DNA damage triggers squamous metaplasia in human lung and mammary cells via mitotic checkpoints

Epithelial transdifferentiation is frequent in tissue hyperplasia and contributes to disease in various degrees. Squamous metaplasia (SQM) precedes epidermoid lung cancer, an aggressive and frequent malignancy, but it is rare in the epithelium of the mammary gland. The mechanisms leading to SQM in the lung have been very poorly investigated. We have studied this issue on human freshly isolated cells and organoids. Here we show that human lung or mammary cells strikingly undergo SQM with polyploidisation when they are exposed to genotoxic or mitotic drugs, such as Doxorubicin or the cigarette carcinogen DMBA, Nocodazole, Taxol or inhibitors of Aurora-B kinase or Polo-like kinase. To note, the epidermoid response was attenuated when DNA repair was enhanced by Enoxacin or when mitotic checkpoints where abrogated by inhibition of Chk1 and Chk2. The results show that DNA damage has the potential to drive SQM via mitotic checkpoints, thus providing novel molecular candidate targets to tackle lung SCC. Our findings might also explain why SCC is frequent in the lung, but not in the mammary gland and why chemotherapy often causes complicating skin toxicity

A Mitosis Block Links Active Cell Cycle with Human Epidermal Differentiation and Results in Endoreplication

How human self-renewal tissues co-ordinate proliferation with differentiation is unclear. Human epidermis undergoes continuous cell growth and differentiation and is permanently exposed to mutagenic hazard. Keratinocytes are thought to arrest cell growth and cell cycle prior to terminal differentiation. However, a growing body of evidence does not satisfy this model. For instance, it does not explain how skin maintains tissue structure in hyperproliferative benign lesions. We have developed and applied novel cell cycle techniques to human skin in situ and determined the dynamics of key cell cycle regulators of DNA replication or mitosis, such as cyclins E, A and B, or members of the anaphase promoting complex pathway: cdc14A, Ndc80/Hec1 and Aurora kinase B. The results show that actively cycling keratinocytes initiate terminal differentiation, arrest in mitosis, continue DNA replication in a special G2/M state, and become polyploid by mitotic slippage. They unambiguously demonstrate that cell cycle progression coexists with terminal differentiation, thus explaining how differentiating cells increase in size. Epidermal differentiating cells arrest in mitosis and a genotoxic-induced mitosis block rapidly pushes epidermal basal cells into differentiation and polyploidy. These observations unravel a novel mitosis-differentiation link that provides new insight into skin homeostasis and cancer. It might constitute a self-defence mechanism against oncogenic alterations such as Myc deregulation

Inertial Movements of the Iris as the Origin of Postsaccadic Oscillations

Recent studies on the human eye indicate that the pupil moves inside the eyeball due to deformations of the iris. Here we show that this phenomenon can be originated by inertial forces undergone by the iris during the rotation of the eyeball. Moreover, these forces affect the iris in such a way that the pupil behaves effectively as a massive particle. To show this, we develop a model based on the Newton equation on the noninertial reference frame of the eyeball. The model allows us to reproduce and interpret several important findings of recent eye-tracking experiments on saccadic movements. In particular, we get correct results for the dependence of the amplitude and period of the postsaccadic oscillations on the saccade size and also for the peak velocity. The model developed may serve as a tool for characterizing eye properties of individuals.Fil: Bouzat, Sebastian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Freije, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Frapiccini, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentin

In vivo measurements to estimate culture status and neutral lipid accumulation in Nannochloropsis oculata CCALA 978: implications for biodiesel oil studies

The development of efficient, rapid and species-specific techniques is indispensable for assessing growth and neutral lipid yield in microalga cultures for biodiesel oil production. Nannochloropsis oculata is a small microalgae with a thick cell wall. In vivo techniques to estimate cell density, chlorophyll a and neutral lipids are reported. A calibration curve of cell density versus optical density was obtained and validated at 540 nm, under different growth phases. Intracellular neutral lipid storage was evaluated with fluorometry and epifluorescent microscopy employing fluorochrome Nile Red. The addition of 5% dimethyl sulfoxide enhanced 12.5 times the fluorescence signal efficiency. In situ fluorescence measurements allowed estimating the neutral lipid content (NR-FI). Besides, no significant differences were found in the lipid neutral content between gravimetric and triolein methods. The relationship between NR-FI and chlorophyll fluorescence signals was used as a neutral lipid accumulation index, which is useful in order to establish the optimum harvesting time. Thus, these procedures may be applied for a better monitoring mode of growth and neutral lipid accumulation in N. oculata's cultures at commercial scale.Fil: Bongiovani, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Popovich, Cecilia Angelines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; ArgentinaFil: Martinez, Ana Maria. Universidad Nacional del Sur. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Freije, Hugo. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Constenla, Diana Teresita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (i); ArgentinaFil: Leonardi, Patricia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentin

Inactivation of p53 in Human Keratinocytes Leads to Squamous Differentiation and Shedding via Replication Stress and Mitotic Slippage

Tumor suppressor p53 is a major cellular guardian of genome integrity, and its inactivation is the most frequent genetic alteration in cancer, rising up to 80% in squamous cell carcinoma (SCC). By adapting the small hairpin RNA (shRNA) technology, we inactivated endogenous p53 in primary epithelial cells from the epidermis of human skin. We show that either loss of endogenous p53 or overexpression of a temperature-sensitive dominant-negative conformation triggers a self-protective differentiation response, resulting in cell stratification and expulsion. These effects follow DNA damage and exit from mitosis without cell division. p53 preserves the proliferative potential of the stem cell compartment and limits the power of proto-oncogene MYC to drive cell cycle stress and differentiation. The results provide insight into the role of p53 in self-renewal homeostasis and help explain why p53 mutations do not initiate skin cancer but increase the likelihood that cancer cells will appear

The Pacific-Atlantic connection: biogeochemical signals in the southern end of the Argentine shelf

The Cape Horn Current transports low-salinity waters from the SE Pacific Ocean into the Atlantic, which are transported further north by the Malvinas current. Biogeochemical signals of this connection were studied by characterization of dissolved organic matter (DOM) by determination of dissolved organic carbon (DOC), fluorescent dissolved organic matter (FDOMc), and DOM humification index (HIX). Further, inorganic nutrients, salinity, temperature, stable isotopic composition of particulate organic nitrogen (δ15N) and chlorophyll a (Chla) were measured in the southern end of the Argentine shelf in March 2012. Three water types were characterized: waters of the Beagle Channel (BCW), coastal waters (CW) and oceanic waters (OW). Highest values of ammonium, DOC, FDOMc and HIX were found in BCW, the lowest in OW, suggesting that terrigenous input is a main source of ammonium and refractory carbon, which is supported by a highly significant inverse correlation of these parameters with salinity. In turn, lowest concentrations of nitrate, silicate and phosphate were found in BCW and CW, and highest in OW, with highly significant correlations of these nutrients with salinity, indicating the contribution of the saltier, nutrient-rich Antarctic Circumpolar Current (ACC) to the Pacific-Atlantic connection system. In general there was an inverse distribution pattern between Chla and those nutrients contributed by the ACC, which is consistent with the transition from coastal waters to the low-silicate, high-nitrate, low-chlorophyll, iron-limited setting of the Subantarctic oceanic waters north of the Polar Front. In contrast, in the low-salinity, internal BCW, high values of ammonium, DOC, HIX and FDOM indicate continental inputs, likely including iron complexes, which could have led to the observed high Chla values. δ15N values were positive in the study region, and same as ammonium, reached a maximum in the inner part of the BCW, declining towards OW. This does not support a previous assumption that rainfall on the SE Pacific could be the source of ammonium and hence explain negative δ15N values previously found in the northern Drake Passage. The highly significant inverse correlations of ammonium, FDOMc, HIX, and DOC with salinity suggest that continental runoff rather than wet deposition is an important source of ammonium and DOM in the Pacific-Atlantic connection.Fil: Garzon Cardona, John Edison. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Martinez, Ana María. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Barrera, Facundo Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Pfaff, F.. Alfred-Wegener-Institut Helmholtz Zentrum für Polar - und Meeresforschung; AlemaniaFil: Koch, B. P.. Alfred-Wegener-Institut Helmholtz Zentrum für Polar - und Meeresforschung; Alemania. University of Applied Sciences; AlemaniaFil: Freije, Rubén Hugo. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Gomez, Eduardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Lara, Ruben Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin