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

Insulin Elevates ID2 Expression in Trophoblasts and Aggravates Preeclampsia in Obese ASB4-Null Mice

Obesity is a risk factor for preeclampsia. We investigated how obesity influences preeclampsia in mice lacking ankyrin-repeat-and-SOCS-box-containing-protein 4 (ASB4), which promotes trophoblast differentiation via degrading the inhibitor of DNA-binding protein 2 (ID2). Asb4^-/- mice on normal chow (NC) develop mild preeclampsia-like phenotypes during pregnancy, including hypertension, proteinuria, and reduced litter size. Wild-type (WT) and Asb4^-/- females were placed on a high-fat diet (HFD) starting at weaning. At the age of 8-9 weeks, they were mated with WT or Asb4^-/- males, and preeclamptic phenotypes were assessed. HFD-WT dams had no obvious adverse outcomes of pregnancy. In contrast, HFD-Asb4^-/- dams had significantly more severe preeclampsia-like phenotypes compared to NC-Asb4^-/- dams. The HFD increased white fat weights and plasma leptin and insulin levels in Asb4^-/- females. In the HFD-Asb4^-/- placenta, ID2 amounts doubled without changing the transcript levels, indicating that insulin likely increases ID2 at a level of post-transcription. In human first-trimester trophoblast HTR8/SVneo cells, exposure to insulin, but not to leptin, led to a significant increase in ID2. HFD-induced obesity markedly worsens the preeclampsia-like phenotypes in the absence of ASB4. Our data indicate that hyperinsulinemia perturbs the timely removal of ID2 and interferes with proper trophoblast differentiation, contributing to enhanced preeclampsia.

Structural variants and tandem repeats in the founder individuals of four F2 pig crosses and implications to F2 GWAS results

BACKGROUND

Structural variants and tandem repeats are relevant sources of genomic variation that are not routinely analyzed in genome wide association studies mainly due to challenging identification and genotyping. Here, we profiled these variants via state-of-the-art strategies in the founder animals of four F2 pig crosses using whole-genome sequence data (20x coverage). The variants were compared at a founder level with the commonly screened SNPs and small indels. At the F2 level, we carried out an association study using imputed structural variants and tandem repeats with four growth and carcass traits followed by a comparison with a previously conducted SNPs and small indels based association study.

RESULTS

A total of 13,201 high confidence structural variants and 103,730 polymorphic tandem repeats (with a repeat length of 2-20 bp) were profiled in the founders. We observed a moderate to high (r from 0.48 to 0.57) level of co-localization between SNPs or small indels and structural variants or tandem repeats. In the association step 56.56% of the significant variants were not in high LD with significantly associated SNPs and small indels identified for the same traits in the earlier study and thus presumably not tagged in case of a standard association study. For the four growth and carcass traits investigated, many of the already proposed candidate genes in our previous studies were confirmed and additional ones were identified. Interestingly, a common pattern on how structural variants or tandem repeats regulate the phenotypic traits emerged. Many of the significant variants were embedded or nearby long non-coding RNAs drawing attention to their functional importance. Through which specific mechanisms the identified long non-coding RNAs and their associated structural variants or tandem repeats contribute to quantitative trait variation will need further investigation.

CONCLUSIONS

The current study provides insights into the characteristics of structural variants and tandem repeats and their role in association studies. A systematic incorporation of these variants into genome wide association studies is advised. While not of immediate interest for genomic prediction purposes, this will be particularly beneficial for elucidating biological mechanisms driving the complex trait variation.

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.

Placental mitochondrial function as a driver of angiogenesis and placental dysfunction

The placenta is a highly vascularized and complex foetal organ that performs various tasks, crucial to a healthy pregnancy. Its dysfunction leads to complications such as stillbirth, preeclampsia, and intrauterine growth restriction. The specific cause of placental dysfunction remains unknown. Recently, the role of mitochondrial function and mitochondrial adaptations in the context of angiogenesis and placental dysfunction is getting more attention. The required energy for placental remodelling, nutrient transport, hormone synthesis, and the reactive oxygen species leads to oxidative stress, stemming from mitochondria. Mitochondria adapt to environmental changes and have been shown to adjust their oxygen and nutrient use to best support placental angiogenesis and foetal development. Angiogenesis is the process by which blood vessels form and is essential for the delivery of nutrients to the body. This process is regulated by different factors, pro-angiogenic factors and anti-angiogenic factors, such as sFlt-1. Increased circulating sFlt-1 levels have been linked to different preeclamptic phenotypes. One of many effects of increased sFlt-1 levels, is the dysregulation of mitochondrial function. This review covers mitochondrial adaptations during placentation, the importance of the anti-angiogenic factor sFlt-1in placental dysfunction and its role in the dysregulation of mitochondrial function.

Genomic imprinting, growth and maternal–fetal interactions

In the 1980s, mouse nuclear transplantation experiments revealed that both male and female parental genomes are required for successful development to term (McGrath and Solter, 1983; Surani and Barton, 1983). This non-equivalence of parental genomes is because imprinted genes are predominantly expressed from only one parental chromosome. Uniparental inheritance of these genomic regions causes paediatric growth disorders such as Beckwith–Wiedemann and Silver–Russell syndromes (reviewed in Peters, 2014). More than 100 imprinted genes have now been discovered and the functions of many of these genes have been assessed in murine models. The first such genes described were the fetal growth factor insulin-like growth factor 2 (Igf2) and its inhibitor Igf2 receptor (Igf2r) (DeChiara et al., 1991; Lau et al., 1994; Wang et al., 1994). Since then, it has emerged that most imprinted genes modulate fetal growth and resource acquisition in a variety of ways. First, imprinted genes are required for the development of a functional placenta, the organ that mediates the exchange of nutrients between mother and fetus. Second, these genes act in an embryo-autonomous manner to affect the growth rate and organogenesis. Finally, imprinted genes can signal the nutritional status between mother and fetus, and can modulate levels of maternal care. Importantly, many imprinted genes have been shown to affect postnatal growth and energy homeostasis. Given that abnormal birthweight correlates with adverse adult metabolic health, including obesity and cardiovascular disease, it is crucial to understand how the modulation of this dosage-sensitive, epigenetically regulated class of genes can contribute to fetal and postnatal growth, with implications for lifelong health and disease.

Perinatal nutrition interacts with genetic background to alter behavior in a parent-of-origin-dependent manner in adult Collaborative Cross mice

Previous studies in animal models and humans have shown that exposure to nutritional deficiencies in the perinatal period increases the risk of psychiatric disease. Less well understood is how such effects are modulated by the combination of genetic background and parent-of-origin (PO). To explore this, we exposed female mice from 20 Collaborative Cross (CC) strains to protein deficient, vitamin D deficient, methyl donor enriched or standard diet during the perinatal period. These CC females were then crossed to a male from a different CC strain to produce reciprocal F1 hybrid females comprising 10 distinct genetic backgrounds. The adult F1 females were then tested in the open field, light/dark, stress-induced hyperthermia, forced swim and restraint stress assays. Our experimental design allowed us to estimate effects of genetic background, perinatal diet, PO and their interactions on behavior. Genetic background significantly affected all assessed phenotypes. Perinatal diet exposure interacted with genetic background to affect body weight, basal body temperature, anxiety-like behavior and stress response. In 8 of 9 genetic backgrounds, PO effects were observed on multiple phenotypes. Additionally, we identified a small number of diet-by-PO effects on body weight, stress response, anxiety- and depressive-like behavior. Our data show that rodent behaviors that model psychiatric disorders are affected by genetic background, PO and perinatal diet, as well as interactions among these factors.

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.

Central and peripheral irisin differentially regulate blood pressure

INTRODUCTION

Irisin is a newly identified 112 amino acid hormone, derived as a product of fibronectin type III domain containing 5 (FNDC5), which is highly related to metabolic activity in skeletal muscle and brown fat. The effects of irisin on cardiovascular functions are unknown.

PURPOSE

To explore the effects of central and peripheral irisin on cardiovascular functions.

METHODS

Irisin was either administrated into 3rd ventricle of rats or intravenously, and its effects on blood pressure and cardiac contractibility measured.

RESULTS

Administration of recombinant human irisin into the 3rd brain ventricle of rats activated neurons in the paraventricular nuclei of the hypothalamus. Central administration of irisin increased blood pressure and cardiac contractibility. Exogenous irisin reversed atenolol-induced inhibition of cardiac contractibility. In contrast, peripheral administration of irisin reduced blood pressure in both control and spontaneously hypertensive rats. Irisin dilated mesenteric artery rings through ATP-sensitive potassium channels.

CONCLUSION

Our studies indicate that central and peripheral irisin may differentially regulate cardiovascular activities.

Expression of ankyrin repeat and SOCS box containing 4 (ASB4) confers migration and invasion properties of hepatocellular carcinoma cells

Ankyrin repeat and SOCS box containing 4 (ASB4) involves in physiological process of ubiquitin-mediated proteasomal degradation. Our previous study demonstrated high expression of ASB4 in hepatocellular carcinoma (HCC) cell lines. This study further reveals its clinical implications and tumorigenic properties in HCC. Analysis of 217 HCC gene expression profiles followed by validation in a separate cohort of 50 cases illustrated high ASB4 in HCC. Among the 50 cases, 54% of tumors exhibited more than 2-fold up-regulation of ASB4. Elevated ASB4 associated with low serum level of a HCC serological marker alpha-fetoprotein (AFP), postulating of its use to differentiate AFP-negative HCC. Suppression of ASB4 in PLC and MHCC97-L HCC cells hindered the cell migration and invasion. Reciprocally, enhanced migration rate was measured when ASB4 was ectopically expressed in Hep3B HCC cells. Cross comparison of results derived from in silico predictions of seed-matched sequences and by analyzing human HCC databases with matched microRNA and gene expression profiles, microRNA-200 (miR-200) family members including miR-200a and miR-200b were predicted to regulate ASB4 expression in HCC. MiR-200a showed inversed expression level with ASB4 in several of studied HCC cell lines. Dual luciferase reporter assay confirmed the presence of miR-200a binding site on the 3' untranslated region of ASB4. Reduced ASB4 level was noticed under the influence of miR-200a mimic treatment, for which this mimic-induced effect was neutralized with miR-200a inhibitor. In conclusion, this study demonstrates for the first time on the involvement of ASB4 in HCC and that its level is regulated by miR-200a.

The ubiquitin ligase ASB4 promotes trophoblast differentiation through the degradation of ID2

Vascularization of the placenta is a critical developmental process that ensures fetal viability. Although the vascular health of the placenta affects both maternal and fetal well being, relatively little is known about the early stages of placental vascular development. The ubiquitin ligase Ankyrin repeat, SOCS box-containing 4 (ASB4) promotes embryonic stem cell differentiation to vascular lineages and is highly expressed early in placental development. The transcriptional regulator Inhibitor of DNA binding 2 (ID2) negatively regulates vascular differentiation during development and is a target of many ubiquitin ligases. Due to their overlapping spatiotemporal expression pattern in the placenta and contrasting effects on vascular differentiation, we investigated whether ASB4 regulates ID2 through its ligase activity in the placenta and whether this activity mediates vascular differentiation. In mouse placentas, ASB4 expression is restricted to a subset of cells that express both stem cell and endothelial markers. Placentas that lack Asb4 display immature vascular patterning and retain expression of placental progenitor markers, including ID2 expression. Using JAR placental cells, we determined that ASB4 ubiquitinates and represses ID2 expression in a proteasome-dependent fashion. Expression of ASB4 in JAR cells and primary isolated trophoblast stem cells promotes the expression of differentiation markers. In functional endothelial co-culture assays, JAR cells ectopically expressing ASB4 increased endothelial cell turnover and stabilized endothelial tube formation, both of which are hallmarks of vascular differentiation within the placenta. Co-transfection of a degradation-resistant Id2 mutant with Asb4 inhibits both differentiation and functional responses. Lastly, deletion of Asb4 in mice induces a pathology that phenocopies human pre-eclampsia, including hypertension and proteinuria in late-stage pregnant females. These results indicate that ASB4 mediates vascular differentiation in the placenta via its degradation of ID2.

The SOCS box-adapting proteins for ubiquitination and proteasomal degradation

The suppressor of cytokine signalling (SOCS) box was first identified in the SH2-containing SOCS box family (cytokine-inducible SH2-containing protein, SOCS1-7) and is a 40-amino acid motif, which functions to recruit an E3 ubiquitin ligase complex consisting of the adapter proteins elongins B and C, Rbx2 and the scaffold protein Cullin5. The SOCS box is found in a diverse array of intracellular signalling molecules, many of which contain different protein interaction domains such as SPRY and WD40 domains, leucine and ankyrin repeats or other functional domains such as GTPases. In general, the SOCS box-containing proteins are thought to act as substrate-recognition modules to mediate the polyubiquitination and subsequent degradation of substrate proteins by the 26S proteasome.

Regulation of ankyrin repeat and suppressor of cytokine signalling box protein 4 expression in the immortalized murine endothelial cell lines MS1 and SVR: a role for tumour necrosis factor alpha and oxygen

During vascular development, endothelial cells are exposed to a variety of rapidly changing factors, including fluctuating oxygen levels. We have previously shown that ankyrin repeat and suppressor of cytokine signalling box protein 4 (ASB4) is the most highly differentially expressed gene in the vascular lineage during early differentiation and is expressed in the embryonic vasculature at a time when oxygen tension is rising because of the onset of placental blood flow. To further our understanding of the regulation of ASB4 expression in endothelial cells, we tested the effect of various stressors for their ability to alter ASB4 expression in the immortalized murine endothelial cell lines MS1 and SVR. ASB4 expression is decreased during hypoxic insult and shear stress, whereas it is increased in response to tumour necrosis factor alpha (TNF-α). Further investigation indicated that nuclear factor kappa B (NF-κB) is the responsible transcription factor involved in the TNF-α-induced upregulation of ASB4, placing ASB4 downstream of NF-κB in the TNF-α signalling cascade and identifying it as a potential regulator for TNF-α's numerous functions associated with inflammation, angiogenesis and apoptosis.

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.