NBS1 Heterozygosity and Cancer Risk

Biallelic mutations in the NBS1 gene are responsible for the Nijmegen breakage syndrome (NBS), a rare autosomal recessive disorder characterized by chromosome instability and hypersensitivity to ionising radiation (IR). Epidemiological data evidence that the NBS1 gene can be considered a susceptibility factor for cancer development, as demonstrated by the fact that almost 40% of NBS patients have developed a malignancy before the age of 21. Interestingly, also NBS1 heterozygotes, which are clinically asymptomatic, display an elevated risk to develop some types of malignant tumours, especially breast, prostate and colorectal cancers, lymphoblastic leukaemia, and non-Hodgkin’s lymphoma (NHL). So far, nine mutations in the NBS1 gene have been found, at the heterozygous state, in cancer patients. Among them, the 657del5, the I171V and the R215W mutations are the most frequently described. The pathogenicity of these mutations is presumably connected with their occurrence in the highly conserved BRCT tandem domains of the NBS1 protein, which are present in a large superfamily of proteins, and are recognized as major mediators of processes related to cell-cycle checkpoint and DNA repair

Design e simulazione di un convertitore DC-DC per applicazioni automotive implementato mediante tecnologia GaN

L’obiettivo dell’elaborato è quello di presentare una soluzione di collegamento ed interfacciamento tra il supercondensatore (SC) dell’HESS (sistema ibrido di accumulo dell’energia situato all’interno di un veicolo elettrico) e il DC-link (bus che fornisce la potenza necessaria all’inverter che pilota il motore elettrico) attraverso un convertitore DC-DC ad alta efficienza che utilizzi tecnologie di potenza al nitruro di gallio (GaN). Il convertitore presentato è un convertitore DC-DC bidirezionale in configurazione Half-Bridge, esso dovrà funzionare in modalità Boost, ogni qualvolta il motore richieda energia extra dal SC, in modalità Buck per ricaricare il SC durante la frenata rigenerativa. In seguito ad un’introduzione ai veicoli elettrici, alla loro architettura e al perché il SC è così fondamentale, verrà presentata una breve introduzione ai convertitori di potenza (Capitolo 1). Si passerà poi alla presentazione delle tecnologie GaN mostrando come esse rappresentino il futuro dell’elettronica di potenza grazie ai loro numerosi vantaggi (Capitolo 2). Nel capitolo 3 si entrerà nel vivo della progettazione, è qui che sarà progettata ed implementata la soluzione proposta. Verrà effettuata una prima simulazione del circuito, tenendo conto degli effetti parassiti dei soli componenti, attraverso l’ausilio del software LTSpice. Il Capitolo 4 prevede una breve introduzione alle tecniche di layout, utili nella costruzione del circuito stampato presentata all’interno del medesimo capitolo. Il PCB sarà modellato mediante un secondo software denominato KiCAD. Infine, nel Capitolo 5, si procederà con la simulazione elettromagnetica del circuito stampato, essa permetterà di individuare gli effetti parassiti dovuti alle non idealità del layout e di mostrare l’effettiva differenza di efficienza tra un caso semi-ideale e un caso semi-reale

Cutaneous granulomatosis and combined immunodeficiency revealing Ataxia-Telangiectasia: a case report

Ataxia-telangiectasia (A-T) is a complex multisystem disorder characterized by progressive neurological impairment, variable immunodeficiency and oculo-cutaneous telangiectasia. A-T is a member of chromosomal breakage syndromes and it is caused by a mutation in the ataxia-telangiectasia mutated (ATM) gene. Because of a wide clinical heterogeneity, A-T is often difficult to diagnose in children

Status report of a systematic investigation on low-dose ionizing radiation effects in mammalian cells

In the last 15 years a growing interest in the biological effects induced by low doses of ionizing radiation has arisen in the scientific community, due to an increasing number of experimental evidences showing a plethora of non-linear effects occurring after low-dose irradiations. In particular, hyper-radiosensitivity and induced radioresistance (HRS/IRR) have been reported after exposure to low- and high-LET radiation, in human (normal and tumoural) and other mammalian cells in vitro. In this framework, Chinese hamster V79 cells, human primary fibroblasts (HFFF2) and murine embryonic fibroblasts (MEFs) were irradiated with broadbeams of protons in the dose range 0.1–5.0Gy and at 1 Gy/min dose-rate. Cellular response has been evaluated in terms of cell survival, micronuclei induction, chromosomal aberrations and telomere length alterations. For comparison purpose, the same end-points were studied after X/γ-rays irradiation

Seven benzimidazole pesticides combined at sub-threshold levels induce micronuclei in vitro

This article is made available through the Brunel Open Access Publishing Fund. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Benzimidazoles act by disrupting microtubule polymerisation and are capable of inducing the formation of micronuclei. Considering the similarities in their mechanisms of action (inhibition of microtubule assembly by binding to the colchicine-binding site on tubulin monomers), combination effects according to the principles of concentration addition might occur. If so, it is to be expected that several benzimidazoles contribute to micronucleus formation even when each single one is present at or below threshold levels. This would have profound implications for risk assessment, but the idea has never been tested rigorously. To fill this gap, we analysed micronucleus frequencies for seven benzimidazoles, including the fungicide benomyl, its metabolite carbendazim, the anthelmintics albendazole, albendazole oxide, flubendazole, mebendazole and oxibendazole. Thiabendazole was also tested but was inactive. We used the cytochalasin-blocked micronucleus assay with CHO-K1 cells according to OECD guidelines, and employed an automated micronucleus scoring system based on image analysis to establish quantitative concentration–response relationships for the seven active benzimidazoles. Based on this information, we predicted additive combination effects for a mixture of the seven benzimidazoles by using the concepts of concentration addition and independent action. The observed effects of the mixture agreed very well with those predicted by concentration addition. Independent action underestimated the observed combined effects by a large margin. With a mixture that combined all benzimidazoles at their estimated threshold concentrations for micronucleus induction, micronucleus frequencies of ~15.5% were observed, correctly anticipated by concentration addition. On the basis of independent action, this mixture was expected to produce no effects. Our data provide convincing evidence that concentration addition is applicable to combinations of benzimidazoles that form micronuclei by disrupting microtubule polymerisation. They present a rationale for grouping these chemicals together for the purpose of cumulative risk assessment.United Kingdom Food Standards Agenc

Chromosomal Instability and Molecular Defects in Induced Pluripotent Stem Cells from Nijmegen Breakage Syndrome Patients

SummaryNijmegen breakage syndrome (NBS) results from the absence of the NBS1 protein, responsible for detection of DNA double-strand breaks (DSBs). NBS is characterized by microcephaly, growth retardation, immunodeficiency, and cancer predisposition. Here, we show successful reprogramming of NBS fibroblasts into induced pluripotent stem cells (NBS-iPSCs). Our data suggest a strong selection for karyotypically normal fibroblasts to go through the reprogramming process. NBS-iPSCs then acquire numerous chromosomal aberrations and show a delayed response to DSB induction. Furthermore, NBS-iPSCs display slower growth, mitotic inhibition, a reduced apoptotic response to stress, and abnormal cell-cycle-related gene expression. Importantly, NBS neural progenitor cells (NBS-NPCs) show downregulation of neural developmental genes, which seems to be mediated by P53. Our results demonstrate the importance of NBS1 in early human development, shed light on the molecular mechanisms underlying this severe syndrome, and further expand our knowledge of the genomic stress cells experience during the reprogramming process

ECVAM retrospective validation of in vitro micronucleus test (MNT)

In the past decade several studies comparing the in vitro chromosome aberration test (CAT) and the in vitro micronucleus test (MNT) were performed. A high correlation was observed in each of the studies (>85%); however, no formal validation for the micronucleus in vitro assay had been carried out. Therefore, a working group was established by the European Centre for the Validation of Alternative Methods (ECVAM) to perform a retrospective validation of the existing data, in order to evaluate the validity of the in vitro MNT on the basis of the modular validation approach. The primary focus of this retrospective validation was on the evaluation of the potential of the in vitro MNT as alternative to the standard in vitro CAT. The working group evaluated, in a first step, the available published data and came to the conclusion that two studies [German ring trial, von der Hude, W., Kalweit, S., Engelhardt, G. et al. (2000) In-vitro micronucleus assay with Chinese hamster V79 cells: results of a collaborative study with 26 chemicals. Mutat. Res., 468, 137–163, and SFTG International Collaborative Study, Lorge, E., Thybaud, V., Aardema, M., Oliver, J., Wataka, A., Lorenzon, G. and Marzin, D. (2006) SFTG International Collaborative Study on in-vitro micronucleus test I. General conditions and overall conclusions of the study. Mutat. Res., 607, 13–36] met the criteria for a retrospective validation according to the criteria previously defined by the working group. These two studies were evaluated in depth (including the reanalysis of raw data) and provided the information required for assessing the reliability (reproducibility) of the test. For the assessment of the concordance between the in vitro MNT and the in vitro CAT, additional published data were considered. Based on this retrospective validation, the ECVAM Validation Management Team concluded that the in vitro MNT is reliable and relevant and can therefore be used as an alternative method to the in vitro CAT. Following peer review, these conclusions were formally endorsed by the ECVAM Scientific Advisory Committee

Identification of BC005512 as a DNA Damage Responsive Murine Endogenous Retrovirus of GLN Family Involved in Cell Growth Regulation

Genotoxicity assessment is of great significance in drug safety evaluation, and microarray is a useful tool widely used to identify genotoxic stress responsive genes. In the present work, by using oligonucleotide microarray in an in vivo model, we identified an unknown gene BC005512 (abbreviated as BC, official full name: cDNA sequence BC005512), whose expression in mouse liver was specifically induced by seven well-known genotoxins (GTXs), but not by non-genotoxins (NGTXs). Bioinformatics revealed that BC was a member of the GLN family of murine endogenous retrovirus (ERV). However, the relationship to genotoxicity and the cellular function of GLN are largely unknown. Using NIH/3T3 cells as an in vitro model system and quantitative real-time PCR, BC expression was specifically induced by another seven GTXs, covering diverse genotoxicity mechanisms. Additionally, dose-response and linear regression analysis showed that expression level of BC in NIH/3T3 cells strongly correlated with DNA damage, measured using the alkaline comet assay,. While in p53 deficient L5178Y cells, GTXs could not induce BC expression. Further functional studies using RNA interference revealed that down-regulation of BC expression induced G1/S phase arrest, inhibited cell proliferation and thus suppressed cell growth in NIH/3T3 cells. Together, our results provide the first evidence that BC005512, a member from GLN family of murine ERV, was responsive to DNA damage and involved in cell growth regulation. These findings could be of great value in genotoxicity predictions and contribute to a deeper understanding of GLN biological functions

Overview of DISCOVER22 experiment in the framework of INFN-LNGS Cosmic Silence activity: challenges and improvements in underground radiobiology

One of the most intriguing and still pending questions in radiobiology is to understand whether and how natural environmental background radiation has shaped Life over millions of years of evolution on Earth. Deep Underground Laboratories (DULs) represent the ideal below-background exposure facilities where to address such a question. Among the few worldwide DULs, INFN-Laboratorio Nazionale del Gran Sasso (LNGS) is one of the largest in terms of size and infrastructure. Designed and built to host neutrino and dark matter experiments, since the 1990 s the LNGS has been one of the first DULs to systematically host radiobiology experiments. Here we present the DISCOVER22 (DNA Damage and Immune System Cooperation in VEry low Radiation environment 2022) experiment recently started at LNGS. DISCOVER22 aims at investigating how the low radiation background modulates the Immune System (IS) response in in vitro and in vivo models. Underground radiobiology experiments are particularly complex and tricky to design and perform. In these studies, the accurate characterization of exposure scenarios is mandatory, but a challenging aspect is to understand how the very few ionizing tracks in the ultra-Low Radiation Environment (LRE) interact with the living matter in space and time in order to trigger different biological responses. In this Perspective, we describe these challenges and how we address them through a microdosimetric and a radiobiological approaches. We aim at linking physical microdosimetric measurements and the corresponding biological radiation responses by using radiation biophysical models that could shed light on many as yet unresolved questions