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The thermal contribution to photoactivation in A2 visual pigments studied by temperature effects on spectral properties.

Effects of temperature on the spectral properties of visual pigments were measured in the physiological range (5-28 degrees C) in photoreceptor cells of bullfrog (Rana catesbeiana) and crucian carp (Carassius carassius). Absorbance spectra recorded by microspectrophotometry (MSP) in single cells and sensitivity spectra recorded by electroretinography (ERG) across the isolated retina were combined to yield accurate composite spectra from ca. 400 nm to 800 nm. The four photoreceptor types selected for study allowed three comparisons illuminating the properties of pigments using the dehydroretinal (A2) chromophore: (1) the two members of an A1/A2 pigment pair with the same opsin (porphyropsin vs. rhodopsin in bullfrog "red" rods); (2) two A2 pigments with similar spectra (porphyropsin rods of bullfrog and crucian carp); and (3) two A2 pigments with different spectra (rods vs. long-wavelength-sensitive (L-) cones of crucian carp). Qualitatively, the temperature effects on A2 pigments were similar to those described previously for the A1 pigment of toad "red" rods. Warming caused an increase in relative sensitivities at very long wavelengths but additionally a small shift of lambdamax toward shorter wavelengths. The former effect was used for estimating the minimum energy required for photoactivation (Ea) of the pigment. Bullfrog rod opsin with A2 chromophore had Ea = 44.2 +/- 0.9 kcal/mol, significantly lower (one-tailed P < 0.05) than the value Ea = 46.5 +/- 0.8 kcal/mol for the same opsin coupled to A1. The A2 rod pigment of crucian carp had Ea = 42.3 +/- 0.6 kcal/mol, which is significantly higher (one-tailed P < 0.01) than that of the L-cones in the same retina (Ea = 38.3 +/- 0.4 kcal/mol), whereas the difference compared with the bullfrog A2 rod pigment is not statistically significant (two-tailed P = 0.13). No strict connection between lambdamax and Ea appears to exist among A2 pigments any more than among A1 pigments. Still, the A1 --> A2 chromophore substitution in bullfrog opsin causes three changes correlated as originally hypothesized by Barlow (1957): a red-shift of lambdamax, a decrease in Ea, and an increase in thermal noise.

Animals↗
PubMed2000

Halothane binding to a G protein coupled receptor in retinal membranes by photoaffinity labeling.

General anesthetics have been reported to alter the functions of G protein coupled receptor (GPCR) signaling systems. To determine whether these effects might be mediated by direct binding interactions with the GPCR or its associated G protein, we studied the binding character of halothane on mammalian rhodopsin, structurally the best understood GPCR, by using direct photoaffinity labeling with [(14)C]halothane. In the bleached bovine rod disk membranes (RDM), opsin and membrane lipids were dominantly photolabeled with [(14)C]halothane, but none of the three G protein subunits were labeled. In opsin itself, halothane labeling was inhibited by unlabeled halothane with an IC(50) of 0.9 mM and a Hill coefficient of -0.8. The stoichiometry was 1.1:1.0 (halothane:opsin molar ratio). The IC(50) values of isoflurane and 1-chloro-1,2, 2-trifluorocyclobutane were 5.0 and 15 mM, respectively. Ethanol had no effect on opsin labeling by halothane. A nonimmobilizer, 1, 2-dichlorohexafluorocyclobutane, inhibited halothane labeling by 50% at 0.05 mM. The present results demonstrate that halothane binds specifically and selectively to GPCRs in the RDM. The absence of halothane binding to any of the G protein subunits strongly suggests that the functional effects of halothane on GPCR signaling systems are mediated by direct interactions with receptor proteins.

Affinity Labels↗
PubMed1985

Methylation of the active-site lysine of rhodopsin.

Purified bovine rhodopsin was reductively methylated with formaldehyde and pyridine/borane with the incorporation of approximately 20 methyl groups in the protein. Rhodopsin contains 10 non-active-site lysines, which account for the uptake of the 20 methyl groups. The permethylated rhodopsin thus formed is active toward bleaching, regeneration with 11-cis-retinal, and the activation of the GTPase (G protein) when photolyzed. The critical active-site lysine of permethylated rhodopsin can be liberated by photolysis. This lysine can be reductively methylated at 4 degrees C. Methylation under these conditions leads to the incorporations of approximately 1.5 methyl groups per opsin molecule using radioactive formaldehyde, with the ratio of epsilon-dimethyllysine:epsilon-monomethyllysine:lysine being approximately 5:4:1. The modified opsin(s) can regenerate with 11-cis-retinal to produce a mixture of active-site methylated and unmethylated rhodopsins having a lambda max = 512 nm. Using [14C]formaldehyde and [3H]retinal followed by reduction of the Schiff base, digestion, and chromatography showed that the active-site N-methyllysine was bound to the retinal. Treatment of the methylated opsin mixture (containing 1.5 active-site methyl groups) with o-phthalaldehyde/mercaptoethanol to functionalize the opsin bearing unreacted lysine, followed by regeneration with 11-cis-retinal and chromatographic separation, led to the preparation of the pure active-site epsilon-lysine monomethylated rhodopsin with a lambda max = 520 nm, significantly shifted bathochromically from rhodopsin or permethylated rhodopsin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Energetics of primary processes in visula escitation: photocalorimetry of rhodopsin in rod outer segment membranes.

A sensitive technique for the direct calorimetric determination of the energetics of photochemical reactions under low levels of illumination, and its application to the study of primary processes in visula excitation, are described. Enthlpies are reported for various steps in the bleaching of rhodopsin in intact rod outer segment membranes, together with the heats of appropriate model reactions. Protonation changes are also determined calorimetrically by use of buffers with differing heats of proton ionization. Bleaching of rhodopsin is accompanied by significant uptake of heat energy, vastly in excess of the energy required for simple isomerization of the retinal chromophore. Metarhodopsin I formation involves the uptake of about 17 kcal/mol and no net change in proton ionization of the system. Formation of metarhodopsin II requires an additional energy of about 10 kcal/mol and involves the uptake on one hydrogen ion from solution. The energetics of the overall photolysis reaction, rhodopsin leads to opsin + all-trans-retinal, are pH dependent and involve the exposure of an additional titrating group on opsin. This group has a heat of proton ionization of about 12 kcal/mal, characteristic of a primary amine, but a pKa in the region of neutrality. We suggest that this group is the Schiff base lysine of the chromophore binding site of rhodopsin which becomes exposed on photolysis. The low pKa for this active lysine would result in a more stable retinal-opsin linkage, and might be induced by a nearby positively charged group on the protein (either arginine or a second lysine residue). This leads to a model involving intramolecular protonation of the Schiff base nitrogen in the retinal-opsin linkage of rhodopsin, which is consistent with the thermodynamic and spectroscopic properties of the system. We further propose that the metarhodopsin I leads to metarhodopsin II step in the bleaching sequence involves reversible hydrolysis of the Schiff base linkage in the chromophore binding site, and that subsequent steps are the result of migration of the chromophore from this site.

Animals↗
PubMed1997

Expression of bacteriorhodopsin in Sf9 and COS-1 cells.

We report studies on the expression of the archaebacterial membrane protein bacteriorhodopsin in Sf9 insect cells and in COS-1 mammalian cells. In both cell systems, the apoprotein bacterio-opsin was expressed at levels of approximately 1 microgram/10(6) cells. Immunofluorescence studies showed that the expressed protein was accumulated in the endoplasmic reticulum. However, upon addition of all-trans retinal to membranes isolated from either Sf9 or COS-1 cells expressing bacterio-opsin, the characteristic bacteriorhodopsin chromophore (lambda max at approximately 560 nm) was rapidly generated. This is in contrast to bacterio-opsin expressed in E. coli, which cannot be functionally reconstituted with retinal unless it is first denatured, and then renatured in vitro. These studies demonstrate that the bacterio-opsin expressed is correctly folded and show that localization of a heterologously expressed membrane protein in the endoplasmic reticulum does not necessarily imply that it is misfolded.

Animals↗
PubMed2005

A rhodopsin exhibiting binding ability to agonist all-trans-retinal.

Rhodopsins are the members of the family of G protein-coupled receptors that have diverged from ligand-binding receptors into photoreceptive pigments. Vertebrate rhodopsins are able to bind the inverse agonist 11-cis-retinal but are unable to bind the agonist all-trans-retinal, indicating that vertebrate rhodopsin changed its binding ability during the course of molecular evolution. Here, we show that unlike vertebrate rhodopsin, amphioxus rhodopsin is still able to bind the agonist all-trans-retinal. The opsin of amphioxus rhodopsin can also bind 11-cis-retinal to form a photoreceptive pigment that can convert to a red-shifted photoproduct through cis-trans isomerization of the chromophore upon photon absorption. The red-shifted photoproduct is the stable G protein activating state. Incubation of the opsin with all-trans-retinal produces a G protein activating state that is spectroscopically and biochemically indistinguishable from the red-shifted photoproduct, indicating that the opsin possesses agonist-binding ability. The opsin exhibits an approximately 50-fold higher affinity for 11-cis-retinal than for all-trans-retinal, and mutational analyses revealed that Trp-265 situated in helix VI is important for the increase in binding affinity to 11-cis-retinal. These properties of amphioxus rhodopsin suggest that an ancestral rhodopsin increased the affinity for 11-cis-retinal by rearrangement of a structure including Trp-265 to act as a photoreceptor. In addition, an additional mechanism was acquired in vertebrate rhodopsin to prevent completely the binding of exogenous all-trans-retinal during molecular evolution.

Animals↗
PubMed1998

The cyclophilin-like domain mediates the association of Ran-binding protein 2 with subunits of the 19 S regulatory complex of the proteasome.

The combination of the Ran-binding domain 4 and cyclophilin domains of Ran-binding protein 2 selectively associate with a subset of G protein-coupled receptors, red/green opsins, upon cis-trans prolyl isomerase-dependent and direct modification of opsin followed by association of the modified opsin isoform to Ran-binding domain 4. This effect enhances in vivo the production of functional receptor and generates an opsin isoform with no propensity to self-aggregate in vitro. We now show that another domain of Ran-binding protein 2, cyclophilin-like domain, specifically associates with the 112-kDa subunit, P112, and other subunits of the 19 S regulatory complex of the 26 S proteasome in the neuroretina. This association possibly mediates Ran-binding protein 2 limited proteolysis into a smaller and stable isoform. Also, the interaction of Ran-binding protein 2 with P112 regulatory subunit of the 26 S proteasome involves still another protein, a putative kinesin-like protein. Our results indicate that Ran-binding protein 2 is a key component of a macro-assembly complex selectively linking protein biogenesis with the proteasome pathway and, thus, with potential implications for the presentation of misfolded and ubiquitin-like modified proteins to this proteolytic machinery.

Amino Acid Sequence↗
PubMed1956

Retinene isomerase.

Rhodopsin is formed by the condensation of opsin with a cis isomer of retinene, called neo-b. The bleaching of rhodopsin releases all-trans retinene which must be isomerized back to neo-b in order for rhodopsin to regenerate. Both retinene isomers are in equilibrium with the corresponding isomers of vitamin A, through the alcohol dehydrogenase system. An enzyme is found in cattle retinas and frog pigment layers which catalyzes the interconversion of all-trans and neo-b retinene. We call it "retinene isomerase." It is soluble in neutral phosphate buffer, and precipitates between 20 and 35 per cent saturation with ammonium sulfate. In the dark, the isomerase converts all-trans and neo-b retinene to an equilibrium mixture of 5 parts neo-b and 95 parts all-trans. With opsin present to trap neo-b, the isomerase catalyzes the synthesis of rhodopsin from all-trans retinene. This reaction, however, is too slow to account for dark adaptation. Retinene is isomerized by light, but too slowly to supply the retina with neo-b. In aqueous solution the pseudoequilibrium mixture contains about 15 per cent neo-b. When all-trans retinene is irradiated in the presence of isomerase, the rate of formation of neo-b is increased about 5 times, and the pseudoequilibrium shifted so that the mixture now contains about 32 per cent neo-b. The isomerase is specific for all-trans and neo-b retinene. It does not act on two other cis isomers of retinene, nor on all-trans or neo-b vitamin A. The role of the isomerase in vision appears to be as follows: in the light, as rhodopsin is bleached to opsin and all-trans retinene, the latter is in part converted to the neo-b isomer and stored in the pigment epithelium as neo-b vitamin A. During dark adaptation, the dominant process is the trapping by opsin of neo-b retinene supplied from stores of neo-b vitamin A, and the slow isomerase-catalyzed "dark" conversion of all-trans to neo-b retinene.

Animals↗
PubMed2005

Glial remodeling and neural plasticity in human retinal detachment with proliferative vitreoretinopathy.

PURPOSE: To investigate glial remodeling and neuronal plasticity in adult human retinal detachment complicated by proliferative vitreoretinopathy (PVR) and to grade pathologic changes with a severity scoring system. METHODS: Sixteen full-thickness retinectomy specimens obtained at retinal relaxing surgery for PVR were fixed in 4% paraformaldehyde immediately after excision and compared to similarly processed normal donor retinas. Agarose-embedded sections (100-microm-thick) were double labeled for immunohistochemistry by confocal microscopy, with antibodies against rod opsin and GFAP; vimentin and M/L-cone opsin; calbindin D and S-cone opsin; and cytochrome oxidase and synaptophysin. These staining patterns formed the basis of a retinal pathology scoring system, and immunohistochemistry was also used to detect CD68, neurofilaments, protein kinase C, growth-associated protein-43, and a pan-cone-specific enzymatic marker. Morphology was also assessed by light microscopy of resin-embedded semithin sections. RESULTS: Prolonged detachment was characterized by photoreceptor degeneration and intracellular redistribution of opsin proteins to the plasma membrane in the outer nuclear layer (ONL). Remodeling of rod synaptic terminals was characterized by terminal retraction and also by axon extension to the inner retina in most specimens. Rod bipolar cell dendrites extended into the ONL, as did fine, horizontal cell processes. Large ganglion cells showed upregulated neurofilament and GAP-43 expression, with neurites sprouting from somata and axon collaterals. Anti-cytochrome oxidase labeling of surviving inner segments was reduced but detectable in all specimens, as was anti-calbindin D labeling of horizontal and amacrine cells. All specimens demonstrated a marked upregulation of Muller cell and astrocyte expression of GFAP and vimentin. More severe degenerative changes correlated with trauma and prolonged detachment duration when scored according to this system. CONCLUSIONS: The neural and glial components of detached neurosensory retina complicated by PVR exhibit pathology that changes characteristically with increasing detachment severity. Even in advanced degeneration, most of the structural motifs necessary for functional recovery are retained. Evidence of remodeling in the first-, second-, and third-order neurons of detached adult human retina may represent an attempt to re-establish synaptic connectivity.

Adolescent↗
PubMed2006

Heterologous expression of bovine rhodopsin in Drosophila photoreceptor cells.

PURPOSE: Vertebrate and invertebrate visual pigments are similar in amino acid sequence, structural organization, spectral properties, and mechanism of action, but possess different chromophores and trigger phototransduction through distinct biochemical pathways. The bovine opsin gene (Rho) was expressed in Drosophila, to examine the properties of a vertebrate opsin within invertebrate photoreceptor cells. METHODS: Transgenic Drosophila expressing the bovine opsin gene (Rho) in photoreceptors were created. Protein expression and cellular location of bovine rhodopsin was assessed by protein blots and immunofluorescence. The glycosylation state was determined by mobility profiles in SDS-PAGE before and after treatment with endoglycosidase. The rhodopsin chromophore was determined by HPLC-mass spectroscopy (MS) and the spectral properties by spectroscopy. The ability of the bovine rhodopsin to couple to Drosophila phototransduction components was assessed by electroretinography and to couple to vertebrate transducin by light-mediated GTPgammaS-binding assays. RESULTS: Rho showed stable expression even in the absence of endogenous Rh1 opsin and chromophore. It was correctly targeted to the rhabdomeric membranes. Rho remained glycosylated during the maturation process and possessed a distinct glycosylation pattern from that of native Rho. The Drosophila-expressed Rho associated with the 3-hydroxyretinal chromophore but failed to evoke an electroretinogram response from fly photoreceptors. However, the Drosophila-expressed Rho activated transducin in a light-dependent manner. CONCLUSIONS: Drosophila photoreceptors express a vertebrate rhodopsin as a functional visual pigment, but the expression does not activate the Drosophila phototransduction pathway. The system allows the characterization and comparison of vertebrate and invertebrate visual pigment properties in a common cell type.

Animals↗
PubMed2005

Adaptations to an extreme environment: retinal organisation and spectral properties of photoreceptors in Antarctic notothenioid fish.

The Notothenioid suborder of teleosts comprises a number of species that live below the sea ice of the Antarctic. The presence of 'antifreeze' glycoproteins in these fish as an adaptation to freezing temperature has been well documented but little is known about the adaptations of the visual system of these fish to a light environment in which both the quantity and spectral composition of downwelling sunlight has been reduced by passage through ice and snow. In this study, we show that the red/long-wave sensitive (LWS) opsin gene is not present in these fish but a UV-sensitive short-wave sensitive (SWS1) pigment is expressed along with blue-sensitive (SWS2) and green/middle-wave sensitive (Rh2) pigments. The identity and spectral location of maximal absorbance of the SWS1 and Rh2 pigments was confirmed by in vitro expression of the recombinant opsins followed by regeneration with 11-cis retinal. Only the SWS2 pigment showed interspecific variations in peak absorbance. Expression of the Rh2 opsin is localised to double cone receptors in both the central and peripheral retina, whereas SWS2 opsin expression is present only in the peripheral retina. SWS1 cones could not be identified by either microspectrophotometry or in situ hybridisation, presumably reflecting their low number and/or uneven distribution across the retina. A study of photoreceptor organisation in the retina of two species, the shallower dwelling Trematomus hansoni and the deeper dwelling Dissostichus mawsoni, identified a square mosaic in the former, and a row mosaic in the latter species; the row mosaic in Dissostichus mawsoni with less tightly packed cone photoreceptors allows for a higher rod photoreceptor density.

Adaptation, Biological↗
PubMed2004

Novel dominant rhodopsin mutation triggers two mechanisms of retinal degeneration and photoreceptor desensitization.

A variety of rod opsin mutations result in autosomal dominant retinitis pigmentosa and congenital night blindness in humans. One subset of these mutations encodes constitutively active forms of the rod opsin protein. Some of these dominant rod opsin mutant proteins, which desensitize transgenic Xenopus rods, provide an animal model for congenital night blindness. In a genetic screen to identify retinal degeneration mutants in Drosophila, we identified a dominant mutation in the ninaE gene (NinaE(pp100)) that encodes the rhodopsin that is expressed in photoreceptors R1-R6. Deep pseudopupil analysis and histology showed that the degeneration was attributable to a light-independent apoptosis. Whole-cell recordings revealed that the NinaE(pp100) mutant photoreceptor cells were strongly desensitized, which partially masked their constitutive activity. This desensitization primarily resulted from both the persistent binding of arrestin (ARR2) to the NINAE(pp100) mutant opsin and the constitutive activity of the phototransduction cascade. Whereas mutations in several Drosophila genes other than ninaE were shown to induce photoreceptor cell apoptosis by stabilizing a rhodopsin-arrestin complex, NinaE(pp100) represented the first rhodopsin mutation that stabilized this protein complex. Additionally, the NinaE(pp100) mutation led to elevated levels of G(q)alpha in the cytosol, which mediated a novel retinal degeneration pathway. Eliminating both G(q)alpha and arrestin completely rescued the NinaE(pp100)-dependent photoreceptor cell death, which indicated that the degeneration is entirely dependent on both G(q)alpha and arrestin. Such a combination of multiple pathological pathways resulting from a single mutation may underlie several dominant retinal diseases in humans.

Animals↗
PubMed1975

Phosphorylation and dephosphorylation of frog rod outer segment membranes as part of the visual process.

The light-activated phosphorylation of rod outer segment membranes may be an intermediary process controlling photoreceptor responses. We have measured phosphorylation of the opsin moiety of rhodopsin in isolated frog retinas and in rod outer segment suspensions and have demonstrated a phosphorylation-dephosphorylation sequence in the suspensions. The results indicate that these reactions take place in vivo and may be physiologically relevant. Extraction of a protein kinase activity from rod outer segment membranes renders the membranes incapable of phosphorylation, but the light-activated reaction can be reconstituted by mixing the soluble extract and the "depleted" membranes. Illumination of the extract is without effect. Thus the light activation mechanism resides in the membranes. Regeneration of rhodopsin from opsin and 11-cis retinal does not influence the phosphorylation. Once activated, the reaction may use either rhodopsin or opsin as the substrate. Furthermore, 11-cis retinal regenerates rhodopsin from phosphorylated opsin without releasing bound phosphate. The isolated rod outer segment which contains regenerated rhodopsin thus differs from one that is dark adapted in that phosphate can remain bound and the phosphorylation reaction remains activated. Dark adaptation in vivo must include at least two membrane associated reactions beyond regeneration of rhodopsin's spectral properties: dephosphorylation, and the inactivation of the phosphorylation process.

Adenosine Triphosphate↗
PubMed2000

Localization of tubby-like protein 1 in developing and adult human retinas.

PURPOSE: To localize tubby-like protein 1 (TULP1) in developing and adult human retinas. METHODS: TULP1 was localized by immunofluorescence microscopy in human retinas, aged 8.4 fetal weeks to adult. TULP1-positive cells were identified by double labeling with antibodies specific for cones, rods, and astrocytes. RESULTS: In adult retinas, anti-TULP1 labels cone and rod inner segments, somata, and synapses; outer segments are TULP1-negative. A few inner nuclear and ganglion cells are weakly TULP1-positive. In fetal retinas, cells at the outer retinal border are TULP1-positive at 8.4 weeks. At 11 weeks, the differentiating central cones are strongly TULP1-reactive and some are positive for blue cone opsin. At 15.4 weeks, all central cones are strongly positive for TULP1 and many are reactive for red/green cone opsin. At 17.4 weeks, central rods are weakly TULP-reactive. In peripheral retina at 15.4 weeks to 1 month after birth, displaced cones in the nerve fiber layer are positive for TULP1, recoverin, and blue cone opsin. Some ganglion cells are weakly reactive for TULP1 at 11 weeks and later, but astrocytes and the optic nerve are TULP1-negative at all ages examined. CONCLUSIONS: The finding of TULP1 labeling of cones before they are reactive for blue or red/green cone opsin suggests an important role for TULP1 in development. TULP1 expression in both developing and mature cones and rods is consistent with a primary photoreceptor defect in retinitis pigmentosa (RP) caused by TULP1 mutations. Weak TULP1-immunolabeling of some inner retinal neurons in developing and adult retinas suggests that optic disc changes in patients with RP who have TULP1 mutations may be primary as well as secondary to photoreceptor degeneration.

Adult↗
PubMed1987

A rhodopsin gene expressed in photoreceptor cell R7 of the Drosophila eye: homologies with other signal-transducing molecules.

We have isolated an opsin gene from D. melanogaster that is expressed in the ultraviolet-sensitive photoreceptor cell R7 of the Drosophila compound eye. This opsin gene contains no introns and encodes a 383 amino acid polypeptide that is approximately 35% homologous to the blue absorbing ninaE and Rh2 opsins, which are expressed in photoreceptor cells R1-6 and R8, respectively. Amino acid homologies between these different opsins and other signal-transducing molecules suggest an important role for the conserved domains of rhodopsin in the transduction of extracellular signals.

Amino Acid Sequence↗
PubMed1993

Photoreceptors regulating circadian behavior: a mouse model.

Our recent studies have examined circadian photoreception in mice with hereditary retinal disorders (rd/rd and rds/rds). Despite the loss of visual function in these mice, circadian responses to light remain unaffected. Using c-fos expression within the suprachiasmatic nuclei (SCN) as a marker of neural activation of the circadian entrainment pathway, we have found identical levels of Fos in the SCN of rd/rd and +/+ mice in response to retinal illumination. On the basis of action spectrum studies, and measurements of photopigment retinoids using high-pressure liquid chromatography, we believe that the photopigment mediating circadian responses to light is based upon an opsin, and that 11-cis-retinaldehyde is the photopigment chromophore. Preliminary measurements of mouse rod opsin, blue cone, and green-red cone opsin messenger RNA in retinally degenerate mice suggest that none of these opsins is exclusively used to mediate circadian responses to light. Collectively, our data suggest that circadian photoreception can be maintained by a very small number of rod or cone cells without outer segments, or, alternatively, is performed by an unrecognized class of photoreceptive cell within the mammalian retina.

Animals↗
PubMed2002

Early development of the retina and pineal complex in the sea lamprey: comparative immunocytochemical study.

Lampreys have a complex life cycle, with largely differentiated larval and adult periods. Despite the considerable interest of lampreys for understanding vertebrate evolution, knowledge of the early development of their eye and pineal complex is very scarce. Here, the early immunocytochemical organization of the pineal complex and retina of the sea lamprey was studied by use of antibodies against proliferating cell nuclear antigen (PCNA), opsin, serotonin, and gamma-aminobutyric acid (GABA). Cell differentiation in the retina, pineal organ, and habenula begins in prolarvae, as shown by the appearance of PCNA-negative cells, whereas differentiation of the parapineal vesicle was delayed until the larval period. In medium-sized to large larvae, PCNA-immunoreactive (-ir) cells were numerous in regions of the lateral retina near the differentiated part of the larval retina (central retina). A late-proliferating region was observed in the right habenula. Opsin immunoreactivity appears in the pineal vesicle of early prolarvae and 3 or 4 days later in the retina. In the parapineal organ, opsin immunoreactivity was observed only in large larvae. In the pineal organ, serotonin immunoreactivity was first observed in late prolarvae in photoreceptive (photoneuroendocrine) cells, whereas only a few of these cells appeared in the parapineal organ of large larvae. No serotonin immunoreactivity was observed in the larval retina. GABA immunoreactivity appeared earlier in the retina than in the pineal complex. No GABA-ir perikaryon was observed in the retina of larval lampreys, although a few GABA-ir centrifugal fibers innervate the inner retina in late prolarvae. First GABA-ir ganglion cells occur in the pineal organ of 15-17 mm larvae, and their number increases during the larval period. The only GABA-ir structures observed in the parapineal ganglion of larvae were afferent fibers, which appeared rather late in development. The time sequence of development in these photoreceptive structures is rather different from that observed in teleosts and other vertebrates. This suggests that the unusual development of the three photoreceptive organs in lampreys reflects specialization for their different functions during the larval and adult periods.

Aging↗
PubMed2003

Ontogeny of ultraviolet-sensitive cones in the retina of rainbow trout (Oncorhynchus mykiss).

In order to facilitate emerging models of retinal development, we developed electroretinogram and in situ hybridization protocols to examine the ontogeny of photoreceptors in the retina of a land-locked salmonid, the rainbow trout (Oncorhynchus mykiss). We cloned cDNA fragments corresponding to the rod opsin and each of the four cone opsin gene families, which we utilized to produce riboprobes. We established the specificity of the in situ hybridization protocol by examining subcellular signal localization and through double-labeling experiments. We confirm the assumption that the accessory corner cones in the square mosaic are the ultraviolet wavelength-sensitive (UVS) cone photoreceptor (i.e., they express an SWS1 opsin) and observed UVS cones throughout the retina of small trout. Larger fish have a decrease in sensitivity to short wavelength light stimuli and the distribution of UVS cones in the mature retina is limited to the dorsal-temporal quadrant. These larger fish also possess differentiated UVS cones in the peripheral germinal zone (PGZ), including within areas peripheral to mature retina lacking UVS cones. These data are consistent with the loss of putative UVS cones from the PGZ of a migratory salmonid of another genus, and thus the disappearance of UVS cones appears to be general to the Family Salmonidae, regardless of life history strategy. The generation, differentiation, and subsequent loss of UVS cones in the smolt PGZ is a dramatic example of the supposition that the mechanisms of PGZ development recapitulate the retinal embryogenesis of that species.

Aging↗