Irma N. Ramos

LINE-1 silencing by retinoblastoma proteins is effected through the nucleosomal and remodeling deacetylase multiprotein complex

BackgroundLong Interspersed Nuclear Element-1 (L1) is an oncogenic mammalian retroelement silenced early in development via tightly controlled epigenetic mechanisms. We have previously shown that the regulatory region of human and murine L1s interact with retinoblastoma (RB) proteins to effect retroelement silencing. The present studies were conducted to identify the corepressor complex responsible for RB-mediated silencing of L1.MethodsChromatin immunoprecipitation and silencing RNA technology were used to identify the repressor complex that silences L1 in human and murine cells.ResultsComponents of the Nucleosomal and Remodeling Deacetylase (NuRD) multiprotein complex specifically enriched the L1 5′-untranslated DNA sequence in human and murine cells. Genetic ablation of RB proteins in murine cells destabilized interactions within the NuRD macromolecular complex and mediated nuclear rearrangement of Mi2-β, an ATP-dependent helicase subunit with nucleosome remodeling activity. Depletion of Mi2-β, RbAP46 and HDAC2 reduced the repressor activity of the NuRD complex and reactivated a synthetic L1 reporter in human cells. Epigenetic reactivation of L1 in RB-null cells by DNA damage was markedly enhanced compared to wild type cells.ConclusionsRB proteins stabilize interactions of the NuRD corepressor complex within the L1 promoter to effect L1 silencing. L1 retroelements may serve as a scaffold on which RB builds heterochromatic regions that regulate chromatin function.

Environmental Risk Factors of Disease in the Cameron Park Colonia, a Hispanic Community Along the Texas–Mexico Border

Objectives This report summarizes the results of a cross-sectional study in Cameron Park in 2000–2001 to identify disease prevalence and health concerns among colonia residents and to identify environmental exposures to potentially adverse environmental conditions. Results Asthma and allergies were among the most prevalent respiratory diseases reported in both adults and children of Cameron Park. Other diseases affecting the community in higher numbers included diabetes and heart disease/high blood pressure. Among children, the most prevalent health conditions were asthma, followed by lung diseases, allergies, and to a lesser degree, skin rashes. Conclusions These data can be useful in developing education and intervention programs to address the public health and medical issues impacting residents in the Cameron Park Colonia of Texas.

A mutant Ahr allele protects the embryonic kidney from hydrocarbon-induced deficits in fetal programming.

Background: The use of experimental model systems has expedited the elucidation of pathogenetic mechanisms of renal developmental disease in humans and the identification of genes that orchestrate developmental programming during nephrogenesis. Objectives: We conducted studies to evaluate the role of AHR polymorphisms in the disruption of renal developmental programming by benzo(a)pyrene (BaP). Methods: We used metanephric cultures of C57BL/6J (C57) mice expressing the Ahrb-1 allele and B6.D2N-Ahrd/J (D2N) mice expressing a mutant allele deficient in ligand binding (Ahrd) to investigate molecular mechanisms of renal development. Deficits in fetal programming were evaluated in the offspring of pregnant mice treated with BaP during nephrogenesis. Results: Hydrocarbon challenge of metanephri from C57 mice altered Wilms’ tumor suppressor gene (Wt1) mRNA splice variant ratios and reduced mRNAs of the Wt1 transcriptional targets syndecan-1 (Sdc1) paired box gene 2 (Pax2), epidermal growth factor receptor (Egfr), and retinoic acid receptor, alpha (Rarα). These changes correlated with down-regulation of effectors of differentiation [secreted frizzled-related sequence protein 1 (Sfrp1), insulin-like growth factor 1 receptor (Igf1r), wingless-related MMTV-integration site 4 (Wnt4), Lim homeobox protein 1 (Lhx1), E-cadherin]. In contrast, metanephri from D2N mice were spared hydrocarbon-induced changes in Wt1 splice variant ratios and deficits of differentiation. We observed similar patterns of dysmorphogenesis and progressive loss of renal function at postnatal weeks 7 and 52 in the offspring of pregnant C57 but not D2N mice gavaged with 0.1 or 0.5 mg/kg BaP on gestation days 10–13. Conclusions: These findings support a functional link between AHR and WT1 in the regulation of renal morphogenesis and raise important questions about the contribution of human AHR polymorphisms to the fetal origins of adult-onset kidney disease.

The Intersection of Genetics and Epigenetics: Reactivation of Mammalian LINE-1 Retrotransposons by Environmental Injury

Transposable elements such as LINE-1 (long interspersed nuclear element-1 or L1) are mobile genetic moieties within the genome. L1 retrotransposons comprise 21 % of the human genome by mass, and up to 100 are believed to remain retrotransposition competent within the human genome. During embryonic development, the genome undergoes reprogramming events defined by specific patterns of DNA methylation established de novo after implantation and preferentially targeted to repetitive sequences. Recent studies in the Ramos laboratory have shown that the ability of polycyclic aromatic hydrocarbon carcinogens, such as benzo(a)pyrene, to reactivate L1 transcription and retrotransposition in mammalian cells involves dysregulation of epigenetic programming mediated in part via mechanisms involving the aryl hydrocarbon receptor, a ligand-activated transcription factor and regulator of several other biological processes. The most detrimental effect of L1 on the genome is believed to be insertion into functional sequences that severely compromise gene function. Other studies have shown that L1 reactivation mediates changes in genetic programming of differentiation networks. Because L1 insertions can have a profound impact on primary genetic structure as well as epigenetic status of the host, they represent ideal molecular targets for development of novel epigenetic therapies targeting medical conditions that involve derangements of L1 activity.

LINE-1 couples EMT programming with acquisition of oncogenic phenotypes in human bronchial epithelial cells

Although several lines of evidence have established the central role of epithelial-to-mesenchymal-transition (EMT) in malignant progression of non-small cell lung cancers (NSCLCs), the molecular events connecting EMT to malignancy remain poorly understood. This study presents evidence that Long Interspersed Nuclear Element-1 (LINE-1) retrotransposon couples EMT programming with malignancy in human bronchial epithelial cells (BEAS-2B). This conclusion is supported by studies showing that: 1) activation of EMT programming by TGF-β1 increases LINE-1 mRNAs and protein; 2) the lung carcinogen benzo(a)pyrene coregulates TGF-β1 and LINE-1 mRNAs, with LINE-1 positioned downstream of TGF-β1 signaling; and, 3) forced expression of LINE-1 in BEAS-2B cells recapitulates EMT programming and induces malignant phenotypes and tumorigenesis in vivo. These findings identify a TGFβ1-LINE-1 axis as a critical effector pathway that can be targeted for the development of precision therapies during malignant progression of intractable NSCLCs.

Culturally-Tailored Education Programs to Address Health Literacy Deficits and Pervasive Health Disparities among Hispanics in Rural Shelbyville, Kentucky.

Objectives This investigation was conducted to evaluate the impact of culturally-tailored education on health knowledge among Hispanic residents of rural, Shelbyville, KY. Design The program identified specific pathways to address health literacy deficits and disparities identified through a community-wide health assessment completed in 2010. Results A total of 43 Hispanic males who shared deficiencies in community-wide health infrastructure were enrolled in the program. The curriculum included an introductory session followed by five, subject-specific, sessions offered on a weekly basis from February to April 2011. Pre/post-test assessments showed marked improvement in knowledge base for all participants after each session, most notably related to cardiovascular disease, diabetes and metabolic syndrome. The group reconvened in January 2012 for follow-up instruction on cardiovascular disease and diabetes, as well as global assessment of knowledge retention over a nine-month period. Comparisons of pre/post testing in cardiovascular disease and diabetes, as well as global health-related knowledge showed significant gains for all parameters. Conclusions Health education programs that embrace perceptions of the community of their own health, and that integrate knowledge into culturally-sensitive education, significantly improved health knowledge among Hispanic residents in rural Kentucky. Such gains may translate into sustainable improvements in health literacy and help reduce health disparities.

Genetics and epigenetics of pediatric leukemia in the era of precision medicine

Pediatric leukemia represents a heterogeneous group of diseases characterized by germline and somatic mutations that manifest within the context of disturbances in the epigenetic machinery and genetic regulation. Advances in genomic medicine have allowed finer resolution of genetic and epigenetic strategies that can be effectively used to risk-stratify patients and identify novel targets for therapy. This review discusses the genetic and epigenetic mechanisms of leukemogenesis, particularly as it relates to acute lymphocytic leukemias, the mechanisms of epigenetic control of leukemogenesis, namely DNA methylation, histone modifications, microRNAs, and LINE-1 retroelements, and highlights opportunities for precision medicine therapeutics in further guiding disease management. Future efforts to broaden the integration of advances in genomic and epigenomic science into the practice of pediatric oncology will not only identify novel therapeutic strategies to improve clinical outcomes but also improve the quality of life for this unique patient population. Recent findings in precision therapeutics of acute lymphocytic leukemias over the past three years, along with some provocative areas of epigenetics research, are reviewed here.

Health Status, Perceptions and Needs of Hispanics in Rural Shelbyville, Kentucky

This cross-sectional study was completed to characterize the health status, perceptions and needs of Hispanics in Shelbyville, KY, USA. Community Health Workers interviewed 668 Hispanic residents in Shelbyville, KY, USA. Data were collected from 2009 to 2010 and analyzed from 2011 until present. Hispanic immigrants from Mexico and other Central American countries completed the survey. The most common self-reported diseases were allergies, asthma, diabetes, lung disease and cardiovascular disease. High blood pressure and diabetes were the two most common diagnoses among insured, older females. Health education, disease prevention and nutrition were the top health concerns among participants. Deficits in health care infrastructure for this largely transient community may compromise their ability to meet health care needs and concerns. Similar issues may be faced by other disadvantaged Hispanic communities in the continental US and likely to be influenced by anticipated provisions of the Patient Protection and Affordable Care Act.

Bioinformatics and Computational Biology in Toxicology: Gateways for Precision Medicine

The National Center for Biotechnology Information (NCBI) defines bioinformatics as “… the field of science in which biology, computer science, and information technology merge to form a single discipline”. As such, the field of bioinformatics includes computer scientists who develop algorithms for sequence analysis, biostatisticians who develop and implement methods of analyses for large clinical datasets, mathematicians or physical scientists who develop models to describe the interactions of genes, proteins, and small molecules within cells, and all those engaged in the development of software and databases for manipulation, storage, and retrieval of information in support of their research.