Notch signaling induces a transcriptionally permissive state at the Complement C3d Receptor 2 (CR2) promoter in a pre-B cell model.

During mammalian lymphoid development, Notch signaling is necessary at multiple stages of T lymphopoiesis, including lineage commitment, and later stages of T cell effector differentiation. In contrast, outside of a defined role in the development of splenic marginal zone B cells, there is conflicting evidence regarding whether Notch signaling plays functional roles in other B cell sub-populations. Complement receptor 2 (CR2) modulates BCR-signaling and is tightly regulated throughout differentiation. During B lymphopoiesis, CR2 is detected on immature and mature B cells with high surface expression on marginal zone B cells. Here, we have explored the possibility that Notch regulates human CR2 transcriptional activity using in vitro models including a co-culture system, co-transfection gene reporters and chromatin accessibility assays. We provide evidence that Notch signaling regulates CR2 promoter activity in a mature B cell line, as well as the induction of endogenous CR2 mRNA in a non-expressing pre-B cell line. The dynamics of endogenous gene activation suggests additional unidentified factors are required to mediate surface CR2 expression on immature and mature B lineage cells.

Whole-exome sequencing in multiplex preeclampsia families identifies novel candidate susceptibility genes.

OBJECTIVE: Preeclampsia is a common and serious heritable disorder of human pregnancy. Although there have been notable successes in identification of maternal susceptibility genes a large proportion of the heritability of preeclampsia remains unaccounted for. It is has been postulated that rare variation may account for some of this missing heritability. In this study, we performed whole-exome sequencing (WES) in multiplex families to identify rare exonic risk variants. METHODS: We conducted WES in 244 individuals from 34 Australian/New Zealand multiplex preeclampsia families. Variants were tested for association with preeclampsia using a threshold model and logistic regression. RESULTS: We found significant association for two moderately rare missense variants, rs145743393 (Padj = 0.0032, minor allele frequency = 0.016) in the chromosome 1 open reading frame 35 (C1orf35) gene, and rs34270076 (Padj = 0.0128, minor allele frequency = 0.024) in the pyroglutamylated RFamide peptide receptor (QRFPR) gene. To replicate these associations we performed imputation in our Australian genome wide association scan for preeclampsia and found no significant exonic variants in either C1orf35 or QRFPR. However, 11 variants demonstrating nominal significance (P < 0.05) in the genomic region between QRFPR and annexin A5 (ANXA5) were identified. We further leveraged publicly available genome-wide available summary data from the UK Biobank to investigate association of these two variants with the underlying clinical phenotypes of preeclampsia and detected nominal association of the QRFPR variant (rs34270076, P = 0.03) with protein levels in females. CONCLUSION: The study represents the first to use WES in multiplex families for preeclampsia and identifies two novel genes (QRFPR and C1orf35) not previously associated with preeclampsia and find nominal association of rs34270076 with protein levels, a key clinical feature of preeclampsia. We find further support for ANXA5 previously associated with pregnancy complications, including preeclampsia.

Finding potential cis-regulatory loci using allele-specific chromatin accessibility as weights in a kernel-based variance component test.

We present a novel approach to detect potential cis-acting regulatory loci that combines the functional potential, an empirical DNase-seq based estimate of the allele-specificity of DNase-I hypersensitivity sites, with kernel-based variance component association analyses against expression phenotypes. To test our method we used public ENCODE whole genome DNase-I sequencing data, from a single sample, to estimate the functional potentials of the subset of 10,552 noncoding heterozygous single-nucleotide polymorphisms (SNPs) that were also present in the Genetic Analysis Workshop 19 (GAW19) family-based data set. We then built two covariance kernels, one nonweighted and one weighted by the functional potentials, and conducted kernel-based variance component association analyses against the 20,527 transcript expression phenotypes in the GAW19 family-based data set. We found signals of potential cis-regulatory effects, that surpassed the Bonferroni significance threshold, for ten transcripts. Stepwise removal of the cis-located SNPs from the weighted kernel lead to the disappearance of the association signal from our top transcript hit. We found compelling evidence of allele-specific cis-regulation for four transcripts using both kernels, and our results agree with previous research that suggests the involvement of specific cis-located variants in the regulation of their neighboring gene.

Identification of a thalidomide derivative that selectively targets tumorigenic liver progenitor cells and comparing its effects with lenalidomide and sorafenib.

BACKGROUND & AIMS: The availability of non-tumorigenic and tumorigenic liver progenitor cell (LPC) lines affords a method to screen putative anti-liver cancer agents to identify those that are selectively effective. To prove this principle we tested thalidomide and a range of its derivatives and compared them to lenalidomide and sorafenib, to assess their growth-inhibitory effects. METHODS: Cell growth, the mitotic and apoptotic index of cell cultures were measured using the Cellavista instrument (SynenTec) using commercially available reagents. RESULTS: Neither lenalidomide nor thalidomide (100 µM) affected tumorigenic LPCs but killed their non-tumorigenic counterparts. Sorafenib arrested growth in both cell types. All but two derivatives of thalidomide were ineffective; of the two effective derivatives, one (thalidomide C1) specifically affected the tumorigenic cell line (10 µM). Mitotic and apoptotic analyses revealed that thalidomide C1 induced apoptotic cell death and not mitotic arrest. CONCLUSIONS: This study shows that screens incorporating non-tumorigenic and tumorigenic liver cell lines are a sound approach to identify agents that are effective and selective. A high throughput instrument such as the Cellavista affords robust and reproducible objective measurements with a large number of replicates that are reliable. These experiments show that neither lenalidomide nor thalidomide are potentially useful for anti-liver cancer therapy as they kill non-tumorigenic liver cells and not their tumorigenic counterparts. Sorafenib in contrast, is highly effective, but not selective. One tested thalidomide derivative has potential as an anti-tumor drug since it induced growth arrest; and importantly, it selectively induced apoptotic cell death only in tumorigenic liver progenitor cells.

Preferential association of a functional variant in complement receptor 2 with antibodies to double-stranded DNA.

OBJECTIVES: Systemic lupus erythematosus (SLE; OMIM 152700) is characterised by the production of antibodies to nuclear antigens. We previously identified variants in complement receptor 2 (CR2/CD21) that were associated with decreased risk of SLE. This study aimed to identify the causal variant for this association. METHODS: Genotyped and imputed genetic variants spanning CR2 were assessed for association with SLE in 15 750 case-control subjects from four ancestral groups. Allele-specific functional effects of associated variants were determined using quantitative real-time PCR, quantitative flow cytometry, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP)-PCR. RESULTS: The strongest association signal was detected at rs1876453 in intron 1 of CR2 (pmeta=4.2×10(-4), OR 0.85), specifically when subjects were stratified based on the presence of dsDNA autoantibodies (case-control pmeta=7.6×10(-7), OR 0.71; case-only pmeta=1.9×10(-4), OR 0.75). Although allele-specific effects on B cell CR2 mRNA or protein levels were not identified, levels of complement receptor 1 (CR1/CD35) mRNA and protein were significantly higher on B cells of subjects harbouring the minor allele (p=0.0248 and p=0.0006, respectively). The minor allele altered the formation of several DNA protein complexes by EMSA, including one containing CCCTC-binding factor (CTCF), an effect that was confirmed by ChIP-PCR. CONCLUSIONS: These data suggest that rs1876453 in CR2 has long-range effects on gene regulation that decrease susceptibility to lupus. Since the minor allele at rs1876453 is preferentially associated with reduced risk of the highly specific dsDNA autoantibodies that are present in preclinical, active and severe lupus, understanding its mechanisms will have important therapeutic implications.

Focused transcription from the human CR2/CD21 core promoter is regulated by synergistic activity of TATA and Initiator elements in mature B cells.

Complement receptor 2 (CR2/CD21) is predominantly expressed on the surface of mature B cells where it forms part of a coreceptor complex that functions, in part, to modulate B-cell receptor signal strength. CR2/CD21 expression is tightly regulated throughout B-cell development such that CR2/CD21 cannot be detected on pre-B or terminally differentiated plasma cells. CR2/CD21 expression is upregulated at B-cell maturation and can be induced by IL-4 and CD40 signaling pathways. We have previously characterized elements in the proximal promoter and first intron of CR2/CD21 that are involved in regulating basal and tissue-specific expression. We now extend these analyses to the CR2/CD21 core promoter. We show that in mature B cells, CR2/CD21 transcription proceeds from a focused TSS regulated by a non-consensus TATA box, an initiator element and a downstream promoter element. Furthermore, occupancy of the general transcriptional machinery in pre-B versus mature B-cell lines correlate with CR2/CD21 expression level and indicate that promoter accessibility must switch from inactive to active during the transitional B-cell window.

Analysis of tandem E-box motifs within human Complement receptor 2 (CR2/CD21) promoter reveals cell specific roles for RP58, E2A, USF and localized chromatin accessibility.

Complement receptor 2 (CR2/CD21) plays an important role in the generation of normal B cell immune responses. As transcription appears to be the prime mechanism via which surface CR2/CD21 expression is controlled, understanding transcriptional regulation of this gene will have broader implications to B cell biology. Here we report opposing, cell-context specific control of CR2/CD21 promoter activity by tandem E-box elements, spaced 22 bp apart and within 70 bp of the transcription initiation site. We have identified E2A and USF transcription factors as binding to the distal and proximal E-box sites respectively in CR2-positive B-cells, at a site that is hypersensitive to restriction enzyme digestion compared to non-expressing K562 cells. However, additional unidentified proteins have also been found to bind these functionally important elements. By utilizing a proteomics approach we have identified a repressor protein, RP58, binding the distal E-box motif. Co-transfection experiments using RP58 overexpression constructs demonstrated a specific 10-fold repression of CR2/CD21 transcriptional activity mediated through the distal E-box repressor element. Taken together, our results indicate that repression of the CR2/CD21 promoter can occur through one of the E-box motifs via recruitment of RP58 and other factors to bring about a silenced chromatin context within CR2/CD21 non-expressing cells.

Effects of copy number variable regions on local gene expression in white blood cells of Mexican Americans.

Only few systematic studies on the contribution of copy number variation to gene expression variation have been published to date. Here we identify effects of copy number variable regions (CNVRs) on nearby gene expression by investigating 909 CNVRs and expression levels of 12059 nearby genes in white blood cells from Mexican-American participants of the San Antonio Family Heart Study. We empirically evaluate our ability to detect the contribution of CNVs to proximal gene expression (presumably in cis) at various window sizes (up to a 10 Mb distance) between the gene and CNV. We found a ~1-Mb window size to be optimal for capturing cis effects of CNVs. Up to 10% of the CNVs in this study were found to be significantly associated with the expression of at least one gene within their vicinity. As expected, we find that CNVs that directly overlap gene sequences have the largest effects on gene expression (compared with non-overlapping CNVRs located nearby), with positive correlation (except for a few exceptions) between estimated genomic dosage and expression level. We find that genes whose expression level is significantly influenced by nearby CNVRs are enriched for immunity and autoimmunity related genes. These findings add to the currently limited catalog of CNVRs that are recognized as expression quantitative trait loci, and have implications for future study designs as well as for prioritizing candidate causal variants in genomic regions associated with disease.

MACROD2 gene associated with autistic-like traits in a general population sample.

There is now substantial evidence that autistic-like traits in the general population lie on a continuum, with clinical autism spectrum disorders (ASD) representing the extreme end of this distribution. In this study, we sought to evaluate five independently identified genetic associations with ASD with autistic-like traits in the general population. In the study cohort, clinical phenotype and genomewide association genotype data were obtained from the Western Australian Pregnancy Cohort (Raine) Study. The outcome measure used was the Autism Spectrum Quotient (AQ), a quantitative measure of autistic-like traits of individuals in the cohort. Total AQ scores were calculated for each individual, as well as scores for three subscales. Five candidate single nucleotide polymorphism (SNP) associations with ASD, reported in previously published genomewide association studies, were selected using a nominal cutoff value of P less than 1.0×10. We tested whether these five SNPs were associated with total AQ and the subscales, after adjustment for possible confounders. SNP rs4141463 located in the macro domain containing 2 (MACROD2) gene was significantly associated with the Communication/Mindreading subscale. No other SNP was significantly associated with total AQ or the subscales. The MACROD2 gene is a strong positional candidate risk factor for autistic-like traits in the general population.

Ethynylbenzenoid metabolites of Antrodia camphorata: synthesis and inhibition of TNF expression.

An improved synthesis of the anti-inflammatory natural product antrocamphin A (2), involving a key Castro-Stephens reaction, is presented, along with the first total synthesis of its congener antrocamphin B (3). Approaches towards the more complex co-metabolite antrodioxolanone (4) were unsuccessful, but a samarium diiodide-mediated pinacol coupling of antrocamphin B did provide the chiral epimers (51). Antrocamphin A (2) inhibits Tumour Necrosis Factor (TNF) reporter gene expression, but its development as an anti-inflammatory agent may be limited by cytotoxicity.

Molecular prioritization strategies to identify functional genetic variants in the cardiovascular disease-associated expression QTL Vanin-1.

There is now good evidence that non-coding sequence variants are involved in the heritability of many common complex traits. The current 'gold standard' approach for assessing functionality is the in vitro reporter gene assay to assess allelic differences in transcriptional activity, usually followed by electrophoretic mobility shift assays to assess allelic differences in transcription factor binding. Although widely used, these assays have inherent limitations, including the lack of endogenous chromatin context. Here we present a more contemporary approach to assessing functionality of non-coding sequence variation within the Vanin-1 (VNN1) promoter. By combining 'gold standard' assays with in vivo assessments of chromatin accessibility, we greatly increase our confidence in the statistically assigned functional relevance. The standard assays revealed the -137 single nucleotide variant to be functional but the -587 variant to have no functional relevance. However, our in vivo tests show an allelic difference in chromatin accessibility surrounding the -587 variant supporting strong functional potential at both sites. Our approach advances the identification of functional variants by providing strong in vivo biological evidence for function.

Genome-wide association study of autistic-like traits in a general population study of young adults.

Lay abstract: It has been proposed that autistic-like traits in the general population lie on a continuum, with clinical Autism Spectrum Disorder (ASD), representing the extreme end of this distribution. The current study undertook a genome-wide association (GWA) scan of 965 young Western Australian adults to identify novel risk variants associated with autistic-like traits. No associations reached genome-wide significance; however, a review of nominally associated single nucleotide polymorphisms (SNPs) indicated two positional candidate loci that have been previously implicated in autistic-like trait etiology. Scientific abstract: Research has proposed that autistic-like traits in the general population lie on a continuum, with clinical ASD representing the extreme end of this distribution. Inherent in this proposal is that biological mechanisms associated with clinical ASD may also underpin variation in autistic-like traits within the general population. A GWA study using 2,462,046 SNPs was undertaken for ASD in 965 individuals from the Western Australian Pregnancy Cohort (Raine) Study. No SNP associations reached genome-wide significance (p < 5.0 × 10(-8)). However, investigations into nominal observed SNP associations (p < 1.0 × 10(-5)) add support to two positional candidate genes previously implicated in ASD etiology, PRKCB1, and CBLN1. The rs198198 SNP (p = 9.587 × 10(-6)), is located within an intron of the protein kinase C, beta 1 (PRKCB1) gene on chromosome 16p11. The PRKCB1 gene has been previously reported in linkage and association studies for ASD, and its mRNA expression has been shown to be significantly down regulated in ASD cases compared with controls. The rs16946931 SNP (p = 1.78 × 10(-6)) is located in a region flanking the Cerebellin 1 (CBLN1) gene on chromosome 16q12.1. The CBLN1 gene is involved with synaptogenesis and is part of a gene family previously implicated in ASD. This GWA study is only the second to examine SNPs associated with autistic-like traits in the general population, and provides evidence to support roles for the PRKCB1 and CBLN1 genes in risk of clinical ASD.

TNF-inducible expression of lymphotoxin-ß in hepatic cells: an essential role for NF-κB and Ets1 transcription factors.

As TNF is one of the earliest signals that can be detected in the leukocyte-derived inflammatory cascade which drives subsequent cytokine production, we are interested in determining whether TNF is one of the initiating factors controlling liver remodeling and regeneration following chronic liver damage. One of the early responses is the expression of lymphotoxin-ß by hepatic progenitor oval cells. The aim of this study was to determine whether hepatic expression of LT-ß was controlled by TNF and to understand the basis of this regulation. We previously showed that LT-ß expression is transcriptionally controlled via the TNF-induced, inflammatory NF-κB pathway in T lymphocytes. Here we show that TNF is able to upregulate LT-ß expression in hepatic cells at the transcriptional level by the binding of NF-κB p50/p65 heterodimers and Ets1 to their respective sites in the LT-ß promoter.

Genome-wide association scan identifies a risk locus for preeclampsia on 2q14, near the inhibin, beta B gene.

Elucidating the genetic architecture of preeclampsia is a major goal in obstetric medicine. We have performed a genome-wide association study (GWAS) for preeclampsia in unrelated Australian individuals of Caucasian ancestry using the Illumina OmniExpress-12 BeadChip to successfully genotype 648,175 SNPs in 538 preeclampsia cases and 540 normal pregnancy controls. Two SNP associations (rs7579169, p = 3.58×10(-7), OR = 1.57; rs12711941, p = 4.26×10(-7), OR = 1.56) satisfied our genome-wide significance threshold (modified Bonferroni p<5.11×10(-7)). These SNPs reside in an intergenic region less than 15 kb downstream from the 3' terminus of the Inhibin, beta B (INHBB) gene on 2q14.2. They are in linkage disequilibrium (LD) with each other (r(2) = 0.92), but not (r(2)<0.80) with any other genotyped SNP ±250 kb. DNA re-sequencing in and around the INHBB structural gene identified an additional 25 variants. Of the 21 variants that we successfully genotyped back in the case-control cohort the most significant association observed was for a third intergenic SNP (rs7576192, p = 1.48×10(-7), OR = 1.59) in strong LD with the two significant GWAS SNPs (r(2)>0.92). We attempted to provide evidence of a putative regulatory role for these SNPs using bioinformatic analyses and found that they all reside within regions of low sequence conservation and/or low complexity, suggesting functional importance is low. We also explored the mRNA expression in decidua of genes ±500 kb of INHBB and found a nominally significant correlation between a transcript encoded by the EPB41L5 gene, ∼250 kb centromeric to INHBB, and preeclampsia (p = 0.03). We were unable to replicate the associations shown by the significant GWAS SNPs in case-control cohorts from Norway and Finland, leading us to conclude that it is more likely that these SNPs are in LD with as yet unidentified causal variant(s).

Diverse biological activities of the vascular non-inflammatory molecules - the Vanin pantetheinases.

The Vanin genes are a family that encode pantetheinases involved in recycling Coenzyme A, catalysing the breakdown of intermediate pantetheine to vitamin B5 for reuse in CoA biosynthesis. The role of pantetheinase in this most fundamental of cellular processes, was substantially characterised by the 1970s. The next 20 years saw little further interest in pantetheinase until various genetic studies implicated the Vanin locus in a range of normal and disease phenotypes, and a consequent interest in the other product of pantetheinase activity, cysteamine. This report seeks to bring together the early biochemical studies with recent biological data implicating cysteamine as a regulator of the oxidative state of a cell. Numerous studies now report a role for Vanin in inflammation, oxidative stress, cell migration and numerous diseases including cardiovascular disease.

Genetic and molecular functional characterization of variants within TNFSF13B, a positional candidate preeclampsia susceptibility gene on 13q.

BACKGROUND: Preeclampsia is a serious pregnancy complication, demonstrating a complex pattern of inheritance. The elucidation of genetic liability to preeclampsia remains a major challenge in obstetric medicine. We have adopted a positional cloning approach to identify maternal genetic components, with linkages previously demonstrated to chromosomes 2q, 5q and 13q in an Australian/New Zealand familial cohort. The current study aimed to identify potential functional and structural variants in the positional candidate gene TNFSF13B under the 13q linkage peak and assess their association status with maternal preeclampsia genetic susceptibility. METHODOLOGY/PRINCIPAL FINDINGS: The proximal promoter and coding regions of the positional candidate gene TNFSF13B residing within the 13q linkage region was sequenced using 48 proband or founder individuals from Australian/New Zealand families. Ten sequence variants (nine SNPs and one single base insertion) were identified and seven SNPs were successfully genotyped in the total Australian/New Zealand family cohort (74 families/480 individuals). Borderline association to preeclampsia (p = 0.0153) was observed for three rare SNPs (rs16972194, rs16972197 and rs56124946) in strong linkage disequilibrium with each other. Functional evaluation by electrophoretic mobility shift assays showed differential nuclear factor binding to the minor allele of the rs16972194 SNP, residing upstream of the translation start site, making this a putative functional variant. The observed genetic associations were not replicated in a Norwegian case/control cohort (The Nord-Trøndelag Health Study (HUNT2), 851 preeclamptic and 1,440 non-preeclamptic women). CONCLUSION/SIGNIFICANCE: TNFSF13B has previously been suggested to contribute to the normal immunological adaption crucial for a successful pregnancy. Our observations support TNFSF13B as a potential novel preeclampsia susceptibility gene. We discuss a possible role for TNFSF13B in preeclampsia pathogenesis, and propose the rs16972194 variant as a candidate for further functional evaluation.

Efforts toward elucidating Thalidomide's molecular target: an expedient synthesis of the first Thalidomide biotin analogue.

Herein we describe the synthesis of the first Thalidomide-biotin analogue in order to initiate investigations into the unknown molecular mode of action of Thalidomide. In this manner we describe the attachment of biotin tether through the Huisgen 1,3-dipolar cycloaddition or "click" synthetic methodology.

New thalidomide analogues derived through Sonogashira or Suzuki reactions and their TNF expression inhibition profiles.

A library of new thalidomide C4/5 analogues containing either a phenyl or alkyne tether were synthesized using Sonogashira or Suzuki cross coupling reactions from their aryl halogenated precursors. All thalidomide analogues were tested for their ability to inhibit the expression of the proinflammatory cytokine Tumor Necrosis Factor (TNF). More explicitly the use of a novel reporter system utilizing the promoter region of the TNF gene in a human T-cell line provided a rapid and effective measure of NFkappaB transcriptional activity. Several compounds either containing either an aryl-isobutyl or aryl-isopropoxy group were the most effective in inhibiting TNF expression, and were several times more active than thalidomide itself. Five of the more active derivatives indicated an apoptotic response while one of these compounds, containing an aldehyde tether, showed possible influence of cell cycling effects.

Genetic variation in PARL influences mitochondrial content.

Given their involvement in processes necessary for life, mitochondrial damage and subsequent dysfunction can lead to a wide range of human diseases. Previous studies of both animal models and humans have suggested that presenilins-associated rhomboid-like protein (PARL) is a key regulator of mitochondrial integrity and function, and plays a role in cellular apoptosis. As a surrogate measure of mitochondrial integrity, we previously measured mitochondrial content in a Caucasian population consisting of large extended pedigrees, with results highlighting a substantial genetic component to this trait. To assess the influence of variation in the PARL gene on mitochondrial content, we re-sequenced 6.5 kb of the gene, identifying 16 SNPs and genotyped these in 1,086 Caucasian individuals, distributed across 170 families. Statistical genetic analysis revealed that one promoter variant, T-191C, exhibited significant effects (after correction for multiple testing) on mitochondrial content levels. Comparison of the transcription factor binding characteristics of the T-191C promoter SNP by EMSA indicates preferential binding of nuclear factors to the T allele, suggesting functional variation in PARL expression. These results suggest that genetic variation within PARL influences mitochondrial abundance and integrity.

Cell- and stage-specific chromatin structure across the Complement receptor 2 (CR2/CD21) promoter coincide with CBF1 and C/EBP-beta binding in B cells.

Stringent developmental transcription requires multiple transcription factor (TF) binding sites, cell-specific expression of signaling molecules, TFs and co-regulators and appropriate chromatin structure. During B-lymphopoiesis, human Complement receptor 2 (CR2/CD21) is detected on immature and mature B cells but not on B cell precursors and plasma cells. We examined cell- and stage-specific human CR2 gene regulation using cell lines modeling B-lymphopoiesis. Chromatin accessibility assays revealed a region between -409 and -262 with enhanced accessibility in mature B cells and pre-B cells, compared to either non-lymphoid or plasma cell-types, however, accessibility near the transcription start site (TSS) was elevated only in CR2-expressing B cells. A correlation between histone acetylation and CR2 expression was observed, while histone H3K4 dimethylation was enriched near the TSS in both CR2-expressing B cells and non-expressing pre-B cells. Candidate sites within the CR2 promoter were identified which could regulate chromatin, including a matrix attachment region associated with CDP, SATB1/BRIGHT and CEBP-beta sites as well as two CBF1 sites. ChIP assays verified that both CBF1 and C/EBP-beta bind the CR2 promoter in B cells raising the possibility that these factors facilitate or respond to alterations in chromatin structure to control the timing and/or level of CR2 transcription.