Nuclear Hormone Receptor Gene Research Articles

Effects of Different Sources of Culture Substrate on the Growth and Immune Performance of the Red Swamp Crayfish (Procambarus clarkii).

The substrate in the aquatic environment plays a crucial role in nutrient deposition and recovery for the growth of aquatic organisms. In order to optimize the culture medium of Procambarus Clarkii, culture media from different sources were selected in this study to explore their effects on the growth and immune performance of red swamp crayfish. The results showed that the weight gain rate (WGR), body length growth rate (BLGR) and specific growth rate (SGR) in group I2 were the highest, followed by group I1 and group I3. The WGR and SGR of crayfish in the I1 and I2 groups were significantly higher than those in the I3 group (p < 0.05). The activities of acid phosphatase (ACP), alkaline phosphatase (AKP) and superoxide dismutase (SOD) were the highest in group I2, followed by group I3, and the lowest in group I1. The expression trends in growth-related genes, nuclear hormone receptor (E75), molt-inhibiting hormone (MIH) and chitinase genes were similar, and the expression levels in the I2 group were higher than those in the I1 and I3 groups. It was noted that the expression levels of E75 and MIH genes in the I2 group were significantly higher than those in the I3 group (p < 0.05). α diversity analysis of 16S rRNA data showed that there was no statistically significant difference in the abundance of intestinal flora among the three culture substrate groups. The β diversity in the Xitangni group, crayfish Tangni group and Shuitangni group was significantly different. These changes in microbiota suggest that using different substrates to culture crayfish leads to differences in gut microbiota diversity. To sum up, the growth in crayfish and immune performance influenced by the culture substrate condition and aquatic breeding sediment substrates, rather than crab pool and paddy field pond sediment substrates, showed a better effect.

Evolution of the expression and regulation of the nuclear hormone receptor ERR gene family in the chordate lineage

The Estrogen Related Receptor (ERR) nuclear hormone receptor genes have a wide diversity of roles in vertebrate development. In embryos, ERR genes are expressed in several tissues, including the central and peripheral nervous systems. Here we seek to establish the evolutionary history of chordate ERR genes, their expression and their regulation. We examine ERR expression in mollusc, amphioxus and sea squirt embryos, finding the single ERR orthologue is expressed in the nervous system in all three, with muscle expression also found in the two chordates. We show that most jawed vertebrates and lampreys have four ERR paralogues, and that vertebrate ERR genes were ancestrally linked to Estrogen Receptor genes. One of the lamprey paralogues shares conserved expression domains with jawed vertebrate ERRγ in the embryonic vestibuloacoustic ganglion, eye, brain and spinal cord. Hypothesising that conserved expression derives from conserved regulation, we identify a suite of pan-vertebrate conserved non-coding sequences in ERR introns. We use transgenesis in lamprey and chicken embryos to show that these sequences are regulatory and drive reporter gene expression in the nervous system. Our data suggest an ancient association between ERR and the nervous system, including expression in cells associated with photosensation and mechanosensation. This includes the origin in the vertebrate common ancestor of a suite of regulatory elements in the 3’ introns that drove nervous system expression and have been conserved from this point onwards.

Nuclear Receptor Subfamily 2 Group E Member 3 (NR2E3): Role in Retinal Development and Disease.

NR2E3 is a nuclear hormone receptor gene required for the correct development of the retinal rod photoreceptors. Expression of NR2E3 protein in rod cell precursors suppresses cone-specific gene expression and, in concert with other transcription factors including NRL, activates the expression of rod-specific genes. Pathogenic variants involving NR2E3 cause a spectrum of retinopathies, including enhanced S-cone syndrome, Goldmann-Favre syndrome, retinitis pigmentosa, and clumped pigmentary retinal degeneration, with limited evidence of genotype-phenotype correlations. A common feature of NR2E3-related disease is an abnormally high number of cone photoreceptors that are sensitive to short wavelength light, the S-cones. This characteristic has been supported by mouse studies, which have also revealed that loss of Nr2e3 function causes photoreceptors to develop as cells that are intermediate between rods and cones. While there is currently no available cure for NR2E3-related retinopathies, there are a number of emerging therapeutic strategies under investigation, including the use of viral gene therapy and gene editing, that have shown promise for the future treatment of patients with NR2E3 variants and other inherited retinal diseases. This review provides a detailed overview of the current understanding of the role of NR2E3 in normal development and disease, and the associated clinical phenotypes, animal models, and therapeutic studies.

Integrative genetic, genomic and transcriptomic analysis of heat shock protein and nuclear hormone receptor gene associations with spontaneous preterm birth

Heat shock proteins are involved in the response to stress including activation of the immune response. Elevated circulating heat shock proteins are associated with spontaneous preterm birth (SPTB). Intracellular heat shock proteins act as multifunctional molecular chaperones that regulate activity of nuclear hormone receptors. Since SPTB has a significant genetic predisposition, our objective was to identify genetic and transcriptomic evidence of heat shock proteins and nuclear hormone receptors that may affect risk for SPTB. We investigated all 97 genes encoding members of the heat shock protein families and all 49 genes encoding nuclear hormone receptors for their potential role in SPTB susceptibility. We used multiple genetic and genomic datasets including genome-wide association studies (GWASs), whole-exome sequencing (WES), and placental transcriptomics to identify SPTB predisposing factors from the mother, infant, and placenta. There were multiple associations of heat shock protein and nuclear hormone receptor genes with SPTB. Several orthogonal datasets supported roles for SEC63, HSPA1L, SACS, RORA, and AR in susceptibility to SPTB. We propose that suppression of specific heat shock proteins promotes maintenance of pregnancy, whereas activation of specific heat shock protein mediated signaling may disturb maternal–fetal tolerance and promote labor.

Cell free Microcystis aeruginosa spent medium affects Daphnia magna survival and stress response

Primary consumers in freshwater ecosystems, such as the zooplankton organism Daphnia magna, are highly affected by cyanobacteria, both as they may use it as a food source but also by cyanobacterial metabolites present in the water. Here, we investigate the impacts of cyanobacterial metabolites focussing on the environmental realistic scenario of the naturally released mixture without crushing cyanobacterial cells or their uptake as food. Therefore, D. magna were exposed to two concentrations of cell free cyanobacterial spent medium from Microcystis aeruginosa PCC 7806 to represent higher and lower ecologically-relevant concentrations of cyanobacterial metabolites. Including microcystin-LR, 11 metabolites have been detected of which 5 were quantified. Hypothesising concentration and time dependent negative impact, survival, gene expression marking digestion and metabolism, oxidative stress response, cell cycle and molting as well as activities of detoxification and antioxidant enzymes were followed for 7 days. D. magna suffered from oxidative stress as both catalase and glutathione S-transferase enzyme activities significantly decreased, suggesting enzyme exhaustibility after 3 and 7 days. Moreover, gene-expressions of the 4 stress markers (glutathione S-transferase, glutathione peroxidase, catalase and thioredoxin) were merely downregulated after 7 days of exposure. Energy allocation (expression of glyceraldehyde-3-phosphate dehydrogenase) was increased after 3 days but decreased as well after 7 days exposure. Cell cycle was impacted time dependently but differently by the two concentrations, along with an increasing downregulation of myosin heavy chain responsible for cell arrangement and muscular movements. Deregulation of nuclear hormone receptor genes indicate that D. magna hormonal steering including molting seemed impaired despite no detection of microviridin J in the extracts. As a consequence of all those responses and presumably of more than investigated molecular and physiological changes, D. magna survival was impaired over time, in a concentration dependent manner. Our results confirm that besides microcystin-LR, other secondary metabolites contribute to negative impact on D. magna survival and stress response.

The Selection of Reliable Reference Genes for RT-qPCR Analysis of Anisakis simplex Sensu Stricto Gene Expression from Different Developmental Stages

BackgroundAnisakis simplex s. s. is a parasitic nematode with a complex life cycle in which humans can become accidental hosts by consuming raw or not fully cooked fish containing L3 larvae. The growing popularity of raw fish dishes has contributed to an increase in the incidence of anisakiasis, which has spurred scientific efforts to develop new methods for diagnosing and treating the disease and also to investigate the gene expression at different developmental stages of this parasite. The identification of reference genes suitable for the normalization of RT-qPCR data has not been studied with respect to A. simplex s. s.MethodsIn the present study, eight candidate reference genes were analyzed in A. simplex s. s. at two different developmental stages: L3 and L4. The expression stability of these genes was assessed by geNorm and NormFinder softwares.ResultsIn general, our results identified translation elongation factor 1α (ef-1α) and peptidyl-prolyl isomerase 12 (ppi12) as the most stable genes in L3 and L4 developmental stages of A. simplex s. s. Validation of the selected reference genes was performed by profiling the expression of the nuclear hormone receptor gene (nhr 48) in different developmental stages.ConclusionsThis first analysis selecting suitable reference genes for RT-qPCR in A. simplex s. s. will facilitate future functional analyses and deep mining of genetic resources in this parasitic nematode.

Nr2e3 is a genetic modifier that rescues retinal degeneration and promotes homeostasis in multiple models of retinitis pigmentosa

Recent advances in viral vector engineering, as well as an increased understanding of the cellular and molecular mechanism of retinal diseases, have led to the development of novel gene therapy approaches. Furthermore, ease of accessibility and ocular immune privilege makes the retina an ideal target for gene therapies. In this study, the nuclear hormone receptor gene Nr2e3 was evaluated for efficacy as broad-spectrum therapy to attenuate early to intermediate stages of retinal degeneration in five unique mouse models of retinitis pigmentosa (RP). RP is a group of heterogenic inherited retinal diseases associated with over 150 gene mutations, affecting over 1.5 million individuals worldwide. RP varies in age of onset, severity, and rate of progression. In addition, ~40% of RP patients cannot be genetically diagnosed, confounding the ability to develop personalized RP therapies. Remarkably, Nr2e3 administered therapy resulted in reduced retinal degeneration as observed by increase in photoreceptor cells, improved electroretinogram, and a dramatic molecular reset of key transcription factors and associated gene networks. These therapeutic effects improved retinal homeostasis in diseased tissue. Results of this study provide evidence that Nr2e3 can serve as a broad-spectrum therapy to treat multiple forms of RP.

A Novel Micronutrient Blend Mimics Calorie Restriction Transcriptomics in Multiple Tissues of Mice and Increases Lifespan and Mobility in C. elegans.

Background: We previously described a novel micronutrient blend that behaves like a putative calorie restriction mimetic. The aim of this paper was to analyze the beneficial effects of our micronutrient blend in mice and C. elegans, and compare them with calorie restriction. Methods: Whole transcriptomic analysis was performed in the brain cortex, skeletal muscle and heart in three groups of mice: old controls (30 months), old + calorie restriction and old + novel micronutrient blend. Longevity and vitality were tested in C. elegans. Results: The micronutrient blend elicited transcriptomic changes in a manner similar to those in the calorie-restricted group and different from those in the control group. Subgroup analysis revealed that nuclear hormone receptor, proteasome complex and angiotensinogen genes, all of which are known to be directly related to aging, were the most affected. Furthermore, a functional analysis in C. elegans was used. We found that feeding C. elegans the micronutrient blend increased longevity as well as vitality. Conclusions: We describe a micronutrient supplement that causes similar changes (transcriptomic and promoting longevity and vitality) as a calorie restriction in mice and C. elegans, respectively, but further studies are required to confirm these effects in humans.

Meiotic gatekeeper STRA8 suppresses autophagy by repressing Nr1d1 expression during spermatogenesis in mice.

The transition from mitotic to meiotic cell cycles is essential for haploid gamete formation and fertility. Stimulated by retinoic acid gene 8 (Stra8) is an essential gatekeeper of meiotic initiation in vertebrates; yet, the molecular role of STRA8 remains principally unknown. Here we demonstrate that STRA8 functions as a suppressor of autophagy during spermatogenesis in mice. Stra8-deficient germ cells fail to enter meiosis and present aberrant upregulation of autophagy-lysosome genes, commensurate with autophagy activation. Biochemical assays show that ectopic expression of STRA8 alone is sufficient to inhibit both autophagy induction and maturation. Studies also revealed that, Nr1d1, a nuclear hormone receptor gene, is upregulated in Stra8-deficient testes and that STRA8 binds to the Nr1d1 promoter, indicating that Nr1d1 is a direct target of STRA8 transcriptional repression. In addition, it was found that NR1D1 binds to the promoter of Ulk1, a gene essential for autophagy initiation, and that Nr1d1 is required for the upregulated Ulk1 expression in Stra8-deficient testes. Furthermore, both genetic deletion of Nr1d1 and pharmacologic inhibition of NR1D1 by its synthetic antagonist SR8278 exhibit rescuing effects on the meiotic initiation defects observed in Stra8-deficient male germ cells. Together, the data suggest a novel link between STRA8-mediated autophagy suppression and meiotic initiation.

In vivo RNA interference of BmNHR96 enhances the resistance of transgenic silkworm to BmNPV

We previously identified a nuclear hormone receptor gene, BmNHR96, which promotes Bombyx mori nucleopolyhedrovirus (BmNPV) entry into silkworm cells. In an attempt to create an antiviral silkworm strain for better silk production, we used RNAi to downregulate BmNHR96 in silkworm larvae. We screened the resulting BmNHR96-RNAi silkworm strain (NHR) and also explored the antiviral mechanism in vivo. We found that the survival rate of the NHR strain was higher than that of the Dazao strain, when silkworm larvae were infected with BmNPV via oral ODV infection and BV injection. More importantly, the economic characteristics (silk yield) of the transgenic line remained unchanged. These findings reveal that RNAi of BmNHR96 could be an effective way to enhance the tolerance of B. mori to BmNPV infection.

The nuclear hormone receptor gene Nr2c1 (Tr2) is a critical regulator of early retina cell patterning

Nuclear hormone receptors play a major role in the development of many tissues. This study uncovers a novel role for testicular receptor 2 (Tr2, Nr2c1) in defining the early phase of retinal development and regulating normal retinal cell patterning and topography. The mammalian retina undergoes an overlapping yet biphasic period of development to generate all seven retinal cell types. We discovered that Nr2c1 expression coincides with development of the early retinal cells. Loss of Nr2c1 causes a severe vision deficit and impacts early, but not late retina cell types. Retinal cone cell topography is disrupted with an increase in displaced amacrine cells. Additionally, genetic background significantly impacts phenotypic outcome of cone photoreceptor cells but not amacrine cells. Chromatin-IP experiments reveal NR2C1 regulates early cell transcription factors that regulate retinal progenitor cells during development, including amacrine (Satb2) and cone photoreceptor regulators thyroid and retinoic acid receptors. This study supports a role for Nr2c1 in defining the biphasic period of retinal development and specifically influencing the early phase of retinal cell fate.

Protocadherin 19 (PCDH19) interacts with paraspeckle protein NONO to co-regulate gene expression with estrogen receptor alpha (ERα).

De novo and inherited mutations of X-chromosome cell adhesion molecule protocadherin 19 (PCDH19) cause frequent, highly variable epilepsy, autism, cognitive decline and behavioural problems syndrome. Intriguingly, hemizygous null males are not affected while heterozygous females are, contradicting established X-chromosome inheritance. The disease mechanism is not known. Cellular mosaicism is the likely driver. We have identified p54nrb/NONO, a multifunctional nuclear paraspeckle protein with known roles in nuclear hormone receptor gene regulation, as a PCDH19 protein interacting partner. Using breast cancer cells we show that PCDH19-NONO complex is a positive co-regulator of ERα-mediated gene expression. Expression of mutant PCDH19 affects at least a subset of known ERα-regulated genes. These data are consistent with our findings that genes regulated by nuclear hormone receptors and those involved in the metabolism of neurosteroids in particular are dysregulated in PCDH19-epilepsy girls and affected mosaic males. Overall we define and characterize a novel mechanism of gene regulation driven by PCDH19, which is mediated by paraspeckle constituent NONO and is ERα-dependent. This PCDH19-NONO-ERα axis is of relevance not only to PCDH19-epilepsy and its comorbidities but likely also to ERα and generally nuclear hormone receptor-associated cancers.

The Nuclear Hormone Receptor NHR-40 Acts Downstream of the Sulfatase EUD-1 as Part of a Developmental Plasticity Switch in Pristionchus

Developmental plasticity, the ability of one genotype to produce distinct phenotypes in different environments, has been suggested to facilitate phenotypic diversification, and several examples in plants and animals support its macroevolutionary potential [1-8]. However, little is known about associated molecular mechanisms, because environmental effects on development are difficult to study by laboratory approaches. One promising system is the mouth dimorphism of the nematode Pristionchus pacificus [9-12]. Following an irreversible decision in larval development, these nematodes form moveable teeth that occur in either of two discrete morphs. The "eurystomatous" (Eu) form has a wide mouth and two teeth, allowing predatory feeding on other nematodes. In contrast, the alternative ("stenostomatous"; St) form has diminutive mouthparts that largely constrain its diet to microbes. The sulfatase EUD-1 was previously discovered to execute a polyphenism switch based on dosage of functional alleles [13] and confirmed a prediction of evolutionary theory about how developmental switches control plasticity [1, 3]. However, the genetic context of this single gene, and hence the molecular complexity of switch mechanisms, was previously unknown. Here we use a suppressor screen to identify factors downstream of eud-1 in mouth-form regulation. We isolated three dominant, X-linked mutants in the nuclear hormone receptor gene nhr-40 that are haploinsufficient. Both eud-1 nhr-40 double and nhr-40 single mutants are all Eu, whereas transgenic overexpression of nhr-40 does not restore the wild-type phenotype but instead results in nearly all-St lines. Thus, NHR-40 is part of a developmental switch, suggesting that switch mechanisms controlling plasticity consist of multi-component hormonal signaling systems.

Vitamin D Regulates Fatty Acid Composition in Subcutaneous Adipose Tissue Through Elovl3.

Fatty acids (FAs) are a major energy source in the body. White adipose tissue (WAT) is a primary site where FAs are stored as triacylglycerols. Brown adipose tissue also stores and recruits FAs as a carbon source for uncoupled β-oxidation during thermogenesis. The deletion of the vitamin D nuclear hormone receptor (VDR) gene in mice (VDRKO) results in a lean WAT phenotype with increased levels of expression of the brown adipose tissue marker Ucp1 in the WAT. However, the impact of vitamin D/VDR on FA composition in WAT has not been explored in detail. To address this question, we examined the FA composition of sc and visceral white adipose depots of VDRKO mice. We found that the levels of a subset of saturated and monounsaturated FAs of C18-C24 are specifically increased in the sc adipose depot in VDRKO mice. We revealed that a specific elongase enzyme (Elovl3), which has an important role in brown fat biology, is directly regulated by VDR and likely contributes to the altered FA composition in VDRKO mice. We also demonstrate that Elovl3 is regulated by vitamin D in vivo and tissue specifically in the sc WAT depot. We discovered that regulation of Elovl3 expression is mediated by ligand-dependent VDR occupancy of a negative-response element in the promoter proximal region of the Elovl3 gene. These data suggest that vitamin D/VDR tissue specifically modulates FA composition in sc WAT through direct regulation of Elovl3 expression.

Establishment of a cell line from the ash and privet borer beetle Tylonotus bimaculatus Haldeman and assessment of its sensitivity to diacylhydrazine insecticides.

A novel cell line, NRCAN-Tb521, was developed from larvae of the longhorn beetle Tylonotus bimaculatus (Coleoptera: Cerambycidae), a pest of North American ash trees. The cell line has been successfully passaged more than 50 times and displayed very strong attachment to the substrate and a modal chromosomal count distribution of 19. Sequencing of a 649 bp fragment of the mitochondrial cytochrome oxidase I gene confirmed the identity of NRCAN-Tb521 as T. bimaculatus. The response of the cell line to 20-hydroxyecdysone and diacylhydrazine ecdysone agonist insecticides was also studied. At 10(-6) M, 20-hydroxyecdysone, tebufenozide, methoxyfenozide and halofenozide triggered the production of numerous filamentous cytoplasmic extensions, and the cells tended to form aggregates, indicative of a cell differentiation response. This response was followed by a strong decrease in viability after 4 d. Reverse transcription polymerase chain reaction (PCR) experiments and sequencing of PCR fragments showed that the 20E receptor gene EcR is expressed in the cells and that 20E, tebufenozide, methoxyfenozide and halofenozide also induce the expression of the nuclear hormone receptor gene HR3. This report establishes that NRCAN-Tb521 is a valuable in vitro model to study effects of ecdysone agonists in wood-boring cerambycids.

Abstract 1530: Identification of vulnerabilities in lung cancer via pooled short hairpin RNA screening

Abstract A major goal of cancer research is to identify tumor-specific vulnerabilities by which cancer cells can be selectively killed. The clinical success of targeted therapies along with technological advances in genome-wide profiling have spurred large-scale, on-going efforts to systematically map the molecular landscapes of human cancers. These approaches nominate candidate essential or tumor suppressor genes, but are not able to identify all types of acquired vulnerabilities, such as synthetic lethal relationships between aberrantly regulated pathways. Functional studies are therefore an essential complement to these approaches, serving both to confirm the biological roles of candidate cancer genes, and also to identify other vulnerabilities that are acquired as a consequence of observed genetic alterations. Loss-of-function studies using pooled short hairpin RNAi screening is proving to be a powerful method by which new cancer targets can be identified. In order to identify new vulnerabilities in lung cancer, we have chosen a focused approach using mini-libraries of short hairpins against selected genes of interest. Nuclear hormone receptors and their co-regulators are aberrantly regulated in many cancers, and therapies targeting these receptors are currently used in treatment of breast and prostate cancers. Quantitative PCR expression data across a panel of lung cancer cell lines suggests that nuclear hormone receptors may be useful as prognostic biomarkers in lung cancer patients, but the role of these receptors in lung tumor biology is not fully understood. We have used a lentiviral pooled short hairpin library of 1062 shRNAs against 120 nuclear hormone receptor and co-regulator genes to identify lung cancer-specific vulnerabilities, both in vitro and in vivo. Briefly, cells were transduced with the library, allowed to undergo a period of selection and expansion, and then injected subcutaneously into NOD-SCID mice. Tumors were harvested after reaching a volume of 300 mm3. A parallel in vitro screen was also performed, in which transduced cells were cultured for 20 population doublings. The relative abundance of individual shRNAs was quantified by next generation sequencing, and genes for which 3 or more shRNAs exhibited depletion either in vitro or in vivo were nominated as candidate essential genes. A screen performed in the lung adenocarcinoma cell line H1819 identified 10 genes that were required for in vitro survival, including BRCA1 and PHB. Five genes were also identified as being required in vivo but not in vitro, including HDAC1 and NCOR2. None of these were found to be mutated by exome sequencing of H1819. Validation studies and investigations into the role for each of these genes in lung cancer are currently on-going. We conclude that our shRNA mini-library screen identifies unsuspected synthetic lethal relationships and thus new therapeutic targets in lung cancer, including some that are only detected by in vivo screening. Citation Format: Suzie Hight, Ryan Carstens, Luc Girard, David Mangelsdorf, John D. Minna. Identification of vulnerabilities in lung cancer via pooled short hairpin RNA screening. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1530. doi:10.1158/1538-7445.AM2014-1530

Modifier Genes as Therapeutics: The Nuclear Hormone Receptor Rev Erb Alpha (Nr1d1) Rescues Nr2e3 Associated Retinal Disease

Nuclear hormone receptors play a major role in many important biological processes. Most nuclear hormone receptors are ubiquitously expressed and regulate processes such as metabolism, circadian function, and development. They function in these processes to maintain homeostasis through modulation of transcriptional gene networks. In this study we evaluate the effectiveness of a nuclear hormone receptor gene to modulate retinal degeneration and restore the integrity of the retina. Currently, there are no effective treatment options for retinal degenerative diseases leading to progressive and irreversible blindness. In this study we demonstrate that the nuclear hormone receptor gene Nr1d1 (Rev-Erbα) rescues Nr2e3-associated retinal degeneration in the rd7 mouse, which lacks a functional Nr2e3 gene. Mutations in human NR2E3 are associated with several retinal degenerations including enhanced S cone syndrome and retinitis pigmentosa. The rd7 mouse, lacking Nr2e3, exhibits an increase in S cones and slow, progressive retinal degeneration. A traditional genetic mapping approach previously identified candidate modifier loci. Here, we demonstrate that in vivo delivery of the candidate modifier gene, Nr1d1 rescues Nr2e3 associated retinal degeneration. We observed clinical, histological, functional, and molecular restoration of the rd7 retina. Furthermore, we demonstrate that the mechanism of rescue at the molecular and functional level is through the re-regulation of key genes within the Nr2e3-directed transcriptional network. Together, these findings reveal the potency of nuclear receptors as modulators of disease and specifically of NR1D1 as a novel therapeutic for retinal degenerations.

The Adiponectin Receptor Homologs in C. elegans Promote Energy Utilization and Homeostasis

Adiponectin is an adipokine with insulin-sensitising actions in vertebrates. Its receptors, AdipoR1 and AdipoR2, are PAQR-type proteins with 7-transmembrane domains and topologies reversed that of GPCR's, i.e. their C-termini are extracellular. We identified three adiponectin receptor homologs in the nematode C. elegans, named paqr-1, paqr-2 and paqr-3. These are differently expressed in the intestine (the main fat-storing tissue), hypodermis, muscles, neurons and secretory tissues, from which they could exert systemic effects. Analysis of mutants revealed that paqr-1 and -2 are novel metabolic regulators in C. elegans and that they act redundantly but independently from paqr-3. paqr-2 is the most important of the three paqr genes: mutants grow poorly, fail to adapt to growth at low temperature, and have a very high fat content with an abnormal enrichment in long (C20) poly-unsaturated fatty acids when combined with the paqr-1 mutation. paqr-2 mutants are also synthetic lethal with mutations in nhr-49, sbp-1 and fat-6, which are C. elegans homologs of nuclear hormone receptors, SREBP and FAT-6 (a Δ9 desaturase), respectively. Like paqr-2, paqr-1 is also synthetic lethal with sbp-1. Mutations in aak-2, the C. elegans homolog of AMPK, or nhr-80, another nuclear hormone receptor gene, suppress the growth phenotype of paqr-2 mutants, probably because they restore the balance between energy expenditure and storage. We conclude that paqr-1 and paqr-2 are receptors that regulate fatty acid metabolism and cold adaptation in C. elegans, that their main function is to promote energy utilization rather than storage, and that PAQR class proteins have regulated metabolism in metazoans for at least 700 million years.

Nuclear Receptor Rev-erb Alpha (Nr1d1) Functions in Concert with Nr2e3 to Regulate Transcriptional Networks in the Retina

The majority of diseases in the retina are caused by genetic mutations affecting the development and function of photoreceptor cells. The transcriptional networks directing these processes are regulated by genes such as nuclear hormone receptors. The nuclear hormone receptor gene Rev-erb alpha/Nr1d1 has been widely studied for its role in the circadian cycle and cell metabolism, however its role in the retina is unknown. In order to understand the role of Rev-erb alpha/Nr1d1 in the retina, we evaluated the effects of loss of Nr1d1 to the developing retina and its co-regulation with the photoreceptor-specific nuclear receptor gene Nr2e3 in the developing and mature retina. Knock-down of Nr1d1 expression in the developing retina results in pan-retinal spotting and reduced retinal function by electroretinogram. Our studies show that NR1D1 protein is co-expressed with NR2E3 in the outer neuroblastic layer of the developing mouse retina. In the adult retina, NR1D1 is expressed in the ganglion cell layer and is co-expressed with NR2E3 in the outer nuclear layer, within rods and cones. Several genes co-targeted by NR2E3 and NR1D1 were identified that include: Nr2c1, Recoverin, Rgr, Rarres2, Pde8a, and Nupr1. We examined the cyclic expression of Nr1d1 and Nr2e3 over a twenty-four hour period and observed that both nuclear receptors cycle in a similar manner. Taken together, these studies reveal a novel role for Nr1d1, in conjunction with its cofactor Nr2e3, in regulating transcriptional networks critical for photoreceptor development and function.

Azadirachtin Interacts with Retinoic Acid Receptors and Inhibits Retinoic Acid-mediated Biological Responses

Considering the role of retinoids in regulation of more than 500 genes involved in cell cycle and growth arrest, a detailed understanding of the mechanism and its regulation is useful for therapy. The extract of the medicinal plant Neem (Azadirachta indica) is used against several ailments especially for anti-inflammatory, anti-itching, spermicidal, anticancer, and insecticidal activities. In this report we prove the detailed mechanism on the regulation of retinoic acid-mediated cell signaling by azadirachtin, active components of neem extract. Azadirachtin repressed all trans-retinoic acid (ATRA)-mediated nuclear transcription factor κB (NF-κB) activation, not the DNA binding but the NF-κB-dependent gene expression. It did not inhibit IκBα degradation, IκBα kinase activity, or p65 phosphorylation and its nuclear translocation but inhibited NF-κB-dependent reporter gene expression. Azadirachtin inhibited TRAF6-mediated, but not TRAF2-mediated NF-κB activation. It inhibited ATRA-induced Sp1 and CREB (cAMP-response element-binding protein) DNA binding. Azadirachtin inhibited ATRA binding with retinoid receptors, which is supported by biochemical and in silico evidences. Azadirachtin showed strong interaction with retinoid receptors. It suppressed ATRA-mediated removal of retinoid receptors, bound with DNA by inhibiting ATRA binding to its receptors. Overall, our data suggest that azadirachtin interacts with retinoic acid receptors and suppresses ATRA binding, inhibits falling off the receptors, and activates transcription factors like CREB, Sp1, NF-κB, etc. Thus, azadirachtin exerts anti-inflammatory and anti-metastatic responses by a novel pathway that would be beneficial for further anti-inflammatory and anti-cancer therapies.