Joseph C Besharse is a Cell Biologist with a long career in biomedical research. His research on fundamental mechanisms of retinal photoreceptors is highly regarded by his peers. He has studied both the cellular mechanism assembly of the ciliary outer segment and its temporal regulation by circadian clocks.
ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several e... more ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several epigean, plethodontid species indicate that the principal postembryonic degenerative changes in the eyes of T. spelaeus involve the eyelids and cornea, visual cells, outer plexiform layer, and the pigment epithelium. Ordinarily these changes were initiated after metamorphosis, before attainment of sexual maturity, but a few larvae had degenerating retinae.The corneal epithelium becomes irregular and thin as eyelids develop during and after metamorphosis, but retains its larval structure in animals in which eyelid overlap is incomplete. Disruption and vacuolation of the lens sometimes occurs in postmetamorphic animals with degenerating visual cells. Retinal degeneration involves reduction of the inner and outer segments of visual cells, loss of the outer plexiform layer, and retraction of apical processes of the pigment epithelium. In its earliest stage, retinal reduction is first apparent at the retinal margin where visual cells are normally less well-differentiated, but in its terminal stage reduction has gone to completion over the entire retina. Extent of retinal degeneration in adults is directly related to postmetamorphic age but there is variability in each age group. Females generally have smaller eyes, and more extensive degeneration of visual cells than males. The loss of visual function in adults is correlated with extensive visual cell degeneration.
... Blondel Thibaut Bogli Alfred Boiron Patrick Bojilova Elena Kirilova Bole Joze Bondesan Aldino... more ... Blondel Thibaut Bogli Alfred Boiron Patrick Bojilova Elena Kirilova Bole Joze Bondesan Aldino Borges Paulo AV Boros A. Bosàk Pavel Boston Penelope J. Botea Francisc Botosaneanu Lazare Bourne John D. Bouvet Yvette Bowman Thomas E. Boyer Daniel Brandon Ronald A ...
Melatonin synthesis in retinal photoreceptors is stimulated at night by a circadian oscillator an... more Melatonin synthesis in retinal photoreceptors is stimulated at night by a circadian oscillator and suppressed acutely by light. To identify photoreceptor mechanisms involved in the acute suppression of melatonin synthesis, an action spectrum was measured for dark-adapted Xenopus laevis eyecups at night. Intensity-response curves at six wavelengths from 400 to 650 nm were parallel, suggesting that a single photopigment predominates in melatonin suppression. Half-saturating intensities at 400, 440, 480, and 533 nm were not significantly different from one another, at 1-2 x 10(8) quanta cm(-2) s(-1). Significantly higher intensities of 580- and 650-nm light were required for melatonin suppression. These results indicate a predominant role for the principal green-absorbing rods in acute regulation of retinal melatonin synthesis in response to light, and argue against an important role for the red-absorbing cones. Higher than expected sensitivity at short wavelengths suggests that photoreceptors sensitive to blue and/or violet light may also contribute to melatonin suppression.
Advances in Experimental Medicine and Biology, Feb 1, 2003
PHOTORECEPTOR INTERSEGMENTAL TRANSPORT AND RETINAL DEGENERATION A conserved pathway common to mot... more PHOTORECEPTOR INTERSEGMENTAL TRANSPORT AND RETINAL DEGENERATION A conserved pathway common to motile and sensory cilia Joseph C. Besharse1, Sheila A. Baker1, Katherine Luby-Phelps', and Gregory J. Pazour2 1. INTRODUCTION During early development of ...
ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several e... more ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several epigean, plethodontid species indicate that the principal postembryonic degenerative changes in the eyes of T. spelaeus involve the eyelids and cornea, visual cells, outer plexiform layer, and the pigment epithelium. Ordinarily these changes were initiated after metamorphosis, before attainment of sexual maturity, but a few larvae had degenerating retinae.The corneal epithelium becomes irregular and thin as eyelids develop during and after metamorphosis, but retains its larval structure in animals in which eyelid overlap is incomplete. Disruption and vacuolation of the lens sometimes occurs in postmetamorphic animals with degenerating visual cells. Retinal degeneration involves reduction of the inner and outer segments of visual cells, loss of the outer plexiform layer, and retraction of apical processes of the pigment epithelium. In its earliest stage, retinal reduction is first apparent at the retinal margin where visual cells are normally less well-differentiated, but in its terminal stage reduction has gone to completion over the entire retina. Extent of retinal degeneration in adults is directly related to postmetamorphic age but there is variability in each age group. Females generally have smaller eyes, and more extensive degeneration of visual cells than males. The loss of visual function in adults is correlated with extensive visual cell degeneration.
Pigmented mice differ from frogs in that lighting regime has only a small effect on rod outer seg... more Pigmented mice differ from frogs in that lighting regime has only a small effect on rod outer segment turnover. During 8 days in constant light or darkness, disc addition measured as total displacement of a radioactive band in rod outer segments of mice which has received injections of tritiated amino acids was never modified by more than 7% compared to cyclic light controls. Disc shedding continued in each lighting regime, and as judged from outer segment dimensions, disc shedding approximately balanced disc addition.
The photoreceptor outer segment (OS), a well-defined sensory cilium, provides an important contex... more The photoreceptor outer segment (OS), a well-defined sensory cilium, provides an important context for the study of intraflagellar transport (IFT). The early phases of OS development involve successive events that are common to virtually all cilia. Additionally, intense protein trafficking occurs through the cilium and relies on IFT to maintain proper cellular morphology and optimize the photosensitive function. In the past decade, progress has been made in the characterization of photoreceptor OS trafficking in murine and amphibian models. Recently, powerful and cost-effective molecular tools and techniques for zebrafish have opened new opportunities to study photoreceptor IFT. Studies using zebrafish take advantage of its rapid embryogenesis to characterize the early events involved in photoreceptor ciliogenesis and OS assembly. In this overview, we describe phenotypes associated with knockdown strategies or genetic mutations of IFT components in zebrafish and detail a general exp...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2000
A circadian clock is located in the retinal photoreceptors of the African clawed frog Xenopus lae... more A circadian clock is located in the retinal photoreceptors of the African clawed frog Xenopus laevis. These photoreceptor clocks are thought to govern a wide variety of output rhythms, including melatonin release and gene expression. Both light and dopamine phase shift the retinal clock in a phase-dependent manner. Two homologs of the Drosophila period gene have been cloned in Xenopus, and one of these (xPer2) is acutely regulated by light. Light and dopamine induce xPer2 mRNA in a similar manner. In addition, the increase of xPer2 mRNA in response to light and dopamine is the same at all times of day tested. In contrast, xPer1 mRNA exhibits circadian oscillations but is relatively insensitive to phase-shifting treatments of light or dopamine. Our data suggest that xPer2 functions as the molecular link between the light/dark cycle and the circadian clock.
The photoreceptor connecting cilium bears a unique transmembrane assemblage which stably links ce... more The photoreceptor connecting cilium bears a unique transmembrane assemblage which stably links cell surface glycoconjugates with the underlying axonemal cytoskeleton. Structural similarities between the photoreceptor connecting cilium and the transition zone of motile cilia suggests that this assemblage may also be present in motile cilia. Using a subcellular fraction enriched in detergent-extracted photoreceptor axonemes, three high molecular mass glycoconjugates (425, 600, and 700 kD) were previously identified as potential components of the assemblage. Through oligosaccharide characterization and binding of a specific monoclonal antibody, we have verified the localization of the 425 kD glycoconjugate to the transmembrane assemblage. Binding of the lectin peanut agglutinin (PNA) to the 425 kD glycoconjugate on nitrocellulose blots, and to isolated detergent-extracted axonemes, was assessed following treatment with the enzymes neuraminidase and O-glycanase. Changes in binding to th...
To determine whether photoreceptor degeneration in the Ozark cave salamander is associated with c... more To determine whether photoreceptor degeneration in the Ozark cave salamander is associated with cessation or changes in the kinetics of outer segment (OS) renewal, an autoradiographic study of 3H-leucine incorporation in photoreceptors was carried out. Six days after isotope injection rods and cones showed labeling in both inner and outer segments. Cone OS were diffusely labeled whereas rods contained a band of radioactivity at the base of the OS. At 13 and 21 days the radioactive band in rods was located progressively nearer the distal tip of the OS. The rate of rod OS renewal ranged from 0.30 to 0.38 mu of OS length per day at 18 degrees C. L-thyroxin induced metamorphosis and light increased the renewal rate compared to larvae in darkness, and adults with photoreceptors in an early stage of degeneration had a slightly higher renewal rate than larvae. Light and electron microscope autoradiographs of degenerate photoreceptors revealed that even in the final stages of degeneration w...
Membrane turnover in outer segments of Rana pipiens red rods (ROS) was studied in tadpoles mainta... more Membrane turnover in outer segments of Rana pipiens red rods (ROS) was studied in tadpoles maintained under cyclic lighting (12L:12D) at 23 ~ 28 ~ and 33~ Large fragments (>2 /Jan in diameter or length) were shed from the ROS tips shortly after the onset of light. These were phagocytized by the pigment epithelium (PE) which caused an increase in
ABSTRACT Differential display is ideally suited for the identification of genes involved in compl... more ABSTRACT Differential display is ideally suited for the identification of genes involved in complex physiological events. Unlike subtractive hybridization techniques, differential display requires no previous knowledge about the dynamics of “important” gene products. Since the only limitation is the number of samples that can be run on a single sequencing gel, comparison of many subtly different conditions can be assessed, and mRNAs that vary in interesting ways can be identified.
ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several e... more ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several epigean, plethodontid species indicate that the principal postembryonic degenerative changes in the eyes of T. spelaeus involve the eyelids and cornea, visual cells, outer plexiform layer, and the pigment epithelium. Ordinarily these changes were initiated after metamorphosis, before attainment of sexual maturity, but a few larvae had degenerating retinae.The corneal epithelium becomes irregular and thin as eyelids develop during and after metamorphosis, but retains its larval structure in animals in which eyelid overlap is incomplete. Disruption and vacuolation of the lens sometimes occurs in postmetamorphic animals with degenerating visual cells. Retinal degeneration involves reduction of the inner and outer segments of visual cells, loss of the outer plexiform layer, and retraction of apical processes of the pigment epithelium. In its earliest stage, retinal reduction is first apparent at the retinal margin where visual cells are normally less well-differentiated, but in its terminal stage reduction has gone to completion over the entire retina. Extent of retinal degeneration in adults is directly related to postmetamorphic age but there is variability in each age group. Females generally have smaller eyes, and more extensive degeneration of visual cells than males. The loss of visual function in adults is correlated with extensive visual cell degeneration.
... Blondel Thibaut Bogli Alfred Boiron Patrick Bojilova Elena Kirilova Bole Joze Bondesan Aldino... more ... Blondel Thibaut Bogli Alfred Boiron Patrick Bojilova Elena Kirilova Bole Joze Bondesan Aldino Borges Paulo AV Boros A. Bosàk Pavel Boston Penelope J. Botea Francisc Botosaneanu Lazare Bourne John D. Bouvet Yvette Bowman Thomas E. Boyer Daniel Brandon Ronald A ...
Melatonin synthesis in retinal photoreceptors is stimulated at night by a circadian oscillator an... more Melatonin synthesis in retinal photoreceptors is stimulated at night by a circadian oscillator and suppressed acutely by light. To identify photoreceptor mechanisms involved in the acute suppression of melatonin synthesis, an action spectrum was measured for dark-adapted Xenopus laevis eyecups at night. Intensity-response curves at six wavelengths from 400 to 650 nm were parallel, suggesting that a single photopigment predominates in melatonin suppression. Half-saturating intensities at 400, 440, 480, and 533 nm were not significantly different from one another, at 1-2 x 10(8) quanta cm(-2) s(-1). Significantly higher intensities of 580- and 650-nm light were required for melatonin suppression. These results indicate a predominant role for the principal green-absorbing rods in acute regulation of retinal melatonin synthesis in response to light, and argue against an important role for the red-absorbing cones. Higher than expected sensitivity at short wavelengths suggests that photoreceptors sensitive to blue and/or violet light may also contribute to melatonin suppression.
Advances in Experimental Medicine and Biology, Feb 1, 2003
PHOTORECEPTOR INTERSEGMENTAL TRANSPORT AND RETINAL DEGENERATION A conserved pathway common to mot... more PHOTORECEPTOR INTERSEGMENTAL TRANSPORT AND RETINAL DEGENERATION A conserved pathway common to motile and sensory cilia Joseph C. Besharse1, Sheila A. Baker1, Katherine Luby-Phelps', and Gregory J. Pazour2 1. INTRODUCTION During early development of ...
ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several e... more ABSTRACT Comparative histological observations of the eyes of Typhlotriton spelaeus and several epigean, plethodontid species indicate that the principal postembryonic degenerative changes in the eyes of T. spelaeus involve the eyelids and cornea, visual cells, outer plexiform layer, and the pigment epithelium. Ordinarily these changes were initiated after metamorphosis, before attainment of sexual maturity, but a few larvae had degenerating retinae.The corneal epithelium becomes irregular and thin as eyelids develop during and after metamorphosis, but retains its larval structure in animals in which eyelid overlap is incomplete. Disruption and vacuolation of the lens sometimes occurs in postmetamorphic animals with degenerating visual cells. Retinal degeneration involves reduction of the inner and outer segments of visual cells, loss of the outer plexiform layer, and retraction of apical processes of the pigment epithelium. In its earliest stage, retinal reduction is first apparent at the retinal margin where visual cells are normally less well-differentiated, but in its terminal stage reduction has gone to completion over the entire retina. Extent of retinal degeneration in adults is directly related to postmetamorphic age but there is variability in each age group. Females generally have smaller eyes, and more extensive degeneration of visual cells than males. The loss of visual function in adults is correlated with extensive visual cell degeneration.
Pigmented mice differ from frogs in that lighting regime has only a small effect on rod outer seg... more Pigmented mice differ from frogs in that lighting regime has only a small effect on rod outer segment turnover. During 8 days in constant light or darkness, disc addition measured as total displacement of a radioactive band in rod outer segments of mice which has received injections of tritiated amino acids was never modified by more than 7% compared to cyclic light controls. Disc shedding continued in each lighting regime, and as judged from outer segment dimensions, disc shedding approximately balanced disc addition.
The photoreceptor outer segment (OS), a well-defined sensory cilium, provides an important contex... more The photoreceptor outer segment (OS), a well-defined sensory cilium, provides an important context for the study of intraflagellar transport (IFT). The early phases of OS development involve successive events that are common to virtually all cilia. Additionally, intense protein trafficking occurs through the cilium and relies on IFT to maintain proper cellular morphology and optimize the photosensitive function. In the past decade, progress has been made in the characterization of photoreceptor OS trafficking in murine and amphibian models. Recently, powerful and cost-effective molecular tools and techniques for zebrafish have opened new opportunities to study photoreceptor IFT. Studies using zebrafish take advantage of its rapid embryogenesis to characterize the early events involved in photoreceptor ciliogenesis and OS assembly. In this overview, we describe phenotypes associated with knockdown strategies or genetic mutations of IFT components in zebrafish and detail a general exp...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2000
A circadian clock is located in the retinal photoreceptors of the African clawed frog Xenopus lae... more A circadian clock is located in the retinal photoreceptors of the African clawed frog Xenopus laevis. These photoreceptor clocks are thought to govern a wide variety of output rhythms, including melatonin release and gene expression. Both light and dopamine phase shift the retinal clock in a phase-dependent manner. Two homologs of the Drosophila period gene have been cloned in Xenopus, and one of these (xPer2) is acutely regulated by light. Light and dopamine induce xPer2 mRNA in a similar manner. In addition, the increase of xPer2 mRNA in response to light and dopamine is the same at all times of day tested. In contrast, xPer1 mRNA exhibits circadian oscillations but is relatively insensitive to phase-shifting treatments of light or dopamine. Our data suggest that xPer2 functions as the molecular link between the light/dark cycle and the circadian clock.
The photoreceptor connecting cilium bears a unique transmembrane assemblage which stably links ce... more The photoreceptor connecting cilium bears a unique transmembrane assemblage which stably links cell surface glycoconjugates with the underlying axonemal cytoskeleton. Structural similarities between the photoreceptor connecting cilium and the transition zone of motile cilia suggests that this assemblage may also be present in motile cilia. Using a subcellular fraction enriched in detergent-extracted photoreceptor axonemes, three high molecular mass glycoconjugates (425, 600, and 700 kD) were previously identified as potential components of the assemblage. Through oligosaccharide characterization and binding of a specific monoclonal antibody, we have verified the localization of the 425 kD glycoconjugate to the transmembrane assemblage. Binding of the lectin peanut agglutinin (PNA) to the 425 kD glycoconjugate on nitrocellulose blots, and to isolated detergent-extracted axonemes, was assessed following treatment with the enzymes neuraminidase and O-glycanase. Changes in binding to th...
To determine whether photoreceptor degeneration in the Ozark cave salamander is associated with c... more To determine whether photoreceptor degeneration in the Ozark cave salamander is associated with cessation or changes in the kinetics of outer segment (OS) renewal, an autoradiographic study of 3H-leucine incorporation in photoreceptors was carried out. Six days after isotope injection rods and cones showed labeling in both inner and outer segments. Cone OS were diffusely labeled whereas rods contained a band of radioactivity at the base of the OS. At 13 and 21 days the radioactive band in rods was located progressively nearer the distal tip of the OS. The rate of rod OS renewal ranged from 0.30 to 0.38 mu of OS length per day at 18 degrees C. L-thyroxin induced metamorphosis and light increased the renewal rate compared to larvae in darkness, and adults with photoreceptors in an early stage of degeneration had a slightly higher renewal rate than larvae. Light and electron microscope autoradiographs of degenerate photoreceptors revealed that even in the final stages of degeneration w...
Membrane turnover in outer segments of Rana pipiens red rods (ROS) was studied in tadpoles mainta... more Membrane turnover in outer segments of Rana pipiens red rods (ROS) was studied in tadpoles maintained under cyclic lighting (12L:12D) at 23 ~ 28 ~ and 33~ Large fragments (>2 /Jan in diameter or length) were shed from the ROS tips shortly after the onset of light. These were phagocytized by the pigment epithelium (PE) which caused an increase in
ABSTRACT Differential display is ideally suited for the identification of genes involved in compl... more ABSTRACT Differential display is ideally suited for the identification of genes involved in complex physiological events. Unlike subtractive hybridization techniques, differential display requires no previous knowledge about the dynamics of “important” gene products. Since the only limitation is the number of samples that can be run on a single sequencing gel, comparison of many subtly different conditions can be assessed, and mRNAs that vary in interesting ways can be identified.
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Papers by Joseph C Besharse