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The mRNA level of the aconitase gene acn of Corynebacterium glutamicum is reduced under iron limitation. Here we show that an AraC-type regulator, termed RipA for "regulator of iron proteins A," is involved in this type of regulation. A C. glutamicum DeltaripA mutant has a 2-fold higher aconitase activity than the wild type under iron limitation, but not under iron excess. Comparison of the mRNA profiles of the DeltaripA mutant and the wild type revealed that the acn mRNA level was increased in the DeltaripA mutant under iron limitation, but not under iron excess, indicating a repressor function of RipA. Besides acn, some other genes showed increased mRNA levels in the DeltaripA mutant under iron starvation (i.e. those encoding succinate dehydrogenase (sdhCAB), nitrate/nitrite transporter and nitrate reductase (narKGHJI), isopropylmalate dehydratase (leuCD), catechol 1,2-dioxygenase (catA), and phosphotransacetylase (pta)). Most of these proteins contain iron. Purified RipA binds to the upstream regions of all operons mentioned above and in addition to that of the catalase gene (katA). From 13 identified binding sites, the RipA consensus binding motif RRGCGN(4)RYGAC was deduced. Expression of ripA itself is repressed under iron excess by DtxR, since purified DtxR binds to a well conserved binding site upstream of ripA. Thus, repression of acn and the other target genes indicated above under iron limitation involves a regulatory cascade of two repressors, DtxR and its target RipA. The modulation of the intracellular iron usage by RipA supplements mechanisms for iron acquisition that are directly regulated by DtxR.

Background Trinucleotide repeat expansion is the cause of at least 25 inherited neurological disorders, including Huntington9s disease (HD), fragile X mental retardation, and myotonic dystrophy (DM1). An interesting feature of repeat expansion mutations is that they are genetically unstable, meaning that increased disease severity and decreased age-of-onset are observed as the mutation is transmitted from parent to offspring. Previous studies on spinocerebellar ataxia 7 and DM1 have identified the cis-acting DNA element CTCF to be implicated in repeat expansion. CTCF is a regulatory factor implicated in genomic imprinting, chromatin remodelling, and DNA conformation change. Mutation or CpG methylation of CTCF binding sites promotes triplet repeat instability both in germ line and somatic tissue. Aim As binding sites for CTCF are associated with many highly unstable repeat loci, CTCF may also be involved in regulating genetic instability in HD. Methods We have in silico identified putative CTCF binding sites in the HTT locus. Confirmation of these CTCF binding sites has been achieved by electrophoretic mobility shift assays. Chromatin immunoprecipitation was performed with a CTCF antibody followed by deep sequencing (ChIP-Seq) in two HD patient fibroblasts and two wild-type control cell lines. Results Using electrophoretic mobility shift assay9s we have identified several CTCF binding sites in the HTT locus of which at least three CTCF binding sites are proximal to the CAG repeat. Analysis of the ChIP-Seq data showed 30 CTCF sites on the genome with differential CTCF binding between HD and control fibroblast cell lines. No differences in CTCF binding within the HTT locus were found between the HD and control cell lines. Conclusions No differential binding of CTCF to the HTT locus in fibroblasts that could suggest that CTCF can act as a modulator in genetic repeat instability in HD. Genome wide analysis and ChIP-Seq in brain tissue will determine if CTCF could be involved in HD pathogenesis.

Huntington’s disease (HD) is caused by a CAG CTG expansion in the huntingtin (HTT) gene. While most research has focused on the HTT polyGln-expansion protein, we recently reported that four...

Death by polyglutamine: expanding our knowledge

Neurofibromatosis, Huntington's disease, and myotonic dystrophy are three hereditary disorders affecting the nervous system. They have in common the basic principles of autosomal dominant inheritance: an affected individual has one parent with the disorder; the disorder affects males and females in approximately equal numbers; and an affected individual has a 50 percent risk of transmitting the disorder to every child. Furthermore, each of the three disorders have additional features that complicate genetic counseling and decisions about reproduction. Neurofibromatosis has an extremely variable expressivity, making the identification of affected individuals difficult and allowing for some reduction in the risk figures; although there is a 50 percent risk of a child inheriting the mutant gene, only one-fourth to one-third of these will experience serious consequences. Huntington's disease has a fairly typical course with degeneration occurring over 10 to 20 years. The frequent late onset of the disorder and the lack of any preclinical test for detecting carriers create problems for those at risk who wish to have children but do not want to pass the disorder to future generations. Both variable expressivity and variable onset are found in myotonic dystrophy. In addition, there is a risk of the severe early onset myotonic dystrophy when the mother is the affected parent. Genetic counseling should be available to patients and families with these three disorders. Nurses who have an understanding of the dynamics of these particular disorders can be empathetic to patients who face personal and family problems caused by the conditions. Alert nursing staff, in casual discussion with patients, may learn of hereditary disorders in a family or may notice symptoms that could lead to diagnosis of one of these disorders. Finally, nurses who are aware of the variations in genetic transmission of these disorders, may be in position to instruct and reinforce genetic counseling that the family has received.

A group of mutations characterized by trinucleotide repeat expansion causes human diseases such as the Fragile X syndrome, Huntington disease (HD), and myotonic dystrophy. Methods based on PCR amplification of the CGG and CAG repeats region could facilitate the development of a rapid screening assay; unfortunately, amplification across CGG and CAG repeats can be inefficient and unreliable due to the G + C base composition. The utility of the PCR on modified DNA for amplification of the CGG and CAG repeats at the Fragile X syndrome and HD has been reported. In the present study, we analyzed the utility of PCR on modified DNA as a rapid screening method for diagnosis of patients with Fragile X syndrome and HD. A comparative analysis realized with 38 Fragile X and 29 HD patients showed that the molecular diagnosis by simple PCR on modified DNA has a sensitivity and specificity of 100% in Fragile X patients and 94.1% and 91.6% in HD patients. The results achieved from the statistical analysis allowed us to conclude that the amplification by simple PCR on modified DNA is a reliable and useful method for the molecular diagnosis of the Fragile X syndrome, but not for the HD.

Profile of Eric Green

The expansion of CAG/CTG repeats is responsible for many diseases, including Huntington's disease (HD) and myotonic dystrophy 1. CAG/CTG expansions are unstable in selective somatic tissues, which accelerates disease progression. The mechanisms underlying repeat instability are complex, and it remains unclear whether chromatin structure and/or transcription contribute to somatic CAG/CTG instability in vivo. To address these issues, we investigated the relationship between CAG instability, chromatin structure, and transcription at the HD locus using the R6/1 and R6/2 HD transgenic mouse lines. These mice express a similar transgene, albeit integrated at a different site, and recapitulate HD tissue-specific instability. We show that instability rates are increased in R6/2 tissues as compared to R6/1 matched-samples. High transgene expression levels and chromatin accessibility correlated with the increased CAG instability of R6/2 mice. Transgene mRNA and H3K4 trimethylation at the HD locus were increased, whereas H3K9 dimethylation was reduced in R6/2 tissues relative to R6/1 matched-tissues. However, the levels of transgene expression and these specific histone marks were similar in the striatum and cerebellum, two tissues showing very different CAG instability levels, irrespective of mouse line. Interestingly, the levels of elongating RNA Pol II at the HD locus, but not the initiating form of RNA Pol II, were tissue-specific and correlated with CAG instability levels. Similarly, H3K36 trimethylation, a mark associated with transcription elongation, was specifically increased at the HD locus in the striatum and not in the cerebellum. Together, our data support the view that transcription modulates somatic CAG instability in vivo. More specifically, our results suggest for the first time that transcription elongation is regulated in a tissue-dependent manner, contributing to tissue-selective CAG instability.

© The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. <br>Background: Increasing attention is being focused on the influence of rapid increases in atmospheric CO2 concentration on nutrient cycling in ecosystems. An understanding of how elevated CO2 affects plant utilization and acquisition of phosphorus (P) will be critical for P management to maintain ecosystem sustainability in P-deficient regions. • Scope: This review focuses on the impact of elevated CO2 on plant P demand, utilization in plants and P acquisition from soil. Several knowledge gaps on elevated CO2-P associations are highlighted. • Conclusions: Significant increases in P demand by plants are likely to happen under elevated CO2 due to the stimulation of photosynthesis, and subsequent growth responses. Elevated CO2 alters P acquisition through changes in root morphology and increases in rooting depth. Moreover, the quantity and composition of root exudates are likely to change under elevated CO2, due to the changes in carbon fluxes along the glycolytic pathway and the tricarboxylic acid cycle. As a consequence, these root exudates may lead to P mobilization by the chelation of P from sparingly soluble P complexes, by the alteration of the biochemical environment and by changes to microbial activity in the rhizosphere. Future research on chemical, molecular, microbiological and physiological aspects is needed to improve understanding of how elevated CO2 might affect the use and acquisition of P by plants.

A Non-Q/N-Rich Prion Domain of a Foreign Prion, [Het-s], Can Propagate as a Prion in Yeast

EVA1A is an autophagy-related protein, which plays an important role in embryonic neurogenesis. In this study, we found that loss of EVA1A could decrease neural differentiation in the brain of adult Eva1a-/- mice. To determine the mechanism underlying this phenotype, we performed label-free quantitative proteomics and bioinformatics analysis using the brains of Eva1a-/- and wild-type mice. We identified 11 proteins that were up-regulated and 17 that were down-regulated in the brains of the knockout mice compared to the wild-type counterparts. Bioinformatics analysis indicated that biological processes, including ATP synthesis, oxidative phosphorylation, and the TCA cycle, are involved in the EVA1A regulatory network. In addition, gene set enrichment analysis showed that neurodegenerativediseases, such as Alzheimer's disease and Huntington's disease, were strongly associated with Eva1a knockout. Western blot experiments showed changes in the expression of nicotinamide nucleotide transhydrogenase, an important mitochondrial enzyme involved in the TCA cycle, in the brains of Eva1a knockout mice. Our study provides valuable information on the molecular functions and regulatory network of the Eva1a gene, as well as new perspectives on the relationship between autography-related proteins and neural differentiation.

Patient-centered care for individuals with myotonic dystrophy (DM1) and Huntington's disease (HD)-chronic, progressive, and life-limiting neurological conditions-may be challenged by patients' cognitive and behavioral impairments. However, no research has explored health care providers' (HCPs') perspectives about patient-centered care provision for these patients along their disease trajectory. Constructivist grounded theory informed the iterative data collection and analysis process. Eleven DM1 or HD HCPs participated in semistructured interviews, and three stages of coding were used to analyze their interview transcripts. Codes were collapsed into themes and categories. Three categories including an evolving care approach, fluid roles, and making a difference were identified. Participants described that their clinical care approach evolved depending on the patient's disease stage and caregivers' degree of involvement. HCPs described that their main goal was to provide hope to patients and caregivers through medical management, crisis prevention, support, and advocacy. Despite the lack of curative treatments, HCPs perceived that patients benefited from ongoing clinical care provided by proactive clinicians. Providing care for individuals with DM1 and HD is a balancing act. HCPs must strike a balance between (1) the frustrations and rewards of patient-centered care provision, (2) addressing symptoms and preventing and managing crises while focusing on patients' and caregivers' quality of life concerns, and (3) advocating for patients while addressing caregivers' needs. This raises important questions: Is patient-centered care possible for patients with cognitive decline? Does chronic neurological care need to evolve to better address patients' and caregivers' complex needs?

Genetic diseases that are accompanied by central nervous system involvement are often fatal. Among these are the autosomal dominant neurogenetic diseases caused by nucleotide repeat expansion. For example, Huntington's disease (HD) and spinal cerebellar ataxia are caused by expansion of a tract of CAGs encoding glutamine. In HD and the other CAG-repeat expansion diseases, the expansion is in the coding region. Myotonic dystrophy is caused by repeat expansions of CUG or CCTG in noncoding regions, and the mutant RNA is disease causing. Treatments for these disorders are limited to symptomatic intervention. RNA interference (RNAi), which is a method for inhibiting target gene expression, provides a unique tool for therapy by attacking the fundamental problem directly. In this review, we describe briefly several representative disorders and their respective molecular targets, and methods to accomplish therapeutic RNAi. Finally, we summarize studies performed to date.

Anticipation is the clinical phenomenon in which disease onset becomes progressively earlier with increasing severity in successive generations.1 Because this phenomenon seemed counter to simple genetic principles, geneticists long dismissed anticipation as an artifact of ascertainment biases. The universal acceptance of anticipation as a genuine biological process did not come until 1992 when the discovery of an unstable CGG repeat expansion gave a molecular explanation for anticipation in fragile X syndrome.2 Subsequent identification of expansion mutations involving unstable CTG/CAG repeats solved the controversies of anticipation in diseases such as myotonic dystrophy; Huntington’s disease (HD); spinocerebellar ataxia (SCA) types 1, 2, 3, and 7; and dentatorubral pallidoluysian atrophy (DRPLA).3,4 Two key observations provided the molecular explanation: 1) intergenerational increases of the size of the expanded repeat allele and 2) an inverse correlation between the size of the expanded allele and the age at onset. Two articles in this issue of Neurology revisit anticipation from unique angles. First, MacDonald et al. show data suggesting the presence of a genetic factor other than the HD gene …