Differential binding and transcriptional behaviour of two highly related orphan receptors, ROR alpha(4) and ROR beta(1)

Pleiotropy between language impairment and broader behavioral disorders-an investigation of both common and rare genetic variants

BACKGROUND

Language plays a major role in human behavior. For this reason, neurodevelopmental and psychiatric disorders in which linguistic ability is impaired could have a big impact on the individual's social interaction and general wellbeing. Such disorders tend to have a strong genetic component, but most past studies examined mostly the linguistic overlaps across these disorders; investigations into their genetic overlaps are limited. The aim of this study was to assess the potential genetic overlap between language impairment and broader behavioral disorders employing methods capturing both common and rare genetic variants.

METHODS

We employ polygenic risk scores (PRS) trained on specific language impairment (SLI) to evaluate genetic overlap across several disorders in a large case-cohort sample comprising ~13,000 autism spectrum disorder (ASD) cases, including cases of childhood autism and Asperger's syndrome, ~15,000 attention deficit/hyperactivity disorder (ADHD) cases, ~3000 schizophrenia cases, and ~21,000 population controls. We also examine rare variants in SLI/language-related genes in a subset of the sample that was exome-sequenced using the SKAT-O method.

RESULTS

We find that there is little evidence for genetic overlap between SLI and ADHD, schizophrenia, and ASD, the latter being in line with results of linguistic analyses in past studies. However, we observe a small, significant genetic overlap between SLI and childhood autism specifically, which we do not observe for SLI and Asperger's syndrome. Moreover, we observe that childhood autism cases have significantly higher SLI-trained PRS compared to Asperger's syndrome cases; these results correspond well to the linguistic profiles of both disorders. Our rare variant analyses provide suggestive evidence of association for specific genes with ASD, childhood autism, and schizophrenia.

CONCLUSIONS

Our study provides, for the first time, to our knowledge, genetic evidence for ASD subtypes based on risk variants for language impairment.

Antiinflammatory activity of ANGPTL4 facilitates macrophage polarization to induce cardiac repair

Mesenchymal stem cells (MSCs) can suppress pathological inflammation. However, the mechanisms underlying the association between MSCs and inflammation remain unclear. Under coculture conditions with macrophages, MSCs highly expressed angiopoietin-like 4 (ANGPTL4) to blunt the polarization of macrophages toward the proinflammatory phenotype. ANGPTL4-deficient MSCs failed to inhibit the inflammatory macrophage phenotype. In inflammation-related animal models, the injection of coculture medium or ANGPTL4 protein increased the antiinflammatory macrophages in both peritonitis and myocardial infarction. In particular, cardiac function and pathology were markedly improved by ANGPTL4 treatment. We found that retinoic acid-related orphan receptor α (RORα) was increased by inflammatory mediators, such as IL-1β, and bound to ANGPTL4 promoter in MSCs. Collectively, RORα-mediated ANGPTL4 induction was shown to contribute to the antiinflammatory activity of MSCs against macrophages under pathological conditions. This study suggests that the capability of ANGPTL4 to induce tissue repair is a promising opportunity for safe stem cell-free regeneration therapy from a translational perspective.

Retinoid-Related Orphan Receptor β and Transcriptional Control of Neuronal Differentiation

The ability to generate neuronal diversity is central to the function of the nervous system. Here we discuss the key neurodevelopmental roles of retinoid-related orphan receptor β (RORβ) encoded by the Rorb (Nr1f2) gene. Recent studies have reported loss of function of the human RORB gene in cases of familial epilepsy and intellectual disability. Principal sites of expression of the Rorb gene in model species include sensory organs, the spinal cord, and brain regions that process sensory and circadian information. Genetic analyses in mice have indicated functions in circadian behavior, vision, and, at the cellular level, the differentiation of specific neuronal cell types. Studies in the retina and sensory areas of the cerebral cortex suggest that this orphan nuclear receptor acts at decisive steps in transcriptional hierarchies that determine neuronal diversity.

Retinoic acid-related orphan receptor RORβ, circadian rhythm abnormalities and tumorigenesis (Review)

Nuclear receptors are a superfamily of transcription factors including the steroid hormone receptors, non-steroid hormone receptors and the orphan nuclear receptor family. Retinoic acid-related orphan receptor (ROR)β, as a member of the orphan nuclear receptor family, plays an important regulatory role in the maintenance of a variety of physiological and pathological processes. RORβ has been determined to act as an osteogenic repressor in regulating bone formation, and is involved in regulating circadian rhythm. The findings of recent studies concerning the association between tumorigenesis and circadian rhythm have shown that an aberrant circadian rhythm may promote tumorigenesis and tumor progression. The mechanisms discussed in this review demonstrate how aberrant RORβ-induced circadian rhythm may become a new direction for future studies on tumorigenesis and strategy design for cancer prevention.

Control of gene expression by the retinoic acid-related orphan receptor alpha in HepG2 human hepatoma cells

Retinoic acid-related Orphan Receptor alpha (RORα; NR1F1) is a widely distributed nuclear receptor involved in several (patho)physiological functions including lipid metabolism, inflammation, angiogenesis, and circadian rhythm. To better understand the role of this nuclear receptor in liver, we aimed at displaying genes controlled by RORα in liver cells by generating HepG2 human hepatoma cells stably over-expressing RORα. Genes whose expression was altered in these cells versus control cells were displayed using micro-arrays followed by qRT-PCR analysis. Expression of these genes was also altered in cells in which RORα was transiently over-expressed after adenoviral infection. A number of the genes found were involved in known pathways controlled by RORα, for instance LPA, NR1D2 and ADIPOQ in lipid metabolism, ADIPOQ and PLG in inflammation, PLG in fibrinolysis and NR1D2 and NR1D1 in circadian rhythm. This study also revealed that genes such as G6PC, involved in glucose homeostasis, and AGRP, involved in the control of body weight, are also controlled by RORα. Lastly, SPARC, involved in cell growth and adhesion, and associated with liver carcinogenesis, was up-regulated by RORα. SPARC was found to be a new putative RORα target gene since it possesses, in its promoter, a functional RORE as evidenced by EMSAs and transfection experiments. Most of the other genes that we found regulated by RORα also contained putative ROREs in their regulatory regions. Chromatin immunoprecipitation (ChIP) confirmed that the ROREs present in the SPARC, PLG, G6PC, NR1D2 and AGRP genes were occupied by RORα in HepG2 cells. Therefore these genes must now be considered as direct RORα targets. Our results open new routes on the roles of RORα in glucose metabolism and carcinogenesis within cells of hepatic origin.

Activation of the Blue Opsin Gene in Cone Photoreceptor Development by Retinoid-Related Orphan Receptor β

Color vision requires the expression of opsin photopigments with different wavelength sensitivities in retinal cone photoreceptors. The basic color visual system of mammals is dichromatic, involving differential expression in the cone population of two opsins with sensitivity to short (S, blue) or medium (M, green) wavelengths. However, little is known of the factors that directly activate these opsin genes and thereby contribute to the S or M opsin identity of the cone. We report that the orphan nuclear receptor RORβ (retinoid-related orphan receptor β) activates the S opsin gene (Opn1sw) through binding sites upstream of the gene. RORβ lacks a known physiological ligand and activates the Opn1sw promoter modestly alone but strongly in synergy with the retinal cone-rod homeobox factor (CRX), suggesting a cooperative means of enhancing RORβ activity. Comparison of wild-type and mutant lacZ reporter transgenes showed that the RORβ-binding sites in Opn1sw are required for expression in mouse retina. RORβ-deficient mice fail to induce S opsin appropriately during postnatal cone development. Photoreceptors in these mice also lack outer segments, indicating additional functions for RORβ in photoreceptor morphological maturation. The results identify Opn1sw as a target gene for RORβ and suggest a key role for RORβ in regulating opsin expression in the color visual system.

The Gene Encoding Fibrinogen-β Is a Target for Retinoic Acid Receptor-Related Orphan Receptor α

Fibrinogen is a plasma protein synthesized by the liver. It is composed of three chains (alpha, beta, gamma). In addition to its main function as a coagulation factor, this acute phase protein is also a risk marker for atherosclerosis. Retinoic acid receptor-related orphan receptor (ROR)alpha is a nuclear receptor modulating physiopathological processes such as cerebellar ataxia, inflammation, atherosclerosis, and angiogenesis. In this study, we identified RORalpha as a regulator of fibrinogen-beta gene expression in human hepatoma cells and in mouse liver. A putative RORalpha response element (RORE) was identified in the human fibrinogen-beta promoter. EMSA showed that RORalpha binds specifically to this RORE, and cotransfection experiments in HepG2 hepatoma cells indicated that this RORE confers RORalpha-dependent transcriptional activation to both the human fibrinogen-beta and the thymidine kinase promoters. Stable transfection experiments in HepG2 and Hep3B hepatoma cells demonstrated that overexpression of RORalpha specifically increases endogenous fibrinogen-beta mRNA levels. Chromatin immunoprecipitation experiments revealed that the fibrinogen-beta RORE is occupied by RORalpha in HepG2 cells. Thus, the human fibrinogen-beta gene is a direct target for RORalpha. Furthermore, fibrinogen-beta mRNA levels in liver and plasma fibrinogen concentrations are specifically decreased in staggerer mice, which are homozygous for a deletion invalidating the Rora gene. Taken together, these data add further evidence for an important role of RORalpha in the control of liver gene expression with potential pathophysiological consequences on coagulation and cardiovascular risk.

Differential transcription of the orphan receptor RORbeta in nuclear extracts derived from Neuro2A and HeLa cells

An important model system for studying the process leading to productive transcription is provided by the superfamily of nuclear receptors, which are for the most part ligand-controlled transcription factors. Over the past years several 'orphan' nuclear receptors have been isolated for which no ligand has yet been identified. Very little is known about how these 'orphan' receptors regulate transcription. In this study we have analysed the biochemical and transcriptional properties of the neuronally expressed orphan nuclear receptor RORbeta (NR1F2) and compared them with the retinoic acid receptor heterodimer RXRalpha-RARalpha (NR2B1-NR1B1) and Gal-VP16 in vitro. Although RORbeta binds to its DNA-binding sites with comparatively low affinity, it efficiently directs transcription in nuclear extracts derived from a neuronal cell line, Neuro2A, but not in nuclear extracts from non-neuronal HeLa cells. In contrast, RXRalpha-RARalpha and the acidic transcription factor Gal-VP16 support transcription in Neuro2A and HeLa nuclear extracts equally efficiently. These observations point to a different (co)factor requirement for transactivation by members of the NR1 subfamily of nuclear receptors.