MacroH2A histone variants limit chromatin plasticity through two distinct mechanisms

MacroH2A histone variants suppress tumor progression and act as epigenetic barriers to induced pluripotency. How they impart their influence on chromatin plasticity is not well understood. Here, we analyze how the different domains of macroH2A proteins contribute to chromatin structure and dynamics. By solving the crystal structure of the macrodomain of human macroH2A2 at 1.7 Å, we find that its putative binding pocket exhibits marked structural differences compared with the macroH2A1.1 isoform, rendering macroH2A2 unable to bind ADP‐ribose. Quantitative binding assays show that this specificity is conserved among vertebrate macroH2A isoforms. We further find that macroH2A histones reduce the transient, PARP1‐dependent chromatin relaxation that occurs in living cells upon DNA damage through two distinct mechanisms. First, macroH2A1.1 mediates an isoform‐specific effect through its ability to suppress PARP1 activity. Second, the unstructured linker region exerts an additional repressive effect that is common to all macroH2A proteins. In the absence of DNA damage, the macroH2A linker is also sufficient for rescuing heterochromatin architecture in cells deficient for macroH2A.     

Exogenous estrogen therapy,testicular cancer,and the male to female transgender population: a case report

Background

Over the last 40 years, there has been a significant increase in the incidence of testicular cancer. The epidemiologic evidence to understand this phenomenon is unclear, however exogenous estrogen exposure is thought to be a driver in the development of testicular cancer. This is of particular importance in the transgender population because utilization of exogenous estrogen therapy is an essential aspect of the transition process.

Case

We present the case of a 38-year-old Caucasian male to female transgender patient who presented with metastatic testicular cancer 15 months after initiating estrogen therapy. She presented to our emergency department with worsening back pain and fatigue. A clinical examination revealed a right-sided testicular mass. A computed tomography scan of her abdomen/pelvis identified a right groin lesion measuring 6.4 cm, a retroperitoneal mass causing right-sided hydronephrosis, an extensive deep vein thrombosis, and pathologic abdominal lymphadenopathy. Germ cell tumor markers revealed an alpha-fetoprotein of <?2.5 μg/L and a beta-human chorionic gonadotrophin of 2526 IU/L. Her lactate dehydrogenase was 5294 U/L. Medical oncology advised the discontinuation of hormonal therapy at this time. On the basis of elevation in germ cell tumor markers and the burden of disease, she was treated with four cycles of bleomycin, etoposide, and cisplatin chemotherapy. A decision to defer upfront radical inguinal orchiectomy was made due to not wanting to have an early interruption in anticoagulation.Following the completion of the chemotherapy, a 6 cm retroperitoneal mass persisted. Due to the location of the mass and surgical morbidity associated with excision, she was followed with positron emission tomography-computed tomography by Uro-oncology, with no evidence of recurrent disease 2 years since the time of diagnosis.

Conclusions

While there are recognized risks associated with estrogen therapy less is known about the extent to which exogenous estrogen can serve as a driver of malignancy. With recent experimental evidence revealing a pro-growth impact of estrogen on human testicular cells, continued reporting of similar cases in the literature is imperative to see if a link between exogenous estrogen exposure and testicular cancer exists.

     

Docking Study of Ligands into the Colchicine Binding Site of Tubulin

Cancer is a major cause of mortality in developed countries, following only cardiovascular diseases. Death of cancerous cells can be achieved by stopping mitosis and the antimitotic class of drugs formed by the spindle poisons can be used for this purpose. Their role is to disorganize the mitotic spindle by targeting its main constituent, the microtubules, themselves made of heterodimers of α and β-tubulin. They disrupt the dynamics of the microtubules either by stabilizing them, as do paclitaxel or epothilones, or destabilizing them, as do colchicine. The binding site of colchicine seems to lie between the two units of the tubulin dimer. Here, we report on the characterization of this site by the docking of a series of reference compounds, and the subsequent docking of ligands prepared in our laboratory.     

Photoacoustic imaging of the human placental vasculature

Minimally invasive fetal interventions require accurate imaging from inside the uterine cavity. Twin‐to‐twin transfusion syndrome (TTTS), a condition considered in this study, occurs from abnormal vascular anastomoses in the placenta that allow blood to flow unevenly between the fetuses. Currently, TTTS is treated fetoscopically by identifying the anastomosing vessels, and then performing laser photocoagulation. However, white light fetoscopy provides limited visibility of placental vasculature, which can lead to missed anastomoses or incomplete photocoagulation. Photoacoustic (PA) imaging is an alternative imaging method that provides contrast for hemoglobin, and in this study, two PA systems were used to visualize chorionic (fetal) superficial and subsurface vasculature in human placentas. The first system comprised an optical parametric oscillator for PA excitation and a 2D Fabry‐Pérot cavity ultrasound sensor; the second, light emitting diode arrays and a 1D clinical linear‐array ultrasound imaging probe. Volumetric photoacoustic images were acquired from ex vivo normal term and TTTS‐treated placentas. It was shown that superficial and subsurface branching blood vessels could be visualized to depths of approximately 7 mm, and that ablated tissue yielded negative image contrast. This study demonstrated the strong potential of PA imaging to guide minimally invasive fetal therapies.      

Banana (Musa spp.) as a model to study the meristem proteome: acclimation to osmotic stress

Banana (Musa spp.) multiple shoot meristems are an excellent model to study the meristem proteome. Using a 2-DE protocol developed for small amounts of tissue and MS-based cross species polypeptide identification, we have revealed the meristem proteome and investigated the influence of sucrose-mediated osmotic stress in a dehydration-tolerant variety. Proteins that were significantly up- or down-regulated due to the high-sucrose treatment were classified using non-parametric univariate statistics. Our results suggest that the maintenance of an osmoprotective intracellular sucrose concentration, the enhanced expression of particular genes of the energy-conserving glycolysis and the conservation of the cell wall integrity are essential to maintain homeostasis, to acclimate and to survive dehydration. By comparing the dehydration-tolerant variety with a dehydration-sensitive variety, we were able to distinguish several genotype-specific proteins (isoforms), and could associate the dehydration-tolerant variety with proteins involved in energy metabolism (e.g., phosphoglycerate kinase, phosphoglucomutase, UDP-glucose pyrophosphorylase) and proteins that are associated with stress adaptation (e.g., OSR40-like protein, abscisic stress ripening protein-like protein). This work shows that proteome analysis can be used successfully to perform quantitative difference analysis and to characterize genetic variations in a recalcitrant crop.     

Overview of cell shape: cytoskeletons shape bacterial cells

An evolving hypothesis is that bacterial cell shape is determined by cytoskeletal elements that localize peptidoglycan synthetic machineries. In most bacteria FtsZ assembles into the Z ring which recruits the machinery necessary for cytokinesis. Most rod shaped cells require MreB which assembles into cables that run between the poles of the cell and distribute various components of peptidoglycan metabolism along the cell length. Cells with other shapes have additional cytoskeletal elements that either localize synthetic machineries or possibly influence their activity.