Master Regulator Of Gene Expression Research Articles

Epigenetic priming of an epithelial enhancer by p63 and CTCF controls expression of a skin-restricted gene XP33

The transcription factor p63 is a renowned master regulator of gene expression of stratified epithelia. While multiple proteins have been identified as p63 bona fide targets, little is known about non-coding RNAs (ncRNAs) whose transcription is controlled by p63. Here, we describe a skin-specific non-coding RNA XP33 as a novel target of p63. XP33 levels are increased during keratinocyte differentiation in vitro, while its depletion results in decreased expression of late cornified gene LCE2D. By using publicly available multi-omics data, we show that CTCF and p63 establish an epithelial enhancer to prime XP33 transcription in a tissue-restricted manner. XP33 promoter and enhancer form a chromatin loop exclusively in keratinocytes but not in other cell types. Moreover, the XP33 enhancer is occupied by differentiation-specific factors that control XP33 transcription. Altogether, we identify a tissue-specific non-coding RNA whose expression is epigenetically regulated by p63 and CTCF.

Effects of a High-Fat Diet and Docosahexaenoic Acid during Pregnancy on Fatty Acid Composition in the Fetal Livers of Mice.

A high-fat diet (HFD) during pregnancy promotes fat accumulation and reduces docosahexaenoic acid (DHA) levels in the liver of the offspring at postnatal ages, which can depend on fetal sex. However, the prenatal mechanisms behind these associations are still unclear. Thus, we analyzed if an HFD alters DHA content and the expression of molecules related to fatty acid (FA) metabolism in the fetal liver. Female C57BL/6 mice were fed a control diet or HFD for 4-6 weeks before pregnancy until the gestational day (GD) 17.5. A subgroup of each diet received DHA (100 mg/Kg) orally from GD 6.5 until 16.5. On GD 17.5, maternal livers, placentas, and livers from male and female fetuses were collected for FA profiling with gas-chromatography and gene expression of molecules related to FA metabolism using qPCR. PPAR-α protein expression was evaluated using Western blot. The gene expression of placental FA transporters was also assessed. An HFD increased eicosapentaenoic acid (EPA) and decreased DHA levels and protein expression of PPAR-α in the fetal livers of both sexes. DHA increased the gene expression of Ppara, Cpt1, and Acsl1 in the livers of female fetuses. Therefore, an HFD reduces DHA levels and PPAR-α, a master regulator of gene expression, in the fetal liver. In turn, the livers of female fetuses seem to be more sensitive to DHA action.

A TIAM1-TRIM28 complex mediates epigenetic silencing of protocadherins to promote migration of lung cancer cells

Lung cancer is the leading cause of cancer deaths. Its high mortality is associated with high metastatic potential. Here, we show that the RAC1-selective guanine nucleotide exchange factor T cell invasion and metastasis-inducing protein 1 (TIAM1) promotes cell migration and invasion in the most common subtype of lung cancer, non-small-cell lung cancer (NSCLC), through an unexpected nuclear function. We show that TIAM1 interacts with TRIM28, a master regulator of gene expression, in the nucleus of NSCLC cells. We reveal that a TIAM1-TRIM28 complex promotes epithelial-to-mesenchymal transition, a phenotypic switch implicated in cell migration and invasion. This occurs through H3K9me3-induced silencing of protocadherins and by decreasing E-cadherin expression, thereby antagonizing cell-cell adhesion. Consistently, TIAM1 or TRIM28 depletion suppresses the migration of NSCLC cells, while migration is restored by the simultaneous depletion of protocadherins. Importantly, high nuclear TIAM1 in clinical specimens is associated with advanced-stage lung adenocarcinoma, decreased patient survival, and inversely correlates with E-cadherin expression.

A phase 1/2 open-label study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of OTX-2002 as a single agent and in combination with standard of care in patients with hepatocellular carcinoma and other solid tumor types known for association with the MYC oncogene (MYCHELANGELO I).

TPS627 Background: MYC, or c-MYC, is a master regulator of gene expression that controls cell growth and proliferation. Dysregulation of MYC is frequently identified in various cancer types, including hepatocellular carcinoma (HCC), where it is overexpressed in up to 70% viral and alcohol-related disease.1 While MYC represents an attractive therapeutic target, it has historically been considered undruggable due to a lack of a structured binding pocket and its tightly autoregulated expression. OTX-2002 is a first-in-class, engineered and programable mRNA therapeutic called Omega Epigenomic Controllers (OECs) that modulates MYC gene expression pre-transcriptionally by creating epigenetic marks at two different structural and regulatory elements within the insulated genomic domain where MYC resides. In vitro studies have demonstrated that downregulation of MYC through OTX-2002 led to loss of viability in HCC cells while sparing normal hepatocytes. In HCC xenograft mouse models, OTX-2002 demonstrated anti-tumor activity as monotherapy and in combinations with standard of care therapies in HCC.2 Methods: OTX-2002 is being evaluated in an open-label, non-randomized, phase 1/2 study (MYCHELANGELO I) in patients with HCC and other advanced solid tumor types (NCT05497453). The study consists of two parts. Part 1 dose escalation explores ascending doses of intravenous OTX-2002 monotherapy given every 2 weeks to identify dose limiting toxicities, maximum tolerated dose, and recommended dose for expansion (RDE) in patients with HCC and other solid tumors using a classic 3+3 design. Upon identification of the RDE, a monotherapy expansion in advanced HCC patients is planned to explore the preliminary anti-tumor activity of OTX-2002. Part 2 will evaluate OTX-2002 in combination with HCC standard of care in the same HCC population as that of Part 1 expansion. The safety of OTX-2002 at the selected dose in combination with a tyrosine kinase inhibitor or immune checkpoint inhibitor will be evaluated in a safety run-in; expansion will follow to identify the preliminary anti-tumor activity of the combinations. Key eligibility criteria for HCC patients include: 1) Barcelona Clinical Liver Cancer (BCLC) stage B or C disease, 2) Child-Pugh A liver function, 3) received at least 1 prior systemic therapy. The MYCHELANGELO I study began enrollment in August 2022, and Part 1 dose escalation is ongoing in the US.

The nuclear factor of activated T cells 5 (NFAT5) contributes to the renal corticomedullary differences in gene expression

The corticomedullary osmotic gradient between renal cortex and medulla induces a specific spatial gene expression pattern. The factors that controls these differences are not fully addressed. Adaptation to hypertonic environment is mediated by the actions of the nuclear factor of activated T-cells 5 (NFAT5). NFAT5 induces the expression of genes that lead to intracellular accumulation of organic osmolytes. However, a systematical analysis of the NFAT5-dependent gene expression in the kidneys was missing. We used primary cultivated inner medullary collecting duct (IMCD) cells from control and NFAT5 deficient mice as well as renal cortex and inner medulla from principal cell specific NFAT5 deficient mice for gene expression profiling. In primary NFAT5 deficient IMCD cells, hyperosmolality induced changes in gene expression were abolished. The majority of the hyperosmolality induced transcripts in primary IMCD culture were determined to have the greatest expression in the inner medulla. Loss of NFAT5 altered the expression of more than 3000 genes in the renal cortex and more than 5000 genes in the inner medulla. Gene enrichment analysis indicated that loss of NFAT5 is associated with renal inflammation and increased expression of kidney injury marker genes, like lipocalin-2 or kidney injury molecule-1. In conclusion we show that NFAT5 is a master regulator of gene expression in the kidney collecting duct and in vivo loss of NFAT function induces a kidney injury like phenotype.

HuR-Targeted Inhibition Impairs Th2 Proinflammatory Responses in Asthmatic CD4+ T Cells.

RNA-binding protein HuR (ELAVL1) is a master regulator of gene expression in human pathophysiology. Its dysregulation plays an important role in many diseases. We hypothesized that HuR plays an important role in Th2 inflammation in asthma in both mouse and human. To address this, we used a model of airway inflammation in a T cell-specific knockout mouse model, distal lck-Cre HuRfl/fl, as well as small molecule inhibitors in human peripheral blood-derived CD4+ T cells. Peripheral CD4+ T cells were isolated from 26 healthy control subjects and 45 asthmatics (36 type 2 high and 9 non-type 2 high, determined by blood eosinophil levels and fraction of exhaled NO). Our mouse data showed conditional ablation of HuR in T cell-abrogated Th2 differentiation, cytokine production, and lung inflammation. Studies using human T cells showed that HuR protein levels in CD4+ T cells were significantly higher in asthmatics compared with healthy control subjects. The expression and secretion of Th2 cytokines were significantly higher in asthmatics compared with control subjects. AMP-activated protein kinase activator treatment reduced the expression of several cytokines in both type 2 high and non-type 2 high asthma groups. However, the effects of CMLD-2 (a HuR-specific inhibitor) were more specific to endotype-defining cytokines in type 2 high asthmatics. Taken together, these data suggest that HuR plays a permissive role in both allergen and non-allergen-driven airway inflammation by regulating key genes, and that interfering with its function may be a novel method of asthma treatment.

Regulation of microglial transcription factor MEF2C by Alzheimer’s disease‐relevant stimuli

The transcription factor, myocyte enhancer factor-2C (MEF2C), is a master regulator of gene expression in microglia, the brain-resident immune cells. In recent years, microglia have become increasingly recognized as key players in Alzheimer's disease (AD)- they are thought to be protective in early AD and detrimental in late AD by producing pro-inflammatory cytokines that contribute to brain inflammation. Both AD and aging have been associated with increased microglial inflammatory responses and chronic inflammation. MEF2C was recently identified as an 'off-factor' helping to restrain the microglial inflammatory response and may therefore be a potential target for AD treatment. This research project aimed to understand the regulation of microglial MEF2C by AD-relevant inflammatory stimuli lipopolysaccharide (LPS) and polyinosinic:polycytidylic (polyI:C).Mouse microglial cell line, BV2, was exposed to LPS or PolyI:C for 3 h and 24 h. Levels of MEF2C protein and RNA were measured by western blot and qPCR, respectively. Furthermore, MEF2C activity in response to the inflammatory stimuli was investigated by measuring the cytoplasmic and nuclear localisation of MEF2C inhibitor histone deacetylase 4 (HDAC4) and by analysing the expression of two predicted target genes of MEF2C, Ccl3 and Mndal, by qPCR.Expression of whole-cell microglial MEF2C was reduced in BV2 cells exposed to LPS and PolyI:C for 3hrs but was increased at 24hrs LPS exposure relative to the control. Cytoplasmic HDAC4 expression was reduced with LPS exposure, which was more pronounced at the 24-hour BV2 cells exposure. In addition, the inflammatory stimuli increased the amount of a potential amino-terminal HDAC4 fragment in the nucleus. Furthermore, Ccl3 and Mndal expression in response to LPS and PolyI:C at 3 hours was reduced.This research project provided evidence that AD-relevant inflammatory stimuli downregulate microglial MEF2C expression. In addition, MEF2C transcriptional activity was reduced by these inflammatory stimuli, possibly via induction of caspase-3, leading to fragmentation of HDAC4 and subsequent translocation of HDAC4 amino-terminal fragment into the nucleus at MEF2C-targeted promoters. Overall, this provided a mechanistic insight on how the crucial function of MEF2C is lost during inflammatory conditions.

CTCF as a regulator of alternative splicing: new tricks for an old player.

Three decades of research have established the CCCTC-binding factor (CTCF) as a ubiquitously expressed chromatin organizing factor and master regulator of gene expression. A new role for CTCF as a regulator of alternative splicing (AS) has now emerged. CTCF has been directly and indirectly linked to the modulation of AS at the individual transcript and at the transcriptome-wide level. The emerging role of CTCF-mediated regulation of AS involves diverse mechanisms; including transcriptional elongation, DNA methylation, chromatin architecture, histone modifications, and regulation of splicing factor expression and assembly. CTCF thereby appears to not only co-ordinate gene expression regulation but contributes to the modulation of transcriptomic complexity. In this review, we highlight previous discoveries regarding the role of CTCF in AS. In addition, we summarize detailed mechanisms by which CTCF mediates AS regulation. We propose opportunities for further research designed to examine the possible fate of CTCF-mediated alternatively spliced genes and associated biological consequences. CTCF has been widely acknowledged as the ‘master weaver of the genome’. Given its multiple connections, further characterization of CTCF’s emerging role in splicing regulation might extend its functional repertoire towards a ‘conductor of the splicing orchestra’.

Inhibition of GATA3 and Th2 cytokines expression in type 2 high asthmatics by a small molecule targeting RNA-binding protein HuR

Abstract RNA-binding protein human antigen R (HuR) is a master regulator of gene expression in human pathophysiology. Our animal studies in the past showed multiple critical roles for HuR in regulating proinflammatory markers in CD4+ T cells. We hypothesized HuR plays an important role in expression of GATA3 and Th2 cytokines in type 2 high asthma and its inhibition impairs these Th2 inflammatory responses. Peripheral CD4+ T cells were isolated from 26 healthy controls and 32 type 2 high asthmatics (blood eosinophil ≥300 cells/μl or FeNO levels ≥25ppb) and stimulated with anti-CD3/CD28 for 4 days, followed by determination of GATA3 and cytokines expression by flow cytometry and LEGENDplex. HuR levels were quantitated by Western blot, flow cytometry, and qPCR. Inhibition of inflammatory responses was evaluated using a cumarin-derived small molecule named CMLD-2 (a HuR-specific inhibitor). Actinomycin D treatment was used to measure mRNA decay rates of targeted HuR mRNAs. HuR protein levels in CD4+ T cells was significantly higher in type 2 high asthmatics compared to healthy controls. The expression and secretion of Th2 cytokines were significantly higher in asthmatics compared to controls. Our further mRNA and protein studies in type 2 high asthmatics showed reduced expression of GATA3 and Th2 cytokines after CMLD-2 treatment. There was also a significant reduction in gata3 mRNA stability with CMLD-2 treatment, compared with vehicle in the asthmatics. Our study is the first to demonstrate the role of RNA-binding protein HuR in type 2 high asthmatics and that interfering with HuR action using CMLD-2 ameliorates GATA3 and Th2 cytokines production. This data suggests HuR may serve as a novel and powerful therapeutic target to treat type 2 high asthmatics.

Cohesin: behind dynamic genome topology and gene expression reprogramming.

Beyond its originally discovered role tethering replicated sister chromatids, cohesin has emerged as a master regulator of gene expression. Recent advances in chromatin topology resolution and single-cell studies have revealed that cohesin has a pivotal role regulating highly dynamic chromatin interactions linked to transcription control. The dynamic association of cohesin with chromatin and its capacity to perform loop extrusion contribute to the heterogeneity of chromatin contacts. Additionally, different cohesin subcomplexes, with specific properties and regulation, control gene expression across the cell cycle and during developmental cell commitment. Here, we discuss the most recent literature in the field to highlight the role of cohesin in gene expression regulation during transcriptional shifts and its relationship with human diseases.

HuR-targeted Inhibition Impairs Th2 Proinflammatory Responses in Asthmatic CD4+ T cells

RNA-binding protein human antigen R (HuR, elavl1) is a master regulator of gene expression in human pathophysiology. Its dysregulation plays an important role in many diseases. We hypothesized that HuR plays an important role in human Th2 asthma (especially type 2-high) and that its inhibition impairs Th2-inflammatory responses.

Abstract P117: Blood Pressure Heterosis And Genotype-Specific Regulation Of C17h6orf52

Although blood pressure (BP) is highly heritable, the genetic etiology is complex, and causative genes do not completely explain observed variation. Using the Lyon Hypertensive (LH) rat—a well-characterized polygenic inbred model—we previously identified a novel candidate gene ( C17h6orf52 ) as a master regulator of gene expression regulating cardiometabolic traits. CRISPR-Cas9 gene editing was used to generate a mutation in C17h6orf52 , and blood pressure in homozygous wildtype (WT), heterozygous (HET) and homozygous mutant (MUT) females was characterized via radiotelemetry. Herein, we show evidence of BP heterosis (i.e. hybrid vigor) in females from the C17h6orf52 strain. Systolic (SBP) and diastolic (DBP) pressures (mmHg) were determined in WT, HET, and MUT male and female rats on normal chow (CHOW), and 4% salt (NaCl) diet (to determine salt sensitivity). All measures are presented as mean±SEM, and significant results are indicated according to statistical test. No significant differences were identified in males, but the HET females (n=5) had significantly lower systolic blood pressure than either WT (n=7) or MUT (n=8) at both baseline and salt-stressed conditions: SBP-CHOW: (WT: 144±3.28; HET: 136.0±0.83 * ; MUT: 142.6±2.13)DBP-CHOW: (WT: 98.3±2.29; HET: 94.0±0.68; MUT: 97.4±1.76)SBP-NaCl: (WT: 150.4±3.40; HET: 142.2±1.19 * ; MUT: 150.2±1.83)DBP-NaCl: (WT: 103.3±2.75; HET: 98.2±1.68; MUT: 103.1±1.68) Tissues were collected to assess C17h6orf52 expression relative to WT, displayed below as confidence intervals. While there were no differences between WT and MUT expression, liver C17h6orf52 was significantly overexpressed in heterozygous females. C17h6orf52 2^-ddCT: (WT: 0.91-1.09, n=8; HET: 1.33-1.73 $ , n=5; MUT: 0.85-1.19, n=8) There were no striking differences in any metabolic phenotypes, such as body weight and adiposity, thus these data suggest that C17h6orf52 is protective against increases in blood pressure specifically. Continued study will attempt to tease apart allele-specific regulation and protein functions in heterozygous animals of both sexes. * p<0.05 by Kruskal-Wallis $ p<0.05 by 1-WAY ANOVA

Circular RNAs and cancer: Opportunities and challenges.

Circular RNAs (circRNAs) are covalently circularized RNA moieties that despite being relatively abundant were only recently identified and have only begun to be investigated within the last couple of years. Even though there are many thousands of genes that appear capable of producing circRNAs, and the fact that many circRNAs appear to be highly evolutionarily conserved, the function of all but a few remain to be fully explored. What has been determined, however, is that circRNAs play key regulatory roles in many aspects of biology with focus being given to their function in cancer. Most of the studies to date have found that circRNAs act as master regulator of gene expression most often than not acting to regulate levels though sequestration or "sponging" of other gene expression regulators, particularly miRNAs. They can also function directly modulating transcription, or by interfering with splicing mechanisms. Some circRNAs can also be translated into functional proteins or peptides. A combination of tissue and developmental stage specific expression along with an innate resistance to RNAse activity means that circRNAs show perhaps their greatest potential as novel biomarkers of cancer. In this chapter we consider the current state of knowledge regarding these molecules, their synthesis, function, and association with cancer. We also consider some of the challenges that remain to be overcome to allow this emerging class of RNAs to fulfill their potential in clinical practice.

Biological and Clinical Relevance of microRNAs in Mitochondrial Diseases/Dysfunctions.

Mitochondrial dysfunction arises from an inadequate number of mitochondria, an inability to provide necessary substrates to mitochondria, or a dysfunction in their electron transport and a denosine triphosphate synthesis machinery. Occurrences of mitochondrial dysfunction are due to genetic or environmental changes in the mitochondria or in the nuclear DNA that codes mitochondrial components. Currently, drug options are available, yet no treatment exists in sight of this disease and needs a new insight into molecular and signaling pathways for this disease. microRNAs (miRNAs) are small, endogenous, and noncoding RNAs function as a master regulator of gene expression. The evolution of miRNAs in the past two decades emerged as a key regulator of gene expression that controls physiological pathological cellular differentiation processes, and metabolic homeostasis such as development and cancer. It has been known that miRNAs are a potential biomarker in both communicable and noncommunicable diseases. But, in the case of mitochondrial dysfunction in miRNAs, the number of studies and investigations are comparatively less than those on other diseases and dysfunctions. In this review, we have elaborated the roles of miRNAs in the mitochondrial diseases and dysfunctions.

Prion-like p53 Amyloids in Cancer.

The global transcription factor, p53, is a master regulator of gene expression in cells. Mutations in the TP53 gene promote unregulated cell growth through the inactivation of downstream effectors of the p53 pathway. In fact, mutant p53 is highly prone to misfolding and frequently resides inside the cell as large aggregates, causing loss of physiological function of the tumor-suppressor protein. Here, we review the plausible reasons for functional loss of p53, including amyloid formation leading to unhindered cancer progression. We discuss previous as well as recent findings regarding the amyloid formation of p53 in vitro and in vivo. We elaborate on prion-like properties of p53 amyloids and their possible involvement in cancer progression. Because the p53 pathway is historically most targeted for the development of anticancer therapeutics, we have also summarized some of the recent approaches and advances in reviving the antiproliferative activities of wild-type p53. In this Perspective, we provide insight into understanding p53 as a prion-like protein and propose cancer to be recognized as an amyloid or prion-like disease.

Abstract 053: Gene Editing Yields a Novel Rat Model of Cardiometabolic Disease

Despite strong evidence that the Metabolic Syndrome (MetS) is highly heritable, the genetic etiology is complex and few causative genes are known. Using the Lyon Hypertensive (LH) rat we previously identified a novel candidate MetS gene ( C17h6orf52 ) as a putative master regulator of gene expression with pleiotropic effects on body weight and blood pressure regulation. In this study, CRISPR-Cas9 gene editing was used to generate mutations in C17h6orf52 , and females from the resulting strains, designated M1 and M2, were characterized, with all measures presented as mean±SEM. Lean and fat body mass as a percentage of total body composition was measured via nuclear magnetic resonance (NMR), and resting metabolic rate (RMR) was measured via indirect calorimetry. Blood pressure (BP) measurements were obtained via radiotelemetry. Surprisingly, the M1 and M2 mutations in C17h6orf52 result in different splicing variants that are shown to differentially modulate several cardiometabolic phenotypes. The M1 mutation causes significant changes in BP, body composition and RMR, without affecting body weight. The M2 mutation significantly increased body weight and adiposity without changing BP or RMR. These data suggest that C17h6orf52 is protective against cardiometabolic risk factors, given that the mutation confers a greater burden of MetS features on an already obese and hypertensive rat. The continued study of this rat model of MetS has the potential to functionally validate an uncharacterized regulatory gene and provide novel targets for pharmacological intervention in the treatment of cardiometabolic diseases. * p<0.05 by Students t-test & p<0.05 by ANCOVA $ p<0.05 by 2-WAY ANOVA

ZO-2 Is a Master Regulator of Gene Expression, Cell Proliferation, Cytoarchitecture, and Cell Size.

ZO-2 is a cytoplasmic protein of tight junctions (TJs). Here, we describe ZO-2 involvement in the formation of the apical junctional complex during early development and in TJ biogenesis in epithelial cultured cells. ZO-2 acts as a scaffold for the polymerization of claudins at TJs and plays a unique role in the blood–testis barrier, as well as at TJs of the human liver and the inner ear. ZO-2 movement between the cytoplasm and nucleus is regulated by nuclear localization and exportation signals and post-translation modifications, while ZO-2 arrival at the cell border is triggered by activation of calcium sensing receptors and corresponding downstream signaling. Depending on its location, ZO-2 associates with junctional proteins and the actomyosin cytoskeleton or a variety of nuclear proteins, playing a role as a transcriptional repressor that leads to inhibition of cell proliferation and transformation. ZO-2 regulates cell architecture through modulation of Rho proteins and its absence induces hypertrophy due to inactivation of the Hippo pathway and activation of mTOR and S6K. The interaction of ZO-2 with viral oncoproteins and kinases and its silencing in diverse carcinomas reinforce the view of ZO-2 as a tumor regulator protein.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

CRISPR‐Cas9 Gene Editing Yields a Novel Rat Model of Cardiometabolic Disease

Despite strong evidence that the Metabolic Syndrome (MetS) and its defining features (central obesity, dyslipidemia, hypertension, hyperglycemia) are highly heritable, the genetic etiology is complex and relatively few causative genes are known. For this reason, we employ the Lyon Hypertensive (LH) rat, a well‐characterized polygenic inbred MetS model. Previous genetic and computational approaches identified a novel gene (C17h6orf52) as a putative master regulator of gene expression and oxidative phosphorylation with pleiotropic effects on body weight and blood pressure regulation.In this study, two different frameshift mutations were generated independently by CRISPR‐Cas9 gene editing, producing either a 5 base pair deletion or a 10 base pair insertion in exon 2 of C17h6orf52, and females from the resulting mutant rat strains, designated M1 and M2, respectively, were characterized (Table 1). Herein, mutations in C17h6orf52 are shown to significantly increase blood pressure and serum cholesterol in vivo, despite no significant changes in body composition or body weight in LH‐derived female rats.Either mutation appears to cause modest, but significant or nearly significant, increases in blood pressure on a 0.3% NaCl diet. M1−/− females exhibit significantly increased systolic and diastolic blood pressure, while M2−/− females' systolic and diastolic blood pressure is more moderately elevated. This effect is potentiated when animals are administered a high salt diet. Finally, although neither total nor low‐density lipoprotein (LDL) cholesterol is changed in the M1 female rats with respect to their wildtype control, M2 females develop higher serum cholesterol, as well as significantly higher LDL cholesterol.The differences in phenotype between the M1 and M2 mutations were unexpected. Preliminary data indicates that 5 base pair deletion present in the M1−/− rats results in two distinct splicing variants that may be contributing to the observed phenotype differences. Nevertheless, these data suggest that C17h6orf52 is protective against cardiometabolic risk factors, given that C17h6orf52 mRNA is more highly expressed in MetS‐susceptible LH rats than MetS resistant Lyon Normotensive (LN) rats, and the mutation confers a greater burden of MetS features on an already obese and hypertensive rat. The continued study of this rat model of Metabolic Syndrome has the potential to functionally validate an uncharacterized regulatory gene, and provide novel targets for pharmacological intervention in the treatment of obesity.Support or Funding InformationR01HL089895, R21DK089417, T32GM008629, 14GRNT20410043This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Endonuclease and redox activities of human apurinic/apyrimidinic endonuclease 1 have distinctive and essential functions in IgA class switch recombination

The base excision repair (BER) pathway is an important DNA repair pathway and is essential for immune responses. In fact, it regulates both the antigen-stimulated somatic hypermutation (SHM) process and plays a central function in the process of class switch recombination (CSR). For both processes, a central role for apurinic/apyrimidinic endonuclease 1 (APE1) has been demonstrated. APE1 acts also as a master regulator of gene expression through its redox activity. APE1's redox activity stimulates the DNA-binding activity of several transcription factors, including NF-κB and a few others involved in inflammation and in immune responses. Therefore, it is possible that APE1 has a role in regulating the CSR through its function as a redox coactivator. The present study was undertaken to address this question. Using the CSR-competent mouse B-cell line CH12F3 and a combination of specific inhibitors of APE1's redox (APX3330) and repair (compound 3) activities, APE1-deficient or -reconstituted cell lines expressing redox-deficient or endonuclease-deficient proteins, and APX3330-treated mice, we determined the contributions of both endonuclease and redox functions of APE1 in CSR. We found that APE1's endonuclease activity is essential for IgA-class switch recombination. We provide evidence that the redox function of APE1 appears to play a role in regulating CSR through the interleukin-6 signaling pathway and in proper IgA expression. Our results shed light on APE1's redox function in the control of cancer growth through modulation of the IgA CSR process.