Summary
When electron microscopy (EM) was introduced in the 1930s it gave scientists their first look into the nanoworld of cells. Over the last 80 years EM has vastly increased our understanding of ...the complex cellular structures that underlie the diverse functions that cells need to maintain life. One drawback that has been difficult to overcome was the inherent lack of volume information, mainly due to the limit on the thickness of sections that could be viewed in a transmission electron microscope (TEM). For many years scientists struggled to achieve three‐dimensional (3D) EM using serial section reconstructions, TEM tomography, and scanning EM (SEM) techniques such as freeze‐fracture. Although each technique yielded some special information, they required a significant amount of time and specialist expertise to obtain even a very small 3D EM dataset. Almost 20 years ago scientists began to exploit SEMs to image blocks of embedded tissues and perform serial sectioning of these tissues inside the SEM chamber. Using first focused ion beams (FIB) and subsequently robotic ultramicrotomes (serial block‐face, SBF‐SEM) microscopists were able to collect large volumes of 3D EM information at resolutions that could address many important biological questions, and do so in an efficient manner. We present here some examples of 3D EM taken from the many diverse specimens that have been imaged in our core facility. We propose that the next major step forward will be to efficiently correlate functional information obtained using light microscopy (LM) with 3D EM datasets to more completely investigate the important links between cell structures and their functions.
Lay Description
Life happens in three dimensions. For many years, first light, and then EM struggled to image the smallest parts of cells in 3D. With recent advances in technology and corresponding improvements in computing, scientists can now see the 3D world of the cell at the nanoscale. In this paper we present the results of high resolution 3D imaging in a number of diverse cells and tissues from multiple species. 3D reconstructions of cell structures often revealed them to be significantly more complex when compared to extrapolations made from 2D studies. Correlating functional 3D LM studies with 3D EM results opens up the possibility of making new strides in our understanding of how cell structure is connected to cell function.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Stem cells ensure tissue development, homeostasis and repair. We have recently developed new methods to study by lineage tracing the cellular hierarchy and clonal dynamics that govern the ...development and homeostasis of the mammary gland. I will present new studies combining lineage tracing, clonal analysis, lineage ablation, single cell RNA sequencing, chromatin profiling, and functional experiments in vivo to investigate the cellular and molecular mechanisms regulating multipotency and lineage restriction during mammary gland development and the cellular reprograming occurring after oncogene expression. Defining the mechanisms regulating tissue expansion and cell fate during development and adult regeneration and understanding how these mechanisms are corrupted during tumorigenesis will have important implications for regenerative medicine and cancer therapy.
This work is supported by the ERC, WELBIO, FNRS, TELEVIE, and the Fondation Baillet-Latour.
Citation Format: C Blanpain. Cellular Plasticity, Fate, Potential and Lineage Commitment of Mammary Gland Stem Cells abstract. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr ES10-1.
ABSTRACT
Two meteorite pieces have been recovered in Italy, near the town of Cavezzo (Modena), on 2020 January 4th. The associated fireball was observed on the evening of New Year’s Day 2020 by eight ...all-sky cameras of the PRISMA fireball network, a partner of FRIPON. The computed trajectory had an inclination angle of approximately 68° and a velocity at infinity of 12.8 km s−1. Together with the relatively low terminal height, estimated as 21.5 km, those values were indicating the significant possibility of a meteorite dropping event, as additionally confirmed by the non-zero residual total mass. The strewn-field was computed taking into account the presence of two bright light flashes, revealing that the meteoroid had been very likely subject to fragmentation. Three days after the event, two samples, weighing 3.1 and 52.2 g, were collected as a result of a dedicated field search and thanks to the involvement of the local people. The two pieces were immediately recognized as freshly fallen fragments of meteorite. The computed orbital elements, compared with the ones of known Near-Earth Asteroids from the NEODyS database, are compatible with one asteroid only; 2013 VC10. The estimated original mass of the meteoroid, 3.5 kg, and size, approximately 13 cm, is so far the smallest among the current 35 cases in which meteorites were recovered from precise strewn-field computation thanks to observational data. This result demonstrates the effectiveness of accurate processing of fireball network data even on challenging events generated by small size meteoroids.
Unrepaired DNA double-strand breaks (DSBs) cause genetic instability that leads to malignant transformation or cell death. Cells respond to DSBs with the ordered recruitment of signaling and repair ...proteins to the sites of DNA lesions. Coordinated protein SUMOylation and ubiquitylation have crucial roles in regulating the dynamic assembly of protein complexes at these sites. However, how SUMOylation influences protein ubiquitylation at DSBs is poorly understood. We show herein that Rnf4, an E3 ubiquitin ligase that targets SUMO-modified proteins, accumulates in DSB repair foci and is required for both homologous recombination (HR) and non-homologous end joining repair. To establish a link between Rnf4 and the DNA damage response (DDR) in vivo, we generated an Rnf4 allelic series in mice. We show that Rnf4-deficiency causes persistent ionizing radiation-induced DNA damage and signaling, and that Rnf4-deficient cells and mice exhibit increased sensitivity to genotoxic stress. Mechanistically, we show that Rnf4 targets SUMOylated MDC1 and SUMOylated BRCA1, and is required for the loading of Rad51, an enzyme required for HR repair, onto sites of DNA damage. Similarly to inactivating mutations in other key regulators of HR repair, Rnf4 deficiency leads to age-dependent impairment in spermatogenesis. These findings identify Rnf4 as a critical component of the DDR in vivo and support the possibility that Rnf4 controls protein localization at DNA damage sites by integrating SUMOylation and ubiquitylation events.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
ABSTRACT
The increase in detector sensitivity and availability in the past three decades has allowed us to derive knowledge of the meteoroid flux and impact energy into the Earth’s atmosphere. We ...present the multi-instrument detected 2018 December 22 fireball over Western Pyrenees, and compare several techniques aiming to obtain a reliable method to be used when measuring impacts of similar scale. From trajectory data alone, we found a bulk density of 3.5 g cm−3 to be the most likely value for the Pyrenean meteoroid. This allowed to further constrain the dynamic mass, which translated into a kinetic energy of 1 ton TNT (4.184 × 109 J). For the second energy derivation, via the fireball’s corrected optical radiation, we obtained a more accurate empirical relation measuring well-studied bolides. The result approximates to 1.1 ton TNT, which is notably close to the nominal dynamic result, and agrees with the lower margin of the seismic-based energy estimation, yet way lower than the infrasound estimate. Based on the relation derived in this study, we consider the nominal estimate from both the dynamic and photometric methods to be the most accurate value of deposited energy (1 ton TNT). We show that the combination of these two methods can be used to infer the meteoroid density. Among the methods presented in this paper, we found that the optical energy is the most reliable predictor of impact energy near the ton TNT-scale.
IntroductionThe identification of specific cell type from which cancer arises and the cancer cell population that resists upon therapy leading to tumour relapse constitute the main topics of our ...research. We use the basal cell carcinoma (BCC), the most frequent cancer in humans, as a cancer model for our studies.Material and methodsWe used lineage tracing approach to elucidate the cell at the origin of BCC and study the cancer cell population responsible for relapse following therapy discontinuation.Results and discussionsTo uncover the cancer cell of origin in BCC and the changes in the cellular dynamics that lead to tumour initiation, we assessed the impact of oncogenic hedgehog signalling activation in distinct cell populations and their capacity to induce BCC. We found that only stem cells, and not progenitors, were competent to initiate tumour formation upon oncogenic hedgehog signalling. Interestingly, this difference was due to the hierarchical organisation of tumour growth in oncogene-targeted stem cells, characterised by an increase of symmetric self-renewing divisions and a higher p53-dependent resistance to apoptosis, leading to rapid clonal expansion and progression into invasive tumours.11 Sánchez-Danés A, Hannezo E, Larsimont JC, Liagre M, Youssef KK, Simons BD, Blanpain C. Defining the clonal dynamics leading to mouse skin tumour initation. Nature. 2016 Jul 8;536(7616):298–303. doi: 10.1038/nature19069To study the cancer cell population that mediates BCC relapse upon therapy, we treated two different genetic BCC mouse models with a Smoothened inhibitor (Smoi), the most commonly drug used to treat locally advanced and metastatic BCC. The mechanism by which Smoi leads BCC regression and emergence of resistant tumour cells are currently unknown. We found that Smoi mediates BCC regression by promoting epidermal differentiation and that during the course of Smoi administration, some BCC become resistant to therapy mimicking the situation found in humans. We identify Lgr5 as a marker expressed in the resistant tumour cell population upon Smoi administration.Finally, we demonstrate that combination of Smoi administration with Lgr5 lineage ablation leads to BCC eradication.ConclusionWe demonstrated that stem cells cells are competent to initiate basal cell carcinoma, whereas, committed progenitors resistant.We demonstrated that Smoi administration in combination with Lgr5 lineage ablation leads to BCC eradication, constituting a clinically promising approach to overcome resistance to therapy and cure BCC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Most epithelial tissues self-renew throughout adult life due to the presence of multipotent stem cells and/or unipotent progenitor cells. Epithelial stem cells are specified during development and ...are controlled by epithelial-mesenchymal interactions. Despite morphological and functional differences among epithelia, common signaling pathways appear to control epithelial stem cell maintenance, activation, lineage determination, and differentiation. Additionally, deregulation of these pathways can lead to human disorders including cancer. Understanding epithelial stem cell biology has major clinical implications for the diagnosis, prevention, and treatment of human diseases, as well as for regenerative medicine.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study reports results of total arsenic (Astot) and various As species in 75 samples of cereals and cereal products bought on the Belgian market. In addition to rice, the samples were wheat, ...pasta, bread and some breakfast cereals.
The inorganic species arsenite (AsIII) and arsenate (AsV), and the organic As compounds dimethyl arsinate (DMA) and monomethyl arsonate (MA) were the only As species detected. Mean Astot was 0.150 ± 0.089 mg kg−1 in rice and 0.012 ± 0.008 mg kg− in the non-rice cereals. The inorganic arsenic fraction (Asi = AsIII + AsV) dominated in all samples and was in the range 55%–100%. Significantly higher Astot and Asi concentrations were observed in white rice and brown rice compared to Basmati rice. Within the group of non-rice cereals bread and pasta showed significantly lower concentrations compared to wheat. All 30 rice samples were conform to the European maximum limits for Asi, laid down in Commission Regulation (EU) 2015/1006. Although regulatory limits certainly can help to protect consumer health, our results suggest that the currently fixed European maximum levels are, in Belgium, not expected to have any impact on the human exposure to Asi, which is a known carcinogenic substance.
•Asi concentrations in rice were on average 0.107 ± 0.072 mg kg−1 versus 0.012 ± 0.008 mg kg−1 in non-rice cereals.•The inorganic arsenic fraction (Asi = AsIII + AsV) dominated in all samples and was in the range 55%–100% of Astot.•All rice samples under study were conform to the European maximum limits for Asi.•EU MLs for Asi in rice will probably not have any impact on dietary exposure to Asi of the general Belgium population.•Asi intake through cereals by Belgium adults was 0.04 μg kgbw−1 d−1 and 74 times lower than the BMDL0.5 proposed by JECFA.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Natural peptides displaying agonist activity on the orphan G protein-coupled receptor GPR54 were isolated from human placenta. These 54-, 14,- and 13-amino acid peptides, with a common RF-amide C ...terminus, derive from the product of KiSS-1, a metastasis suppressor gene for melanoma cells, and were therefore designated kisspeptins. They bound with low nanomolar affinities to rat and human GPR54 expressed in Chinese hamster ovary K1 cells and stimulated PIP2 hydrolysis, Ca2+ mobilization, arachidonic acid release, ERK1/2 and p38 MAP kinase phosphorylation, and stress fiber formation but inhibited cell proliferation. Human GPR54 was highly expressed in placenta, pituitary, pancreas, and spinal cord, suggesting a role in the regulation of endocrine function. Stimulation of oxytocin secretion after kisspeptin administration to rats confirmed this hypothesis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Stem cells are characterized by their ability to self-renew and differentiate into the different cell lineages of their tissue of origin. The discovery of stem cells in adult tissues, together with ...the description of specific markers for their isolation, has opened up new lines of investigation, expanding the horizons of biomedical research and raising new hope in the treatment of many diseases. In this article, we review in detail the main characteristics of the stem cells that produce the specialized cells of the skin (epidermal, mesenchymal, and melanocyte stem cells) and their potential implications and applications in diseases affecting the skin. Part I deals with the principal characteristics and potential applications of epidermal stem cells in dermatology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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