Papers of the Month
By David Banks, Deacqunita Diggs, Mahita Kadmiel, Simone Otto, and Qing Xu
NTP scientists detail importance of aquatic models in toxicological research
Researchers at the National Toxicology Program (NTP) participated in a workshop, Collaborative Workshop on Aquatic Models and 21st Century Toxicology, on the importance of using freshwater fish, such as zebrafish, to determine the toxic effects of harmful chemicals in the environment. The workshop was co-sponsored by NTP and North Carolina State University (NCSU). The resulting report included a review of emerging issues, and recommendations for enhancing the use of small fish species in toxicology studies, as well as new technologies to better understand how toxicants affect development and health. Participants agreed that standardized protocols for absorption, distribution, metabolism, and excretion of chemicals would facilitate this goal.
Research has shown that fish and humans have similar responses in development and physiology when exposed to chemicals. Zebrafish can be useful in screening chemicals, because they are extremely fecund, or fertile, genetically diverse, transparent during the period of organ development, and they develop rapidly. Their transparency and high fecundity make it easy for scientists to observe chemical effects on development. These characteristics also allow researchers to test the effects of single or multiple chemical exposures on development and disease.
The workshop underscored the fact that aquatic models have helped further the study of cardiovascular toxicology, neurotoxicology, and immunotoxicology. The majority of participants indicated that follow-up workshops should include regulators and industry representatives. The next meeting is expected to take place in early 2017. (DD)
Planchart A, Mattingly CJ, Allen D, Ceger P, Casey W, Hinton D, Kanungo J, Kullman SW, Tal T, Bondesson M, Burgess SM, Sullivan C, Kim C, Behl M, Padilla S, Reif DM, Tanguay RL, Hamm J. 2016. Advancing toxicology research using in vivo high throughput toxicology with small fish models. ALTEX; doi:10.14573/altex.1601281 [Online 21 June 2016].
DNA methylation biomarkers detect aggressive prostate cancer
Scientists from NIEHS and other research groups have discovered novel DNA methylation biomarkers that predict the clinical outcomes of prostate cancer patients after tumor surgery. These findings may lead to new diagnostic tools and provide guidance for targeted therapy after surgery.
The severity of prostate cancer is typically graded by Gleason scores based on tumor growth patterns, which are often unreliable. To improve the accuracy of post-surgery assessment, the researchers hypothesized that methylation patterns of tumor DNA may serve as a biomarker for determining high-risk patients whose tumors may spread and lead to death.
The study included two independent groups of prostate cancer patients who had their tumors removed and were then followed for more than five years. Profiling the methylation levels of tumor DNA from the first group of 430 patients revealed 42 genome sites that were differentially methylated in lethal tumors compared to nonrecurrent ones. Eight of these biomarkers, involving five genes that play roles in hypoxia response and cancer development, were confirmed in tumor DNA from a second group of 80 patients. The study further shows that methylation biomarkers improve the outcome prediction more than Gleason scores, though the underlying molecular mechanisms demand further examination. (Story) (QX)
Zhao S, Geybels MS, Leonardson A, Rubicz R, Kolb S, Yan Q, Klotzle B, Bibikova M, Hurtado-Coll A, Troyer D, Lance R, Lin D, Wright JL, Ostrander EA, Fan JB, Feng Z, Stanford JL. 2016. Epigenome-wide tumor DNA methylation profiling identifies novel prognostic biomarkers of metastatic-lethal progression in men with clinically localized prostate cancer. Clin Cancer Res; doi:10.1158/1078-0432.CCR-16-0549 [Online 29 June 2016].
A novel toolkit to uncover brain function
NIEHS researchers have created sophisticated mouse models to better understand brain function. The new mouse models will allow researchers to noninvasively study a small group of cells whose change in activity could be linked to changes in physiological and behavioral outcome.
The scientists have expanded upon the technology used in designer receptors exclusively activated by designer drugs (DREADDs). DREADDs are engineered G protein coupled receptors that can be activated exclusively by synthetic small molecules, but not by their natural ligands. Preclinical studies in rodents suggest that DREADDs may have many therapeutic applications, including the treatment of seizures, Parkinson’s disease, and addiction.
The researchers used the mutated human Gq-coupled M3 muscarinic receptor (hM3Dq), one of the most frequently used DREADDs, and generated two mouse lines that expressed a fusion protein of hM3Dq. This fusion protein was designed to increase effective expression levels by concentrating hM3Dq to the cell body and dendrites. In addition, they included a fluorescent protein to allow identification of cell populations harboring hM3Dq during different stages of mouse development. Furthermore, the researchers demonstrated that this modified hM3Dq can be activated noninvasively and dose-dependently, in a cell-type specific manner, to result in changes such as body temperature and behavior. Although the study focuses on neuronal and glial cells, and functions of the brain, these tools can be extended to virtually any cell type throughout the body that has the Gq-coupled signaling pathway. (MK)
Sciolino NR, Plummer NW, Chen YW, Alexander GM, Robertson SD, Dudek SM, McElligott ZA, Jensen P. 2016. Recombinase-dependent mouse lines for chemogenetic activation of genetically defined cell types. Cell Rep 15(11):2563−2573. (
Heavy air pollution exposure increases risk of Parkinson’s disease for some
NIEHS researchers and their collaborators report no significant association between Parkinson’s disease (PD) risk in older adults and exposure to particulate matter in ambient or immediate surrounding air pollution. However, they did find that gender and smoking status make a difference.
Using data provided by the NIH-AARP Diet and Health Study, the scientists defined PD cases by contacting those who self-reported PD and confirming the diagnosis with a physician. They geocoded addresses of participants and members of a selected control group, and then determined their exposure to air pollution by integrating U.S. Environmental Protection Agency data. Exposure was defined as daily contact with particulate matter less than 10 microns (PM10) or 2.5 microns (PM2.5) in size, and hourly exposure to nitric dioxide.
The researchers found an increased risk of PD in women exposed to higher levels of PM10, women exposed to PM2.5 and PM10 who had never smoked, and never-smokers exposed to PM2.5.
The harmful effects of air pollution on the heart and lungs are well-documented, although effects on the brain are less understood. The work provides evidence for some association between air quality and PD risk. (DB)
Liu R, Young MT, Chen JC, Kaufman JD, Chen H. 2016. Ambient air pollution exposures and risk of Parkinson Disease. Environ Health Perspect; doi:10.1289/EHP135 [Online 10 June 2016].
Scientists discover a role for transcription factor GLIS3 in spermatogenesis
For the first time, NIEHS researchers established the importance of Kruppel-like zinc finger transcription factor GLI-similar 3 (GLIS3) in spermatogenesis, or the production of sperm. The protein is important in a variety of body processes, and deficits in Glis3 lead to several conditions, such as diabetes. The new findings could be used to develop new therapies for male infertility.
The scientists used mice whose cells expressed fluorescent GLIS3 attached to a fusion protein to study protein expression, and used knockout mice that cannot produce GLIS3, to determine the effects of GLIS3 loss. Immunohistochemistry, flow cytometry, and quantitative real-time polymerase chain reaction (PCR) were used to determine that GLIS3 expression is limited to undifferentiated spermatogonia, an early stage of sperm. Cell proliferation assays, microarray, and PCR analysis further supported their findings that spermatogenesis is impaired in GLIS3 knockout mice.
This research illustrates the critical role of GLIS3 in spermatogonial stem cells. Without these undifferentiated stem cells, the testes are unable to make mature sperm. The researchers conclude that GLIS3 is also an important regulator of the proliferation and differentiation of spermatogonia. (SO)
Kang HS, Chen LY, Lichti-Kaiser K, Liao G, Gerrish K, Bortner CD, Yao HH, Eddy EM, Jetten AM. 2016. Transcription factor GLIS3: a new and critical regulator of postnatal stages of mouse spermatogenesis. Stem Cells; doi:10.1002/stem.2449 [Online 28 June 2016].