Role of macrophage in ocular neovascularization

Ocular neovascularization is the leading cause of blindness in clinical settings. Pathological angiogenesis of the eye can be divided into corneal neovascularization (CoNV), retinal neovascularization (RNV, including diabetic retinopathy and retinopathy of prematurity), and choroidal neovascularization (CNV) based on the anatomical location of abnormal neovascularization. Although anti-Vascular endothelial growth factor (VEGF) agents have wide-ranging clinical applications and are an effective treatment for neovascular eye disease, many deficiencies in this treatment strategy remain. Recently, emerging evidence has demonstrated that macrophages are vital during the process of physiological and pathological angiogenesis. Monocyte-macrophage lineage is diverse and plastic, they can shift between different activation modes and have different functions. Due to the obvious regulatory effect of macrophages on inflammation and angiogenesis, macrophages have been increasingly studied in the field of ophthalmology. Here, we detail how macrophage activated and the role of different subtypes of macrophages in the pathogenesis of ocular neovascularization. The complexity of macrophages has recently taken center stage owing to their subset diversity and tightly regulated molecular and metabolic phenotypes. In this review, we reveal the functional and phenotypic characterization of macrophage subsets associated with ocular neovascularization, more in-depth research is needed to explore the specific mechanisms by which macrophages regulate angiogenesis as well as macrophage polarization. Targeted regulation of macrophage differentiation based on their phenotype and function could be an effective approach to treat and manage ocular neovascularization in the future.

Quantitative evaluation of choroidal and retinal microvasculature post-alcohol consumption: A pilot study

PURPOSE

The aim of this study was to assess the impact of acute, heavy alcohol consumption on the ocular microvasculature, providing insight into the largely unexplored response of microvascular structures to excessive drinking.

METHODS

Healthy volunteers in this prospective pilot study were tasked with consuming spirits, wine, and water at different times. Alcohol intake was measured according to body weight (g/kg). The ocular microvascular parameters primarily including choroidal volume (CV) and choroidal vessel volume (CVV) reflecting arteriolovenularity, and choroidal capillary density (CCD) reflecting capillary, were evaluated using swept-source optical coherence tomography angiography at baseline and 0.5-, 1-, 2-, and 3-hour post-consumption.

RESULTS

A total of 34 eyes underwent 170 successful examinations in this study. After consuming spirits or wine, we observed significant decreases in CV and CVV values (all P < 0.01 for 0.5-, 1-, 2-, and 3-hour post-consumption), along with significant increase in CCD (P < 0.05 at 0.5-, 1-, 2-hour post-spirits consumption and 1-hour post-wine consumption). The most pronounced changes occurred 1-hour after spirits or wine consumption (all P < 0.001 in both univariate and multivariate model). However, post-consumption changes in the ocular microvasculature showed no significant differences between spirits and wine (P > 0.05). Additionally, no significant differences were observed in any parameters after water intake (all P > 0.05).

CONCLUSIONS

Excessive alcohol consumption leads to ocular arteriolovenular vasoconstriction and capillary vasodilation, most evident 1-hour post-consumption of spirits and wine. Our research provides insight into alcohol's immediate ocular microvascular effects, hinting at systemic microvascular effects.

Merocyanines form bacteriorhodopsins with strongly bathochromic absorption maxima

There is a need to shift the absorbance of biomolecules to the optical transparency window of tissue for applications in optogenetics and photo-pharmacology. There are a few strategies to achieve the so-called red shift of the absorption maxima. Herein, a series of 11 merocyanine dyes were synthesized and employed as chromophores in place of retinal in bacteriorhodopsin (bR) to achieve a bathochromic shift of the absorption maxima relative to bR's [Formula: see text] of 568 nm. Assembly with the apoprotein bacterioopsin (bO) led to stable, covalently bound chromoproteins with strongly bathochromic absorbance bands, except for three compounds. Maximal red shifts were observed for molecules 9, 2, and 8 in bR where the [Formula: see text] was 766, 755, and 736 nm, respectively. While these three merocyanines have different end groups, they share a similar structural feature, namely, a methyl group which is located at the retinal equivalent position 13 of the polyene chain. The absorption and fluorescence data are also presented for the retinal derivatives in their aldehyde, Schiff base (SB), and protonated SB (PSB) forms in solution. According to their hemicyanine character, the PSBs and their analogue bRs exhibited fluorescence quantum yields (Φf) several orders of magnitude greater than native bR (Φf 0.02 to 0.18 versus 1.5 × 10-5 in bR) while also exhibiting much smaller Stokes shifts than bR (400 to 1000 cm-1 versus 4030 cm-1 in bR). The experimental results are complemented by quantum chemical calculations where excellent agreement between the experimental [Formula: see text] and the calculated [Formula: see text] was achieved with the second-order algebraic-diagrammatic construction [ADC(2)] method. In addition, quantum mechanics/molecular mechanics (QM/MM) calculations were employed to shed light on the origin of the bathochromic shift of merocyanine 2 in bR compared with native bR.

Protonation of Asp116 and distortion of the all-trans retinal chromophore in Krokinobacter eikastus rhodopsin 2 causes a redshift in absorption maximum upon dehydration

Water is usually indispensable for protein function. For ion-pumping rhodopsins, water molecules inside the proteins play an important role in ion transportation. In addition to amino acid residues, water molecules regulate the colors of retinal proteins. It was reported that a sodium-pumping rhodopsin, Krokinobacter eikastus rhodopsin 2 (KR2), showed a color change from red to purple upon dehydration under crystalline conditions. Here, we applied comprehensive visible and IR absorption spectroscopy and resonance Raman spectroscopy to KR2 in liposomes under hydration-controlled conditions. A large increase in the hydrogen-out-of-plane (HOOP) vibration at 947 (H-C11=C12-H Au mode) and moderate increases at 893 (C7-H and C10-H) and 808 (C14-H) cm-1 were observed under dehydrated conditions, which were assigned by using systematically deuterated retinal. Moreover, the Asn variant at Asp116, which functions as a counter ion for the protonated retinal Schiff base (PRSB), caused a large redshift in the absorption maximum and constitutive increase in the HOOP modes under hydrated and dehydrated conditions. The protonation of a counter ion at Asp116 clearly causes a redshift in the absorption maximum as the all-trans retinal chromophore twists upon dehydration. Namely, the results strongly suggested that water molecules are important for maintaining the hydrogen-bonding network at the PRSB and deprotonation state of Asp116 in KR2.

Natural Retinol Analogs Potentiate the Effects of Retinal on Aged and Photodamaged Skin: Results from In Vitro to Clinical Studies

INTRODUCTION

Plants are a source of natural ingredients with retinol-like properties that can deliver anti-aging benefits without the side effects typically associated with retinoid use. We hypothesized that by combining two such analogs, bakuchiol (BAK) and Vigna aconitifolia extract (VAE), with the potent retinoid retinal (RAL), the anti-photoaging potential of RAL could be enhanced without compromising its skin irritation profile. The purpose of this study was to demonstrate that BAK and VAE potentiate the anti-photoaging activity of RAL.

METHODS

Gene expression profiling of full-thickness reconstructed skin was first used to examine the impact of BAK or VAE in combination with RAL on skin biology. Next, the irritative potential of this combination, and its capacity to reverse key signs of photoaging in an ex vivo model was assessed. Finally, a proof-of-concept open label clinical study was performed to evaluate the anti-photoaging capacity and skin compatibility of a cosmetic formulation (tri-retinoid complex; 3RC) containing this complex in combination with other well characterized anti-photoaging ingredients.

RESULTS

In vitro profiling suggested that combining 0.1% RAL with BAK or VAE potentiates the effect of RAL on keratinocyte differentiation and skin barrier function without affecting its skin irritation profile. When formulated with other anti-photoaging ingredients, such as niacinamide and melatonin, 3RC reversed ultraviolet radiation-induced deficits in structural components of the dermal extracellular matrix, including hyaluronic acid and collagen. In vivo, it led to a reversal of clinical signs of age and photodamage, with statistically significant improvement to skin firmness (+5.6%), skin elasticity (+13.9%), wrinkle count (-43.2%), and skin tone homogeneity (+7.0%), observed within 28 days of once nightly use. Notably, the number of crow's feet wrinkles was reduced in 100% of subjects. Furthermore, 3RC was very well tolerated.

CONCLUSION

These data suggest that 3RC is a highly effective and well-tolerated treatment for photoaging.

Loss of flrt2 gene leads to microphthalmia in zebrafish

As a member of the fibronectin leucine-rich transmembrane (flrt) gene family, fibronectin leucine-rich transmembrane 2 (flrt2) is strongly expressed in a subset of sclerotome cells, and the resultant protein interacts with FGFR1 in the FGF signaling pathway during development. Studies on flrt2 have focused mainly on its roles in the brain, heart and chondrogenesis. However, reports on its expression and function in the zebrafish retina are lacking. Here, we detected the high expression of flrt2 in zebrafish retina using in situ hybridization technique and developed an flrt2-knockout (KO) zebrafish line using CRISPR/Cas9 genome editing. Quantitative real-time PCR was used to measure the expression levels of flrt2, which results in an approximately 60% mRNA reduction. The flrt2-KO zebrafish eyes' altered morphological, cellular, and molecular events were identified using BrdU labeling, TUNEL assay, immunofluorescent staining, fluorescent dye injection and RNA sequencing. Abnormal eye development, known as microphthalmia, was found in flrt2-KO larvae, and the retinal progenitor cells exhibited increased apoptosis, perhaps owing to the combined effects of crx, neurod4, atoh7, and pcdh8 downregulation and Casp3a and Caspbl upregulation. In contrast, the retinal neural development, as well as retinal progenitor cell differentiation and proliferation, were not affected by the flrt2 deletion. Thus, flrt2 appears to play important roles in retinal development and function, which may provide the basis for further investigations into the molecular mechanisms of retinal development and evolution.

Characterization of retinal chromophore and protonated Schiff base in Thermoplasmatales archaeon heliorhodopsin using solid-state NMR spectroscopy

Heliorhodopsin (HeR) is a seven-helical transmembrane protein with a retinal chromophore that corresponds to a new rhodopsin family. HeR from the archaebacterium Thermoplasmatales archaeon (TaHeR) exhibits unique features, such as the inverted protein orientation in the membrane compared to other rhodopsins and a long photocycle. Here, we used solid-state nuclear magnetic resonance (NMR) spectroscopy to investigate the ¹³C and ¹⁵N NMR signals of the retinal chromophore and protonated Schiff base (RPSB) in TaHeR embedded in POPE/POPG membrane. Although the 14- and 20-¹³C retinal signals indicated 13-trans/15-anti (all-trans) configurations, the 20-¹³C chemical shift value was different from that of other microbial rhodopsins, indicating weakly steric hinderance between Phe203 and the C20 methyl group. ¹⁵N RPSB/λ_max plot deviated from the linear correlation based on retinylidene-halide model compounds. Furthermore, ¹⁵N chemical shift anisotropy (CSA) suggested that Ser112 and Ser234 polar residues distinguish the electronic environment tendencies of RPSB from those of other microbial rhodopsins. Our NMR results revealed that the retinal chromophore and the RPSB in TaHeR exhibit unique electronic environments.

Kinetic study on the molecular mechanism of light-driven inward proton transport by schizorhodopsins

Schizorhodopsins (SzRs) are light-driven inward proton pumping membrane proteins. A H⁺ is released to the cytoplasmic solvent from the chromophore, retinal Schiff base (RSB), after light absorption, and then another H⁺ is bound to the RSB at the end of photocyclic reaction. However, the mechanistic detail of H⁺ transfers in SzR is almost unknown. Here we studied the deuterium isotope effect and the temperature dependence of the reaction rate constants of elementary steps in the photocycles of SzRs. The former indicated that deprotonation and reprotonation of RSB is mainly accomplished by H⁺ hopping between heavy atoms with similar H⁺ affinity. Furthermore, the temperature dependence of the rate constants revealed that most of H⁺ transfer events have a high entropy barrier. In contrast, the activation enthalpy and entropy of extremely thermostable SzR (MsSzR) are significantly higher than other types of SzRs (SzR1 and MtSzR) suggesting that its highly thermostable structure is optimized with at the cost of slower reaction rates at ambient temperatures.

Biomolecular modifications in the sacfry of Mogurnda adspersa in response to copper stress

Copper (Cu) is one of the most harmful contaminants in fresh-water systems. Fish larvae such as sacfry are particularly vulnerable to metals such as copper (Cu) due to a less-developed excretory organ system and permeable skin that can absorb metals directly from the water. However, the sublethal effects of metals on this life stage are not well understood. This study assessed the sublethal toxicity of Cu on purple-spotted gudgeon sacfry (PSG, Mogurnda adspersa). For this purpose, 96 h Cu toxicity bioassays were performed and toxic effects of Cu on PSG were measured at different levels of biological organization, from the individual (loss of equilibrium, wet weight), to tissue (chemical changes in retinal tissue composition) and molecular responses (whole body amino acid (AA) profiles). The EC₁₀ and EC₅₀ (ECx: effect concentration that affected X% of test organisms) were found to be 12 (9 - 15) µg Cu L^-1 and 22 (19 - 24) µg Cu L^-1, respectively. Copper stress caused a decrease in total amino acid content and changed the AA profile of PSG compared to the controls. Proton-induced X-ray emission (PIXE) mapping techniques showed accumulation of Cu in the retinal tissues disturbing the distribution of other elements such as zinc, sulfur, phosphorus and potassium. Fourier-transform infrared (FTIR) microspectroscopy of control and Cu treated eye tissues revealed a change in protein secondary structure in retinal tissues in response to Cu accumulation, as well as decreased levels of the molecular retinal, consistent with the degradation of rhodopsin, a key protein in the visual sensory system. This is the first study to demonstrate the multi-level responses of PSG arising from exposure to environmentally realistic Cu concentrations and suggests that AA profiling can serve as a useful tool to assess the impacts of metals on fresh-water organisms.

Readability and Accountability of Online Patient Education Materials for Common Retinal Diseases

Patients often utilize the internet to vlearn about retinal diseases. Our results demonstrate that online patient education materials related to common retinal diseases are often written at higher than recommended reading levels and lack accountability.

Microbial Rhodopsins

The first microbial rhodopsin, a light-driven proton pump bacteriorhodopsin from Halobacterium salinarum (HsBR), was discovered in 1971. Since then, this seven-α-helical protein, comprising a retinal molecule as a cofactor, became a major driver of groundbreaking developments in membrane protein research. However, until 1999 only a few archaeal rhodopsins, acting as light-driven proton and chloride pumps and also photosensors, were known. A new microbial rhodopsin era started in 2000 when the first bacterial rhodopsin, a proton pump, was discovered. Later it became clear that there are unexpectedly many rhodopsins, and they are present in all the domains of life and even in viruses. It turned out that they execute such a diversity of functions while being "nearly the same." The incredible evolution of the research area of rhodopsins and the scientific and technological potential of the proteins is described in the review with a focus on their function-structure relationships.

Solid-State NMR Spectroscopy on Microbial Rhodopsins

Microbial rhodopsins represent the most abundant phototrophic systems known today. A similar molecular architecture with seven transmembrane helices and a retinal cofactor linked to a lysine in helix 7 enables a wide range of functions including ion pumping, light-controlled ion channel gating, or sensing. Deciphering their molecular mechanisms therefore requires a combined consideration of structural, functional, and spectroscopic data in order to identify key factors determining their function. Important insight can be gained by solid-state NMR spectroscopy by which the large homo-oligomeric rhodopsin complexes can be studied directly within lipid bilayers. This chapter describes the methodological background and the necessary sample preparation requirements for the study of photointermediates, for the analysis of protonation states, H-bonding and chromophore conformations, for 3D structure determination, and for probing oligomer interfaces of microbial rhodopsins. The use of data extracted from these NMR experiments is discussed in the context of complementary biophysical methods.

Assessing the Role of Melatonin in the Modulation of Visual Functions in the Mouse

The electroretinogram (ERG) is a noninvasive method to evaluate retinal function. It can be applied to patients to be diagnosed a variety of retinal pathologies such as photoreceptor dystrophy, diabetic retinopathy, macular degeneration, and glaucoma. ERG has also been a reliable tool to assess retinal functions in animal studies that range from fish to humans. Melatonin is a neurohormone that regulates several retinal functions within the retina, and previous studies have shown that melatonin plays an important role in the modulation of the ERG in humans and other vertebrates. This chapter describes experimental methods to evaluate retinal function using ERG in the mouse and how to assess the contribution of melatonin. An introduction is provided for materials, environmental settings, recording procedures, and analysis necessary for ERG measurements.

Crystallographic Studies of Rhodopsins: Structure and Dynamics

Crystal structures have provided detailed insight in the architecture of rhodopsin photoreceptors. Of particular interest are the protein-chromophore interactions that govern the light-induced retinal isomerization and ultimately induce the large structural changes important for the various biological functions of the family. The reaction intermediates occurring along the rhodopsin photocycle have vastly differing lifetimes, from hundreds of femtoseconds to milliseconds. Detailed insight at high spatial and temporal resolution can be obtained by time-resolved crystallography using pump-probe approaches at X-ray free-electron lasers. Alternatively, cryotrapping approaches can be used. Both the approaches are described, including illumination and sample delivery. The importance of appropriate photoexcitation avoiding multiphoton absorption is stressed.

Rhodopsins at a glance

Rhodopsins are photoreceptive membrane proteins consisting of a common heptahelical transmembrane architecture that contains a retinal chromophore. Rhodopsin was first discovered in the animal retina in 1876, but a different type of rhodopsin, bacteriorhodopsin, was reported to be present in the cell membrane of an extreme halophilic archaeon, Halobacterium salinarum, 95 years later. Although these findings were made by physiological observation of pigmented tissue and cell bodies, recent progress in genomic and metagenomic analyses has revealed that there are more than 10,000 microbial rhodopsins and 9000 animal rhodopsins with large diversity and tremendous new functionality. In this Cell Science at a Glance article and accompanying poster, we provide an overview of the diversity of functions, structures, color discrimination mechanisms and optogenetic applications of these two rhodopsin families, and will also highlight the third distinctive rhodopsin family, heliorhodopsin.

A novel thermophilic β-carotene 15,15'-monooxygenase with broad substrate specificity from the marine bacterium Candidatus Pelagibacter sp. HTCC7211

To characterize a novel thermophilic β-carotene 15,15'-monooxygenase BCMO₇₂₁₁ isolated from the marine bacterium Candidatus Pelagibacter sp. HTCC7211. BCMO₇₂₁₁ was functionally overexpressed in Escherichia coli and purified to homogeneity by Ni-NTA affinity chromatography and Superdex-200 gel filtration chromatography. Labeling experiments with H₂¹⁸O demonstrated that the oxygen atom in the terminal aldehyde group of the produced retinal molecules was provided from both molecular oxygen and water, indicating that BCMO₇₂₁₁ is the first characterized bacterial β-carotene 15,15'-monooxygenase. BCMO₇₂₁₁ exhibited broad carotenoid substrate specificity toward α-carotene, β-cryptoxanthin, β-carotene, zeaxanthin, and lutein. The optimum temperature, pH, and concentrations of the substrate and enzyme for retinal production were 60 °C, 9.0, 500 mg β-carotene/L, and 2.5 U/ml, respectively. Under optimum conditions, 888.3 mg/L retinal was produced in 60 min with a conversion rate of 89.0% (w/w). BCMO₇₂₁₁ is a potential candidate for the enzymatic synthesis of retinal in biotechnological applications.

Anatomical and functional outcomes in combined rhegmatogenous retinal and choroidal detachment pre-treated with systemic corticosteroid: a case series

BACKGROUND

Combined rhegmatogenous retinal and choroidal detachment (CRRCD) is a rare phenomenon. It is important that CRRCD is recognised preoperatively so that corticosteroids may be administered as this may make repair surgery easier to do.

AIMS

We here report on the anatomical and visual outcomes of 3 patients treated for CRRCD.

METHODS

Retrospective review of 3 eyes of 3 patients with CRRCD which underwent scleral buckle, vitrectomy, and silicone oil insertion. Data including visual acuity, intraocular pressure, ocular inflammatory status, the presence of subretinal fluid, the presence of retinal breaks, the presence of proliferative vitreoretinopathy, demographic information, medical and ophthalmic history, administration of perioperative corticosteroids, surgical techniques, and complications was collected.

RESULTS

Patients were aged 60, 66, and 62 years old at the time of surgery. There was a minimum follow-up time of 20 months. Initial visual acuity was 4/60. Initial intraocular pressure was 3 mmHg, 7 mmHg, and 7 mmHg. All eyes had deep, inflamed anterior chambers at the time of presentation. All eyes underwent 20-gauge vitrectomy, scleral buckle, and silicone oil insertion. All patients received a perioperative course of oral corticosteroids. Final visual acuity was 6/12, 6/7.5, and 6/18.

CONCLUSION

These 3 patients had good anatomical and functional results following surgery for CRRCD. All patients had visual acuity of 6/18 or better at last review.

Histopathological, immunohistochemical and molecular biologic study of an enucleated specimen of a case of Eales' disease

Eales' disease is a retinal vasculitis characterized by retinal inflammation, ischemia, and neovascularization. Exact pathogenesis of this disease is yet to be found out. We present a 29-year-old male, diagnosed with Eales' disease in both eyes with persistent intraocular inflammation. Enucleation of the pthisical right eye was subjected for histopathological examination immunohistochemistry and molecular biologic study for mycobacterial tuberculosis DNA. Our study showed that Eales disease is probably a T cell mediated disease which is triggered by mycobacterial TB DNA. Further studies are needed to confirm our findings.

Smartphone fundus photography: a narrative review

Background

The idea to use smartphone for fundus photography was put forward in 2010. Over the last decade, there has been a dramatic development in this field. This narrative review focuses on the principle of smartphone fundus photography, how to master this technique, problems encountered by the beginners, camera applications/devices designed for this purpose and the safety profile of smartphone flashlights for retinal photoreceptors.

Discussion

Smartphone fundus photography using a condensing lens is based on the same principle as indirect ophthalmoscopy. Smartphone flashlight serves the purpose of light source or illuminating system. Real and inverted image of the retina is focused by the smartphone camera after adjustment of the filming distance. Beginners can face difficulties like adjustment of the filming distance, glare from condensing lens and reflection from the ceiling lights. Mobile camera applications and holding devices designed for this purpose can help the beginners to address these difficulties. There have been safety concerns about photo-biological risk for retinal photoreceptors by flashlight. Although the spectral irradiance on the retina, while using smartphone for fundus imaging is within the safety limits set by ISO 15004-2.2. The safety profile of latest model flashlights which deliver more power compared to older flashlights, need to be assessed.

Conclusion

Smartphone fundus photography is a cheap, cost effective, portable and a convenient method for retinal imaging. With practice and use of smartphone camera applications designed for this purpose, the beginners can master this technique. By training young ophthalmology residents and ophthalmic primary caretakers, this retinal imaging technique can be utilized for artificial intelligence, patient diagnostic and educational purposes.

Evaluation of spice and herb as phyto-derived selective modulators of human retinaldehyde dehydrogenases using a simple in vitro method

Selective modulation of retinaldehyde dehydrogenases (RALDHs)-the main aldehyde dehydrogenase (ALDH) enzymes converting retinal into retinoic acid (RA), is very important not only in the RA signaling pathway but also for the potential regulatory effects on RALDH isozyme-specific processes and RALDH-related cancers. However, very few selective modulators for RALDHs have been identified, partly due to variable overexpression protocols of RALDHs and insensitive activity assay that needs to be addressed. In the present study, deletion of the N-terminal disordered regions is found to enable simple preparation of all RALDHs and their closest paralog ALDH2 using a single protocol. Fluorescence-based activity assay was employed for enzymatic activity investigation and screening for RALDH-specific modulators from extracts of various spices and herbs that are well-known for containing many phyto-derived anti-cancer constituents. Under the established conditions, spice and herb extracts exhibited differential regulatory effects on RALDHs/ALDH2 with several extracts showing potential selective inhibition of the activity of RALDHs. In addition, the presence of magnesium ions was shown to significantly increase the activity for the natural substrate retinal of RALDH3 but not the others, while His-tag cleavage considerably increased the activity of ALDH2 for the non-specific substrate retinal. Altogether we propose a readily reproducible workflow to find selective modulators for RALDHs and suggest potential sources of selective modulators from spices and herbs.

Bilateral preretinal hemorrhage associated with Kikuchi-Fujimoto disease

Purpose

To present a case of a patient with human immunodeficiency virus (HIV) disease and Kikuchi-Fujimoto disease (KFD) who presented with a unique pattern of retinopathy.

Observations

A 7-year-old Taiwanese girl with HIV disease who was recently diagnosed with KFD had a sudden onset of blurry vision in both eyes one month after her KFD systemic symptoms had relatively resolved. Ophthalmic examination showed decreased visual acuity in both eyes (OU). On fundus examination, she had bilateral preretinal, subhyaloid, and vitreous hemorrhage that was more severe than anemic retinopathy.

Conclusion

Ocular manifestations in Kikuchi-Fujimoto disease are rare; however, if they occur, presentations may vary. The exact etiology of the disease has remained elusive and controversial. This case is the first report of a patient with HIV disease and KFD presenting with ocular involvement. Furthermore, bilateral preretinal, subhyaloid, and vitreous hemorrhage, which was beyond anemic retinopathy, is an unprecedented manifestation of KFD that has not been previously reported. This case highlights the necessity for clinicians to consider all possible differential diagnoses when evaluating patients with similar findings to identify the best therapeutic approach and avoid unnecessary treatment.

History and Perspectives of Ion-Transporting Rhodopsins

The first light-sensing proteins used in optogenetics were rhodopsins. The word "rhodopsin" originates from the Greek words "rhodo" and "opsis," indicating rose and sight, respectively. Although the classical meaning of rhodopsin is the red-colored pigment in our eyes, the modern meaning of rhodopsin encompasses photoactive proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins possess 11-cis and all-trans retinal, respectively, to capture light in seven transmembrane α-helices, and photoisomerizations into all-trans and 13-cis forms, respectively, initiate each function. We are able to find ion-transporting proteins in microbial rhodopsins, such as light-gated channels and light-driven pumps, which are the main tools in optogenetics. In this chapter, historical aspects and molecular properties of rhodopsins are introduced. In the first part, "what is rhodopsin?", general introduction of rhodopsin is presented. Then, molecular mechanism of bacteriorodopsin, a light-driven proton pump and the best-studied microbial rhodopsin, is described. In the section of channelrhodopsin, the light-gated ion channel, molecular properties, and several variants are introduced. As the history has proven, understanding the molecular mechanism of microbial rhodopsins is a prerequisite for useful functional design of optogenetics tools in future.

Diversity, Mechanism, and Optogenetic Application of Light-Driven Ion Pump Rhodopsins

Ion-transporting microbial rhodopsins are widely used as major molecular tools in optogenetics. They are categorized into light-gated ion channels and light-driven ion pumps. While the former passively transport various types of cations and anions in a light-dependent manner, light-driven ion pumps actively transport specific ions, such as H⁺, Na⁺, Cl^-, against electrophysiological potential by using light energy. Since the ion transport by these pumps induces hyperpolarization of membrane potential and inhibit neural firing, light-driven ion-pumping rhodopsins are mostly applied as inhibitory optogenetics tools. Recent progress in genome and metagenome sequencing identified more than several thousands of ion-pumping rhodopsins from a wide variety of microbes, and functional characterization studies has been revealing many new types of light-driven ion pumps one after another. Since light-gated channels were reviewed in other chapters in this book, here the rapid progress in functional characterization, molecular mechanism study, and optogenetic application of ion-pumping rhodopsins were reviewed.

Development of chiral fluorinated alkyl derivatives of emixustat as drug candidates for the treatment of retinal degenerative diseases

The discovery of how a photon is converted into a chemical signal is one of the most important achievements in the field of vision. A key molecule in this process is the visual chromophore retinal. Several eye diseases are attributed to the abnormal metabolism of retinal in the retina and the retinal pigment epithelium. Also, the accumulation of two toxic retinal derivatives, N-retinylidene-N-retinylethanolamine and the retinal dimer, can damage the retina leading to blindness. RPE65 (Retinal pigment epithelium-specific 65 kDa protein) is one of the central enzymes that regulates the metabolism of retinal and the formation of its toxic metabolites. Its inhibition might decrease the rate of the retina's degeneration by limiting the amount of retinal and its toxic byproducts. Two RPE65 inhibitors, (R)-emixustat and (R)-MB001, were recently developed for this purpose.

Charge Transport by Light-Activated Rhodopsins Determined by Electrophysiological Recordings

Electrophysiological experiments are required to determine the ion transport properties of light-activated currents from microbial rhodopsin expressing cells. The recordings set the quantitative basis for correlation with spectroscopic data and for understanding of channel gating, ion transport vectoriality, or ion selectivity. This chapter focuses on voltage-clamp recordings of channelrhodopsin-2-expressing cells, and it will describe different illumination protocols that reveal the kinetic properties of gating. While the opening and closing reaction is determined from a single turnover upon a short laser flash, desensitization of the light-gated currents is studied under continuous illumination. Recovery from the desensitized state is probed after prolonged illumination with a subsequent light activation upon different dark intervals. Compiling the experimental data will define a minimum number of states in kinetic schemes used to describe the light-gated currents in channelrhodopsins, and emphasis will be given on how to correlate the results with the different time-resolved spectroscopic experiments.

The Role of ALDH in the Metastatic Potential of Osteosarcoma Cells and Potential ALDH Targets

Aldehyde dehydrogenases are a family of enzymes that oxidize aldehydes to carboxylic acids. These enzymes are important in cellular homeostasis during oxidative stress by the elimination of toxic aldehyde by-products from various cellular processes. In osteosarcoma, aldehyde dehydrogenase 1A1has been described as a cancer stem cell marker. Its activity has been found to correlate with metastatic potential and the metastatic phenotype. As such, a more complete understanding of aldehyde dehydrogenase in osteosarcoma will give us a deeper knowledge of its impact on osteosarcoma metastatic potential. Our hope is that this knowledge can be translated into novel antimetastatic therapeutic strategies and thus improve osteosarcoma prognoses.

Unexpected molecular diversity of vertebrate nonvisual opsin Opn5

Animals depend on light from their external environment to provide information for physiological functions such as vision, photoentrainment of circadian and circannual rhythms, photoperiodism, and background adaptation. Animals have a variety of photoreceptor cells that perform these functions, not only in the retina but also in other tissues, including brain tissue. In these cells, opsins function as universal photoreceptive proteins responsible for both visual and nonvisual photoreception. All opsins identified thus far bind either 11-cis or all-trans retinal as a chromophore and are classified into several groups based on their amino acid sequences. Opn5 forms an independent group that has diversified among vertebrate species. Most mammals only have one Opn5 gene, Opn5m, while nonmammalian vertebrates have two additional Opn5 subtypes, Opn5L1 and Opn5L2. Among these subtypes, Opn5m and Opn5L2 are UV-sensitive pigments in the dark. UV irradiation converts them into the visible light-sensitive active state, which converts back to the dark state by visible light irradiation. Opn5m and Opn5L2 therefore behave as bistable pigments. By contrast, Opn5L1 exclusively binds all-trans retinal to form the active state in the dark. Opn5L1 is converted to the resting state by light irradiation and subsequently reverts to the active state by a thermal process. Thus, Opn5L1 is categorized as a unique reverse photoreceptor whose activity is regulated by its photocyclic reaction. In this review, I introduce the diversity of molecular properties that have been described for vertebrate Opn5 subtypes and their physiological relevance.

Biophysics of rhodopsins and optogenetics

Rhodopsins are photoreceptive proteins and key tools in optogenetics. Although rhodopsin was originally named as a red-colored pigment for vision, the modern meaning of rhodopsin encompasses photoactive proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins respectively possess 11-cis and all-trans retinal, respectively. As cofactors bound with their animal and microbial rhodopsin (seven transmembrane α-helices) environments, 11-cis and all-trans retinal undergo photoisomerization into all-trans and 13-cis retinal forms as part of their functional cycle. While animal rhodopsins are G protein coupled receptors, the function of microbial rhodopsins is highly divergent. Many of the microbial rhodopsins are able to transport ions in a passive or an active manner. These light-gated channels or light-driven pumps represent the main tools for respectively effecting neural excitation and silencing in the emerging field of optogenetics. In this article, the biophysics of rhodopsins and their relationship to optogenetics are reviewed. As history has proven, understanding the molecular mechanism of microbial rhodopsins is a prerequisite for their rational exploitation as the optogenetics tools of the future.

Retinal-based polyene fluorescent probe for selectively detection of Cu2+ in physiological saline and serum

Retinal is a flexible natural chromophore and widely present in organisms. The slender conjugated polyene structure retinal is conducive to entering protein structure. In this work, a novel turn-on fluorescent probe for Cu²⁺ based on retinal and phenylenediamine was designed and synthesized. The probe achieved recognition of copper ions in human serum complex protein environment. Furthermore, the high sensitivity, selectivity for Cu²⁺ and the sensing mechanism was also investigated.

Blue light-triggered photochemistry and cytotoxicity of retinal

The chemical- and photo- toxicity of chromophore retinal on cells have long been debated. Although we recently showed that retinal and blue light exposure interrupt cellular signaling, a comprehensive study examining molecular underpinnings of this perturbation and its consequences to cellular fate is lacking. Here, we report molecular evidence for blue light excited-retinal induced oxidative damage of polyunsaturated lipid anchors in membrane-interacting signaling molecules and DNA damage in cells using live-cell imaging and in vitro experimentation. The incurred molecular damage irreversibly disrupted subcellular localization of these molecules, a crucial criterion for their signaling. We further show retinal accumulation in lipid-bilayers of cell membranes could enhance the lifetime of retinal in cells. Comparative response-signatures suggest that retinal triggers reactions upon photoexcitation similar to photodynamic therapy agents and generate reactive oxygen species in cells. Additionally, data also shows that exposing retinal-containing cells to sunlight induces substantial cytotoxicity. Collectively, our results explain a likely in vivo mechanism and reaction conditions under which bio-available retinal in physiological light conditions damages cells.

Manipulation of retinoic acid signaling in the nucleus accumbens shell alters rat emotional behavior

Novel targets for depression and anxiety disorders are necessary for the development of more effective pharmacotherapeutics. Our previous study found that the retinoic acid (RA) signaling pathway is the signaling pathway most enhanced in the nucleus accumbens (NAc) shell, a region important for depression, anxiety, and addiction. Genetic manipulations of RA signaling in the NAc affecting addiction-related behavior prompted our study of the role of retinoic acid signaling in depression-related and anxiety-related behavior using in vivo RNA interference. Knockdown of the retinoic acid degradation enzyme cytochrome p450 family 26 subfamily b member 1 (Cyp26b1) in the nucleus accumbens shell increased depression-related behavior while decreasing anxiety-like behavior. Knockdown of the retinoic acid binding protein, cellular RA binding protein 2 (Crabp2), also increased depression-related behavior. Knockdown of another RA binding partner fatty acid binding protein 5 (Fabp5), did not alter these behaviors. These results further support the contention that RA signaling in the NAc shell can affect emotional behavior and that targeting some components of this pathway could be a promising avenue for developing novel treatments for depression and anxiety.

Tobacco smoking is an independent factor associated with retinal damage in systemic lupus erythematosus: a cross-sectional and retrospective study

To analyze the influence of tobacco smoking on systemic lupus erythematosus (SLE) clinical features and damage. Cross-sectional and retrospective, case-control study comparing SLE patients with and without tobacco exposure. Cumulative clinical data and comorbidities were collected, and severity (Katz index) and damage (SLICC/ACR damage index) (SDI) indices were calculated. Pack-years (PY) was used to estimate lifetime tobacco exposure. A logistic regression was carried out to explore the impact of tobacco use on retinal damage. 216 patients were included. The mean age was 49 years (± 12.7), 93% were females, and median disease duration was 17 years [interquartile range (IQR):9-25]. Fifty-three percent of patients were smokers at some point. The median PY was 13 (IQR: 6-20.5). Only 54.8% of active smokers recalled having been informed of the negative effects of smoking, versus 83.3% of never smokers (< 0.001). In a bivariant analysis, an association between tobacco use at any time and discoid lupus [OR: 3.5(95%CI 1.5-8.9); p = 0.002] photosensitivity [OR: 2.06(95%CI 1.16-3.7); p = 0.01] and peripheral arteriopathy (p = 0.007) was found. Considering SDI item by item, a significant association with retinal damage, adjusted for age [OR: 1.03(95%CI 1-1.07); p = 0.04], was found. Using PYs, an association was found with discoid lupus (p = 0.01), photosensitivity (p = 0.03) and peripheral arteriopathy (p = 0.01), global SDI > 0 (p = 0.002) and retinal damage (p = 0.02). In a multivariate analysis exploring factors associated with retinal damage, any previous smoking history and SDI remained associated with retinal damage. Tobacco smoking is associated with cutaneous manifestations and damage and is an independent predictor of retinal damage in SLE patients.

Quantum Mechanical and Molecular Mechanics Modeling of Membrane-Embedded Rhodopsins

Computational chemistry provides versatile methods for studying the properties and functioning of biological systems at different levels of precision and at different time scales. The aim of this article is to review the computational methodologies that are applicable to rhodopsins as archetypes for photoactive membrane proteins that are of great importance both in nature and in modern technologies. For each class of computational techniques, from methods that use quantum mechanics for simulating rhodopsin photophysics to less-accurate coarse-grained methodologies used for long-scale protein dynamics, we consider possible applications and the main directions for improvement.

Dispersion characterization of magnetic actuated needleless injections with particle image velocimetry

Conventional needle-based approaches in intravitreal drug delivery carry needle-stick-injury risk and could scare patients (belonephobia). Alternatively, our group has explored the application of an electromagnetic needleless injector in this paper. This work aims to improve intravitreal drug delivery, which in the future could assist physicians with automation and benefit patients by providing a needleless approach. Electromagnetic needleless intravitreal injections lack quantification studies. We investigate the delivery properties of the needleless injector where the characterization can be used to refine the design parameters of the prototype in subsequent iterations. Experiments were performed to characterize the injectant delivered from the electromagnetic needleless injector. Penetration tests were conducted to observe the influences of various injection barriers and tissues. Ultrasonic imaging modality was explored for future applications of the prototype. The dispersion of the injectant was controllable where injection depth and distribution is dependent on the input voltage. The synthetic barriers highlighted significant energy losses for penetration (maximum velocity falls from 4.46 to 1.57 mm/s with a 0.1-mm barrier). The biological barriers were difficult to penetrate with the current prototype. Our results indicate that the current electromagnetic injector offers controllable dispersion (depth and distribution) correlated with input voltages, which should have increased injection power for use with biological tissue. Ultrasonic imaging modality produced velocity profiles comparable to the optical approach which is promising for future in vivo studies. The influences of injection barriers should be further investigated in in vivo experiments with ultrasonic imaging modalities. Graphical abstract .

Extremophilic models for astrobiology: haloarchaeal survival strategies and pigments for remote sensing

Recent progress in extremophile biology, exploration of planetary bodies in the solar system, and the detection and characterization of extrasolar planets are leading to new insights in the field of astrobiology and possible distribution of life in the universe. Among the many extremophiles on Earth, the halophilic Archaea (Haloarchaea) are especially attractive models for astrobiology, being evolutionarily ancient and physiologically versatile, potentially surviving in a variety of planetary environments and with relevance for in situ life detection. Haloarchaea are polyextremophilic with tolerance of saturating salinity, anaerobic conditions, high levels of ultraviolet and ionizing radiation, subzero temperatures, desiccation, and toxic ions. Haloarchaea survive launches into Earth's stratosphere encountering conditions similar to those found on the surface of Mars. Studies of their unique proteins are revealing mechanisms permitting activity and function in high ionic strength, perchlorates, and subzero temperatures. Haloarchaea also produce spectacular blooms visible from space due to synthesis of red-orange isoprenoid carotenoids used for photoprotection and photorepair processes and purple retinal chromoproteins for phototrophy and phototaxis. Remote sensing using visible and infrared spectroscopy has shown that haloarchaeal pigments exhibit both a discernable peak of absorption and a reflective "green edge". Since the pigments produce remotely detectable features, they may influence the spectrum from an inhabited exoplanet imaged by a future large space-based telescope. In this review, we focus primarily on studies of two Haloarchaea, Halobacterium sp. NRC-1 and Halorubrum lacusprofundi.

Retinal signs and risk of incident dementia in the Atherosclerosis Risk in Communities study

INTRODUCTION

The easily-imaged retinal microvasculature may reflect the brain microvasculature and therefore be related to dementia.

METHODS

In a population-based study of 12,482 adults aged 50-73 years (22% African American), we estimated the relationship of retinal characteristics from fundus photography (1993-1995) with incident all-cause dementia (1993-1995 to 2011-2013) and with etiologic subtype of dementia/mild cognitive impairment (2011-13).

RESULTS

A total of 1259 (10%) participants developed dementia over a mean 15.6 years. Moderate/severe (vs. no) retinopathy (hazard ratio [HR], 1.86; 95% confidence interval [CI]: 1.36-2.55) and central retinal arteriolar equivalent (narrowest quartile vs. widest three quartiles; HR, 1.26; 95% CI: 1.09-1.45) were associated with all-cause dementia. Results were qualitatively stronger (but not statistically significantly different) in participants with diabetes. Retinopathy was associated with a joint outcome of cerebrovascular-related, but not Alzheimer's disease-related, dementia/mild cognitive impairment (HR, 2.29; 95% CI: 1.24-4.23).

DISCUSSION

Exploration of measures in the eye may provide surrogate indices of microvascular lesions relevant to dementia.

Retinal tissue preparation for high-resolution live imaging of photoreceptors expressing multiple transgenes

Live imaging has become the favorite method in recent years to study the protein transport, localization and dynamics in live cells. Protein transport is extremely essential for proper function of photoreceptors. Aberration in the proper transport of proteins gives rise to the loss of photoreceptor and blindness. On the other hand, the ease of generation of transgenic Xenopus laevis tadpoles and the advantage of high resolution live confocal imaging provide new insight into understanding protein dynamics in photoreceptors. There are several steps for quantifying and visualizing fluorescently tagged proteins in photoreceptors starting with assembly of plasmids, generation of transgenic tadpoles, preparation of retinal tissues, imaging the transgenic photoreceptors and finally analyzing the recorded data. The focus of this manuscript is to describe how to prepare retinal tissues suited for live cell imaging and provide our readers with a tutorial video. We also give a summary of steps leading to a successful experiment that might be designed for imaging the ultrastructures of photoreceptors, the expression of two or more different fluorescently tagged proteins, their localization, distribution, or protein dynamics within photoreceptors. •Retinal tissue live imaging demonstrates the ultrastructures of photoreceptors.•High resolution live confocal imaging provides new insight into understanding the pathophysiology of photoreceptors.

Melanopsin (Opn4) utilizes Gαi and Gβγ as major signal transducers

Melanopsin (Opn4), a ubiquitously expressed photoreceptor in all classes of vertebrates, is crucial for both visual and non-visual signaling. Opn4 supports visual functions of the eye by sensing radiance levels and discriminating contrast and brightness. Non-image-forming functions of Opn4 not only regulate circadian behavior, but also control growth and development processes of the retina. It is unclear how a single photoreceptor could govern such a diverse range of physiological functions; a role in genetic hardwiring could be one explanation, but molecular and mechanistic evidence is lacking. In addition to its role in canonical G_q pathway activation, here we demonstrate that Opn4 efficiently activates G_i heterotrimers and signals through the G protein βγ. Compared with the low levels of G_i pathway activation observed for several G_q-coupled receptors, the robust Gα_i and Gβγ signaling of Opn4 led to both generation of PIP₃ and directional migration of RAW264.7 macrophages. We propose that the ability of Opn4 to signal through Gα_i and Gβγ subunits is a major contributor to its functional diversity.

Hydrogen-bonding network at the cytoplasmic region of a light-driven sodium pump rhodopsin KR2

Light-driven sodium-pumping rhodopsins are able to actively transport sodium ions. Structure/function studies of Krokinobacter eikastus rhodopsin 2 (KR2) identified N61 and G263 at the cytoplasmic surface constituting the "Ion-selectivity filter" for sodium ions, while retinal Schiff base acts as the light "Switch and Gate" for transport of sodium ions. Q123 is located between the two regions, and plays an important role for the pump function, which was implicated by functional, spectroscopic, X-ray crystallographic and computational studies. According to the atomic structure of KR2, Q123 is involved in the hydrogen-bonding network at the cytoplasmic region, together with S64, protein-bound waters, and peptide carbonyl of K255 bound to the chromophore. To gain the detailed structural information around Q123, here we compared light-induced difference Fourier-transform infrared (FTIR) spectra at 77 K between the wild-type (WT) and mutant proteins of KR2, such as Q123A, Q123V, and S64A. The obtained spectra were very similar between WT and these mutants, whereas the observed mutation effects enabled us to identify vibrations of the hydrogen-bonding network at the Q123 and S64 region. This is unique for KR2, not for the corresponding mutations in a light-driven proton-pump bacteriorhodopsin (BR). Hydrogen-bonding alteration is absent for the mutants of KR2, suggesting that proper inter-helical connectivity of helices B, C, and G is important for protein structural changes for sodium-pump function, which is controlled by the region around Q123.

Catalysis of Ground State cis[Formula: see text] trans Isomerization of Bacteriorhodopsin's Retinal Chromophore by a Hydrogen-Bond Network

For the photocycle of the membrane protein bacteriorhodopsin to proceed efficiently, the thermal 13-cis to all-trans back-isomerization of the retinal chromophore must return the protein to its resting state on a time-scale of milliseconds. Here, we report on quantum mechanical/molecular mechanical energy calculations examining the structural and energetic determinants of the retinal cis-trans isomerization in the protein environment. The results suggest that a hydrogen-bonded network consisting of the retinal Schiff base, active site amino acid residues, and water molecules can stabilize the twisted retinal, thus reducing the intrinsic energy cost of the cis-trans thermal isomerization barrier.

Change in retinal structural anatomy during the preclinical stage of Alzheimer's disease

INTRODUCTION

We conducted a 27-month longitudinal study of mid-life adults with preclinical Alzheimer's disease (AD), using spectral domain optical coherence tomography to compare changes in volume and thickness in all retinal neuronal layers to those of age-matched healthy control subjects.

METHODS

Fifty-six older adults (mean age = 65.36 years) with multiple risk factors for AD completed spectral domain optical coherence tomography retinal imaging and cognitive testing at baseline. Twenty-seven months later, they completed the same examinations and an 18F-florbetapir positron emission tomography imaging study.

RESULTS

Compared to healthy control subjects, those in the preclinical stage of AD showed a significant decrease in macular retinal nerve fiber layer (mRNFL) volume, over a 27-month follow-up interval period, as well as a decrease in outer nuclear layer and inner plexiform layer volumes and thickness in the inferior quadrant. However, only the mRNFL volume was linearly related to neocortical positron emission tomography amyloid standardized uptake value ratio after controlling for any main effects of age (R2 = 0.103; ρ = 0.017). Furthermore, the magnitude of mRNFL volume reduction was significantly correlated with performance on a task of participants' abilities to efficiently integrate visual and auditory speech information (McGurk effect).

DISCUSSION

We observed a decrease in mRNFL, outer nuclear layer, and inner plexiform layer volumes, in preclinical AD relative to controls. Moreover, the largely myelinated axonal loss in the RNFL is related to increased neocortical amyloid-β accumulation after controlling for age. Volume loss in the RNFL, during the preclinical stage, is not related to performance on measures of episodic memory or problem solving. However, this retinal change does appear to be modestly related to relative decrements in performance on a measure of audiovisual integration efficiency that has been recently advanced as a possible early cognitive marker of mild cognitive impairment.

Conversion of microbial rhodopsins: insights into functionally essential elements and rational protein engineering

Technological progress has enabled the successful application of functional conversion to a variety of biological molecules, such as nucleotides and proteins. Such studies have revealed the functionally essential elements of these engineered molecules, which are difficult to characterize at the level of an individual molecule. The functional conversion of biological molecules has also provided a strategy for their rational and atomistic design. The engineered molecules can be used in studies to improve our understanding of their biological functions and to develop protein-based tools. In this review, we introduce the functional conversion of membrane-embedded photoreceptive retinylidene proteins (also called rhodopsins) and discuss these proteins mainly on the basis of results obtained from our own studies. This information provides insights into the molecular mechanism of light-induced protein functions and their use in optogenetics, a technology which involves the use of light to control biological activities.

Functions of Intracellular Retinoid Binding-Proteins

Multiple binding and transport proteins facilitate many aspects of retinoid biology through effects on retinoid transport, cellular uptake, metabolism, and nuclear delivery. These include the serum retinol binding protein sRBP (aka Rbp4), the plasma membrane sRBP receptor Stra6, and the intracellular retinoid binding-proteins such as cellular retinol-binding proteins (CRBP) and cellular retinoic acid binding-proteins (CRABP). sRBP transports the highly lipophilic retinol through an aqueous medium. The major intracellular retinol-binding protein, CRBP1, likely enhances efficient retinoid use by providing a sink to facilitate retinol uptake from sRBP through the plasma membrane or via Stra6, delivering retinol or retinal to select enzymes that generate retinyl esters or retinoic acid, and protecting retinol/retinal from excess catabolism or opportunistic metabolism. Intracellular retinoic acid binding-proteins (CRABP1 and 2, and FABP5) seem to have more diverse functions distinctive to each, such as directing retinoic acid to catabolism, delivering retinoic acid to specific nuclear receptors, and generating non-canonical actions. Gene ablation of intracellular retinoid binding-proteins does not cause embryonic lethality or gross morphological defects. Metabolic and functional defects manifested in knockouts of CRBP1, CRBP2 and CRBP3, however, illustrate their essentiality to health, and in the case of CRBP2, to survival during limited dietary vitamin A. Future studies should continue to address the specific molecular interactions that occur between retinoid binding-proteins and their targets and their precise physiologic contributions to retinoid homeostasis and function.

Measurement of GPCR-G protein activity in living cells

G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors in eukaryotic genomes. They control a variety of cellular and physiological processes such as hormone secretion and heart rate, and therefore are associated with a majority of pathological conditions including cancer and heart diseases. Currently established assays to measure ligand-induced activation of GPCRs and G proteins possess limitations such as being time consuming, indirect, and expensive. Thus, an efficient method to measure GPCR-G protein activation is required to identify novel pharmacological modulators to control them and gain insights about molecular underpinnings of the associated pathways. Activation of GPCRs induces dissociation of G protein heterotrimers to form GαGTP and free Gβγ. Free Gβγ subunits have been shown to translocate reversibly from the plasma membrane to internal membranes. Gβγ translocation therefore represents the GPCR-G protein activation, and thus, imaging of this process can be used to quantify the kinetics and magnitude of the pathway activation-deactivation in real time in living cells. The objective of this chapter is to elaborate the protocols of (i) generation and optimization of the required sensor constructs; (ii) development of cell culture, transient transfection, imaging, and optogenetic procedures; (iii) imaging and data analysis methods; and (iv) stable cell line generation, pertaining to this assay to measure GPCR-G protein activation.

Two independent but synchronized Gβγ subunit-controlled pathways are essential for trailing-edge retraction during macrophage migration

Chemokine-induced directional cell migration is a universal cellular mechanism and plays crucial roles in numerous biological processes, including embryonic development, immune system function, and tissue remodeling and regeneration. During the migration of a stationary cell, the cell polarizes, forms lamellipodia at the leading edge (LE), and triggers the concurrent retraction of the trailing edge (TE). During cell migration governed by inhibitory G protein (G_i)-coupled receptors (GPCRs), G protein βγ (Gβγ) subunits control the LE signaling. Interestingly, TE retraction has been linked to the activation of the small GTPase Ras homolog family member A (RhoA) by the Gα_12/13 pathway. However, it is not clear how the activation of G_i-coupled GPCRs at the LE orchestrates the TE retraction in RAW264.7 macrophages. Here, using an optogenetic approach involving an opsin to activate the G_i pathway in defined subcellular regions of RAW cells, we show that in addition to their LE activities, free Gβγ subunits also govern TE retraction by operating two independent, yet synchronized, pathways. The first pathway involves RhoA activation, which prevents dephosphorylation of the myosin light chain, allowing actomyosin contractility to proceed. The second pathway activates phospholipase Cβ and induces myosin light chain phosphorylation to enhance actomyosin contractility through increasing cytosolic calcium. We further show that both of these pathways are essential, and inhibition of either one is sufficient to abolish the G_i-coupled GPCR-governed TE retraction and subsequent migration of RAW cells.

Applying next generation sequencing with microdroplet PCR to determine the disease-causing mutations in retinal dystrophies

Background

Inherited Retinal dystrophy (IRD) is a broad group of inherited retinal disorders with heterogeneous genotypes and phenotypes. Next generation sequencing (NGS) methods have been broadly applied for analyzing patients with IRD. Here we report a novel approach to enrich the target gene panel by microdroplet PCR.

Methods

This assay involved a primer library which targeted 3071 amplicons from 2078 exons comprised of 184 genes involved in retinal function and/or retinal development. We amplified the target regions using the RainDance target enrichment PCR method and sequenced the products using the MiSeq NGS platform.

Results

In this study, we analyzed 82 samples from 67 families with IRD. Bioinformatics analysis indicated that this procedure was able to reach 99% coverage of target sequences with an average sequence depth of reads at 119×. The variants detected by this study were filtered, validated, and prioritized by pathogenicity analysis. Genotypes and phenotypes were correlated by determining a consistent relationship in 38 propands (56.7%). Pathogenic variants in genes related to retinal function were found in another 11 probands (16.4%), but the clinical correlations showed inconsistencies and insufficiencies in these patients.

Conclusions

The application of NGS in IRD clinical molecular diagnosis provides a powerful approach to exploring the etiology and pathology in patients. It is important for the clinical laboratory to interpret the molecular findings in the context of patient clinical presentations because accurate interpretation of pathogenic variants is critical for delivering solid clinical molecular diagnosis to clinicians and patients and improving the standard care of patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-017-0549-5) contains supplementary material, which is available to authorized users.

All-trans retinal levels and formation of lipofuscin precursors after bleaching in rod photoreceptors from wild type and Abca4-/- mice

The accumulation of lipofuscin in the cells of the retinal pigment epithelium (RPE) is thought to play an important role in the development and progression of degenerative diseases of the retina. The bulk of RPE lipofuscin originates in reactions of the rhodopsin chromophore, retinal, with components of the photoreceptor outer segment. The 11-cis retinal isomer is generated in the RPE and supplied to rod photoreceptor outer segments where it is incorporated as the chromophore of rhodopsin. It is photoisomerized during light detection to all-trans and subsequently released by photoactivated rhodopsin as all-trans retinal, which is removed through reduction to all-trans retinol in a reaction requiring metabolic input in the form of NADPH. Both 11-cis and all-trans retinal can form lipofuscin precursor fluorophores in rod photoreceptor outer segments. Increased accumulation of lipofuscin has been suggested to result from excess formation of lipofuscin precursors due to buildup of all-trans retinal released by light exposure. In connection with this suggestion, the Abca4 transporter protein, an outer segment protein defects in which result in recessive Stargardt disease, has been proposed to promote the removal of all-trans retinal by facilitating its availability for reduction. To examine this possibility, we have measured the outer segment levels of all-trans retinal, all-trans retinol, and of lipofuscin precursors after bleaching by imaging the fluorescence of single rod photoreceptors isolated from wild type and Abca4^-/- mice. We found that all-trans retinol and all-trans retinal levels increased after bleaching in both wild type and Abca4^-/- rods. At all times after bleaching, there was no significant difference in all-trans retinal levels between the two strains. All-trans retinol levels were not significantly different between the two strains at early times, but were lower in Abca4^-/- rods at times longer than 20 min after bleaching. Bleaching in the presence of lower metabolic substrate concentrations resulted in higher all-trans retinal levels and increased formation of lipofuscin precursors in both wild type and Abca4^-/- rods. The results show that conditions that result in buildup of all-trans retinal levels result in increased generation of lipofuscin precursors in both wild type and Abca4^-/- rods. The results are consistent with the proposal that Abca4 facilitates the reduction of all-trans retinal to retinol; absence of Abca4 however does not appear to be associated with higher all-trans retinal levels compared to wild type.

The prone position during surgery and its complications: a systematic review and evidence-based guidelines

Surgery in the prone position is often a necessity when access to posterior anatomic structures is required. However, many complications are known to be associated with this type of surgery, as physiologic changes occur with increased pressure to anterior structures. While several studies have discussed postoperative vision loss, much fewer studies with lower levels of evidence have addressed other complications. A systematic literature review was conducted using 2 different databases, and 53 papers were regarded as appropriate for inclusion. Qualitative and quantitative analysis was performed. Thirteen complications were identified. Postoperative vision loss and cardiovascular complications, including hypovolemia and cardiac arrest, had the most number of studies and highest level of evidence. Careful planning for optimal positioning, padding, timing, as well as increased vigilance are evidence-based recommendations where operative prone positioning is required.

Photo and Collision Induced Isomerization of a Cyclic Retinal Derivative: An Ion Mobility Study

A cationic degradation product, formed in solution from retinal Schiff base (RSB), is examined in the gas phase using ion mobility spectrometry, photoisomerization action spectroscopy, and collision induced dissociation (CID). The degradation product is found to be N-n-butyl-2-(β-ionylidene)-4-methylpyridinium (BIP) produced through 6π electrocyclization of RSB followed by protonation and loss of dihydrogen. Ion mobility measurements show that BIP exists as trans and cis isomers that can be interconverted through buffer gas collisions and by exposure to light, with a maximum response at λ = 420 nm.Graphical Abstract.