Deletion of RIC8A in neural precursor cells leads to altered neurogenesis and neonatal lethality of mouse

RIC8A is a noncanonical guanine nucleotide exchange factor for a subset of Gα subunits. RIC8A has been reported in different model organisms to participate in the control of mitotic cell division, cell signalling, development and cell migration. Still, the function of RIC8A in the mammalian nervous system has not been sufficiently analysed yet. Adult mice express RIC8A in the brain regions involved in the regulation of memory and emotional behaviour. To elucidate the role of RIC8A in mammalian neurogenesis we have inactivated Ric8a in neural precursor cells using Cre/Lox system. As a result, the conditional knockout mice were born at expected Mendelian ratio, but died or were cannibalized by their mother within 12 h after birth. The cerebral cortex of the newborn Nes;Ric8a^CKO mice was thinner compared to littermates and the basement membrane was discontinuous, enabling migrating neurons to invade to the marginal zone. In addition, the balance between the planar and oblique cell divisions was altered, influencing the neuron production. Taken together, RIC8A has an essential role in the development of mammalian nervous system by maintaining the integrity of pial basement membrane and modulating cell division. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 75: 984–1002, 2015     

Full carbon and greenhouse gas balances of fertilized and nonfertilized reed canary grass cultivations on an abandoned peat extraction area in a dry year

Bioenergy crop cultivation on former peat extraction areas is a potential after‐use option that provides a source of renewable energy while mitigating climate change through enhanced carbon (C) sequestration. This study investigated the full C and greenhouse gas (GHG) balances of fertilized (RCG‐F) and nonfertilized (RCG‐C) reed canary grass (RCG; Phalaris arundinacea) cultivation compared to bare peat (BP) soil within an abandoned peat extraction area in western Estonia during a dry year. Vegetation sampling, static chamber and lysimeter measurements were carried out to estimate above‐ and belowground biomass production and allocation, fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) in cultivated strips and drainage ditches as well as the dissolved organic carbon (DOC) export, respectively. Heterotrophic respiration was determined from vegetation‐free trenched plots. Fertilization increased the above‐ to belowground biomass production ratio and the autotrophic to heterotrophic respiration ratio. The full C balance (incl. CO₂, CH₄ and DOC fluxes from strips and ditches) was 96, 215 and 180 g C m^?2 yr^?1 in RCG‐F, RCG‐C and BP, respectively, suggesting that all treatments acted as C sources during the dry year. The C balance was driven by variations in the net CO₂ exchange, whereas the combined contribution of CH₄ and DOC fluxes was <5%. The GHG balances were 3.6, 7.9 and 6.6 t CO₂ eq ha^?1 yr^?1 in RCG‐F, RCG‐C and BP, respectively. The CO₂ exchange was also the dominant component of the GHG balance, while the contributions of CH₄ and N₂O were <1% and 1–6%, respectively. Overall, this study suggests that maximizing plant growth and the associated CO₂ uptake through adequate water and nutrient supply is a key prerequisite for ensuring sustainable high yields and climate benefits in RCG cultivations established on organic soils following drainage and peat extraction.     

Gata3 is required for early morphogenesis and Fgf10 expression during otic development

Inner ear develops from an induced surface ectoderm placode that invaginates and closes to form the otic vesicle, which then undergoes a complex morphogenetic process to form the membranous labyrinth. Inner ear morphogenesis is severely affected in Gata3 deficient mouse embryos, but the onset and basis of the phenotype has not been known. We show here that Gata3 deficiency leads to severe and unique abnormalities during otic placode invagination. The invagination problems are accompanied often by the formation of a morphological boundary between the dorsal and ventral otic cup and by the precocious appearance of dorsal endolymphatic characteristics. In addition, the endolymphatic domain often detaches from the rest of the otic epithelium during epithelial closure. The expression of several cell adhesion mediating genes is altered in Gata3 deficient ears suggesting that Gata3 controls adhesion and morphogenetic movements in early otic epithelium. Inactivation of Gata3 leads also to a loss of Fgf10 expression in otic epithelium and auditory ganglion demonstrating that Gata3 is an important regulator of Fgf-signalling during otic development.     

Mortality of urban pines in Helsinki explored using tree rings and climate records

The mortality of Scots pine trees in and around Helsinki has been reported in recent years, but the causalities of these deaths have not so far been rigorously examined. Tree-ring analyses have previously shown to effectively reveal historical growth variability and thus hint at the stress factors behind tree mortality. Here, we analyzed the tree rings of pines in two tree classes (living and dead) from an urban park in Helsinki to reveal their growth variations and to examine the obtained chronologies along with climatic data. Guided by tree-ring information, the pine growth over the past century could be divided into four episodes: average growth conditions during the first half of the twentieth century, a suppressed growth period during the 1950s and 1960s, a growth release since the mid-1970s, and a period of recent mortality. The two tree classes became particularly differentiated during the release period in that the growth of surviving pines underwent a more positive and abrupt growth anomaly in comparison to dead pines. The survival of pines could also be linked to their sensitivity to droughts in a long-term context: The growth of still-living pines showed a statistically significant moisture sensitivity over the second half of the century only. The period 2002–2003 (coinciding with drought) was observed as a dendrochronologically dated episode with a 40% mortality. Overall, the results point to the importance of tree competitive strength and climate as predisposing and inciting/contributing factors behind the tree mortality.     

Expression Pattern and Localization Dynamics of Guanine Nucleotide Exchange Factor RIC8 during Mouse Oogenesis

Targeting of G proteins to the cell cortex and their activation is one of the triggers of both asymmetric and symmetric cell division. Resistance to inhibitors of cholinesterase 8 (RIC8), a guanine nucleotide exchange factor, activates a certain subgroup of G protein α-subunits in a receptor independent manner. RIC8 controls the asymmetric cell division in Caenorhabditis elegans and Drosophila melanogaster, and symmetric cell division in cultured mammalian cells, where it regulates the mitotic spindle orientation. Although intensely studied in mitosis, the function of RIC8 in mammalian meiosis has remained unknown. Here we demonstrate that the expression and subcellular localization of RIC8 changes profoundly during mouse oogenesis. Immunofluorescence studies revealed that RIC8 expression is dependent on oocyte growth and cell cycle phase. During oocyte growth, RIC8 is abundantly present in cytoplasm of oocytes at primordial, primary and secondary preantral follicle stages. Later, upon oocyte maturation RIC8 also populates the germinal vesicle, its localization becomes cell cycle dependent, and it associates with chromatin and the meiotic spindle. After fertilization, RIC8 protein converges to the pronuclei and is also detectable at high levels in the nucleolus precursor bodies of both maternal and paternal pronucleus. During first cleavage of zygote RIC8 localizes in the mitotic spindle and cell cortex of forming blastomeres. In addition, we demonstrate that RIC8 co-localizes with its interaction partners Gα_i1/2:GDP and LGN in meiotic/mitotic spindle, cell cortex and polar bodies of maturing oocytes and zygotes. Downregulation of Ric8 by siRNA leads to interferred translocation of Gα_i1/2 to cortical region of maturing oocytes and reduction of its levels. RIC8 is also expressed at high level in female reproductive organs e.g. oviduct. Therefore we suggest a regulatory function for RIC8 in mammalian gametogenesis and fertility.     

Ablation of RIC8A Function in Mouse Neurons Leads to a Severe Neuromuscular Phenotype and Postnatal Death

Resistance to inhibitors of cholinesterase 8 (RIC8) is a guanine nucleotide exchange factor required for the intracellular regulation of G protein signalling. RIC8 activates different Gα subunits via non-canonical pathway, thereby amplifying and prolonging the G protein mediated signal. In order to circumvent the embryonic lethality associated with the absence of RIC8A and to study its role in the nervous system, we constructed Ric8a conditional knockout mice using Cre/loxP technology. Introduction of a synapsin I promoter driven Cre transgenic mouse strain (SynCre) into the floxed Ric8a (Ric8a^F/F) background ablated RIC8A function in most differentiated neuron populations. Mutant SynCre^+/-Ric8^lacZ/F mice were born at expected Mendelian ratio, but they died in early postnatal age (P4-P6). The mutants exhibited major developmental defects, like growth retardation and muscular weakness, impaired coordination and balance, muscular spasms and abnormal heart beat. Histological analysis revealed that the deficiency of RIC8A in neurons caused skeletal muscle atrophy and heart muscle hypoplasia, in addition, the sinoatrial node was misplaced and its size reduced. However, we did not observe gross morphological changes in brains of SynCre^+/-Ric8a^lacZ/F mutants. Our results demonstrate that in mice the activity of RIC8A in neurons is essential for survival and its deficiency causes a severe neuromuscular phenotype.     

Common growth signal and spatial synchrony of the chronologies of tree-rings from pines in the Baltic Sea region over the last nine centuries

The common growth signal and spatial synchrony of nine chronologies of tree rings (Pinus sylvestris L.) from the Baltic Sea region were studied using moving correlations with time windows of 50 and 100 years. Drifts from synchrony to asynchrony and again back to synchrony across several centuries were observed. The chronologies showed higher (or lower) coefficients of correlations and correspondingly gentler (or steeper) declines in spatial synchrony in certain periods. In accordance with research into other ecological phenomena, the origin of the spatial synchrony was found to relate to the intensity of the westerly circulation over the Atlantic and Europe as described by the North Atlantic Oscillation (NAO) index. The tree rings from all of the analysed subregions were found to be wider, identifying faster periods of growth, when there was a positive NAO during the extended winter season from December to March that preceded the period of growth. Previous studies showed that the NAO index can be linked with the growth of tree rings because of factors in the local climate that affect growth, such as temperature and precipitation. Moreover, the spatial synchrony showed multidecadal fluctuations that were correlated with variations of a similar scale in the reconstructed NAO index. However, a high degree of spatial synchrony was observed during the 20^th century in the presence of values of NAO index that were strongly negative. A more detailed view was provided by maps of the correlations in which spatial changes were demonstrated in the growth of pines between the 12^th and the 20^th century. These results could be used as background information in the development of improved proxy-based reconstructions of the NAO index (or other similar meteorological variables), which could also be inferred from tree ring data relating to earlier centuries.     

Temperature regime of planted roofs compared with conventional roofing systems

This paper analyses the temperature regime of an existing green roof and a sod roof, compared with a modified bituminous membrane roof and a steel sheet roof. The measurement period was from June 2004 to December 2007 at three different measurement locations. Results are given both seasonally and daily; indexes to characterize the effects of the temperature of planted roofs are also proposed. In summer, temperatures under both the green roof (100 mm) and the sod roof (150 mm) showed a similar temperature run; undesirable higher temperatures on the surfaces did not cause a notable increase in temperature under the substrate layers. The difference between the temperature amplitude under the substrate layers of the planted roofs and the surfaces of the conventional roofs was on average 20 °C. In autumn and spring, the sod roof's soil layer showed higher temperatures and lower amplitude than the green roof's substrate layer, which cooled more. In winter, temperatures under the substrate layers of the planted roofs were higher than the surfaces of the conventional roofs; average amplitude was 1 °C and 7–8 °C, respectively.