Synthetic retinal analogues modify the spectral and kinetic characteristics of microbial rhodopsin optogenetic tools

Optogenetic tools have become indispensable in neuroscience to stimulate or inhibit excitable cells by light. Channelrhodopsin-2 (ChR2) variants have been established by mutating the opsin backbone or by mining related algal genomes. As an alternative strategy, we surveyed synthetic retinal analogues combined with microbial rhodopsins for functional and spectral properties, capitalizing on assays in C. elegans, HEK cells and larval Drosophila. Compared with all-trans retinal (ATR), Dimethylamino-retinal (DMAR) shifts the action spectra maxima of ChR2 variants H134R and H134R/T159C from 480 to 520 nm. Moreover, DMAR decelerates the photocycle of ChR2(H134R) and (H134R/T159C), thereby reducing the light intensity required for persistent channel activation. In hyperpolarizing archaerhodopsin-3 and Mac, naphthyl-retinal and thiophene-retinal support activity alike ATR, yet at altered peak wavelengths. Our experiments enable applications of retinal analogues in colour tuning and altering photocycle characteristics of optogenetic tools, thereby increasing the operational light sensitivity of existing cell lines or transgenic animals

Synthetic retinal analogues modify the spectral and kinetic characteristics of microbial rhodopsin optogenetic tools

Optogenetic tools have become indispensable in neuroscience to stimulate or inhibit excitable cells by light. Channelrhodopsin-2 (ChR2) variants have been established by mutating the opsin backbone or by mining related algal genomes. As an alternative strategy, we surveyed synthetic retinal analogues combined with microbial rhodopsins for functional and spectral properties, capitalizing on assays in C. elegans, HEK cells and larval Drosophila. Compared with all-trans retinal (ATR), Dimethylamino-retinal (DMAR) shifts the action spectra maxima of ChR2 variants H134R and H134R/T159C from 480 to 520 nm. Moreover, DMAR decelerates the photocycle of ChR2(H134R) and (H134R/T159C), thereby reducing the light intensity required for persistent channel activation. In hyperpolarizing archaerhodopsin-3 and Mac, naphthyl-retinal and thiophene-retinal support activity alike ATR, yet at altered peak wavelengths. Our experiments enable applications of retinal analogues in colour tuning and altering photocycle characteristics of optogenetic tools, thereby increasing the operational light sensitivity of existing cell lines or transgenic animals

Prevalence and Characteristics of Self-Reported Hypothyroidism and Its Association with Nonorgan-Specific Manifestations in US Sarcoidosis Patients: A Nationwide Registry Study

Little is known about the prevalence, clinical characteristics and impact of hypothyroidism in patients with sarcoidosis. We aimed to determine the prevalence and clinical features of hypothyroidism and its relation to organ involvement and other clinical manifestations in patients with sarcoidosis. We conducted a national registry-based study investigating 3835 respondents to the Sarcoidosis Advanced Registry for Cures Questionnaire between June 2014 and August 2019. This registry is based on a self-reported, web-based questionnaire that provides data related to demographics, diagnostics, sarcoidosis manifestations and treatment. We compared sarcoidosis patients with and without self-reported hypothyroidism. We used multivariable logistic regression and adjusted for potential confounders to determine the association of hypothyroidism with nonorgan-specific manifestations. 14% of the sarcoidosis patients self-reported hypothyroidism and were generally middle-aged white women. Hypothyroid patients had more comorbid conditions and were more likely to have multiorgan sarcoidosis involvement, especially with cutaneous, ocular, joints, liver and lacrimal gland involvement. Self-reported hypothyroidism was associated with depression (adjusted odds ratio (aOR) 1.3, 95% CI 1.01–1.6), antidepressant use (aOR 1.3, 95% CI 1.1–1.7), obesity (aOR 1.7, 95% CI 1.4–2.1), sleep apnoea (aOR 1.7, 95% CI 1.3–2.2), chronic fatigue syndrome (aOR 1.5, 95% CI 1.2–2) and was borderline associated with fibromyalgia (aOR 1.3, 95% CI 1–1.8). Physical impairment was more common in patients with hypothyroidism. Hypothyroidism is a frequent comorbidity in sarcoidosis patients that might be a potentially reversible contributor to fatigue, depression and physical impairment in this population. We recommend considering routine screening for hypothyroidism in sarcoidosis patients especially in those with multiorgan sarcoidosis, fatigue and depression

The YaaA Protein of the Escherichia coli OxyR Regulon Lessens Hydrogen Peroxide Toxicity by Diminishing the Amount of Intracellular Unincorporated Iron▿†

Hydrogen peroxide (H2O2) is commonly formed in microbial habitats by either chemical oxidation processes or host defense responses. H2O2 can penetrate membranes and damage key intracellular biomolecules, including DNA and iron-dependent enzymes. Bacteria defend themselves against this H2O2 by inducing a regulon that engages multiple defensive strategies. A previous microarray study suggested that yaaA, an uncharacterized gene found in many bacteria, was induced by H2O2 in Escherichia coli as part of its OxyR regulon. Here we confirm that yaaA is a key element of the stress response to H2O2. In a catalase/peroxidase-deficient (Hpx−) background, yaaA deletion mutants grew poorly, filamented extensively, and lost substantial viability when they were cultured in aerobic LB medium. The results from a thyA forward mutagenesis assay and the growth defect of the yaaA deletion in a recombination-deficient (recA56) background indicated that yaaA mutants accumulated high levels of DNA damage. The growth defect of yaaA mutants could be suppressed by either the addition of iron chelators or mutations that slowed iron import, indicating that the DNA damage was caused by the Fenton reaction. Spin-trapping experiments confirmed that Hpx− yaaA cells had a higher hydroxyl radical (HO•) level. Electron paramagnetic resonance spectroscopy analysis showed that the proximate cause was an unusually high level of intracellular unincorporated iron. These results demonstrate that during periods of H2O2 stress the induction of YaaA is a critical device to suppress intracellular iron levels; it thereby attenuates the Fenton reaction and the DNA damage that would otherwise result. The molecular mechanism of YaaA action remains unknown

Impure and worldly geography: The Africanist discourse of the Royal Geographical Society, 1831-73

This paper argues for a theoretically informed critique of the formation of modern geographical knowledge which focuses upon the written networks through which knowledge is produced and circulated. Drawing on deconstruction and colonial discourse theory, the paper presents a reading of the Royal Geographical Society’s published record of nineteenth-century African exploration. This discourse posits a racially unmarked subject-position as the condition of scientific discussion. The Royal Geographical Society’s geographical knowledge is shown to have been formed through the effacement of alternative subject-positions and the appropriation of other ways of knowing. It is suggested that closer attention to the discursive structures of written networks of knowledge might inform a more nuanced understanding of the reproduction of disciplined knowledge