Adjacent Functional Group Effects on the Assembly of Columnar Liquid Crystals

Although the impact of individual functional groups on the self-assembly of columnar liquid crystal phases has been widely studied, the effect of varying multiple substituents has received much less attention. Herein, we report a series of dibenzo[a,c]phenazines containing an alcohol or ether adjacent to an electron-withdrawing ester or acid. With one exception, these difunctional mesogens form columnar phases. The phase behavior appeared to be dominated by the electron-withdrawing substituent; transition temperatures were similar to derivatives with these groups in isolation. In most instances, the addition of an electron-donating group ortho to an ester or acid suppressed the melting temperature and elevated the clearing temperature, leading to broader liquid crystal thermal ranges. This effect was more pronounced for derivatives functionalized with longer chain hexyloxy groups. These results suggest a potential strategy for controlling the phase ranges of columnar liquid crystals and achieving room temperature mesophases

CCNF mutations in amyotrophic lateral sclerosis and frontotemporal dementia

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are overlapping, fatal neurodegenerative disorders in which the molecular and pathogenic basis remains poorly understood. Ubiquitinated protein aggregates, of which TDP-43 is a major component, are a characteristic pathological feature of most ALS and FTD patients. Here we use genome-wide linkage analysis in a large ALS/FTD kindred to identify a novel disease locus on chromosome 16p13.3. Whole-exome sequencing identified a CCNF missense mutation at this locus. Interrogation of international cohorts identified additional novel CCNF variants in familial and sporadic ALS and FTD. Enrichment of rare protein-altering CCNF variants was evident in a large sporadic ALS replication cohort. CCNF encodes cyclin F, a component of an E3 ubiquitin-protein ligase complex (SCFCyclin F). Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCFCyclin F substrate. This implicates common mechanisms, linked to protein homeostasis, underlying neuronal degeneration

Tidal perturbations and variability in mesopause region over Fort Collins, CO(41N, 105W): continuous multi-day temperature and wind lidar observations

An unusually long data set was acquired at the sodium lidar facility at Colorado State University (41N, 105W), between Sep 18 and Oct 01, 2003, including a 9-day continuous observation. This time is long enough to average out the perturbations of gravity waves and short-period planetary waves. As such, it can be used to define tidal-period perturbations in temperature and horizontal wind. Assuming the sodium mixing ratio is a constant of motion, the observed tidal-period oscillation in sodium density follows that of vertical wind. Thus, the data set defines tidal-period perturbations of temperature and wind vector. The observed amplitudes and phases were compared to Global Scale Wave Model predictions (both GSWM00 and GSWM02). We found excellent agreement in diurnal phases and reasonable agreement in semidiurnal phases. However, GSWM02 overestimates diurnal amplitudes and both model versions underestimate observed semidiurnal amplitudes. Since the data period is long enough for the study of planetary waves and of tidal variability, we perform spectral analysis of the data, revealing a strong quasi 3-day wave in meridional wind, a 14 hour perturbation in zonal wind, and both 14-hour and 10-hour periods in meridional wind, likely the result of nonlinear interactions. The observed semidiurnal amplitudes are much larger than the corresponding diurnal amplitudes above 85 km, and over a few days the diurnal and semidiurnal amplitudes vary by factors of 2–3. Causes for the observed tidal variability in terms of planetary wave modulation and tide-gravity wave interaction are explored qualitatively

Exploiting Molecular Symmetry Reduction to Enrich Liquid Crystal Phase Diversity

The strategic tuning of liquid crystalline phase behaviour by adjusting molecular symmetry was investigated. A family of sixteen symmetrical and unsymmetrical 2,6-di(4’-n-alkoxybenzoyloxy) naphthalene derivatives were prepared and their liquid crystal properties examined by differential scanning calorimetry, polarised optical microscopy, and x-ray diffraction. All mesogens formed nematic phases, with longer-chain analogues also exhibiting smectic C phases at lower temperatures. Melting temperatures of the compounds strongly depend on molecular symmetry, whereas clearing transitions are relatively insensitive to this effect. A detailed analysis indicates that the clearing point can be predicted based on the nature of the terminal alkyl chains, with only a secondary effect from molecular symmetry. Moreover, low symmetry molecules showed a greater tendency to form smectic C phases, which was ascribed to the selective depression of the melting point versus the SmC-N transition. This demonstrates that molecular symmetry-breaking is a valuable tool both for tuning liquid crystalline phase range and for increasing a material’s polymorphism

The making of a mammalian peroxisome, version 2.0: mitochondria get into the mix

This is the author accepted manuscript. The final version is available from Nature Publishing Group via the DOI in this record.A recent report from the laboratory of Heidi McBride (McGill University) presents a role for mitochondria in the de novo biogenesis of peroxisomes in mammalian cells (1). Peroxisomes are essential organelles responsible for a wide variety of biochemical functions, from the generation of bile, to plasmalogen synthesis, reduction of peroxides, and the oxidation of very long chain fatty acids (2). Like mitochondria, peroxisomes proliferate primarily through growth and division of pre-existing peroxisomes (3-6). However, unlike mitochondria, peroxisomes do not fuse (5,7); further, and perhaps most importantly, they can also be born de novo, a process thought to occur through the generation of pre-peroxisomal vesicles that originate from the endoplasmic reticulum (reviewed in (8,9). De novo peroxisome biogenesis has been extensively studies in yeast, with a major focus on the role of the ER in this process. Comprehensive studies in mammalian cells are, however, scarce (5,10-12). By exploiting patient cells lacking mature peroxisomes, Sugiura et al. (1) now assign a role to ER and mitochondria in de novo mammalian peroxisome biogenesis by showing that the formation of immature preperoxisomes occurs through the fusion of Pex3- / Pex14-containing mitochondriaderived vesicles with Pex16-containing ER-derived vesicles

Investigation of autism and GABA receptor subunit genes in multiple ethnic groups

Autism is a neurodevelopmental disorder of complex genetics, characterized by impairment in social interaction and communication, as well as repetitive behavior. Multiple lines of evidence, including alterations in levels of GABA and GABA receptors in autistic patients, indicate that the GABAergic system, which is responsible for synaptic inhibition in the adult brain, may be involved in autism. Previous studies in our lab indicated association of noncoding single nucleotide polymorphisms (SNPs) within a GABA receptor subunit gene on chromosome 4, GABRA4, and interaction between SNPs in GABRA4 and GABRB1 (also on chromosome 4), within Caucasian autism patients. Studies of genetic variation in African-American autism families are rare. Analysis of 557 Caucasian and an independent population of 54 African-American families with 35 SNPs within GABRB1 and GABRA4 strengthened the evidence for involvement of GABRA4 in autism risk in Caucasians (rs17599165, p=0.0015; rs1912960, p=0.0073; and rs17599416, p=0.0040) and gave evidence of significant association in African-Americans (rs2280073, p=0.0287 and rs16859788, p=0.0253). The GABRA4 and GABRB1 interaction was also confirmed in the Caucasian dataset (most significant pair, rs1912960 and rs2351299; p=0.004). Analysis of the subset of families with a positive history of seizure activity in at least one autism patient revealed no association to GABRA4; however, three SNPs within GABRB1 showed significant allelic association; rs2351299 (p=0.0163), rs4482737 (p=0.0339), and rs3832300 (p=0.0253). These results confirmed our earlier findings, indicating GABRA4 and GABRB1 as genes contributing to autism susceptibility, extending the effect to multiple ethnic groups and suggesting seizures as a stratifying phenotype

Association of Genetic Variants With Primary Open-Angle Glaucoma Among Individuals With African Ancestry.

Importance:Primary open-angle glaucoma presents with increased prevalence and a higher degree of clinical severity in populations of African ancestry compared with European or Asian ancestry. Despite this, individuals of African ancestry remain understudied in genomic research for blinding disorders. Objectives:To perform a genome-wide association study (GWAS) of African ancestry populations and evaluate potential mechanisms of pathogenesis for loci associated with primary open-angle glaucoma. Design, Settings, and Participants:A 2-stage GWAS with a discovery data set of 2320 individuals with primary open-angle glaucoma and 2121 control individuals without primary open-angle glaucoma. The validation stage included an additional 6937 affected individuals and 14 917 unaffected individuals using multicenter clinic- and population-based participant recruitment approaches. Study participants were recruited from Ghana, Nigeria, South Africa, the United States, Tanzania, Britain, Cameroon, Saudi Arabia, Brazil, the Democratic Republic of the Congo, Morocco, Peru, and Mali from 2003 to 2018. Individuals with primary open-angle glaucoma had open iridocorneal angles and displayed glaucomatous optic neuropathy with visual field defects. Elevated intraocular pressure was not included in the case definition. Control individuals had no elevated intraocular pressure and no signs of glaucoma. Exposures:Genetic variants associated with primary open-angle glaucoma. Main Outcomes and Measures:Presence of primary open-angle glaucoma. Genome-wide significance was defined as P < 5 × 10-8 in the discovery stage and in the meta-analysis of combined discovery and validation data. Results:A total of 2320 individuals with primary open-angle glaucoma (mean [interquartile range] age, 64.6 [56-74] years; 1055 [45.5%] women) and 2121 individuals without primary open-angle glaucoma (mean [interquartile range] age, 63.4 [55-71] years; 1025 [48.3%] women) were included in the discovery GWAS. The GWAS discovery meta-analysis demonstrated association of variants at amyloid-β A4 precursor protein-binding family B member 2 (APBB2; chromosome 4, rs59892895T>C) with primary open-angle glaucoma (odds ratio [OR], 1.32 [95% CI, 1.20-1.46]; P = 2 × 10-8). The association was validated in an analysis of an additional 6937 affected individuals and 14 917 unaffected individuals (OR, 1.15 [95% CI, 1.09-1.21]; P < .001). Each copy of the rs59892895*C risk allele was associated with increased risk of primary open-angle glaucoma when all data were included in a meta-analysis (OR, 1.19 [95% CI, 1.14-1.25]; P = 4 × 10-13). The rs59892895*C risk allele was present at appreciable frequency only in African ancestry populations. In contrast, the rs59892895*C risk allele had a frequency of less than 0.1% in individuals of European or Asian ancestry. Conclusions and Relevance:In this genome-wide association study, variants at the APBB2 locus demonstrated differential association with primary open-angle glaucoma by ancestry. If validated in additional populations this finding may have implications for risk assessment and therapeutic strategies

Daf-2 Signaling Modifies Mutant SOD1 Toxicity in C. elegans

The DAF-2 Insulin/IGF-1 signaling (IIS) pathway is a strong modifier of Caenorhabditis elegans longevity and healthspan. As aging is the greatest risk factor for developing neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS), we were interested in determining if DAF-2 signaling modifies disease pathology in mutant superoxide dismutase 1 (SOD1) expressing C. elegans. Worms with pan-neuronal G85R SOD1 expression demonstrate significantly impaired locomotion as compared to WT SOD1 expressing controls and they develop insoluble SOD1 aggregates. Reductions in DAF-2 signaling, either through a hypomorphic allele or neuronally targeted RNAi, decreases the abundance of aggregated SOD1 and results in improved locomotion in a DAF-16 dependant manner. These results suggest that manipulation of the DAF-2 Insulin/IGF-1 signaling pathway may have therapeutic potential for the treatment of ALS

MRE11 Function in Response to Topoisomerase Poisons Is Independent of its Function in Double-Strand Break Repair in Saccharomyces cerevisiae

Camptothecin (CPT) and etoposide (ETP) trap topoisomerase-DNA covalent intermediates, resulting in formation of DNA damage that can be cytotoxic if unrepaired. CPT and ETP are prototypes for molecules widely used in chemotherapy of cancer, so defining the mechanisms for repair of damage induced by treatment with these compounds is of great interest. In S. cerevisiae, deficiency in MRE11, which encodes a highly conserved factor, greatly enhances sensitivity to treatment with CPT or ETP. This has been thought to reflect the importance of double-strand break (DSB) repair pathways in the response to these to agents. Here we report that an S. cerevisiae strain expressing the mre11-H59A allele, mutant at a conserved active site histidine, is sensitive to hydroxyurea and also to ionizing radiation, which induces DSBs, but not to CPT or ETP. We show that TDP1, which encodes a tyrosyl-DNA phosphodiesterase activity able to release both 5′- and 3′-covalent topoisomerase-DNA complexes in vitro, contributes to ETP-resistance but not CPT-resistance in the mre11-H59A background. We further show that CPT- and ETP-resistance mediated by MRE11 is independent of SAE2, and thus independent of the coordinated functions of MRE11 and SAE2 in homology-directed repair and removal of Spo11 from DNA ends in meiosis. These results identify a function for MRE11 in the response to topoisomerase poisons that is distinct from its functions in DSB repair or meiotic DNA processing. They also establish that cellular proficiency in repair of DSBs may not correlate with resistance to topoisomerase poisons, a finding with potential implications for stratification of tumors with specific DNA repair deficiencies for treatment with these compounds