Non-visual ocular photoreception

A systematic literature review: building window's influence on indoor circadian health

Light has been shown to have a non-visual impact on the biological aspects of human health, particularly on circadian rhythms. Building windows are a potential means of regulating daylight conditions for circadian health and well-being. As a result of advancements in window and glazing technologies and variations in outdoor solar/sky conditions, understanding daylight's spectral characteristics, which pass through building window systems, is complex. Therefore, a systematic review and summary of the knowledge and evidence available regarding windows' impact on human circadian health is necessary. This study provides an overview of research in this domain, compares approaches and evaluation metrics, and underscores the importance of window parameters' influence on circadian health. Published studies available on various online databases since 2012 were evaluated. The findings of this study define a holistic approach to the melanopic performance of windows and provide an overview of current knowledge regarding the effect of windows on circadian health. Additionally, this work identifies future research directions based on the studies reviewed. This research contributes to the growing body of knowledge on the impact of windows on circadian health, which has implications for the design and construction of buildings in ways that support indoor human health and well-being from the circadian light adequacy perspective.

Comprehensive transcript-level analysis reveals transcriptional reprogramming during the progression of Alzheimer's disease

Background

Alzheimer's disease (AD) is a common neurodegenerative disorder that has a multi-step disease progression. Differences between moderate and advanced stages of AD have not yet been fully characterized.

Materials and methods

Herein, we performed a transcript-resolution analysis in 454 AD-related samples, including 145 non-demented control, 140 asymptomatic AD (AsymAD), and 169 AD samples. We comparatively characterized the transcriptome dysregulation in AsymAD and AD samples at transcript level.

Results

We identified 4,056 and 1,200 differentially spliced alternative splicing events (ASEs) that might play roles in the disease progression of AsymAD and AD, respectively. Our further analysis revealed 287 and 222 isoform switching events in AsymAD and AD, respectively. In particular, a total of 163 and 119 transcripts showed increased usage, while 124 and 103 transcripts exhibited decreased usage in AsymAD and AD, respectively. For example, gene APOA2 showed no expression changes between AD and non-demented control samples, but expressed higher proportion of transcript ENST00000367990.3 and lower proportion of transcript ENST00000463812.1 in AD compared to non-demented control samples. Furthermore, we constructed RNA binding protein (RBP)-ASE regulatory networks to reveal potential RBP-mediated isoform switch in AsymAD and AD.

Conclusion

In summary, our study provided transcript-resolution insights into the transcriptome disturbance of AsymAD and AD, which will promote the discovery of early diagnosis biomarkers and the development of new therapeutic strategies for patients with AD.

Light-induced shifts in opsin gene expression in the four-eyed fish Anableps anableps

The development of the vertebrate eye is a complex process orchestrated by several conserved transcriptional and signaling regulators. Aside from partial or complete loss, examples of exceptional modifications to this intricate organ are scarce. The unique eye of the four-eyed fish Anableps anableps is composed of duplicated corneas and pupils, as well as specialized retina regions associated with simultaneous aerial and aquatic vision. In a previous transcriptomic study of the A. anableps developing eye we identified expression of twenty non-visual and eleven visual opsin genes. Here, we surveyed the expression territories of three non-visual melanopsins genes (opn4×1, opn4×2, opn4m3), one teleost multiple tissue opsin (tmt1b) and two visual opsins (lws and rh2-1) in dorsal and ventral retinas. Our data showed that asymmetry of non-visual opsin expression is only established after birth. During embryonic development, while inside pregnant females, the expression of opn4×1, opn4×2, and tmt1b spans the whole retina. In juvenile fish (post birth), the expression of opn4×1, opn4×2, opn4m3, and tmt1b genes becomes restricted to the ventral retina, which receives aerial light. Raising juvenile fish in clear water instead of the murky waters found in its natural habitat is sufficient to change gene expression territories of opn4×1, opn4×2, opn4m3, tmt1b, and rh2-1, demonstrating that different lighting conditions can shift opsin expression and potentially contribute to changes in spectral sensitivity in the four eyed fish.

Gene expression patterns of novel visual and non-visual opsin families in immature and mature Japanese eel males

This study was carried out to identify and estimate physiological function of a new type of opsin subfamily present in the retina and whole brain tissues of Japanese eel using RNA–Seq transcriptome method. A total of 18 opsin subfamilies were identified through RNA–seq. The visual opsin family included Rh2, SWS2, FWO, DSO, and Exo-Rhod. The non-visual opsin family included four types of melanopsin subfamily (Opn4x1, Opn4x2, Opn4m1, and Opn4m2), peropsin, two types of neuropsin subfamily (Opn5-like, Opn5), Opn3, three types of TMT opsin subfamily (TMT1, 2, 3), VA-opsin, and parapinopsin. In terms of changes in photoreceptor gene expression in the retina of sexually mature and immature male eels, DSO mRNA increased in the maturation group. Analysis of expression of opsin family gene in male eel brain before and after maturation revealed that DSO and SWS2 expression in terms of visual opsin mRNA increased in the sexually mature group. In terms of non-visual opsin mRNA, parapinopsin mRNA increased whereas that of TMT2 decreased in the fore-brain of the sexually mature group. The mRNA for parapinopsin increased in the mid-brain of the sexually mature group, whereas those of TMT1 and TMT3 increased in the hind-brain of the sexually mature group. DSO mRNA also increased in the retina after sexual maturation, and DSO and SWS2 mRNA increased in whole brain part, suggesting that DSO and SWS2 are closely related to sexual maturation.

Avian circadian organization: a chorus of clocks

In birds, biological clock function pervades all aspects of biology, controlling daily changes in sleep: wake, visual function, song, migratory patterns and orientation, as well as seasonal patterns of reproduction, song and migration. The molecular bases for circadian clocks are highly conserved, and it is likely the avian molecular mechanisms are similar to those expressed in mammals, including humans. The central pacemakers in the avian pineal gland, retinae and SCN dynamically interact to maintain stable phase relationships and then influence downstream rhythms through entrainment of peripheral oscillators in the brain controlling behavior and peripheral tissues. Birds represent an excellent model for the role played by biological clocks in human neurobiology; unlike most rodent models, they are diurnal, they exhibit cognitively complex social interactions, and their circadian clocks are more sensitive to the hormone melatonin than are those of nocturnal rodents.

Global daily dynamics of the pineal transcriptome

Transcriptome profiling of the pineal gland has revealed night/day differences in the expression of a major fraction of the genes active in this tissue, with two-thirds of these being nocturnal increases. A set of over 600 transcripts exhibit two-fold to >100-fold daily differences in abundance. These changes appear to be primarily attributable to adrenergic-cyclic-AMP-dependent mechanisms, which are controlled via a neural pathway that includes the suprachiasmatic nucleus, the master circadian oscillator. In addition to melatonin synthesis, night/day differences in gene expression impact genes associated with several specialized functions, including the immune/inflammation response, photo-transduction, and thyroid hormone/retinoic acid biology. The following nonspecialized cellular features are also affected: adhesion, cell cycle/cell death, cytoskeleton, DNA modification, endothelium, growth, RNA modification, small molecule biology, transcription factors, vesicle biology, signaling involving Ca(2+), cyclic nucleotides, phospholipids, mitogen-activated protein kinases, the Wnt signaling pathway, and protein phosphorylation.

Impaired Masking Responses to Light in Melanopsin‐Knockout Mice

There are two ways in which an animal can confine its behavior to a nocturnal or diurnal niche. One is to synchronize an endogenous clock that in turn controls the sleep-wake cycle. The other is to respond directly to illumination with changes in activity. In mice, high illumination levels suppress locomotion (negative masking) and low illumination levels enhance locomotion (positive masking). To investigate the role of the newly discovered opsin-like protein melanopsin in masking, we used 1 h and 3 h pulses of light given in the night, and also a 3.5:3.5 h light-dark (LD) cycle. Mice lacking the melanopsin gene had normal enhancement of locomotion in the presence of dim lights but an impaired suppression of locomotion in the presence of bright light. This impairment was evident only with lights in the order of 10 lux or brighter. This suggests that melanopsin in retinal ganglion cells is involved in masking, as it is in pupil contraction and phase shifts. Melanopsin is especially important in maintaining masking responses over long periods.

Aging in the circadian system: considerations for health, disease prevention and longevity

The circadian system orchestrates internal physiology on a daily schedule to promote optimal health and maximize disease prevention. Chronic disruptions in circadian function are associated with an increase in a variety of disease states including, heart disease, ulcers and diabetes. With advanced age, the genes regulating circadian function at the cellular level become disorganized and the ability of the brain clock to entrain to local time diminishes. As a result, aged individuals exhibit a loss of temporal coordination among bodily systems, leading to deficits in homeostasis and sub-optimal functioning. Such disruptions in the circadian system appear to accelerate the aging process and contribute to senescence, with some systems being more vulnerable than others. This review explores aging-associated changes in circadian function and examines evidence linking such alterations to adverse health consequences in late life and promotion of the aging process.

Intrinsically photosensitive retinal ganglion cells

The recent discovery of melanopsin-expressing retinal ganglion cells that mediate the pupil light reflex has provided new insights into how the pupil responds to different properties of light. These ganglion cells are unique in their ability to transduce light into electrical energy. There are parallels between the electrophysiologic behavior of these cells in primates and the clinical pupil response to chromatic stimuli. Under photopic conditions, a red light stimulus produces a pupil constriction mediated predominantly by cone input via trans-synaptic activation of melanopsin-expressing retinal ganglion cells, whereas a blue light stimulus at high intensity produces a steady-state pupil constriction mediated primarily by direct intrinsic photoactivation of the melanopsin-expressing ganglion cells. Preliminary data in humans suggest that under photopic conditions, cones primarily drive the transient phase of the pupil light reflex, whereas intrinsic activation of the melanopsin-expressing ganglion cells contributes heavily to sustained pupil constriction. The use of chromatic light stimuli to elicit transient and sustained pupil light reflexes may become a clinical pupil test that allows differentiation between disorders affecting photoreceptors and those affecting retinal ganglion cells.

Photoreceptor adaptation in intrinsically photosensitive retinal ganglion cells

A rare type of mammalian retinal ganglion cell (RGC) expresses the photopigment melanopsin and is a photoreceptor. These intrinsically photosensitive RGCs (ipRGCs) drive circadian-clock resetting, pupillary constriction, and other non-image-forming photic responses. Both the light responses of ipRGCs and the behaviors they drive are remarkably sustained, raising the possibility that, unlike rods and cones, ipRGCs do not adjust their sensitivity according to lighting conditions ("adaptation"). We found, to the contrary, that ipRGC sensitivity is plastic, strongly influenced by lighting history. When exposed to a constant, bright background, the background-evoked response decayed, and responses to superimposed flashes grew in amplitude, indicating light adaptation. After extinction of a light-adapting background, sensitivity recovered progressively in darkness, indicating dark adaptation. Because these adjustments in sensitivity persisted when synapses were blocked, they constitute "photoreceptor adaptation" rather than "network adaptation." Implications for the mechanisms generating various non-image-forming visual responses are discussed.

Melanopsin and other novel mammalian opsins

Within the past decade, several non-canonical opsins have been identified in mammals. These include RGR, peropsin, melanopsin, encephalopsin, and neuropsin. Although all are expressed in the eye, it is likely that they serve to mediate non-visual effects of light on physiology. Some of these opsins, however, may play an indirect role in vision by generating appropriate retinoid chromophores for the rod and cone visual pigments or by regulating the sensitivity of the visual system. Here, we survey the current state of knowledge regarding these opsins.

Non-image-forming ocular photoreception in vertebrates

It has been accepted for a hundred years or more that rods and cones are the only photoreceptive cells in the retina. The light signals generated in rods and cones, after processing by downstream retinal neurons (bipolar, horizontal, amacrine and ganglion cells), are transmitted to the brain via the axons of the ganglion cells for further analysis. In the past few years, however, convincing evidence has rapidly emerged indicating that a small subset of retinal ganglion cells in mammals is also intrinsically photosensitive. Melanopsin is the signaling photopigment in these cells. The main function of the inner-retina photoreceptors is to generate and transmit non-image-forming visual information, although some role in conventional vision (image detection) is also possible.

Sleep disturbances in young subjects with visual dysfunction

PURPOSE

To determine whether the type of ophthalmic disease is predictive of sleep and wakefulness disturbances in young subjects with visual dysfunction.

DESIGN

Prospective cohort study.

PARTICIPANTS AND CONTROLS

Twenty-five subjects (ages 12-20) were recruited from the Missouri School for the Blind. Twelve controls with normal sight were recruited from a residential school.

METHODS

Daily activity was monitored for 14 days using wrist actigraphy. Sleep and wakefulness measures were derived from actigraphy records by automated analysis. Visually impaired subjects were prospectively stratified by presence or absence of optic nerve disease.

MAIN OUTCOME MEASURES

Daytime napping and regularity of awakening time (wake-up time instability).

RESULTS

Subjects with optic nerve disease napped in the daytime significantly more than other visually impaired children or normal sighted controls: 28.1+/-4.0 minutes per day (mean +/- standard error) versus 11.9+/-2.4 minutes per day in equally visually impaired subjects with intact optic nerve function versus 6.2+/-2.2 minutes per day in subjects with normal sight (P<0.0001). These subjects also showed significantly more variable awakening times than the other groups. Logistic regression revealed that subjects with optic nerve disease are 9.1 times more likely to demonstrate daily napping of more than 20 minutes per day than equally blind subjects without optic nerve disease (95% confidence interval [CI] = 1.4-58.7, P = 0.02). Blind subjects with optic nerve disease are 21.3 times more likely than children with normal sight to nap more than 20 minutes on average per day (95% CI = 1.2-378, P = 0.04).

CONCLUSIONS

Optic nerve disease is predictive of increased daytime napping in young visually impaired subjects, suggesting that the nature and presence of ophthalmic disease affect the probability of concomitant sleep timing disorders.

Melanopsin and rod-cone photoreceptive systems account for all major accessory visual functions in mice

In the mammalian retina, besides the conventional rod-cone system, a melanopsin-associated photoreceptive system exists that conveys photic information for accessory visual functions such as pupillary light reflex and circadian photo-entrainment. On ablation of the melanopsin gene, retinal ganglion cells that normally express melanopsin are no longer intrinsically photosensitive. Furthermore, pupil reflex, light-induced phase delays of the circadian clock and period lengthening of the circadian rhythm in constant light are all partially impaired. Here, we investigated whether additional photoreceptive systems participate in these responses. Using mice lacking rods and cones, we measured the action spectrum for phase-shifting the circadian rhythm of locomotor behaviour. This spectrum matches that for the pupillary light reflex in mice of the same genotype, and that for the intrinsic photosensitivity of the melanopsin-expressing retinal ganglion cells. We have also generated mice lacking melanopsin coupled with disabled rod and cone phototransduction mechanisms. These animals have an intact retina but fail to show any significant pupil reflex, to entrain to light/dark cycles, and to show any masking response to light. Thus, the rod-cone and melanopsin systems together seem to provide all of the photic input for these accessory visual functions.