annotated transcripts were also different between groups. Adipose tissue of short day-housed cats had greater expression of genes involved with cell growth and differentiation (e.g., myostatin; frizzled-related protein), cell development and structure (e.g., cytokeratins), and protein processing and ubiquitination (e.g., kelch-like proteins). In contrast, short day-housed cats had decreased expression of genes involved with immune function (e.g., plasminogen activator inhibitor 1; chemokine (C-C motif) ligand 2; C-C motif chemokine 5; T-cell activators), and altered expression of genes associated with carbohydrate and lipid metabolism.

Conclusions

Collectively, these gene expression changes suggest that short day housing may promote adipogenesis, minimize inflammation and oxidative stress, and alter nutrient metabolism in feline adipose tissue, even when fed to maintain body weight. Although this study has highlighted molecular mechanisms contributing to the seasonal metabolic changes observed in cats, future research that specifically targets and studies these biological pathways, and the physiological outcomes that are affected by them, is justified.

LGR4 and its ligands, R-spondin 1 and R-spondin 3, regulate food intake in the hypothalamus of male rats

The hypothalamus plays a key role in the regulation of feeding behavior. Several hypothalamic nuclei, including the arcuate nucleus (ARC), paraventricular nucleus, and ventromedial nucleus of the hypothalamus (VMH), are involved in energy homeostasis. Analysis of microarray data derived from ARC revealed that leucine-rich repeat-containing G protein-coupled receptor 4 (LGR4) is highly expressed. LGR4, LGR5, and LGR6 form a subfamily of closely related receptors. Recently, R-spondin (Rspo) family proteins were identified as ligands of the LGR4 subfamily. In the present study, we investigated the distribution and function of LGR4-LGR6 and Rspos (1-4) in the brain of male rat. In situ hybridization showed that LGR4 is expressed in the ARC, VMH, and median eminence of the hypothalamus. LGR4 colocalizes with neuropeptide Y, proopiomelanocortin, and brain-derived neurotrophic factor neurons. LGR5 is not detectable with in situ hybridization; LGR6 is only expressed in the epithelial lining of the lower portion of the third ventricle and median eminence. Rspo1 is expressed in the VMH and down-regulated with fasting. Rspo3 is expressed in the paraventricular nucleus and also down-regulated with fasting. Rspos 1 and 3 colocalize with the neuronal marker HuD, indicating that they are expressed by neurons. Injection of Rspo1 or Rspo3 into the third brain ventricle inhibited food intake. Rspo1 decreased neuropeptide Y and increased proopiomelanocortin expression in the ARC. Rspo1 and Rspo3 mRNA is up-regulated by insulin. These data indicate that Rspo1 and Rspo3 and their receptor LGR4 form novel circuits in the brain to regulate energy homeostasis.

Brain-specific homeobox factor as a target selector for glucocorticoid receptor in energy balance

The molecular basis underlying the physiologically well-defined orexigenic function of glucocorticoid (Gc) is unclear. Brain-specific homeobox factor (Bsx) is a positive regulator of the orexigenic neuropeptide, agouti-related peptide (AgRP), in AgRP neurons of the hypothalamic arcuate nucleus. Here, we show that in response to fasting-elevated Gc levels, Gc receptor (GR) and Bsx synergize to direct activation of AgRP transcription. This synergy is dictated by unique sequence features in a novel Gc response element in AgRP (AgRP-GRE). In contrast to AgRP-GRE, Bsx suppresses transactivation directed by many conventional GREs, functioning as a gene context-dependent modulator of GR actions or a target selector for GR. Consistent with this finding, AgRP-GRE drives fasting-dependent activation of a target gene specifically in GR(+) Bsx(+) AgRP neurons. These results define AgRP as a common orexigenic target gene of GR and Bsx and provide an opportunity to identify their additional common targets, facilitating our understanding of the molecular basis underlying the orexigenic activity of Gc and Bsx.

A novel transcript is up-regulated by fasting in the hypothalamus and enhances insulin signalling

A transcript of unknown function, regulated by fasting and feeding, was identified by microarray analysis. The transcript is up-regulated in the fasting state. An 1168-bp cDNA was cloned from rat hypothalamus and sequenced. This sequence is consistent with adipogenesis down-regulating transcript 3 (AGD3) (also known as human OCC-1) mRNA. A protein sequence identical to AGD3 was determined by mass spectrometry. In the rat brain, AGD3 mRNA is distributed in the arcuate nucleus, ventromedial hypothalamus, amygdaloid nuclei, hippocampus, and somatic cortex. Double in situ hybridisation showed that AGD3 mRNA is co-localised with pro-opiomelanocortin and neuropeptide Y in arcuate nucleus neurones. AGD3 binds with insulin receptor substrate 4 and increases insulin-stimulated phospho-Akt and regulates AMP-activated protein kinase and mammalian target of rapamycin downstream target S6 kinase phosphorylation.

Ankyrin repeat and SOCS box containing protein 4 (Asb-4) colocalizes with insulin receptor substrate 4 (IRS4) in the hypothalamic neurons and mediates IRS4 degradation

Background

The arcuate nucleus of the hypothalamus regulates food intake. Ankyrin repeat and SOCS box containing protein 4 (Asb-4) is expressed in neuropeptide Y and proopiomelanocortin (POMC) neurons in the arcuate nucleus, target neurons in the regulation of food intake and metabolism by insulin and leptin. However, the target protein(s) of Asb-4 in these neurons remains unknown. Insulin receptor substrate 4 (IRS4) is an adaptor molecule involved in the signal transduction by both insulin and leptin. In the present study we examined the colocalization and interaction of Asb-4 with IRS4 and the involvement of Asb-4 in insulin signaling.

Results

In situ hybridization showed that the expression pattern of Asb-4 was consistent with that of IRS4 in the rat brain. Double in situ hybridization showed that IRS4 colocalized with Asb-4, and both Asb-4 and IRS4 mRNA were expressed in proopiomelanocortin (POMC) and neuropeptide Y (NPY) neurons within the arcuate nucleus of the hypothalamus. In HEK293 cells co-transfected with Myc-tagged Asb-4 and Flag-tagged IRS4, Asb-4 co-immunoprecipitated with IRS4; In these cells endogenous IRS4 also co-immunoprecipitated with transfected Myc-Asb-4; Furthermore, Asb-4 co-immunoprecipitated with IRS4 in rat hypothalamic extracts. In HEK293 cells over expression of Asb-4 decreased IRS4 protein levels and deletion of the SOCS box abolished this effect. Asb-4 increased the ubiquitination of IRS4; Deletion of SOCS box abolished this effect. Expression of Asb-4 decreased both basal and insulin-stimulated phosphorylation of AKT at Thr308.

Conclusions

These data demonstrated that Asb-4 co-localizes and interacts with IRS4 in hypothalamic neurons. The interaction of Asb-4 with IRS4 in cell lines mediates the degradation of IRS4 and decreases insulin signaling.

Expression of ankyrin repeat and suppressor of cytokine signaling box protein 4 (Asb-4) in proopiomelanocortin neurons of the arcuate nucleus of mice produces a hyperphagic, lean phenotype

Ankyrin repeat and suppressor of cytokine signaling box-containing protein 4 (Asb-4) is specifically expressed in the energy homeostasis-related brain areas and colocalizes with proopiomelanocortin (POMC) neurons of the arcuate nucleus (ARC). Injection of insulin into the third ventricle of the rat brain increased Asb-4 mRNA expression in the paraventricular nucleus but not in the ARC of the hypothalamus, whereas injection of leptin (ip) increased Asb-4 expression in both mouse paraventricular nucleus and ARC. A transgenic mouse in which Myc-tagged Asb-4 is specifically expressed in POMC neurons of the ARC was made and used to study the effects of Asb-4 on ingestive behavior and metabolic rate. Animals with overexpression of Asb-4 in POMC neurons demonstrated an increase in food intake. However, POMC-Asb-4 transgenic animals gained significantly less weight from 6-30 wk of age. The POMC-Asb-4 mice had reduced fat mass and increased lean mass and lower levels of blood leptin. The transgenic animals were resistant to high-fat diet-induced obesity. Transgenic mice had significantly higher rates of oxygen consumption and carbon dioxide production than wild-type mice during both light and dark periods. The locomotive activity of transgenic mice was increased. The overexpression of Asb-4 in POMC neurons increased POMC mRNA expression in the ARC. The transgenic animals had no observed effect on peripheral glucose metabolism and the activity of the autonomic nervous system. These results indicate that Asb-4 is a key regulatory protein in the central nervous system, involved in the control of feeding behavior and metabolic rate.

Effect of high-fat feeding on expression of genes controlling availability of dopamine in mouse hypothalamus

Objective

Hypothalamic centers integrate external signals of nutrient availability and energy status and initiate responses to maintain homeostasis. Quantifying changes in hypothalamic gene expression in the presence of nutrient excess may identify novel responsive elements.

Methods

Affymetrix Mouse Genome 430 2.0 oligonucleotide microarrays containing 45 102 probe sets were used to interrogate differential expression of genes in dietary-induced obesity model C57BL6 inbred mice fed a high-fat (35% fat; n = 8) or standard (4% fat; n = 6) diet from 3 to 15 wk of age. Ontologies of regulated genes were examined and expression of selected genes was validated by quantitative real-time polymerase chain reaction.

Results

One thousand two hundred twelve unique gene transcripts showed altered expression on the microarrays. Gene ontology analysis revealed changes in neuropeptide genes responding to leptin, Pomc, Cart, Npy, and Agrp, compatible with a homeostatic response to high-fat intake, although mean weight increased 2.3-fold compared with standard fed mice (P < 0.001). Neurotransmitter system ontologies revealed upregulation of five genes controlling availability of dopamine. Changes in Th tyrosine hydroxylase (2.1-fold) and Slc18a2 solute carrier family 18 (vesicular monoamine), member 2 (4.4-fold) controlling synthesis and release, and Slc6a3 solute carrier family 6 (neurotransmitter transporter, dopamine), member 3 (4.8-fold), Snca α-synuclein (1.3-fold), and Maoa monoamine oxidase (1.9-fold) limiting availability were confirmed by quantitative real-time polymerase chain reaction.

Conclusion

Expression of five genes involved in availability of dopamine was increased after a high-fat diet. Failure to reduce dopamine availability sufficiently, to counter the feeding reward effect, could contribute to diet-induced obesity in these mice.

Gene expression profiling of individual hypothalamic nuclei from single animals using laser capture microdissection and microarrays

In order to identify novel genes involved in appetite and body weight regulation we have developed a microarray based method suitable for detecting small changes in gene expression in discrete groups of hypothalamic neurons. The method is based on a combination of stereological sampling, laser capture microdissection (LCM), PCR based amplification (SuperAmp), and one-color cDNA microarray analysis. To validate the method we assessed and compared fasting induced changes in mRNA levels of Neuropeptide Y (NPY) and proopiomelanocortin (POMC) in the hypothalamic arcuate nucleus (ARC) of diet-induced obese rats using cDNA microarrays, quantitative PCR and in situ hybridization. All methods revealed statistically significant fasting-induced changes in NPY and POMC expression. An additional 3480 differentially expressed probes (fold change >1.22, t-test p=0.05) were identified in the microarray analysis. Our findings demonstrate a consistent gene expression pattern across three different gene expression detection methods and strongly suggest that LCM coupled microarray analysis combined with SuperAmp can be used as a semi-quantitative mRNA profiling tool. Importantly, the sensitivity of the method greatly improves the usefulness of the microarray technology for gene expression profiling in non-homogeneous tissues such as the brain.

Ankyrin repeat and SOCS box containing protein 4 (Asb-4) interacts with GPS1 (CSN1) and inhibits c-Jun NH2-terminal kinase activity

Asb-4 is a gene that is specifically expressed in the hypothalamic energy homeostasis-associated areas and is down-regulated in the arcuate nucleus of fasted Sprague Dawley and obese Zucker rats. It has two functional domains, the ankyrin repeat and the SOCS box. The function of Asb-4 is unclear. We used yeast two hybridization to search for protein(s) that interact with Asb-4. With Asb-4 minus its SOCS box (Asb-4/Deltasb) as a bait, we screened mouse testis and arcuate nucleus cDNA libraries and identified G-protein pathway suppressor 1 (GPS1, also known as CSN1) as an Asb-4 interacting protein. GPS1 co-immunoprecipitated with Asb-4 both in vitro and in human HEK293 cells. When Asb-4 and GPS1 were co-transfected into HEK293 cells, expression of Asb-4 reduced the protein level of GPS1. Deletion of the SOCS box (Asb4/Deltasb) did not abolish the inhibitory effect of Asb-4 on GPS1, indicating that the SOCS box was not needed for its inhibitory effect. In NIH 3T3 L1 cells, expression of GPS1 enhanced c-Jun NH2-terminal kinase (JNK) activity. Co-expression of Asb-4 with GPS1 inhibited JNK activity. Treatment of the cells with insulin (20 nM) stimulated JNK activity. Expression of GPS1 potentiated the stimulatory effect of insulin, whereas co-expression of Asb-4 along with GPS1 inhibited JNK activity. In HEK293 cells expression of GPS1 elevated phosphorylation of insulin receptor substrate 1 (IRS-1) at serine307, co-expression of Asb-4 with GPS1 reduced the IRS-1ser307 phosphorylation. The present study demonstrates that Asb-4 interacts with GPS1 and inhibits JNK activity.

Application of DNA Microarrays in the Study of Human Obesity and Type 2 Diabetes

DNA microarrays have provided medical researchers with a powerful tool to study the mechanisms of complex diseases, including obesity and type 2 diabetes (T2D). The technology has been used to dissect virtually every aspect of the genetic and molecular basis of these two diseases. Gene expression profiling is the major application of DNA microarrays so far. Subcutaneous fat, visceral fat, adipocyte and preadipocyte, muscle, liver, pancreas and specific nuclei in the hypothalamus under normal and disease conditions are used in addressing the profile of gene expression in obesity and T2D. Comparisons of fat depots in humans and animal models - including ob/ob and db/db mice, diet-induced obese mice, fa/fa Zucker rats, gene knockout (plin (-/-), GLUT4 (-/-)) and transgenic mice (GLUT4-Tg) - have been employed in microarray experiments. The effects of various interventions, such as hormonal and drug treatments, exercise, and surgery, have been studied to determine the expression profile of different developmental stages in cells and the effect of treatment on the two diseases. In this review, the application of microarrays in elucidating the role of retinol binding protein 4 as a link between obesity and T2D is discussed. The possible role in obesity of a common genetic variant near the INSIG2 gene and the discovery of the BBS9 gene are also discussed. The problems and challenges are summarized under eight categories and suggestions for the future direction of research in this area are proposed.

Epigenetics of autism spectrum disorders

The autism spectrum disorders (ASD) comprise a complex group of behaviorally related disorders that are primarily genetic in origin. Involvement of epigenetic regulatory mechanisms in the pathogenesis of ASD has been suggested by the occurrence of ASD in patients with disorders arising from epigenetic mutations (fragile X syndrome) or that involve key epigenetic regulatory factors (Rett syndrome). Moreover, the most common recurrent cytogenetic abnormalities in ASD involve maternally derived duplications of the imprinted domain on chromosome 15q11-13. Thus, parent of origin effects on sharing and linkage to imprinted regions on chromosomes 15q and 7q suggest that these regions warrant specific examination from an epigenetic perspective, particularly because epigenetic modifications do not change the primary genomic sequence, allowing risk epialleles to evade detection using standard screening strategies. This review examines the potential role of epigenetic factors in the etiology of ASD.