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65-554: Connexins are commonly named according to their molecular weights, e.g. Cx26 is the connexin protein of 26 kDa. A competing nomenclature is the gap junction protein system, where connexins are sorted by their α (GJA) and β (GJB) forms, with additional connexins grouped into the C, D and E groupings, followed by an identifying number, e.g. GJA1 corresponds to Cx43. Following a vote at the Gap Junction Conference (2007) in Elsinore

130-465: A central band known as the visual streak. Around the fovea extends the central retina for about 6 mm and then the peripheral retina. The farthest edge of the retina is defined by the ora serrata . The distance from one ora to the other (or macula), the most sensitive area along the horizontal meridian , is about 32 mm. In section, the retina is no more than 0.5 mm thick. It has three layers of nerve cells and two of synapses , including

195-579: A considered view that the bird retina depends for nutrition and oxygen supply on a specialized organ, called the "pecten" or pecten oculi , located on the blind spot or optic disk. This organ is extremely rich in blood vessels and is thought to supply nutrition and oxygen to the bird retina by diffusion through the vitreous body. The pecten is highly rich in alkaline phosphatase activity and polarized cells in its bridge portion – both befitting its secretory role. Pecten cells are packed with dark melanin granules, which have been theorized to keep this organ warm with

260-449: A gap junction. The crystal structure of the gap junction channel formed by human Cx26 (also known as GJB2) at 3.5 Å resolution is available. The density map showed the two membrane-spanning hemichannels and the arrangement of the four TMSs of the six protomers forming each hemichannel. The hemichannels feature a positively charged cytoplasmic entrance, a funnel, a negatively charged transmembrane pathway, and an extracellular cavity. The pore

325-509: A linear model, this response profile is well described by a difference of Gaussians and is the basis for edge detection algorithms. Beyond this simple difference, ganglion cells are also differentiated by chromatic sensitivity and the type of spatial summation. Cells showing linear spatial summation are termed X cells (also called parvocellular, P, or midget ganglion cells), and those showing non-linear summation are Y cells (also called magnocellular, M, or parasol retinal ganglion cells), although

390-403: A more complex structure such as the inverted retina can generally come about as a consequence of two alternate processes - an advantageous "good" compromise between competing functional limitations, or as a historical maladaptive relic of the convoluted path of organ evolution and transformation. Vision is an important adaptation in higher vertebrates. A third view of the "inverted" vertebrate eye

455-461: A result, the useful lifetime of photoreceptors in invertebrates is much shorter than in vertebrates. Having easily replaced stalk eyes (some lobsters) or retinae (some spiders, such as Deinopis ) rarely occurs. The cephalopod retina does not originate as an outgrowth of the brain, as the vertebrate one does. This difference suggests that vertebrate and cephalopod eyes are not homologous , but have evolved separately. From an evolutionary perspective,

520-528: Is a lack of one or more of the cone subtypes that causes individuals to have deficiencies in colour vision or various kinds of colour blindness . These individuals are not blind to objects of a particular colour, but are unable to distinguish between colours that can be distinguished by people with normal vision. Humans have this trichromatic vision , while most other mammals lack cones with red sensitive pigment and therefore have poorer dichromatic colour vision. However, some animals have four spectral subtypes, e.g.

585-417: Is also available. Changes in retinal blood circulation are seen with aging and exposure to air pollution, and may indicate cardiovascular diseases such as hypertension and atherosclerosis. Determining the equivalent width of arterioles and venules near the optic disc is also a widely used technique to identify cardiovascular risks. The retina translates an optical image into neural impulses starting with

650-537: Is called mesopic vision . At mesopic light levels, both the rods and cones are actively contributing pattern information. What contribution the rod information makes to pattern vision under these circumstances is unclear. The response of cones to various wavelengths of light is called their spectral sensitivity. In normal human vision, the spectral sensitivity of a cone falls into one of three subtypes, often called blue, green, and red, but more accurately known as short, medium, and long wavelength-sensitive cone subtypes. It

715-426: Is different from Wikidata All set index articles Retina The retina (from Latin rete  'net'; pl.   retinae or retinas ) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs . The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within

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780-464: Is hyperpolarised. The amount of neurotransmitter released is reduced in bright light and increases as light levels fall. The actual photopigment is bleached away in bright light and only replaced as a chemical process, so in a transition from bright light to darkness the eye can take up to thirty minutes to reach full sensitivity. When thus excited by light, the photoceptor sends a proportional response synaptically to bipolar cells which in turn signal

845-427: Is important for entrainment of circadian rhythms and reflexive responses such as the pupillary light reflex . Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses that are sent to various visual centres of the brain through the fibres of the optic nerve . Neural signals from the rods and cones undergo processing by other neurons, whose output takes

910-403: Is most enhanced. The choroid supplies about 75% of these nutrients to the retina and the retinal vasculature only 25%. When light strikes 11-cis-retinal (in the disks in the rods and cones), 11-cis-retinal changes to all-trans-retinal which then triggers changes in the opsins. Now, the outer segments do not regenerate the retinal back into the cis- form once it has been changed by light. Instead

975-746: Is narrowed at the funnel, which is formed by the six amino-terminal helices lining the wall of the channel, which thus determines the molecular size restriction at the channel entrance. The connexin gene family is diverse, with twenty-one identified members in the sequenced human genome, and twenty in the mouse (nineteen of which are orthologous pairs). They usually weigh between 25 and 60 kDa, and have an average length of 380 amino acids. The various connexins have been observed to combine into both homomeric and heteromeric gap junctions, each of which may exhibit different functional properties including pore conductance, size selectivity, charge selectivity, voltage gating, and chemical gating. A remarkable aspect of connexins

1040-438: Is not direct. Since about 150 million receptors and only 1 million optic nerve fibres exist, convergence and thus mixing of signals must occur. Moreover, the horizontal action of the horizontal and amacrine cells can allow one area of the retina to control another (e.g. one stimulus inhibiting another). This inhibition is key to lessening the sum of messages sent to the higher regions of the brain. In some lower vertebrates (e.g.

1105-423: Is partly transparent, and the accompanying glial cells have been shown to act as fibre-optic channels to transport photons directly to the photoreceptors, light scattering does occur. Some vertebrates, including humans, have an area of the central retina adapted for high-acuity vision. This area, termed the fovea centralis , is avascular (does not have blood vessels), and has minimal neural tissue in front of

1170-525: Is that it combines two benefits - the maintenance of the photoreceptors mentioned above, and the reduction in light intensity necessary to avoid blinding the photoreceptors, which are based on the extremely sensitive eyes of the ancestors of modern hagfish (fish that live in very deep, dark water). A recent study on the evolutionary purpose for the inverted retina structure from the APS (American Physical Society) says that "The directional of glial cells helps increase

1235-400: Is that they have a relatively short half life of only a few hours. The result is the presence of a dynamic cycle by which connexins are synthesized and replaced. It has been suggested that this short life span allows for more finely regulated physiological processes to take place, such as in the myometrium . As they are being translated by ribosomes, connexins are inserted into the membrane of

1300-624: The ER and passing through the ERGIC , the folded connexins will usually enter the cis -Golgi network. However, some connexins, such as Cx26 may be transported independent of the Golgi. After being inserted into the plasma membrane of the cell, the hemichannels freely diffuse within the lipid bilayer. Through the aid of specific proteins, mainly cadherins , the hemichannels are able to dock with hemichannels of adjacent cells forming gap junctions. Recent studies have shown

1365-831: The cytoskeleton , and the activation of intracellular signaling pathways. Thus, connexins and pannexins have multifaceted contributions to brain development and specific processes in the neuro-glio-vascular unit, including synaptic transmission and plasticity, glial signaling, vasomotor control, cell movement, and blood-brain barrier integrity in the mature CNS. Different connexins may exhibit differing specificities for solutes. For example, adenosine passed about 12-fold better through channels formed by Cx32 while AMP and ADP passed about 8-fold better, and ATP greater than 300-fold better, through channels formed by Cx43. Thus, addition of phosphate to adenosine appears to shift its relative permeability from channels formed by Cx32 to channels formed by Cx43. This may have functional consequence because

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1430-527: The endoplasmic reticulum (ER). It is in the ER that connexins are properly folded, yielding two extracellular loops, EL-1 and EL-2. It is also in the ER that the oligomerization of connexin molecules into hemichannels begins, a process which may continue in the UR-Golgi intermediate compartment as well. The arrangements of these hemichannels can be homotypic, heterotypic, and combined heterotypic/heteromeric. After exiting

1495-408: The ophthalmic artery bifurcates and supplies the retina via two distinct vascular networks: the choroidal network, which supplies the choroid and the outer retina, and the retinal network, which supplies the retina's inner layer. Although the inverted retina of vertebrates appears counter-intuitive, it is necessary for the proper functioning of the retina. The photoreceptor layer must be embedded in

1560-425: The outer plexiform layer and the inner plexiform layer . In the outer neuropil layer, the rods and cones connect to the vertically running bipolar cells , and the horizontally oriented horizontal cells connect to ganglion cells. The central retina predominantly contains cones, while the peripheral retina predominantly contains rods. In total, the retina has about seven million cones and a hundred million rods. At

1625-412: The photosensitive ganglion cells ; and transmission along the optic nerve. At each synaptic stage, horizontal and amacrine cells also are laterally connected. The optic nerve is a central tract of many axons of ganglion cells connecting primarily to the lateral geniculate body , a visual relay station in the diencephalon (the rear of the forebrain). It also projects to the superior colliculus ,

1690-787: The pigeon ), control of messages is "centrifugal" – that is, one layer can control another, or higher regions of the brain can drive the retinal nerve cells, but in primates, this does not occur. Using optical coherence tomography (OCT), 18 layers can be identified in the retina. The layers and anatomical correlation are: From innermost to outermost, the layers identifiable by OCT are as follows: on OCT anatomical boundaries? references (unclear if it can be observed on OCT) b) Müller cell nuclei (obliquely orientated fibres; not present in mid-peripheral or peripheral retina) Poorly distinguishable from RPE. Previously: "cone outer segment tips line" (COST) homogenous region of variable reflectivity Retinal development begins with

1755-403: The receptive field of the cell. The receptive fields of retinal ganglion cells comprise a central, approximately circular area, where light has one effect on the firing of the cell, and an annular surround, where light has the opposite effect. In ON cells, an increment in light intensity in the centre of the receptive field causes the firing rate to increase. In OFF cells, it makes it decrease. In

1820-425: The retinal ganglion cells . The photoreceptors are also cross-linked by horizontal cells and amacrine cells , which modify the synaptic signal before it reaches the ganglion cells, the neural signals being intermixed and combined. Of the retina's nerve cells, only the retinal ganglion cells and few amacrine cells create action potentials . In the retinal ganglion cells there are two types of response, depending on

1885-431: The suprachiasmatic nucleus , and the nucleus of the optic tract . It passes through the other layers, creating the optic disc in primates. Additional structures, not directly associated with vision, are found as outgrowths of the retina in some vertebrate groups. In birds , the pecten is a vascular structure of complex shape that projects from the retina into the vitreous humour ; it supplies oxygen and nutrients to

1950-520: The N-T axis is coordinated by expression of the forkhead transcription factors FOXD1 and FOXG1 . Additional gradients are formed within the retina. This spatial distribution may aid in proper targeting of RGC axons that function to establish the retinotopic map. The retina is stratified into distinct layers, each containing specific cell types or cellular compartments that have metabolisms with different nutritional requirements. To satisfy these requirements,

2015-488: The absorption of stray light falling on the pecten. This is considered to enhance metabolic rate of the pecten, thereby exporting more nutritive molecules to meet the stringent energy requirements of the retina during long periods of exposure to light. The bifurcations and other physical characteristics of the inner retinal vascular network are known to vary among individuals, and these individual variances have been used for biometric identification and for early detection of

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2080-454: The brain, the retina is isolated from the vascular system by the blood–brain barrier . The retina is the part of the body with the greatest continuous energy demand. The vertebrate retina is inverted in the sense that the light-sensing cells are in the back of the retina, so that light has to pass through layers of neurons and capillaries before it reaches the photosensitive sections of the rods and cones. The ganglion cells, whose axons form

2145-411: The centre of the macula is the foveal pit where the cones are narrow and long, and arranged in a hexagonal mosaic , the most dense, in contradistinction to the much fatter cones located more peripherally in the retina. At the foveal pit, the other retinal layers are displaced, before building up along the foveal slope until the rim of the fovea, or parafovea , is reached, which is the thickest portion of

2210-532: The channels formed by these proteins (called pannexins ) act as very large transmembrane pores that connect the intra- and extracellular compartments. Within the CNS , gap junctions provide electrical coupling between progenitor cells, neurons, and glial cells. By using specific connexin knockout mice , studies revealed that cell coupling is essential for visual signaling. In the retina , ambient light levels influence cell coupling provided by gap junction channels, adapting

2275-483: The clarity of human vision. But we also noticed something rather curious: the colours that best passed through the glial cells were green to red, which the eye needs most for daytime vision. The eye usually receives too much blue—and thus has fewer blue-sensitive cones. Further computer simulations showed that green and red are concentrated five to ten times more by the glial cells, and into their respective cones, than blue light. Instead, excess blue light gets scattered to

2340-606: The community agreed to use the GJ nomenclature system for the genes that encode connexins, but wished to retain the connexin nomenclature for the encoded proteins using the weight of the human protein for the numbering of orthologous proteins. Connexins contain four highly ordered transmembrane segments (TMSs), primarily unstructured C and N cytoplasmic termini, a cytoplasmic loop (CL) and two extra-cellular loops, (EL-1) and (EL-2). Connexins are assembled in groups of six to form hemichannels, or connexons, and two hemichannels then combine to form

2405-422: The correspondence between X and Y cells (in the cat retina) and P and M cells (in the primate retina) is not as simple as it once seemed. In the transfer of visual signals to the brain, the visual pathway , the retina is vertically divided in two, a temporal (nearer to the temple) half and a nasal (nearer to the nose) half. The axons from the nasal half cross the brain at the optic chiasma to join with axons from

2470-2792: The development of arterial disease. Gap junction protein From Misplaced Pages, the 💕 Gap junction proteins Gap junction α (GJA) proteins GJA1 , Cx43, gap junction alpha-1 protein GJA2 , Cx38, gap junction alpha-2 protein GJA3 , Cx46, gap junction alpha-3 protein GJA4 , Cx37, gap junction alpha-4 protein GJA5 , Cx40, gap junction alpha-5 protein GJA6 , Cx33 gap junction alpha-6 protein GJA7 , Cx44.3-45.6, gap junction alpha-7 protein GJA8 , Cx50, gap junction alpha-8 protein GJA9 , Cx58, gap junction alpha-9 protein GJA10 , Cx62, gap junction alpha-10 protein GJA11 , Cx59, gap junction alpha-11 protein GJA12 , Cx46.6, gap junction alpha-12 protein Gap junction β (GJB) proteins GJB1 , Cx32, gap junction beta-1 protein GJB2 , Cx26, gap junction beta-2 protein GJB3 , Cx31, gap junction beta-3 protein GJB4 , Cx30.3, gap junction beta-4 protein GJB5 , Cx31.1, gap junction beta-5 protein GJB6 , Cx30, gap junction beta-6 protein GJB7 , Cx25, gap junction beta-7 protein Gap junction γ (GJC) proteins GJC1 , Cx45.6, gap junction gamma-1 protein GJC2 , Cx47, gap junction gamma-2 protein GJC3 , Cx29, gap junction gamma-3 protein Gap junction δ (GJD) proteins GJD1 , Cx29, gap junction delta-1 protein GJD2 , Cx36, gap junction delta-2 protein GJD3 , Cx31.9, gap junction delta-3 protein GJD4 , Cx40.1, gap junction delta-4 protein Gap junction ε (GJE) proteins GJE1 , Cx23, gap junction epsilon-1 protein See also [ edit ] Tight junction protein [REDACTED] Index of articles associated with

2535-402: The energy status of a cell could be controlled via connexin expression and channel formation. The transport reaction catalyzed by connexin gap junctions is: Gap junctions are essential for many physiological processes, such as the coordinated depolarization of cardiac muscle , proper embryonic development, and the conducted response in microvasculature. For this reason, deletion or mutation of

2600-525: The establishment of the eye fields mediated by the SHH and SIX3 proteins, with subsequent development of the optic vesicles regulated by the PAX6 and LHX2 proteins. The role of Pax6 in eye development was elegantly demonstrated by Walter Gehring and colleagues, who showed that ectopic expression of Pax6 can lead to eye formation on Drosophila antennae, wings, and legs. The optic vesicle gives rise to three structures:

2665-535: The existence of communication between adherens junctions and gap junctions, suggesting a higher level of coordination than previously thought. Connexin gap junctions are found only in vertebrates , while a functionally analogous (but genetically unrelated) group of proteins, the innexins , are responsible for gap junctions in invertebrate species. Innexin orthologs have also been identified in Chordates , but they are no longer capable of forming gap junctions. Instead,

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2730-407: The eye, and may also aid in vision. Reptiles have a similar, but much simpler, structure. In adult humans, the entire retina is about 72% of a sphere about 22 mm in diameter. The entire retina contains about 7 million cones and 75 to 150 million rods. The optic disc, a part of the retina sometimes called "the blind spot" because it lacks photoreceptors, is located at the optic papilla , where

2795-496: The form of action potentials in retinal ganglion cells whose axons form the optic nerve. In vertebrate embryonic development , the retina and the optic nerve originate as outgrowths of the developing brain, specifically the embryonic diencephalon ; thus, the retina is considered part of the central nervous system (CNS) and is actually brain tissue. It is the only part of the CNS that can be visualized noninvasively . Like most of

2860-503: The neural retina, the retinal pigmented epithelium, and the optic stalk. The neural retina contains the retinal progenitor cells (RPCs) that give rise to the seven cell types of the retina. Differentiation begins with the retinal ganglion cells and concludes with production of the Muller glia. Although each cell type differentiates from the RPCs in a sequential order, there is considerable overlap in

2925-517: The onset of disease. The mapping of vascular bifurcations is one of the basic steps in biometric identification. Results of such analyses of retinal blood vessel structure can be evaluated against the ground truth data of vascular bifurcations of retinal fundus images that are obtained from the DRIVE dataset. In addition, the classes of vessels of the DRIVE dataset have also been identified, and an automated method for accurate extraction of these bifurcations

2990-445: The optic nerve are devoted to the fovea. The resolution limit of the fovea has been determined to be around 10,000 points. The information capacity is estimated at 500,000 bits per second (for more information on bits, see information theory ) without colour or around 600,000 bits per second including colour. When the retina sends neural impulses representing an image to the brain, it spatially encodes (compresses) those impulses to fit

3055-421: The optic nerve, are at the front of the retina; therefore, the optic nerve must cross through the retina en route to the brain. No photoreceptors are in this region, giving rise to the blind spot . In contrast, in the cephalopod retina, the photoreceptors are in front, with processing neurons and capillaries behind them. Because of this, cephalopods do not have a blind spot. Although the overlying neural tissue

3120-478: The optic-nerve fibres leave the eye. It appears as an oval white area of 3 mm . Temporal (in the direction of the temples) to this disc is the macula , at whose centre is the fovea , a pit that is responsible for sharp central vision, but is actually less sensitive to light because of its lack of rods. Human and non-human primates possess one fovea, as opposed to certain bird species, such as hawks, that are bifoviate, and dogs and cats, that possess no fovea, but

3185-747: The patterned excitation of the colour-sensitive pigments of its rods and cones, the retina's photoreceptor cells . The excitation is processed by the neural system and various parts of the brain working in parallel to form a representation of the external environment in the brain. The cones respond to bright light and mediate high-resolution colour vision during daylight illumination (also called photopic vision ). The rod responses are saturated at daylight levels and do not contribute to pattern vision. However, rods do respond to dim light and mediate lower-resolution, monochromatic vision under very low levels of illumination (called scotopic vision ). The illumination in most office settings falls between these two levels and

3250-499: The photoreceptors, thereby minimizing light scattering. The cephalopods have a non-inverted retina, which is comparable in resolving power to the eyes of many vertebrates. Squid eyes do not have an analog of the vertebrate retinal pigment epithelium (RPE). Although their photoreceptors contain a protein, retinochrome, that recycles retinal and replicates one of the functions of the vertebrate RPE, cephalopod photoreceptors are likely not maintained as well as in vertebrates, and that as

3315-458: The resting state the cell is depolarised. The photon causes the retinal bound to the receptor protein to isomerise to trans-retinal . This causes the receptor to activate multiple G-proteins . This in turn causes the Ga-subunit of the protein to activate a phosphodiesterase (PDE6), which degrades cGMP, resulting in the closing of Na+ cyclic nucleotide-gated ion channels (CNGs). Thus the cell

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3380-419: The retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception . The retina serves a function which is in many ways analogous to that of the film or image sensor in a camera . The neural retina consists of several layers of neurons interconnected by synapses and is supported by an outer layer of pigmented epithelial cells. The primary light-sensing cells in

3445-414: The retina are the photoreceptor cells , which are of two types: rods and cones . Rods function mainly in dim light and provide monochromatic vision. Cones function in well-lit conditions and are responsible for the perception of colour through the use of a range of opsins , as well as high-acuity vision used for tasks such as reading. A third type of light-sensing cell, the photosensitive ganglion cell ,

3510-450: The retina. The macula has a yellow pigmentation, from screening pigments, and is known as the macula lutea. The area directly surrounding the fovea has the highest density of rods converging on single bipolar cells. Since its cones have a much lesser convergence of signals, the fovea allows for the sharpest vision the eye can attain. Though the rod and cones are a mosaic of sorts, transmission from receptors, to bipolars, to ganglion cells

3575-511: The retinal is pumped out to the surrounding RPE where it is regenerated and transported back into the outer segments of the photoreceptors. This recycling function of the RPE protects the photoreceptors against photo-oxidative damage and allows the photoreceptor cells to have decades-long useful lives. The bird retina is devoid of blood vessels, perhaps to give unobscured passage of light for forming images, thus giving better resolution. It is, therefore,

3640-490: The retinal pigment epithelium (RPE), which performs at least seven vital functions, one of the most obvious being to supply oxygen and other necessary nutrients needed for the photoreceptors to function. The energy requirements of the retina are even greater than that of the brain. This is due to the additional energy needed to continuously renew the photoreceptor outer segments, of which 10% are shed daily. Energy demands are greatest during dark adaptation when its sensitivity

3705-500: The rods and cones. Light is absorbed by the retinal pigment epithelium or the choroid (both of which are opaque). The white blood cells in the capillaries in front of the photoreceptors can be perceived as tiny bright moving dots when looking into blue light. This is known as the blue field entoptic phenomenon (or Scheerer's phenomenon). Between the ganglion-cell layer and the rods and cones are two layers of neuropils , where synaptic contacts are made. The neuropil layers are

3770-477: The same name This set index article includes a list of related items that share the same name (or similar names). If an internal link incorrectly led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Gap_junction_protein&oldid=1157965070 " Category : Set index articles Hidden categories: Articles with short description Short description

3835-418: The surrounding rods. This optimization is such that color vision during the day is enhanced, while night-time vision suffers very little". The vertebrate retina has 10 distinct layers. From closest to farthest from the vitreous body: These layers can be grouped into four main processing stages—photoreception; transmission to bipolar cells ; transmission to ganglion cells , which also contain photoreceptors,

3900-450: The temporal half of the other eye before passing into the lateral geniculate body . Although there are more than 130 million retinal receptors, there are only approximately 1.2 million fibres (axons) in the optic nerve. So, a large amount of pre-processing is performed within the retina. The fovea produces the most accurate information. Despite occupying about 0.01% of the visual field (less than 2° of visual angle ), about 10% of axons in

3965-430: The timing of when individual cell types differentiate. The cues that determine a RPC daughter cell fate are coded by multiple transcription factor families including the bHLH and homeodomain factors. In addition to guiding cell fate determination, cues exist in the retina to determine the dorsal-ventral (D-V) and nasal-temporal (N-T) axes. The D-V axis is established by a ventral to dorsal gradient of VAX2 , whereas

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4030-476: The trout adds an ultraviolet subgroup to short, medium, and long subtypes that are similar to humans. Some fish are sensitive to the polarization of light as well. In the photoreceptors, exposure to light hyperpolarizes the membrane in a series of graded shifts. The outer cell segment contains a photopigment . Inside the cell the normal levels of cyclic guanosine monophosphate (cGMP) keep the Na+ channel open, and thus in

4095-436: The unique ribbon synapse . The optic nerve carries the ganglion-cell axons to the brain, and the blood vessels that supply the retina. The ganglion cells lie innermost in the eye while the photoreceptive cells lie beyond. Because of this counter-intuitive arrangement, light must first pass through and around the ganglion cells and through the thickness of the retina, (including its capillary vessels, not shown) before reaching

4160-503: The various connexin isoforms produces distinctive phenotypes and pathologies. While mutations in Cx43 are mostly linked to oculodentodigital dysplasia, Cx47 mutations are associated with Pelizaeus-Merzbacher -like disease and lymphedema. Cx40 mutations are principally linked to atrial fibrillation. Mutations in Cx37 have not yet been described, but polymorphisms in the Cx37 gene have been implicated in

4225-643: The visual function for various lighting conditions. Cell coupling is governed by several mechanisms, including connexin expression. Decrock et al. . have discussed a multilevel platform via which connexins and pannexins can influence the following cellular functions within a tissue: (1) connexin gap junctional channels (GJCs) enable direct cell-cell communication of small molecules, (2) connexin hemichannels and pannexin channels can contribute to autocrine / paracrine signaling pathways, and (3) different structural domains of these proteins allow for channel-independent functions, such as cell-cell adhesion , interactions with

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