scholarly journals Co-expression of xenopsin and rhabdomeric opsin in photoreceptors bearing microvilli and cilia

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Oliver Vöcking ◽  
Ioannis Kourtesis ◽  
Sharat Chandra Tumu ◽  
Harald Hausen
Keyword(s):  
Visual Pigment ◽  
Photoreceptor Cell ◽  
Gene Loss ◽  
Photoreceptor Cells ◽  
Common Origin ◽  
Opsin Gene ◽  
Cell Type ◽  
Rods And Cones ◽  
Gene Structures ◽  
And Function

Ciliary and rhabdomeric opsins are employed by different kinds of photoreceptor cells, such as ciliary vertebrate rods and cones or protostome microvillar eye photoreceptors, that have specialized structures and molecular physiologies. We report unprecedented cellular co-expression of rhabdomeric opsin and a visual pigment of the recently described xenopsins in larval eyes of a mollusk. The photoreceptors bear both microvilli and cilia and express proteins that are orthologous to transporters in microvillar and ciliary opsin trafficking. Highly conserved but distinct gene structures suggest that xenopsins and ciliary opsins are of independent origin, irrespective of their mutually exclusive distribution in animals. Furthermore, we propose that frequent opsin gene loss had a large influence on the evolution, organization and function of brain and eye photoreceptor cells in bilaterian animals. The presence of xenopsin in eyes of even different design might be due to a common origin and initial employment of this protein in a highly plastic photoreceptor cell type of mixed microvillar/ciliary organization.

scholarly journals FINE STRUCTURE OF THE EYE OF A CHAETOGNATH

1964 ◽  
Vol 21 (1) ◽  
pp. 115-132 ◽  
Author(s):  
Richard M. Eakin ◽  
Jane A. Westfall
Keyword(s):  
Fine Structure ◽  
Photoreceptor Cell ◽  
Sensory Cell ◽  
Pigment Cell ◽  
Evolutionary Relationship ◽  
Cell Process ◽  
Rods And Cones ◽  
Fine Structure And Function ◽  
And Function ◽  
Relationship Of

Electron microscopy reveals a star-like pigment cell at the center of the eye of the arrow-worm, Sagitta scrippsae. Between the arms of the pigment cell are clusters of photoreceptor cell processes, each process consisting of: (1) a tubular segment containing longitudinally arranged microtubules about 500 A in diameter and 20 µ in length; (2) a remarkable conical body, composed of cords and large granules, situated at the base of the tubular segment; and (3) a connecting piece which, like that of rods and cones, connects the process with the sensory cell proper and through which runs a fibrillar apparatus consisting of nine peripheral double tubules. Beneath the connecting piece lies a typical centriole with a striated rootlet. The receptor cell process is deeply recessed into the sensory cell which may possess a corona of microvilli at its inner surface. A nerve fiber arises from the outer end of the cell and passes into the optic nerve. Additional features are some supporting cells, an external layer of flattened epithelial cells, and an over-all investment of basement membrane and thick fibrous capsule. The fine structure and function of these elements of the eye are discussed in relation to earlier studies with the light microscope. The ciliary nature of the photoreceptor cell process in S. scrippsae points to a probable evolutionary relationship of chaetognaths to echinoderms and chordates.

scholarly journals Dysfunction of Heterotrimeric Kinesin-2 in Rod Photoreceptor Cells and the Role of Opsin Mislocalization in Rapid Cell Death

2010 ◽  
Vol 21 (23) ◽  
pp. 4076-4088 ◽  
Author(s):  
Vanda S. Lopes ◽  
David Jimeno ◽  
Kornnika Khanobdee ◽  
Xiaodan Song ◽  
Bryan Chen ◽  
...  
Keyword(s):  
Cell Death ◽  
Outer Segment ◽  
Photoreceptor Cell ◽  
Photoreceptor Cells ◽  
Cell Loss ◽  
Rod Photoreceptor ◽  
Retinal Degenerations ◽  
Cell Counts ◽  
And Function

Due to extensive elaboration of the photoreceptor cilium to form the outer segment, axonemal transport (IFT) in photoreceptors is extraordinarily busy, and retinal degeneration is a component of many ciliopathies. Functional loss of heterotrimeric kinesin-2, a major anterograde IFT motor, causes mislocalized opsin, followed by rapid cell death. Here, we have analyzed the nature of protein mislocalization and the requirements for the death of kinesin-2-mutant rod photoreceptors. Quantitative immuno EM showed that opsin accumulates initially within the inner segment, and then in the plasma membrane. The light-activated movement of arrestin to the outer segment is also impaired, but this defect likely results secondarily from binding to mislocalized opsin. Unlike some other retinal degenerations, neither opsin–arrestin complexes nor photoactivation were necessary for cell loss. In contrast, reduced rod opsin expression provided enhanced rod and cone photoreceptor survival and function, as measured by photoreceptor cell counts, apoptosis assays, and ERG analysis. The cell death incurred by loss of kinesin-2 function was almost completely negated by Rho−/−. Our results indicate that mislocalization of opsin is a major cause of photoreceptor cell death from kinesin-2 dysfunction and demonstrate the importance of accumulating mislocalized protein per se, rather than specific signaling properties of opsin, stemming from photoactivation or arrestin binding.

scholarly journals Samd7 is a cell type-specific PRC1 component essential for establishing retinal rod photoreceptor identity

2017 ◽  
Vol 114 (39) ◽  
pp. E8264-E8273 ◽  
Author(s):  
Yoshihiro Omori ◽  
Shun Kubo ◽  
Tetsuo Kon ◽  
Mayu Furuhashi ◽  
Hirotaka Narita ◽  
...  
Keyword(s):  
Gene Expression ◽  
Photoreceptor Cell ◽  
Ectopic Expression ◽  
Neuronal Cell ◽  
Photoreceptor Cells ◽  
Rod Photoreceptor ◽  
Cell Type ◽  
A Cell ◽  
Cell Type Specific ◽  
Null Mutant Mice

Precise transcriptional regulation controlled by a transcription factor network is known to be crucial for establishing correct neuronal cell identities and functions in the CNS. In the retina, the expression of various cone and rod photoreceptor cell genes is regulated by multiple transcription factors; however, the role of epigenetic regulation in photoreceptor cell gene expression has been poorly understood. Here, we found that Samd7, a rod-enriched sterile alpha domain (SAM) domain protein, is essential for silencing nonrod gene expression through H3K27me3 regulation in rod photoreceptor cells. Samd7-null mutant mice showed ectopic expression of nonrod genes including S-opsin in rod photoreceptor cells and rod photoreceptor cell dysfunction. Samd7 physically interacts with Polyhomeotic homologs (Phc proteins), components of the Polycomb repressive complex 1 (PRC1), and colocalizes with Phc2 and Ring1B in Polycomb bodies. ChIP assays showed a significant decrease of H3K27me3 in the genes up-regulated in the Samd7-deficient retina, showing that Samd7 deficiency causes the derepression of nonrod gene expression in rod photoreceptor cells. The current study suggests that Samd7 is a cell type-specific PRC1 component epigenetically defining rod photoreceptor cell identity.

An opsin gene expressed in only one photoreceptor cell type of the Drosophila eye

Cell ◽  
1986 ◽  
Vol 44 (5) ◽  
pp. 705-710 ◽  
Author(s):  
Alan F. Cowman ◽  
Charles S. Zuker ◽  
Gerald M. Rubin
Keyword(s):  
Photoreceptor Cell ◽  
Opsin Gene ◽  
Cell Type ◽  
Drosophila Eye

scholarly journals Multiple rod–cone and cone–rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression

2016 ◽  
Vol 283 (1823) ◽  
pp. 20152624 ◽  
Author(s):  
Bruno F. Simões ◽  
Filipa L. Sampaio ◽  
Ellis R. Loew ◽  
Kate L. Sanders ◽  
Robert N. Fisher ◽  
...  
Keyword(s):  
Photoreceptor Cells ◽  
Opsin Gene ◽  
Future Research ◽  
Rod Photoreceptor ◽  
Radical Theory ◽  
Rods And Cones ◽  
Fundamental Properties ◽  
Light Levels ◽  
Reverse Complement ◽  
Functional Implications

In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor ‘transmutation’. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1 , sws1 and lws , in retinal mRNA of an ecologically and taxonomically diverse sample of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels.

scholarly journals STRUCTURAL BASIS FOR WAVELENGTH DISCRIMINATION IN THE BANKED RETINA OF THE FIREFLY SQUID WATASENIA SCINTILLANS

1994 ◽  
Vol 193 (1) ◽  
pp. 1-12 ◽  
Author(s):  
M Michinomae ◽  
H Masuda ◽  
M Seidou ◽  
Y Kito
Keyword(s):  
Visual Pigment ◽  
Outer Segment ◽  
Photoreceptor Cell ◽  
Structural Basis ◽  
Ventral Part ◽  
Cell Type ◽  
Electron Microscopic ◽  
Absorbance Maximum ◽  
Wavelength Discrimination ◽  
Microscopic Investigations

There is a greatly thickened region of retina in the ventral part of the eye of the firefly squid Watasenia scintillans, with an outer segment (OS) layer around 600 µm thick. The distal two-thirds of this OS layer is yellow and contains a visual pigment, based on 4-hydroxyretinal (A4), with an absorbance maximum at 470 nm. The proximal third is pink and contains a visual pigment, based on dehydroretinal (A2), with an absorbance maximum at 500 nm. Light and electron microscopic investigations demonstrate the presence of four types of photoreceptor cell. In the pink layer, three of the four types (alpha, ß and gamma) produce no microvilli and are columnar in structure. These cells form square microvillous rhabdoms only in the distal yellow layer. The fourth cell type (delta) produces microvilli in the pink layer only. These observations led us to propose that the A2-based visual pigment is contained in the pink-layer cells and that the A4-based visual pigment is contained in the three types of yellow-layer cells. The absorbance of fresh retina was determined by microspectrophotometry. The yellow OS layer, with an absorbance of 0.7 per 100 µm thickness at 470 nm, is expected to act as a short-wavelength cut-off filter to the underlying pink OS cells, shifting their photosensitivity peak by an estimated 50 nm to 550 nm. Possible wavelength discrimination by this squid is discussed.

scholarly journals Two visual pigments in a single photoreceptor cell: identification and histological localization of three mRNAs encoding visual pigment opsins in the retina of the butterfly Papilio xuthus.

1998 ◽  
Vol 201 (9) ◽  
pp. 1255-1261 ◽  
Author(s):  
J Kitamoto ◽  
K Sakamoto ◽  
K Ozaki ◽  
Y Mishina ◽  
K Arikawa
Keyword(s):  
In Situ Hybridization ◽  
Visual Pigment ◽  
Photoreceptor Cell ◽  
Wavelength Region ◽  
Photoreceptor Cells ◽  
Visual Pigments ◽  
Cell Identification ◽  
Papilio Xuthus

This paper describes the localization of newly identified visual pigment opsins in the tiered retina of the Japanese yellow swallowtail Papilio xuthus. We first cloned three cDNAs encoding visual pigment opsins, PxRh1, PxRh2 and PxRh3, and then carried out histological in situ hybridization to localize their mRNAs in the retina. By combining the present data with our previous electrophysiological results, we concluded that both PxRh1 and PxRh2 correspond to visual pigments expressed in photoreceptor cells sensitive in the green wavelength region (green receptors), whereas PxRh3 corresponds to a pigment in red receptors. The in situ hybridization studies showed that some photoreceptor cells express two opsin mRNAs. In the ventral half of the eye, all green receptors in the distal tier were labelled by both PxRh1 and PxRh2 probes. The labelling by the PxRh2 and PxRh3 probes was detected throughout the eye in the proximal tier; in 18 % of ommatidia, the probes labelled the same photoreceptor cell. These results suggest that the possible co-localization of two different visual pigments will broaden the sensitivity spectrum of the photoreceptor cells.

scholarly journals Differential Regulation of Gonadotropins as Revealed by Transcriptomes of Distinct LH and FSH Cells of Fish Pituitary

2021 ◽  
Vol 22 (12) ◽  
pp. 6478
Author(s):  
Lian Hollander-Cohen ◽  
Matan Golan ◽  
Berta Levavi-Sivan
Keyword(s):  
Follicle Stimulating Hormone ◽  
Differential Regulation ◽  
Receptor Expression ◽  
Hormone Regulation ◽  
Fish Reproduction ◽  
Cell Type ◽  
Conserved Genes ◽  
Transgenic Tilapia ◽  
And Function ◽  
Direct Regulation

From mammals to fish, reproduction is driven by luteinizing hormone (LH) and follicle-stimulating hormone (FSH) temporally secreted from the pituitary gland. Teleost fish are an excellent model for addressing the unique regulation and function of each gonadotropin cell since, unlike mammals, they synthesize and secrete LH and FSH from distinct cells. Only very distant vertebrate classes (such as fish and birds) demonstrate the mono-hormonal strategy, suggesting a potential convergent evolution. Cell-specific transcriptome analysis of double-labeled transgenic tilapia expressing GFP and RFP in LH or FSH cells, respectively, yielded genes specifically enriched in each cell type, revealing differences in hormone regulation, receptor expression, cell signaling, and electrical properties. Each cell type expresses a unique GPCR signature that reveals the direct regulation of metabolic and homeostatic hormones. Comparing these novel transcriptomes to that of rat gonadotrophs revealed conserved genes that might specifically contribute to each gonadotropin activity in mammals, suggesting conserved mechanisms controlling the differential regulation of gonadotropins in vertebrates.

scholarly journals Epigenetic reprogramming of cell identity: lessons from development for regenerative medicine

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Amitava Basu ◽  
Vijay K. Tiwari
Keyword(s):  
Regenerative Medicine ◽  
Cell Types ◽  
Direct Conversion ◽  
Cellular Reprogramming ◽  
Specific Cell ◽  
Cell Type ◽  
Pathological Conditions ◽  
Gene Regulatory ◽  
Induced Pluripotent ◽  
And Function

AbstractEpigenetic mechanisms are known to define cell-type identity and function. Hence, reprogramming of one cell type into another essentially requires a rewiring of the underlying epigenome. Cellular reprogramming can convert somatic cells to induced pluripotent stem cells (iPSCs) that can be directed to differentiate to specific cell types. Trans-differentiation or direct reprogramming, on the other hand, involves the direct conversion of one cell type into another. In this review, we highlight how gene regulatory mechanisms identified to be critical for developmental processes were successfully used for cellular reprogramming of various cell types. We also discuss how the therapeutic use of the reprogrammed cells is beginning to revolutionize the field of regenerative medicine particularly in the repair and regeneration of damaged tissue and organs arising from pathological conditions or accidents. Lastly, we highlight some key challenges hindering the application of cellular reprogramming for therapeutic purposes.

scholarly journals Mutations in calphotin, the gene encoding a Drosophila photoreceptor cell-specific calcium-binding protein, reveal roles in cellular morphogenesis and survival.

Genetics ◽  
1994 ◽  
Vol 138 (2) ◽  
pp. 413-421 ◽  
Author(s):  
Y Yang ◽  
D Ballinger
Keyword(s):  
Calcium Binding ◽  
Photoreceptor Cell ◽  
Cell Structure ◽  
Specific Protein ◽  
Cell Organelle ◽  
Cell Type ◽  
Gene Encoding ◽  
Cellular Morphogenesis ◽  
Transgenic Flies ◽  
Drosophila Photoreceptor

Abstract Calphotin is a Drosophila photoreceptor cell-specific protein expressed very early in eye development, at the time when cell-type decisions are being made. Calphotin is a very hydrophobic and proline-rich protein which lacks obvious transmembrane domains. The cDNA encoding Calphotin was mapped to a region removed by a set of existing chromosomal deletions. Mutations that alter photoreceptor cell structure and development were isolated that fail to complement these deletions. These mutations fall into two classes. Class I mutations alter the structure of the rhabdomere, a photoreceptor cell organelle specialized for phototransduction. Class II mutations have rough eyes, due to misorientation of the rhabdomeres and photoreceptor cell death. Transformation rescue of these phenotypes in transgenic flies bearing calphotin genomic DNA indicates that both classes of mutations are in the calphotin gene. Analysis of these mutations suggest that Calphotin plays important roles in both rhabdomere development and in photoreceptor cell survival.

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