The pupillary light reflex (PLR) adapts the amount of light reaching the retina, protecting it and improving image formation. Two PLR mechanisms have been described in vertebrates. First, the pretectum receives retinal inputs and projects to the Edinger-Westphal nucleus (EWN), which targets the ciliary ganglion through the oculomotor nerve (nIII). Postganglionic fibers enter the eye-globe, traveling to the iris sphincter muscle. Additionally, some vertebrates exhibit an iris-intrinsic PLR mechanism mediated by sphincter muscle cells that express melanopsin inducing muscle contraction. Given the high degree of conservation of the lamprey visual system, we investigated the mechanisms underlying the PLR to shed light onto their evolutionary origins. Recently, a PLR mediated by melanopsin was demonstrated in lampreys, suggested to be brain mediated. Remarkably, we found that PLR is instead mediated by direct retino-iridal cholinergic projections. This retina-mediated PLR acts synergistically with an iris-intrinsic mechanism that, as in other vertebrates, is mediated by melanopsin and has contribution of gap junctions between muscle fibers. In contrast, we show that lampreys lack the brain-mediated PLR. Our results suggest that two eye-intrinsic PLR mechanisms were present in early vertebrate evolution, whereas the brain-mediated PLR has a more recent origin.

Melanopsin is a photopigment belonging to the G Protein-Coupled Receptor (GPCR) family expressed in a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) and responsible for a variety of processes. The bistability and, thus, the possibility to function under low retinal availability would make melanopsin a powerful optogenetic tool. Here, we aim to utilize mouse melanopsin to trigger macrophage migration by its subcellular optical activation with localized blue light, while simultaneously imaging the migration with red light. To reduce melanopsin\'s red light sensitivity, we employ a combination of in silico structure prediction and automated quantum mechanics/molecular mechanics modeling to predict minimally invasive mutations to shift its absorption spectrum towards the shorter wavelength region of the visible spectrum without compromising the signaling efficiency. The results demonstrate that it is possible to achieve melanopsin mutants that resist red light-induced activation but are activated by blue light and display properties indicating preserved bistability. Using the A333T mutant, we show that the blue light-induced subcellular melanopsin activation triggers localized PIP3 generation and macrophage migration, which we imaged using red light, demonstrating the optogenetic utility of minimally engineered melanopsins.

Light is fundamental for biological life, with most mammals possessing light-sensing photoreceptors in various organs. Opsin3 is highly expressed in adipose tissue which has extensive communication with other organs, particularly with the brain through the sympathetic nervous system (SNS). Our study reveals a new light-triggered crosstalk between adipose tissue and the hypothalamus. Direct blue-light exposure to subcutaneous white fat improves high-fat diet-induced metabolic abnormalities in an Opsin3-dependent manner. Metabolomic analysis shows that blue light increases circulating levels of histidine, which activates histaminergic neurons in the hypothalamus and stimulates brown adipose tissue (BAT) via SNS. Blocking central actions of histidine and denervating peripheral BAT blunts the effects of blue light. Human white adipocytes respond to direct blue light stimulation in a cell-autonomous manner, highlighting the translational relevance of this pathway. Together, these data demonstrate a light-responsive metabolic circuit involving adipose-hypothalamus communication, offering a potential strategy to alleviate obesity-induced metabolic abnormalities.

Migraine is a complex disorder characterized by episodes of moderate-to-severe, often unilateral headaches and generally accompanied by nausea, vomiting, and increased sensitivity to light (photophobia), sound (phonophobia), and smell (hyperosmia). Photophobia is considered the most bothersome symptom of migraine attacks. Although the underlying mechanism remains unclear, the intrinsically photosensitive retinal ganglion cells (ipRGCs) are considered to be involved in photophobia associated with migraine. In this study, we investigated the association between the sensitivity of ipRGCs and migraines and cortical spreading depression (CSD), which may trigger migraine attacks. The pupillary responses closely associated with the function of ipRGCs in patients with migraine who were irradiated with lights were evaluated. Blue (486 nm) light irradiation elicited a response from ipRGCs; however, red light (560 nm) had no such effect. Melanopsin, a photosensitive protein, phototransduces in ipRGCs following blue light stimulation. Hypersensitivity of ipRGCs was observed in patients with migraine. CSD was more easily induced with blue light than with incandescent light using a mouse CSD model. Moreover, CSD was suppressed, even in the presence of blue light, after injecting opsinamide, a melanopsin inhibitor. The hypersensitivity of ipRGCs in patients with migraine may induce CSD, resulting in migraine attacks.

The photopigment-encoding visual opsin genes that mediate color perception show great variation in copy number and adaptive function across vertebrates. An open question is how this variation has been shaped by the interaction of lineage-specific structural genomic architecture and ecological selection pressures. We contribute to this issue by investigating the expansion dynamics and expression of the duplicated Short-Wavelength-Sensitive-1 opsin (SWS1) in sea snakes (Elapidae). We generated one new genome, 45 resequencing datasets, 10 retinal transcriptomes, and 81 SWS1 exon sequences for sea snakes, and analyzed these alongside 16 existing genomes for sea snakes and their terrestrial relatives. Our analyses revealed multiple independent transitions in SWS1 copy number in the marine Hydrophis clade, with at least three lineages having multiple intact SWS1 genes: the previously studied Hydrophis cyanocinctus and at least two close relatives of this species; Hydrophis atriceps and Hydrophis fasciatus; and an individual Hydrophis curtus. In each lineage, gene copy divergence at a key spectral tuning site resulted in distinct UV and Violet/Blue-sensitive SWS1 subtypes. Both spectral variants were simultaneously expressed in the retinae of H. cyanocinctus and H. atriceps, providing the first evidence that these SWS1 expansions confer novel phenotypes. Finally, chromosome annotation for nine species revealed shared structural features in proximity to SWS1 regardless of copy number. If these features are associated with SWS1 duplication, expanded opsin complements could be more common in snakes than is currently recognized. Alternatively, selection pressures specific to aquatic environments could favor improved chromatic distinction in just some lineages.

UNASSIGNED: The purpose of this study was to evaluate pupillary light reflex (PLR) to chromatic flashes in patients with early-onset high-myopia (eoHM) without (myopic controls = M-CTRL) and with (female-limited myopia-26 = MYP-26) genetic mutations in the ARR3 gene encoding the cone arrestin.
UNASSIGNED: Participants were 26 female subjects divided into 3 groups: emmetropic controls (E-CTRL, N = 12, mean age = 28.6 ± 7.8 years) and 2 myopic (M-CTRL, N = 7, mean age = 25.7 ± 11.5 years and MYP-26, N = 7, mean age = 28.3 ± 15.4 years) groups. In addition, one hemizygous carrier and one control male subject were examined. Direct PLRs were recorded after 10-minute dark adaptation. Stimuli were 1-second red (peak wavelength = 621 nm) and blue (peak wavelength = 470 nm) flashes at photopic luminance of 250 cd/m². A 2-minute interval between the flashes was introduced. Baseline pupil diameter (BPD), peak pupil constriction (PPC), and postillumination pupillary response (PIPR) were extracted from the PLR. Group comparisons were performed with ANOVAs.
UNASSIGNED: Dark-adapted BPD was comparable among the groups, whereas PPC to the red light was slightly reduced in patients with myopia (P = 0.02). PIPR at 6 seconds elicited by the blue flash was significantly weaker (P < 0.01) in female patients with MYP-26, whereas it was normal in the M-CTRL group and the asymptomatic male carrier.
UNASSIGNED: L/M-cone abnormalities due to ARR3 gene mutation is currently claimed to underlie the pathological eye growth in MYP-26. Our results suggest that malfunction of the melanopsin system of intrinsically photosensitive retinal ganglion cells (ipRGCs) is specific to patients with symptomatic MYP-26, and may therefore play an additional role in the pathological eye growth of MYP-26.

Among tetrapod (terrestrial) vertebrates, amphibians remain more closely tied to an amphibious lifestyle than amniotes, and their visual opsin genes may be adapted to this lifestyle. Previous studies have discussed physiological, morphological, and molecular changes in the evolution of amphibian vision. We predicted the locations of the visual opsin genes, their neighboring genes, and the tuning sites of the visual opsins, in 39 amphibian genomes. We found that all of the examined genomes lacked the Rh2 gene. The caecilian genomes have further lost the SWS1 and SWS2 genes; only the Rh1 and LWS genes were retained. The loss of the SWS1 and SWS2 genes in caecilians may be correlated with their cryptic lifestyles. The opsin gene syntenies were predicted to be highly similar to those of other bony vertebrates. Moreover, dual syntenies were identified in allotetraploid Xenopus laevis and X. borealis. Tuning site analysis showed that only some Caudata species might have UV vision. In addition, the S164A that occurred several times in LWS evolution might either functionally compensate for the Rh2 gene loss or fine-tuning visual adaptation. Our study provides the first genomic evidence for a caecilian LWS gene and a genomic viewpoint of visual opsin genes by reviewing the gains and losses of visual opsin genes, the rearrangement of syntenies, and the alteration of spectral tuning in the course of amphibians\' evolution.

Gene duplication is one of the most important sources of novel genotypic diversity and the subsequent evolution of phenotypic diversity. Determining the evolutionary history and functional changes of duplicated genes is crucial for a comprehensive understanding of adaptive evolution. The evolutionary history of visual opsin genes is very dynamic, with repeated duplication events followed by sub- or neofunctionalization. While duplication of the green-sensitive opsins rh2 is common in teleost fish, fewer cases of multiple duplication events of the red-sensitive opsin lws are known. In this study, we investigate the visual opsin gene repertoire of the anabantoid fishes, focusing on the five lws opsin genes found in the genus Betta. We determine the evolutionary history of the lws opsin gene by taking advantage of whole-genome sequences of nine anabantoid species, including the newly assembled genome of Betta imbellis. Our results show that at least two independent duplications of lws occurred in the Betta lineage. The analysis of amino acid sequences of the lws paralogs of Betta revealed high levels of diversification in four of the seven transmembrane regions of the lws protein. Amino acid substitutions at two key-tuning sites are predicted to lead to differentiation of absorption maxima (λmax) between the paralogs within Betta. Finally, eye transcriptomics of B. splendens at different developmental stages revealed expression shifts between paralogs for all cone opsin classes. The lws genes are expressed according to their relative position in the lws opsin cluster throughout ontogeny. We conclude that temporal collinearity of lws expression might have facilitated subfunctionalization of lws in Betta and teleost opsins in general.

The daily light-dark cycle is a key zeitgeber (time cue) for entraining an organism\'s biological clock, whereby light sensing by retinal photoreceptors, particularly intrinsically photosensitive retinal ganglion cells, stimulates the suprachiasmatic nucleus of the hypothalamus, a central pacemaker that in turn orchestrates the rhythm of peripheral metabolic activities. Non-rhythmic effects of light on metabolism have also been long known, and their transduction mechanisms are only beginning to unfold. Here, we summarize emerging evidence that, in mammals, light exposure or deprivation profoundly affects glucose homeostasis, thermogenesis and other metabolic activities in a clock-independent manner. Such light regulation could involve melanopsin-based, intrinsically photosensitive retinal ganglion cell-initiated brain circuits via the suprachiasmatic nucleus of the hypothalamus and other nuclei, or direct stimulation of opsins expressed in the hypothalamus, adipose tissue, blood vessels and skin to regulate sympathetic tone, lipolysis, glucose uptake, mitochondrial activation, thermogenesis, food intake, blood pressure and melanogenesis. These photic signalling events may coordinate with circadian-based mechanisms to maintain metabolic homeostasis, with dysregulation of this system underlying metabolic diseases caused by aberrant light exposure, such as environmental night light and shift work.

The ambient daylight variation is coded by melanopsin photoreceptors and their luxotonic activity increases towards midday when colour temperatures are cooler, and irradiances are higher. Although melanopsin and cone photoresponses can be mediated via separate pathways, the connectivity of melanopsin cells across all levels of the retina enables them to modify cone signals. The downstream effects of melanopsin-cone interactions on human vision are however, incompletely understood. Here, we determined how the change in daytime melanopsin activation affects the human cone pathway signals in the visual cortex. A 5-primary silent-substitution method was developed to evaluate the dependence of cone-mediated signals on melanopsin activation by spectrally tuning the lights and stabilizing the rhodopsin activation under a constant cone photometric luminance. The retinal (white noise electroretinogram) and cortical responses (visual evoked potential) were simultaneously recorded with the photoreceptor-directed lights in 10 observers. By increasing the melanopsin activation, a reverse response pattern was observed with cone signals being supressed in the retina by 27% (p = 0.03) and subsequently amplified by 16% (p = 0.01) as they reach the cortex. We infer that melanopsin activity can amplify cone signals at sites distal to retinal bipolar cells to cause a decrease in the psychophysical Weber fraction for cone vision.