Photoperiodism of Diapause Induction in the Silkworm, Bombyx mori.

The silkworm Bombyx mori exhibits a photoperiodic response (PR) for embryonic diapause induction. This article provides a comprehensive review of literature on the silkworm PR, starting from early works on population to recent studies uncovering the molecular mechanism. Makita Kogure (1933) conducted extensive research on the PR, presenting a pioneering paper on insect photoperiodism. In the 1970s and 80s, artificial diets were developed, and the influence of nutrition on PR was well documented. The photoperiodic photoreceptor has been investigated from organ to molecular level in the silkworm. Culture experiments demonstrated that the photoperiodic induction can be programmed in an isolated brain (Br)-subesophageal ganglion (SG) complex with corpora cardiaca (CC)-corpora allata (CA). The requirement of dietary vitamin A for PR suggests the involvement of opsin pigment in the photoperiodic reception, and a cDNA encoding an opsin (Boceropsin) was cloned from the brain. The effector system concerning the production and secretion of diapause hormone (DH) has also been extensively investigated in the silkworm. DH is produced in a pair of posterior cells of SG, transported to CC by nervi corporis cardiaci, and ultimately released into the hemolymph. Possible involvement of GABAergic and corazonin (Crz) signal pathways was suggested in the control of DH secretion. Knockout (KO) experiments of GABA transporter (GAT) and circadian clock genes demonstrated that GAT plays a crucial role in PR through circadian control. A model outlining the PR mechanism, from maternal photoperiodic light reception to DH secretion, has been proposed.

Diurnal and circadian regulation of opsin-like transcripts in the eyeless cnidarian Hydra.

Opsins play a key role in the ability to sense light both in image-forming vision and in non-visual photoreception (NVP). These modalities, in most animal phyla, share the photoreceptor protein: an opsin-based protein binding a light-sensitive chromophore by a lysine (Lys) residue. So far, visual and non-visual opsins have been discovered throughout the Metazoa phyla, including the photoresponsive Hydra, an eyeless cnidarian considered the evolutionary sister species to bilaterians. To verify whether light influences and modulates opsin gene expression in Hydra, we utilized four expression sequence tags, similar to two classic opsins (SW rhodopsin and SW blue-sensitive opsin) and two non-visual opsins (melanopsin and peropsin), in investigating the expression patterns during both diurnal and circadian time, by means of a quantitative RT-PCR. The expression levels of all four genes fluctuated along the light hours of diurnal cycle with respect to the darkness one and, in constant dark condition of the circadian cycle, they increased. The monophasic behavior in the L12:D12 cycle turned into a triphasic expression profile during the continuous darkness condition. Consequently, while the diurnal opsin-like expression revealed a close dependence on light hours, the highest transcript levels were found in darkness, leading us to novel hypothesis that in Hydra, an "internal" biological rhythm autonomously supplies the opsins expression during the circadian time. In conclusion, in Hydra, both diurnal and circadian rhythms apparently regulate the expression of the so-called visual and non-visual opsins, as already demonstrated in higher invertebrate and vertebrate species. Our data confirm that Hydra is a suitable model for studying ancestral precursor of both visual and NVP, providing useful hints on the evolution of visual and photosensory systems.

Opsin mutants alter host plant selection by color vision in the nocturnal invasive pest Tuta absoluta.

In insects, vision is crucial in finding host plants, but its role in nocturnal insects is largely unknown. Vision involves responses to specific spectra of photon wavelengths and opsins plays an important role in this process. Long-wavelength sensitive opsin (LW opsin) and blue-sensitive opsin (BL opsin) are main visual opsin proteins and play important in behavior regulation.We used CRISPR/Cas9 technology to mutate the long-wavelength-sensitive and blue wavelength-sensitive genes and explored the role of vision in the nocturnal invasive pest Tuta absoluta. Light wave experiments revealed that LW2(-/-) and BL(-/-) mutants showed abnormal wavelength tropism. Both LW2 and BL mutations affected the preference of T. absoluta for the green environment. Mutations in LW2 and BL are necessary to inhibit visual attraction. The elimination of LW2 and BL affected the preference of leaf moths for green plants, and mutations in both induced a preference in moths for white plants. Behavioral changes resulting from LW2(-/-) and BL(-/-) mutants were not affected by sense of smell, further supporting the regulatory role of vision in insect behavior. To the best of our knowledge, this is the first study to reveal that vision, not smell, plays an important role in the host-seeking behavior of nocturnal insects at night, of which LW2 and BL opsins are key regulatory factors. These study findings will drive the development of the "vision-ecology" theory.

Functional opsin patterning for Drosophila color vision is established through signaling pathways in adjacent object-detection neurons.

Vision is mainly based on two different tasks, object detection and color discrimination, carried out by photoreceptor (PR) cells. The Drosophila compound eye consists of ∼800 ommatidia. Every ommatidium contains eight PR cells, six outer cells (R1-R6) and two inner cells (R7 and R8), by which object detection and color vision are achieved, respectively. Expression of opsin genes in R7 and R8 is highly coordinated through the instructive signal from R7 to R8, and two major ommatidial subtypes are distributed stochastically; pale type expresses Rh3/Rh5 and yellow type expresses Rh4/Rh6 in R7/R8. The homeodomain protein Defective proventriculus (Dve) is expressed in yellow-type R7 and in six outer PRs, and it is involved in Rh3 repression to specify the yellow-type R7. dve mutant eyes exhibited atypical coupling, Rh3/Rh6 and Rh4/Rh5, indicating that Dve activity is required for proper opsin coupling. Surprisingly, Dve activity in R1 is required for the instructive signal, whereas activity in R6 and R7 blocks the signal. Our results indicate that functional coupling of two different neurons is established through signaling pathways from adjacent neurons that are functionally different.

Differential Photosensitivity of Fibroblasts Obtained from Normal Skin and Hypertrophic Scar Tissues.

It is unclear whether normal human skin tissue or abnormal scarring are photoreceptive. Therefore, this study investigated photosensitivity in normal skin tissue and hypertrophic scars. The expression of opsins, which are photoreceptor proteins, in normal dermal fibroblasts (NDFs) and hypertrophic scar fibroblasts (HSFs) was examined. After exposure to blue light (BL), changes in the expression levels of αSMA and clock-related genes, specifically PER2 and BMAL1, were examined in both fibroblast types. Opsins were expressed in both fibroblast types, with OPN3 exhibiting the highest expression levels. After peripheral circadian rhythm disruption, BL induced rhythm formation in NDFs. In contrast, although HSFs showed changes in clock-related gene expression levels, no distinct rhythm formation was observed. The expression level of αSMA was significantly higher in HSFs and decreased to the same level as that in NDFs upon BL exposure. When OPN3 knocked-down HSFs were exposed to BL, the reduction in αSMA expression was inhibited. This study showed that BL exposure directly triggers peripheral circadian synchronization in NDFs but not in HSFs. OPN3-mediated BL exposure inhibited HSFs. Although the current results did not elucidate the relationship between peripheral circadian rhythms and hypertrophic scars, they show that BL can be applied for the prevention and treatment of hypertrophic scars and keloids.

Protocol for induction of heterosynaptic long-term potentiation in the mouse hippocampus via dual-opsin stimulation technique.

Cholecystokinin (CCK) is the most abundant neuropeptide that broadly regulates the physiological status of animals. Here, we present a two-color laser theta burst stimulation (L-TBS) protocol for simultaneous activation of Schaffer collateral and perforant pathway in the hippocampus of CCK Cre mice. We describe steps for heterosynaptic long-term potentiation induction by L-TBS. This technique allows for the examination of the neurotransmitter roles in synaptic modulation and facilitates the exploration of pathological mechanisms in genetic models of brain disorders in mice. For complete details on the use and execution of this protocol, please refer to Su et al.1.

Nonvisual system-mediated body color change in fish reveals nonvisual function of Opsin 3 in skin.

Body-color changes in many poikilothermic animals can occur quickly. This color change is generally initiated by visual system, followed by neuromuscular or neuroendocrine control. We have previously showed that the ventral skin color of the large yellow croaker (Larimichthys crocea) presents golden yellow in dark environment and quickly changes to silvery white in light environment. In the present study, we found that the light-induced whitening of ventral skin color was independent of visual input. Using light-emitting diode sources of different wavelength with same luminance (150 lx) but different absolute irradiance (0.039-0.333 mW/cm2), we further found that the blue light (λmax = 480 nm, 0.107 mW/cm2) is more effectively in induction of whitening of ventral skin color in compare with other light sources. Interestingly, the result of RT-PCR showed opsin 3 transcripts expressed in xanthophores. Recombinant protein of Opsin 3 with 11-cis retinal formed functional blue-sensitive pigment, with an absorption maximum at 468 nm. The HEK293T cells transfected with Opsin 3 showed a blue light-evoked Ca2+ response. Knock-down of Opsin 3 expression blocked the light-induced xanthosomes aggregation in vitro. Moreover, the light-induced xanthosomes aggregation was mediated via Ca2+-PKC and Ca2+-CaMKII pathways, and relied on microtubules and dynein. Decrease of cAMP levels was a prerequisite for xanthosomes aggregation. Our results provide a unique organism model exhibiting light-induced quick body color change, which was independent of visual input but rather rely on non-visual function of Opsin 3 within xanthophore.

Retinoic acid signaling regulates spatiotemporal specification of human green and red cones.

Trichromacy is unique to primates among placental mammals, enabled by blue (short/S), green (medium/M), and red (long/L) cones. In humans, great apes, and Old World monkeys, cones make a poorly understood choice between M and L cone subtype fates. To determine mechanisms specifying M and L cones, we developed an approach to visualize expression of the highly similar M- and L-opsin mRNAs. M-opsin was observed before L-opsin expression during early human eye development, suggesting that M cones are generated before L cones. In adult human tissue, the early-developing central retina contained a mix of M and L cones compared to the late-developing peripheral region, which contained a high proportion of L cones. Retinoic acid (RA)-synthesizing enzymes are highly expressed early in retinal development. High RA signaling early was sufficient to promote M cone fate and suppress L cone fate in retinal organoids. Across a human population sample, natural variation in the ratios of M and L cone subtypes was associated with a noncoding polymorphism in the NR2F2 gene, a mediator of RA signaling. Our data suggest that RA promotes M cone fate early in development to generate the pattern of M and L cones across the human retina.

Three different seasonally expressed opsins are present in the brain of the Eared Dove, an opportunist breeder.

Birds living at high latitudes perceive the photoperiod through deep-brain photoreceptors (DBP) located in deep-brain neurons. During long photoperiods the information transmitted by these photoreceptors increases the activity of the hypothalamic-pituitary-gonadal (HPG) axis, leading to gonadal development. The presence of photopigments such as VA-Opsin, Opn4, Opn5 and Opn2 in brain areas implicated in reproductive behaviors has been firmly established in several avian species with seasonal breeding, whereas their existence in opportunistic breeding birds remains unconfirmed. The Eared Dove is an urban and peri-urban dove that breeds throughout the year. Males of this species do not exhibit the typical gonadal regression/recrudescence cycle, thus posing the question of what occurs upstream of the HPG axis. We addressed this issue by first studying the presence of diverse opsins located in DBP in the brains of Eared Dove males and whether these photopigments changed their expression throughout the year. We carried out an immunohistochemistry analysis on three different opsins: Opn2 (rhodopsin), Opn3 and Opn5. Our results demonstrate the discrete neuroanatomical distribution of these opsins in the brain of Eared Dove males and strongly indicate different seasonal expressions. In the anterior region of the hypothalamus, Opn2-positive cells were detected throughout the year. By contrast, Opn5 was found to be strongly and seasonally expressed during winter in the anterior and the hypothalamic region. Opn3 was also found to be significantly and seasonally expressed during winter in the hypothalamic region. We thus demonstrate for the first time that males of the Eared Dove, have three different deep-brain opsin-expressing photoreceptors with differential location/distribution in the anterior and hypothalamic region and differential seasonality. The persistence of Opn2 and the strong seasonal expression of nonvisual photopigments Opn3 and Opn5 in two areas of the avian brain, which are associated with reproduction, could be the primary distinction between seasonal and opportunistic breeders.

Unstable environmental conditions constrain the fine-tune between opsin sensitivity and underwater light in an Amazon forest stream fish.

Visual adaptations can stem from variations in amino acid composition, chromophore utilization, and differential opsin gene expression levels, enabling individuals to adjust their light sensitivity to environmental lighting conditions. In stable environments, adaptations often involve amino acid substitutions, whereas in unstable conditions, differential gene expression may be a more relevant mechanism. Amazon forest streams present diverse underwater lighting conditions and experience short-term water colour fluctuations. In these environments, it is less likely for genetic and amino acid sequences to undergo modifications that tailor opsin proteins to the prevailing lighting conditions, particularly in species having several copies of the same gene. The sailfin tetra, Crenuchus spilurus, inhabits black and clear water Amazon forest streams. The long-wavelength sensitivity (LWS) is an important component for foraging and courtship. Here, we investigated LWS opsin genes in the sailfin tetra. Three copies of LWS1 and two copies of LWS2 genes were found. The maximum absorbance wavelength (λmax) estimated from the amino acid sequences of LWS1 genes exhibited variation among the different copies. In contrast, the copies of LWS2 genes showed identical expected λmax values. Although the amino acid positions affecting λmax varied among LWS genes, they remained consistent among populations living in different water colours. The relative expression levels of LWS genes differed between gene copies. While not formally tested, our results suggest that in fluctuating environments, visual adaptations may primarily stem from alterations in gene expression profiles and/or chromophore usage rather than precise genetic tuning of protein light sensitivity to environmental lighting conditions.

Knockout of SWS2 in zebrafish (Danio rerio) reveals its roles in feeding and phototactic behaviors.

Common ancestor of vertebrates had four cone opsin subfamilies to obtain color vision: ultraviolet-sensitive (SWS1), blue-sensitive (SWS2), middle wavelength sensitive (RH2) and long wavelength sensitive (LWS). Nevertheless, eutherian mammals had lost the SWS2 and RH2 opsins during their nocturnal lifestyle. Many studies had demonstrated the role of SWS1 and LWS cones in feeding, mate choice and skin pigment cell formation. However, the role of SWS2 and RH2 cones remain elusive. In the present study, we used an ideal model visual system, zebrafish, which still have the four cone opsins, to generate a SWS2 knockout zebrafish line. Through various behavioral test, we found that sws2-/- zebrafish larvae exhibited increased food intake compared with WT. Additionally, there were significantly increased the gene expression of phototransduction pathways in sws2-/- zebrafish larvae. Compared to WT, mutant zebrafish showed weaker phototaxis of red light and changed sensitivity of yellow, red and blue lights. But both mutant and WT zebrafish preferred the red light than other wavelengths of light. Taken together, we proposed that SWS2 cone is not necessary for feeding and phototaxis in zebrafish.

Developmental and environmental plasticity in opsin gene expression in Lake Victoria cichlid fish.

In many organisms, sensory abilities develop and evolve according to the changing demands of navigating, foraging, and communication across different environments and life stages. Teleost fish inhabit heterogeneous light environments and exhibit a large diversity in visual system properties among species. Cichlids are a classic example of this diversity; visual system variation is generated by different tuning mechanisms that involve both genetic factors and phenotypic plasticity. Here, we document the developmental progression of visual pigment gene expression in Lake Victoria cichlids and test if these patterns are influenced by variation in light conditions. We reared two sister species of Pundamilia to adulthood in two distinct visual conditions that resemble the light environments that they naturally inhabit in Lake Victoria. We also included interspecific first-generation hybrids. We focused on the four opsins that are expressed in Pundamilia adults (using real-time quantitative polymerase chain reaction (RT-qPCR)) (SWS2B, SWS2A, RH2A, and LWS) at 17 time points. We find that opsin expression profiles progress from shorter-wavelength sensitive opsins to longer-wavelength sensitive opsins with increasing age, in both species and their hybrids. The developmental trajectories of opsin expression also responded plastically to the visual conditions. Developmental and environmental plasticity in opsin expression may provide an important stepping stone in the evolution of cichlid visual system diversity.

Light-specific wavelengths differentially affect the exploration rate, opercular beat, skin color change, opsin transcripts, and the oxi-redox system of the longsnout seahorse Hippocampus reidi.

Light is a strong stimulus for the sensory and endocrine systems. The opsins constitute a large family of proteins that can respond to specific light wavelengths. Hippocampus reidi is a near-threatened seahorse that has a diverse color pattern and sexual dimorphism. Over the years, H. reidi's unique characteristics, coupled with its high demand and over-exploitation for the aquarium trade, have raised concerns about its conservation, primarily due to their significant impact on wild populations. Here, we characterized chromatophore types in juvenile and adult H. reidi in captivity, and the effects of specific light wavelengths with the same irradiance (1.20 mW/cm2) on color change, growth, and survival rate. The xanthophores and melanophores were the major components of H. reidi pigmentation with differences in density and distribution between life stages and sexes. In the eye and skin of juveniles, the yellow (585 nm) wavelength induced a substantial increase in melanin levels compared to the individuals kept under white light (WL), blue (442 nm), or red (650 nm) wavelengths. In addition, blue and yellow wavelengths led to a higher juvenile mortality rate in comparison to the other treatments. Adult seahorses showed a rhythmic color change over 24 h, the highest reflectance values were obtained in the light phase, representing a daytime skin lightening for individuals under WL, blue and yellow wavelength, with changes in the acrophase. The yellow wavelength was more effective on juvenile seahorse pigmentation, while the blue wavelength exerted a stronger effect on the regulation of adult physiological color change. Dramatic changes in the opsin mRNA levels were life stage-dependent, which may infer ontogenetic opsin functions throughout seahorses' development. Exposure to specific wavelengths differentially affected the opsins mRNA levels in the skin and eyes of juveniles. In the juveniles, skin transcripts of visual (rh1, rh2, and lws) and non-visual opsins (opn3 and opn4x) were higher in individuals under yellow light. While in the juvenile's eyes, only rh1 and rh2 had increased transcripts influenced by yellow light; the lws and opn3 mRNA levels were higher in juveniles' eyes under WL. Prolonged exposure to yellow wavelength stimulates a robust increase in the antioxidant enzymes sod1 and sod2 mRNA levels. Our findings indicate that changes in the visible light spectrum alter physiological processes at different stages of life in H. reidi and may serve as the basis for a broader discussion about the implications of artificial light for aquatic species in captivity.

A pan-cancer analysis of RGR opsin expression and its downregulation associated with poor prognosis in glioma.

Retinal G protein-coupled receptor (RGR) serves a retinal photoisomerase function to mediate retinoid metabolism and visual chromophore regeneration in the human eyes. Retinoids display critical functions in cell proliferation, differentiation, and apoptosis. Abnormal retinoid metabolism may contribute to tumor development. However, in human tumor tissues, the expression of RGR remains uncharacterized. Herein, we performed the analysis of RGR expression in 620 samples from 24 types of tumors by immunohistochemistry (IHC) and 33 cancer types from the Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA), and Gene Expression Omnibus (GEO) databases by bioinformatic analyses. Furthermore, the biological role of RGR in glioma cells was investigated using molecular biology approaches in vitro. Notably, we found that brain lower grade glioma (LGG), in contrast to other tumor types, had the highest median score of IHC and RNA level of RGR expression. Survival analysis showed that low RGR expression was associated with worse overall survival in LGG (p<0.0001). RGR expression levels in glioma were also associated with pathological subtypes, grades, and isocitrate dehydrogenase (IDH) mutations. Moreover, its molecular function was closely associated with cadherin-related family member 1 (CDHR1), a tumor suppressive protein in glioma, suggesting that RGR might negatively regulate the tumorigenesis and progression of LGG through interacting with CDHR1. Our findings provide new insight into the role of RGR in human cancer, especially in glioma.

Molluscan Genomes Reveal Extensive Differences in Photopigment Evolution Across the Phylum.

In animals, opsins and cryptochromes are major protein families that transduce light signals when bound to light-absorbing chromophores. Opsins are involved in various light-dependent processes, like vision, and have been co-opted for light-independent sensory modalities. Cryptochromes are important photoreceptors in animals, generally regulating circadian rhythm, they belong to a larger protein family with photolyases, which repair UV-induced DNA damage. Mollusks are great animals to explore questions about light sensing as eyes have evolved multiple times across, and within, taxonomic classes. We used molluscan genome assemblies from 80 species to predict protein sequences and examine gene family evolution using phylogenetic approaches. We found extensive opsin family expansion and contraction, particularly in bivalve xenopsins and gastropod Go-opsins, while other opsins, like retinochrome, rarely duplicate. Bivalve and gastropod lineages exhibit fluctuations in opsin repertoire, with cephalopods having the fewest number of opsins and loss of at least 2 major opsin types. Interestingly, opsin expansions are not limited to eyed species, and the highest opsin content was seen in eyeless bivalves. The dynamic nature of opsin evolution is quite contrary to the general lack of diversification in mollusk cryptochromes, though some taxa, including cephalopods and terrestrial gastropods, have reduced repertoires of both protein families. We also found complete loss of opsins and cryptochromes in multiple, but not all, deep-sea species. These results help set the stage for connecting genomic changes, including opsin family expansion and contraction, with differences in environmental, and biological features across Mollusca.

Behavioral photosensitivity of multi-color-blind medaka: enhanced response under ultraviolet light in the absence of short-wavelength-sensitive opsins.

BACKGROUND: The behavioral photosensitivity of animals could be quantified via the optomotor response (OMR), for example, and the luminous efficiency function (the range of visible light) should largely rely on the repertoire and expression of light-absorbing proteins in the retina, i.e., the opsins. In fact, the OMR under red light was suppressed in medaka lacking the red (long-wavelength sensitive [LWS]) opsin. RESULTS: We investigated the ultraviolet (UV)- or blue-light sensitivity of medaka lacking the violet (short-wavelength sensitive 1 [SWS1]) and blue (SWS2) opsins. The sws1/sws2 double or sws1/sws2/lws triple mutants were as viable as the wild type. The remaining green (rhodopsin 2 [RH2]) or red opsins were not upregulated. Interestingly, the OMR of the double or triple mutants was equivalent or even increased under UV or blue light (λ = 350, 365, or 450 nm), which demonstrated that the rotating stripes (i.e., changes in luminance) could fully be recognized under UV light using RH2 alone. The OMR test using dichromatic stripes projected onto an RGB display consistently showed that the presence or absence of SWS1 and SWS2 did not affect the equiluminant conditions. CONCLUSIONS: RH2 and LWS, but not SWS1 and SWS2, should predominantly contribute to the postreceptoral processes leading to the OMR or, possibly, to luminance detection in general, as the medium-wavelength-sensitive and LWS cones, but not the SWS cones, are responsible for luminance detection in humans.

Molecular Evolution of Malacostracan Short Wavelength Sensitive Opsins.

Investigations of the molecular mechanisms behind detection of short, and particularly ultraviolet, wavelengths in arthropods have relied heavily on studies from insects due to the relative ease of heterologous expression of modified opsin proteins in model organisms like Drosophila. However, species outside of the Insecta can provide information on mechanisms for spectral tuning as well as the evolutionary history of pancrustacean visual pigments. Here we investigate the basis of spectral tuning in malacostracan short wavelength sensitive (SWS) opsins using phylogenetic comparative methods. Tuning sites that may be responsible for the difference between ultraviolet (UV) and violet visual pigment absorbance in the Malacostraca are identified, and the idea that an amino acid polymorphism at a single site is responsible for this shift is shown to be unlikely. Instead, we suggest that this change in absorbance is accomplished through multiple amino acid substitutions. On the basis of our findings, we conducted further surveys to identify spectral tuning mechanisms in the order Stomatopoda where duplication of UV opsins has occurred. Ancestral state reconstructions of stomatopod opsins from two main clades provide insight into the amino acid changes that lead to differing absorption by the visual pigments they form, and likely contribute the basis for the wide array of UV spectral sensitivities found in this order.

Modulating signalling lifetime to optimise a prototypical animal opsin for optogenetic applications.

Animal opsins are light activated G-protein-coupled receptors, capable of optogenetic control of G-protein signalling for research or therapeutic applications. Animal opsins offer excellent photosensitivity, but their temporal resolution can be limited by long photoresponse duration when expressed outside their native cellular environment. Here, we explore methods for addressing this limitation for a prototypical animal opsin (human rod opsin) in HEK293T cells. We find that the application of the canonical rhodopsin kinase (GRK1)/visual arrestin signal termination mechanism to this problem is complicated by a generalised suppressive effect of GRK1 expression. This attenuation can be overcome using phosphorylation-independent mutants of arrestin, especially when these are tethered to the opsin protein. We further show that point mutations targeting the Schiff base stability of the opsin can also reduce signalling lifetime. Finally, we apply one such mutation (E122Q) to improve the temporal fidelity of restored visual responses following ectopic opsin expression in the inner retina of a mouse model of retinal degeneration (rd1). Our results reveal that these two strategies (targeting either arrestin binding or Schiff-base hydrolysis) can produce more time-delimited opsin signalling under heterologous expression and establish the potential of this approach to improve optogenetic performance.

Opsin 5 mediates violet light-induced early growth response-1 expression in the mouse retina.

Myopia is an abnormal vision condition characterized by difficulties in seeing distant objects. Myopia has become a public health issue not only in Asian countries but also in Western countries. Previously, we found that violet light (VL, 360-400 nm wavelength) exposure effectively suppressed myopia progression in experimental chick and mice models of myopia. The inhibitory effects of VL on myopia progression are reduced in retina-specific opsin 5 (Opn5) knockout (KO) mice. Furthermore, VL exposure upregulated early growth response-1 (Egr-1) expression in the chorioretinal tissues of chicks. However, the expression of EGR-1 and role of OPN5 in mice following VL exposure remain unclear. In this study, we examined whether VL exposure-induced EGR-1 upregulation depends on Opn5 expression in the mouse retina. EGR-1 mRNA and protein expressions increased in the mouse retina and mouse retinal 661W cells following VL exposure. These increases were consistently reduced in retina specific Opn5 conditional KO mice and Opn5 KO 661W cells. Our results suggest that OPN5 mediates VL-induced EGR-1 upregulation in mice. These molecular targets could be considered for the prevention and treatment of myopia.

Opsin 3 expression in human Langerhans cell histiocytosis and its mediation of ELD-1 cellular function.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a type of -histiocytic disorder characterized by aberrant function, differentiation or proliferation of mononuclear phagocyte system cells, however, the pathogenesis is not fully understood. Opsin 3 (OPN3) plays an important role in regulating cell function. OBJECTIVES: We aimed to investigate OPN3 expression in LCH and Langerhans cells and evaluate its possible regulation of cellular function in a Langerhans cell-like cell line (ELD-1). MATERIALS & METHODS: Expression of OPN3 in LCH and paired adjacent healthy skin tissue was determined using microscopic tools (immunohistochemical and immunofluorescence staining) and RNA scope. OPN3 protein and mRNA levels in primary dendritic cells and ELD-1 were measured by real-time quantitative PCR and western blotting, respectively. The effects of reduced or over-expressed OPN3 mRNA level, via a lentiviral vector, were examined on ELD-1 proliferation, migration, cell cycle and apoptosis using the Cell Counting Kit 8, EdU-594 kit, Transwell assays and Cell Cycle Analysis Kit and Annexin V-PE apoptosis kit, respectively. Lastly, the signalling pathway mediating these functions was investigated via RNA sequencing and western blotting. RESULTS: OPN3 was highly expressed in human LCH tissue compared to healthy tissue, and was expressed in primary dendritic cells and ELD-1. Knockdown of OPN3 in ELD-1 inhibited cell proliferation, the cell cycle, and cell migration, while over-expression reversed these processes. These functions correlated with induction of the MAPK (p38/JNK/ERK) signalling pathway. CONCLUSION: Our results provide insight into the role of OPN3 in LCH which may become a molecular target for the clinical treatment of LCH.