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  • Cloning of opsin cDNAs from the brain of Anolis carolinensis

    27 November 2018

    Purpose. We have previously shown that a range of different anti-opsin antibodies labelled CSF-contacting neurons in the septal area of the brain of the lizard Anolis carolinensis. This makes these cells strong candidates for the deep brain photoreceptors that mediate circadian responses to light in this species. In an attempt to characterize these putative photoreceptors and their transduction machinery we have started to isolate cDNA clones encoding their opsin(s). Methods. Initially, we used degenerate opsin primers in reverse transcription PCR with RNA from Anolis brain. The amplified DNA was subcloned and sequenced. Subsequently, a λgt11 cDNA library was constructed with Anolis brain mRNA. This library was screened with the PCR-amplified cDNA, as well as a chicken pineal opsin cDNA. Results. An 0.4 kb PCR product was obtained. Sequence analysis showed it to be identical with the rhodopsin-like gene previously cloned from an Anolis genomic library by Kawamura and Yokoyama (Gene 1995;149:267-270). Screening of the library with both probes gave several positive clones, the analysis of which is in progress. Conclusions. The detection of a message for the putative Anolis pineal opsin in the brain indicates that it is expressed in the deep brain photoreceptor as well as (or possibly instead of) in the pineal organ. We intend to further investigate this by cDNA cloning from pineal and ocular photoreceptors, as well as screening for other transduction genes.

  • Characterization of a putative novel opsin from atlantic salmon

    27 November 2018

    Purpose. To investigate the structural characteristics of a putative novel opsin family. Methods. We have initiated a screen of salmon ocular opsins. Degenerate PCR primers were designed against evolutionarily conserved structural domains of opsins. cDNA was synthesized from ocular RNA. Opsin cDNAs were amplified using opsin specific degenerate primers. cDNAs were subsequently subcloned and sequenced. 5′ and 3′ RACE PCR was used to isolate the complete coding region. Phylogenetic trees of cloned opsins were generated using commercially available software (PAUP). Results. Within opsin families, opsins from different species show amino acid identity of 65-95%. Between families, they show amino acid identity of 40-50%. During our screen we isolated an opsin cDNA partial clone (tentatively called salopsin) whose deduced translation (153 amino acids) showed approximately 40% identity to all other vertebrate opsin families, including pinopsin. Salopsin contains a Schiff base lysine for chromophore binding, a cysteine involved in an intramolecular disulfide bond, and three hydrophobic domains corresponding to the expected transmembrane domains of other opsins. Additionally, salopsin contains differences in conserved residues within suggested transducin interacting domains, and a deletion of two amino acids within the second intradiskal loop. In the various phylogenetic trees generated, salopsin was placed as either a third clade at the long wavelength/short wavelength duplication event, or as a separate clade preceding it. Salopsin was never placed within another opsin family. Conclusions. Based upon the amino acid identity of salopsin (≈ 40%) to all other vertebrate opsin families, we propose that it may form a novel opsin family. Salopsin has several structural features common to vertebrate opsins yet contains differences in functionally important residues. Finally, phylogenetic analysis places salopsin as a separate early clade in vertebrate opsin evolution. We have begun further studies to determine the structural features and functional importance of salopsin.

  • Developmental pathways towards mood disorders in adult life: Is there a role for sleep disturbances?

    27 November 2018

    INTRODUCTION: Mood disorders are among the most prevalent and serious mental disorders and rank high among to the leading global burdens of disease. The developmental psychopathology framework can offer a life course perspective on them thus providing a basis for early prevention and intervention. Sleep disturbances, are considered risk factors for mood disorders across childhood, adolescence and adulthood. Assuming that sleep disturbances may play a pivotal role in the pathogenesis of mood disorders from a life course point of view, we reviewed the data on developmental pathways towards mood disorders in adult life in relation to sleep disturbances. METHOD: From February 2017, a systematic search was conducted in PubMed, PsycINFO and Embase electronic databases for literature on developmental pathways to mood disorders in adult life in relation to sleep disturbances and to 1) pre-natal stress, 2) early brain developmental processes, and 3) temperaments, character and attachment style. RESULTS: Eleven, 54 and 15 articles were respectively selected. CONCLUSIONS: Experimental and clinical studies revealed that exposure to prenatal/early life stress results in sleep disturbances such as poor sleep and altered circadian regulation phases and may predict or even precipitate mood disorders in adulthood. Chronic sleep disruption may interfere with neuronal plasticity, connectivity and the developing brain thus contributing to the development of mood disorders. In addition sleep and circadian dysregulations have been shown to be related to those temperaments, character and attachment styles which are considered precursors of mood disorders. Sleep and circadian behaviours may serve as early targets regarding mood disorders.

  • Preface

    27 November 2018

  • A novel and ancient vertebrate opsin.

    27 November 2018

    We describe the identification of a novel opsin gene isolated from the eyes of Atlantic salmon. The cDNA sequence predicts a protein that has the key features of an opsin, but shows only 32-42% amino acid identity to the known opsin families. Phylogenetic analysis suggests that this opsin is a member of a hitherto unrecognised opsin family that diverged early in the evolution of vertebrate photopigments. We have tentatively called this opsin family the vertebrate ancient (VA) opsins. The identification of VA opsin may ultimately help to resolve some of the uncharacterised photoreceptor functions of the eye, which include the regulation of circadian rhythms, pupil size and corneal pigmentation.

  • Vitamin A2-based photopigments within the pineal gland of a fully terrestrial vertebrate.

    27 November 2018

    Fully terrestrial vertebrates were previously thought to exclusively employ vitamin A1 to generate visual pigments. However, recent studies on the visual system of the lizard Anolis carolinensis have shown that its visual pigments are vitamin A2-based. This unexpected result prompted an investigation of the pineal photopigments in this species [13]. HPLC analysis has shown that this extraretinal photoreceptor also exclusively utilizes a vitamin A2-derived chromophore. The adaptive significance of this chromophore within the pineal is unclear. The extended long wavelength sensitivity characteristic of vitamin A2-based visual pigment systems may enhance important visual tasks such as prey detection or mate selection [13]. A similar argument cannot be made for the pineal, whose role is not image formation, but rather detection of the irradiance changes associated with dawn and dusk. We suggest that the pineal may passively utilize whatever retinoids have been adaptively selected by the visual system.

  • Sleep differences in the UK between 1974 and 2015: Insights from detailed time diaries.

    27 November 2018

    It is often stated that sleep deprivation is on the rise, with work suggested as a main cause. However, the evidence for increasing sleep deprivation comes from surveys using habitual sleep questions. An alternative source of information regarding sleep behaviour is time-use studies. This paper investigates changes in sleep time in the UK using the two British time-use studies that allow measuring "time in bed not asleep" separately from "actual sleep time". Based upon the studies presented here, people in the UK sleep today 43 min more than they did in the 1970s because they go to bed earlier (~30 min) and they wake up later (~15 min). The change in sleep duration is driven by night sleep and it is homogeneously distributed across the week. The former results apply to men and women alike, and to individuals of all ages and employment status, including employed individuals, the presumed major victims of the sleep deprivation epidemic and the 24/7 society. In fact, employed individuals have experienced a reduction in short sleeping of almost 4 percentage points, from 14.9% to 11.0%. There has also been a reduction of 15 percentage points in the amount of conflict between workers work time and their sleep time, as measured by the proportion of workers that do some work within their "ideal sleep window" (as defined by their own chronotype).

  • Teleost multiple tissue (tmt) opsin: a candidate photopigment regulating the peripheral clocks of zebrafish?

    27 November 2018

    Isolated organs and cell lines from zebrafish exhibit circadian oscillations in clock gene expression that can be entrained to a 24-h light/dark cycle. The mechanism underlying this cellular photosensitivity is unknown. We report the identification of a novel opsin family, tmt-opsin, that has a genomic structure characteristic of vertebrate photopigments, an amino acid identity equivalent to the known photopigment opsins, and the essential residues required for photopigment function. Significantly, tmt-opsin is expressed in a wide variety of neural and non-neural tissues, including a zebrafish embryonic cell line that exhibits a light entrainable clock. Collectively the data suggest that tmt-opsin is a strong candidate for the photic regulation of zebrafish peripheral clocks.

  • Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice.

    27 November 2018

    In the mammalian retina, a small subset of retinal ganglion cells (RGCs) are intrinsically photosensitive, express the opsin-like protein melanopsin, and project to brain nuclei involved in non-image-forming visual functions such as pupillary light reflex and circadian photoentrainment. We report that in mice with the melanopsin gene ablated, RGCs retrograde-labeled from the suprachiasmatic nuclei were no longer intrinsically photosensitive, although their number, morphology, and projections were unchanged. These animals showed a pupillary light reflex indistinguishable from that of the wild type at low irradiances, but at high irradiances the reflex was incomplete, a pattern that suggests that the melanopsin-associated system and the classical rod/cone system are complementary in function.

  • Photic regulation of Fos-like immunoreactivity in the suprachiasmatic nucleus of the mouse.

    27 November 2018

    In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus functions as the primary pacemaker of the circadian system. Light has been shown to induce Fos-like immunoreactivity (Fos-LI) in the SCN of rats and hamsters. The purpose of the present study was to evaluate extensively the effect of light on Fos-LI in the mouse SCN. Brief pulses of light administered to animals otherwise in constant darkness were found to induce Fos-LI. This photic induction was unaffected by the rd mutation, which causes the profound loss of photoreceptors but fails to affect circadian responses to light. Light regulation of Fos-LI was dependent upon the phase of the circadian cycle in which the light pulse was administered. Phases at which light causes phase shifts of the circadian system were permissive for Fos-LI induction (CT 16 and 24), while phases in which light does not cause phase shifts were not permissive (CT 6 and 9). The time course of the induction at CT 16 was also described. In a light/dark cycle, Fos-LI was found to be rhythmically expressed with Fos-LI elevated soon after the lights came on but remaining low throughout the rest of the cycle. However, this rhythm is a direct consequence of the light because in constant darkness Fos-LI was always low. These results have implications regarding the possible functional roles of Fos in the circadian system and add to our understanding of light regulation of circadian physiology in the mouse.