Proper timing of a quiescence period in precursor prospermatogonia is required for stem cell pool establishment in the male germline

ABSTRACT The stem cell-containing undifferentiated spermatogonial population in mammals, which ensures continual sperm production, arises during development from prospermatogonial precursors. Although a period of quiescence is known to occur in prospermatogonia prior to postnatal spermatogonial transition, the importance of this has not been defined. Here, using mouse models with conditional knockout of the master cell cycle regulator Rb1 to disrupt normal timing of the quiescence period, we found that failure to initiate mitotic arrest during fetal development leads to prospermatogonial apoptosis and germline ablation. Outcomes of single-cell RNA-sequencing analysis indicate that oxidative phosphorylation activity and inhibition of meiotic initiation are disrupted in prospermatogonia that fail to enter quiescence on a normal timeline. Taken together, these findings suggest that key layers of programming are laid down during the quiescent period in prospermatogonia to ensure proper fate specification and fitness in postnatal life.

The North Pyrenean Frontal Thrust: structure, timing and late fluid circulation inferred from seismic and thermal-geochemical analyses of well data

During orogenesis, large-scale thrusts as orogenic fronts can act as conduits and/or barriers for fluid flow. Unravelling the timing and modes of tectonic activation of large-scale faults is crucial to understanding the relationship between fluid flow and deformation. The North Pyrenean Frontal Thrust (NPFT) corresponds to a major basement-involved thrust responsible for the northward overthrust of the pre-orogenic sediments on top of the Aquitaine Foreland Basin. This study questions the timing of activation of this thrust, its geometry, the nature of the last fluids, which circulated there, and its role on the circulation of fluids. The structural study confronted to published thermochronology data led to determine the timing of the two tectonic activations during the NPFT compression phase and to relate them to the fluid circulations. We constrain the first activation at Campanian times and link it to the leak of the deep gas reservoir present in depth, as the NPFT acted as a conduit. Then the NPFT acted as a barrier, probably due to the breccia consolidation during the Paleocene quiescence period. Finally, the Eocene-Oligocene reactivation led to fluid circulation of high salinity fluids from the Triassic evaporites leaching. This latter event is associated with a fracturing event and the late generation of calcite veins studied here. This is the first study in the Pyrenees directly applied to the NPFT which uses the association between fluid inclusions study, seismic and thermochronological data. It highlights that the NPFT may be an important structure responsible of the leakage of deep hydrocarbons reservoirs. It also shows the importance of the determination of the activation steps of large-scale faults to decipher the origin of fluid circulations in space and time.

Short-term variations of diffuse CO2 and H2S at the summit crater of Teide volcano, Tenerife, Canary Islands

<p>Tenerife (2,034 km<sup>2</sup>) is the central and largest island of the Canarian archipelago, located about 100 km west of the African coast between 27º37’ and 29º25’N and between 13º20’ and 18º10’W. The structure of Tenerife is controlled by a volcano-tectonic rift-system with NW, NE and NS directions with Teide volcano located in the intersection of the three rifts. Teide is the highest stratovolcano in the Atlantic Ocean reaching 3,718 m.a.s.l. with its last eruption occurred in 1798 through an adventive cone of Teide-Pico Viejo volcanic complex. Persistent degassing activity, both visible and diffuse, takes place at the summit cone of the volcano, being the diffuse degassing the principle degassing mechanism of Teide (Mori et. al., 2001; Pérez et. al., 2013). As part of the volcanic monitoring program of INVOLCAN in Tenerife, 8 surveys were performed during summer 2019 in order to evaluate the short term variations of diffuse CO<sub>2</sub> and H<sub>2</sub>S emissions in the summit crater. The emissions were calculated using data from 38 sampling sites homogeneously distributed inside the crater covering an area of 6,972 m<sup>2</sup> by means of a portable CO<sub>2</sub> and H<sub>2</sub>S fluxmeter using the accumulation chamber method (Parkinson 1981). During the study period, CO<sub>2</sub> and H<sub>2</sub>S emissions ranged from 33 ± 5 to 93 ± 25 t/d and from 0.6 ± 0.2 to 4 ± 0.1 kg/d, respectively. Despite the small changes observed in the temporal evolution, values are considered normal for a quiescence period in Teide volcanic system. Short term variations in CO<sub>2</sub> and H<sub>2</sub>S emissions indicate changes in the activity of the system and can be useful to understand the behaviour of the volcanic system and as forecast of future volcanic activity.</p><p><strong>References<br></strong>Mori T. et al. (2001). Chemical Geology, 177, 85–99.<br>Parkinson K. J. (1981). Journal of Applied Ecology, 18, 221–228.<br>Pérez N. M. et al. (2013). Journal of the Geological Society, 170, 585–592.</p>

Temporal microstructure of dyadic social behavior during relationship formation in mice

Understanding the temporal dynamics of how unfamiliar animals establish dominant-subordinate relationships and learn to modify their behavior in response to their social partner in context-appropriate manners is critical in biomedical research concerning social competence. Here we observe and analyze the microstructure of social and non-social behaviors as 21 pairs of outbred CD-1 male mice (Mus Musculus) establish dominant-subordinate relationships during daily 20-minute interaction for five consecutive days. Using Kleinberg burst detection algorithm, we demonstrate aggressive and subordinate interactions occur in bursting patterns followed by quiescence period rather than in uniformly distributed across social interactions. Further, we identify three phases of dominant-subordinate relationship development (pre-, middle-, and post-resolution) by combining phi-coefficient and difference methods used to determine at which bursting event mice resolve dominant-subordinate relationships. Using First Order Markov Chains within individuals we show dominant and subordinate animals establish significantly different behavioral repertoire once they resolve the relationships. In both dominant and subordinate mice, the transitions between investigative and agonistic behavior states are not common. Lastly, we introduce Forward Spike Time Tiling Coefficient, the strength of association between the given behavior of one individual with the target behavior of the other individual within a specified time window. With this method, we describe the likelihood of a mouse responding to a behavior with another behavior differ in pre- and post-resolution phases. The data suggest that subordinate mice learn to exhibit subordinate behavior in response to dominant partner’s behaviors while dominant mice become less likely to show subordinate behaviors in response to their partners’ action. Overall, with the tool we present in this study, the data suggest CD-1 male mice are able to establish dominance relationships and modify their behaviors even to the same social cues under different social contexts competently.

Hentei-Dauria fold system of the Mongolia-Okhotsk belt: magmatism, sedimentogenesis, and geodynamics

The geostructural, petrological, geochemical, geochronological and biostratigraphic studies were conducted in the Hentei-Dauria fold system of the Mongolia-Okhotsk orogenic belt. This Paleozoic system is composed mainly of three heterochronous rock associations related to the onset and development of oceanic basins and active margins in the conjugation zone of the Siberian continent and the Mongolia-Okhotsk ocean. This region developed in three stages: (1) Late Caledonian (Ordovician – Early Silurian), (2) Early Hercynian (Late Silurian – Devonian), and (3) Late Hercynian (Carboniferous–Permian). In the Late Caledonian, oceanic seafloor spreading was initiated, deep-sea siliceous deposits were formed, basaltic and andesitic pillow lavas were erupted, and layered and cumulative gabbros, gabbro-dolerite dykes and subduction zones with island-arc magmatism were formed. After a short quiescence period, new zones of spreading and subduction occurred at the active margins of the Mongolia-Okhotsk ocean in the Early Hercynian. In the Late Hercynian, large back-arc sedimentary basins, accretionary prisms and connecting intraplate magmatic complexes were formed in all structures of the Hentei-Dauria fold system. As a result of our studies, we propose a comprehensive model showing the geodynamic development of the Hentei-Dauria fold system that occurred in the area of the Mongolia-Okhotsk Ocean and its margins.

Groundwater modelling of a weathered gneissic cover

Knowledge of the groundwater regime, which is generally necessary in studying the stability of slopes, is of fundamental importance in the analysis of landslides involving intensely weathered rocks, as in the case of a landslide in the western Sila Massif (southern Italy) reactivated by heavy and prolonged rainfall. For this landslide, the total absence of displacements during the actual quiescence period and the long return period of the critical rainfall events did not allow measurement of the critical pore pressures capable of reactivating the landslide. To solve such a problem, a saturated–unsaturated flow model was calibrated taking into account in situ pore pressure measurements acquired over a long period of time. The analyses permitted determination of the role played by the hydraulic heterogeneity of the involved soils and the hydraulic boundary conditions for simulation of the response of in situ pore pressures to rainfall. Such conditions were therefore used to predict the critical unknown values attained during landslide reactivations and were indirectly tested using different models.Key words: landslide, weathered rocks, groundwater monitoring, unsaturated–saturated flow model, rainfall, critical pore pressures.