ALBERT

Description: Mutations in lamin A/C result in a range of tissue-specific disorders collectively called laminopathies. Of these, Emery–Dreifuss and Limb-Girdle muscular dystrophy 1B mainly affect striated muscle. A useful model for understanding both laminopathies and lamin A/C function is the Lmna –/– mouse. We found that skeletal muscle growth and muscle satellite (stem) cell proliferation were both reduced in Lmna –/– mice. Lamins A and C associate with lamina-associated polypeptide 2 alpha (Lap2α) and the retinoblastoma gene product, pRb, to regulate cell cycle exit. We found Lap2α to be upregulated in Lmna –/– myoblasts (MBs). To specifically test the contribution of elevated Lap2α to the phenotype of Lmna –/– mice, we generated Lmna –/– Lap2α –/– mice. Lifespan and body mass were increased in Lmna –/– Lap2α –/– mice compared with Lmna –/– . Importantly, the satellite cell proliferation defect was rescued, resulting in improved myogenesis. Lmna –/– MBs also exhibited increased levels of Smad2/3, which were abnormally distributed in the cell and failed to respond to TGFβ1 stimulation as in control cells. However, using SIS3 to inhibit signaling via Smad3 reduced cell death and augmented MB fusion. Together, our results show that perturbed Lap2α/pRb and Smad2/3 signaling are important regulatory pathways mediating defective muscle growth in Lmna –/– mice, and that inhibition of either pathway alone or in combination can ameliorate this deleterious phenotype.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Doo, S. S., Kealoha, A., Andersson, A., Cohen, A. L., Hicks, T. L., Johnson, Z., I., Long, M. H., McElhany, P., Mollica, N., Shamberger, K. E. F., Silbiger, N. J., Takeshita, Y., & Busch, D. S. The challenges of detecting and attributing ocean acidification impacts on marine ecosystems. ICES Journal of Marine Science, 77(7-8), (2020): 2411-2422, https://doi.org/10.1093/icesjms/fsaa094.

Description: A substantial body of research now exists demonstrating sensitivities of marine organisms to ocean acidification (OA) in laboratory settings. However, corresponding in situ observations of marine species or ecosystem changes that can be unequivocally attributed to anthropogenic OA are limited. Challenges remain in detecting and attributing OA effects in nature, in part because multiple environmental changes are co-occurring with OA, all of which have the potential to influence marine ecosystem responses. Furthermore, the change in ocean pH since the industrial revolution is small relative to the natural variability within many systems, making it difficult to detect, and in some cases, has yet to cross physiological thresholds. The small number of studies that clearly document OA impacts in nature cannot be interpreted as a lack of larger-scale attributable impacts at the present time or in the future but highlights the need for innovative research approaches and analyses. We summarize the general findings in four relatively well-studied marine groups (seagrasses, pteropods, oysters, and coral reefs) and integrate overarching themes to highlight the challenges involved in detecting and attributing the effects of OA in natural environments. We then discuss four potential strategies to better evaluate and attribute OA impacts on species and ecosystems. First, we highlight the need for work quantifying the anthropogenic input of CO2 in coastal and open-ocean waters to understand how this increase in CO2 interacts with other physical and chemical factors to drive organismal conditions. Second, understanding OA-induced changes in population-level demography, potentially increased sensitivities in certain life stages, and how these effects scale to ecosystem-level processes (e.g. community metabolism) will improve our ability to attribute impacts to OA among co-varying parameters. Third, there is a great need to understand the potential modulation of OA impacts through the interplay of ecology and evolution (eco–evo dynamics). Lastly, further research efforts designed to detect, quantify, and project the effects of OA on marine organisms and ecosystems utilizing a comparative approach with long-term data sets will also provide critical information for informing the management of marine ecosystems.

Description: SSD was funded by NSF OCE (grant # 1415268). DSB and PM were supported by the NOAA Ocean Acidification Program and Northwest Fisheries Science Center, MHL was supported by NSF OCE (grant # 1633951), ZIJ was supported by NSF OCE (grant # 1416665) and DOE EERE (grant #DE-EE008518), NJS was supported by NSF OCE (grant # 1924281), ALC was supported by NSF OCE (grant # 1737311), and AA was supported by NSF OCE (grant # 1416518). KEFS, AK, and TLH were supported by Texas A&M University. This is CSUN Marine Biology contribution (# 306).

Description: Chemically tagging groups of stars born in the same birth cluster is a major goal of spectroscopic surveys. To investigate the feasibility of such strong chemical tagging, we perform a blind chemical tagging experiment on abundances measured from APOGEE survey spectra. We apply a density-based clustering algorithm to the 8D chemical space defined by [Mg/Fe], [Al/Fe], [Si/Fe], [K/Fe], [Ti/Fe], [Mn/Fe], [Fe/H], and [Ni/Fe], abundances ratios which together span multiple nucleosynthetic channels. In a high-quality sample of 182 538 giant stars, we detect 21 candidate clusters with more than 15 members. Our candidate clusters are more chemically homogeneous than a population of non-member stars with similar [Mg/Fe] and [Fe/H], even in abundances not used for tagging. Group members are consistent with having the same age and fall along a single stellar-population track in log g versus Teff space. Each group’s members are distributed over multiple kpc, and the spread in their radial and azimuthal actions increases with age. We qualitatively reproduce this increase using N-body simulations of cluster dissolution in Galactic potentials that include transient winding spiral arms. Observing our candidate birth clusters with high-resolution spectroscopy in other wavebands to investigate their chemical homogeneity in other nucleosynthetic groups will be essential to confirming the efficacy of strong chemical tagging. Our initially spatially compact but now widely dispersed candidate clusters will provide novel limits on chemical evolution and orbital diffusion in the Galactic disc, and constraints on star formation in loosely bound groups.

Description: For $q$ an odd prime power with $q 〉 169,$ we prove that there are always three consecutive primitive elements in the finite field $\mathbb {F}_{q}$ . Indeed, there are precisely eleven values of $q \leq 169$ for which this is false. For $4\leq n \leq 8,$ we present conjectures on the size of $q_{0}(n)$ such that $q 〉 q_{0}(n)$ guarantees the existence of $n$ consecutive primitive elements in $\mathbb {F}_{q}$ , provided that $\mathbb {F}_{q}$ has characteristic at least $n$ . Finally, we improve the upper bound on $q_{0}(n)$ for all $n\geq 3$ .

Description: Summer droughts are likely to increase in frequency and intensity across Europe, yet long-lived trees may have a limited ability to tolerate drought. It is therefore critical that we improve our understanding of phenotypic plasticity to drought in natural populations for ecologically and economically important trees such as Populus nigra L. A common garden experiment was conducted using ~500 wild P. nigra trees, collected from 11 river populations across Europe. Phenotypic variation was found across the collection, with southern genotypes from Spain and France characterized by small leaves and limited biomass production. To examine the relationship between phenotypic variation and drought tolerance, six genotypes with contrasting leaf morphologies were subjected to a water deficit experiment. ‘North eastern’ genotypes were collected at wet sites and responded to water deficit with reduced biomass growth, slow stomatal closure and reduced water use efficiency (WUE) assessed by 13 C. In contrast, ‘southern’ genotypes originating from arid sites showed rapid stomatal closure, improved WUE and limited leaf loss. Transcriptome analyses of a genotype from Spain (Sp2, originating from an arid site) and another from northern Italy (Ita, originating from a wet site) revealed dramatic differences in gene expression response to water deficit. Transcripts controlling leaf development and stomatal patterning, including SPCH , ANT , ER , AS1 , AS2 , PHB , CLV1 , ERL1–3 and TMM , were down-regulated in Ita but not in Sp2 in response to drought.

Description: For isohydric trees mid-day water uptake is stable and depends on soil water status, reflected in pre-dawn leaf water potential ( pd ) and mid-day stem water potential ( md ), tree hydraulic conductance and a more-or-less constant leaf water potential ( l ) for much of the day, maintained by the stomata. Stabilization of l can be represented by a linear relationship between canopy resistance ( R c ) and vapor pressure deficit ( D ), and the slope ( B D ) is proportional to the steady-state water uptake. By analyzing sap flow (SF), meteorological and md measurements during a series of wetting and drying ( D / W ) cycles in a nectarine orchard, we found that for the range of md relevant for irrigated orchards the slope of the relationship of R c to D , B D is a linear function of md . R c was simulated using the above relationships, and its changes in the morning and evening were simulated using a rectangular hyperbolic relationship between leaf conductance and photosynthetic irradiance, fitted to leaf-level measurements. The latter was integrated with one-leaf, two-leaf and integrative radiation models, and the latter gave the best results. Simulated R c was used in the Penman–Monteith equation to simulate tree transpiration, which was validated by comparing with SF from a separate data set. The model gave accurate estimates of diurnal and daily total tree transpiration for the range of md s used in regular and deficit irrigation. Diurnal changes in tree water content were determined from the difference between simulated transpiration and measured SF . Changes in water content caused a time lag of 90–105 min between transpiration and SF for md between –0.8 and –1.55 MPa, and water depletion reached 3 l h –1 before noon. Estimated mean diurnal changes in water content were 5.5 l day –1  tree –1 at md of –0.9 MPa and increased to 12.5 l day –1  tree –1 at –1.45 MPa, equivalent to 6.5 and 16.5% of daily tree water use, respectively. Sixteen percent of the dynamic water volume was in the leaves. Inversion of the model shows that md can be predicted from D and R c , which may have some importance for irrigation management to maintain target values of md . That relationship will be explored in future research.

Description: This article describes the use of continuous vector space models for reasoning with a formal knowledge base. The practical significance of these models is that they support fast, approximate but robust inference and hypothesis generation, which is complementary to the slow, exact, but sometimes brittle behaviour of more traditional deduction engines such as theorem provers. The article explains the way logical connectives can be used in semantic vector models, and summarizes the development of Predication-based Semantic Indexing, which involves the use of Vector Symbolic Architectures to represent the concepts and relationships from a knowledge base of subject-predicate-object triples. Experiments show that the use of continuous models for formal reasoning is not only possible, but already demonstrably effective for some recognized informatics tasks, and showing promise in other traditional problem areas. Examples described in this article include: predicting new uses for existing drugs in biomedical informatics; removing unwanted meanings from search results in information retrieval and concept navigation; type inference from attributes; comparing words based on their orthography; and representing tabular data, including modelling numerical values. The algorithms and techniques described in this article are all publicly released and freely available in the Semantic Vectors open-source software package. 1