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Environmental Factor

Environmental Factor

Your Online Source for NIEHS News

September 2021

Papers of the month

DNTP develops whole-genome sequencing of cell-free DNA in blood

Researchers from the Division of the National Toxicology Program have developed a protocol for whole-genome sequencing of low quantities of circulating cell-free DNA. Small amounts of DNA are typically released into blood as byproducts of programmed cell death. Increased levels of circulating cell-free DNA have been associated with environmental stressors and various diseases, including cancer and autoimmune disorders.

Whole-genome sequencing of circulating cell-free DNA could be used for discovering biomarkers or genomic variants associated with diseases. But it has been challenging to detect sequence variants at the whole-genome level due to the limited quantity of circulating cell-free DNA. As a result, few studies have applied whole-genome sequencing to clinical blood samples of cell-free DNA.

The researchers reported procedures for extracting and amplifying low amounts of circulating cell-free DNA, sequencing the whole genome, and analyzing genomic alterations. They applied this approach to cell-free DNA in one-milliliter blood samples obtained from two healthy human donors. This reliable, high-quality method could extend the utility of circulating cell-free DNA for a wide range of research and clinical purposes.

According to the authors, future work is required to refine the technique for clinical studies. Ultimately, whole-genome sequencing of circulating cell-free DNA may hold promise for disease diagnosis, staging, and therapeutic decisions. (JW)

CitationFoley JF, Elgart B, Alex Merrick B, Phadke DP, Cook ME, Malphurs JA, Solomon GG, Shah RR, Fessler MB, Miller FW, Gerrish KE. 2021. Whole genome sequencing of low input circulating cell-free DNA obtained from normal human subjects. Physiol Rep 9(15):e14993.

NR5A1 overexpression disrupted fertility and metabolism in female mice

Researchers at NIEHS have developed a novel mouse model for studying diseases such as polycystic ovary syndrome (PCOS), a condition characterized by abnormally high amounts of androgens, called hyperandrogenism. PCOS is the most common endocrine disorder, affecting 6–20% of women of reproductive age.

The mouse model was generated by overexpressing NR5A1, a key gene that regulates the development of steroid-producing tissues. Steroid hormones, such as androgens and estrogens, are essential for directing not only reproductive function but also glucose metabolism and homeostasis. By increasing expression of NR5A1 in the mouse model, the scientists disrupted steroid hormone production, induced infertility, and prompted weight and fat gain, insulin resistance, and glucose intolerance. These symptoms are all present in patients with PCOS. Further study of this mouse model could provide valuable insight into the connection between the endocrine, reproductive, and metabolic systems. (MH)

CitationRotgers E, Nicol B, Rodriguez K, Rattan S, Flaws JA, Yao HH. 2021. Constitutive expression of Steroidogenic factor-1 (NR5A1) disrupts ovarian functions, fertility, and metabolic homeostasis in female mice. FASEB J 35(8):e21770.

Racial discrimination linked to type 2 diabetes in U.S. women

Racial discrimination is associated with an increased risk of type 2 diabetes mellitus (T2DM) in women, according to NIEHS researchers and their collaborators. The study offers a potential target for intervention and insights into reducing racial disparities in T2DM.

Previous research suggests that experiencing unfair treatment due to race and ethnicity may adversely affect health outcomes. In this study, the researchers examined the association of racial discrimination with T2DM risk. Systemic denial of goods and services can contribute to health behaviors that lead to endocrine abnormalities that promote the development of T2DM.

The study included more than 30,000 women enrolled in the Sister Study, a national effort initiated by NIEHS to identify risk factors for breast cancer. The researchers assessed the lifetime exposure to everyday and major forms of racial discrimination, as well as the incidence of diagnosed T2DM, among White, Black, and Latina women. The scientists found that experiencing major racial discrimination was positively associated with T2DM risk. Compared to White women, major racial discrimination was more frequently reported among Black and Latina women, who also experience a higher incidence of T2DM. The study suggests that ending racial discrimination may help to relieve the health burden of T2DM. (QX)

CitationGaston SA, Atere-Roberts J, Ward J, Slopen NB, Forde AT, Sandler DP, Williams DR, Jackson CL. 2021. Experiences with everyday and major forms of racial/ethnic discrimination and type 2 diabetes risk among White, Black, and Hispanic/Latina women: Findings from the Sister Study. Am J Epidemiol; doi: 10.1093/aje/kwab189 [Online 2 July 2021].

Living in a low-income neighborhood linked to lower lung function

NIEHS researchers found that people living in neighborhoods with socioeconomic disadvantage have an increased risk of poor respiratory health. The scientists noted that greater neighborhood deprivation — living in an area with disadvantages such as lack of access to food, education, health services, and safety — is associated with markers of reduced lung function including lower forced expiratory volume in 1 second, the amount of air exhaled in the first second, and forced vital capacity, the total amount of air exhaled out of the lung.

The scientists analyzed data collected from participants in the Gulf Long-term Follow-up Study, a large and diverse cohort of adults enrolled following the 2010 Deepwater Horizon oil spill. Lung function testing was administered by trained examiners at a home visit. Neighborhood deprivation was measured at the census block-group level using an existing Area Deprivation Index (ADI) that was linked to participant home addresses. Participants also provided information on their income level, education, and financial strain. Statistical analyses found associations between ADI and measures of lung function independent of individual socioeconomic factors.

Because low socioeconomic status is a risk factor for many chronic diseases, the authors suggest clinicians should consider neighborhood factors when evaluating risk for poor lung health among patients. (KC)

CitationLawrence KG, Werder EJ, Sandler DP. 2021. Association of neighborhood deprivation with pulmonary function measures among participants in the Gulf Long-Term Follow-up Study. Environ Res 202:111704.

Synaptic plasticity rescue in a mouse model of Rett syndrome

NIEHS researchers discovered that removal of perineuronal nets (PNNs) — a specialized form of extracellular matrix — in a Mecp2-null mouse model of Rett syndrome (RTT) salvages synaptic plasticity in the hippocampal area CA2 of the brain early in postnatal development. Synaptic plasticity refers to the brain’s ability to respond to environmental stimuli, and RTT is a neurodevelopmental disorder caused by a loss-of-function mutation in the methyl-CpG–binding protein 2 (MECP2) gene. RTT is characterized by normal development in the first year of life, followed by rapid, significant decline in cognitive, motor, and social function. The condition affects 1 in 10,000 girls worldwide.

The authors previously found that PNNs limit synaptic plasticity in CA2, a region associated with social learning in mice and an area that is atypically resistant to long-term potentiation (LTP). LTP is a process that strengthens synapses, or the junction between neurons, and leads to stronger signal transmission. The scientists observed increased PNNs in the CA2 region of postmortem human tissue from an individual with RTT and found that PNNs develop precociously in the murine model of RTT. The research demonstrated that LTP could be induced at CA2 synapses before PNN maturation in wild-type mice and that this period of plasticity was prematurely terminated in Mecp2-null mice. (NA)

CitationCarstens KE, Lustberg DJ, Shaughnessy EK, McCann KE, Alexander GM, Dudek SM. 2021. Perineuronal net degradation rescues CA2 plasticity in a mouse model of Rett syndrome. J Clin Invest 131(16):137221.

(Nicholas Alagna is an Intramural Research Training Award [IRTA] postbaccalaureate fellow in the NIEHS Mechanisms of Mutation Group. Kelley Christensen is a contract writer and editor for the NIEHS Office of Communications and Public Liaison. Mimi Huang, Ph.D., is an IRTA fellow in the DNTP Systems Toxicology Group. Janelle Weaver, Ph.D., is a contract writer for the NIEHS Office of Communications and Public Liaison. Qing Xu is a biologist in the NIEHS Metabolism, Genes, and Environment Group.)

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