Prenatal development of calbindin D-28K and parvalbumin immunoreactivities in the human retina

Development of ON and OFF cholinergic amacrine cells in the human fetal retina

Choline acetyltransferase (ChAT) expressing retinal amacrine cells are present across vertebrates. These interneurons play important roles in the development of retinal projections to the brain and in motion detection, specifically in generating direction-selective responses to moving stimuli. ChAT amacrine cells typically comprise two spatially segregated populations that form circuits in the 'ON' or 'OFF' synaptic layers of the inner retina. This stereotypic arrangement is also found across the adult human retina, with the notable exception that ChAT expression is evident in the ON but not OFF layer of the fovea, a region specialized for high-acuity vision. We thus investigated whether the human fovea exhibits a developmental path for ON and OFF ChAT cells that is retinal location-specific. Our analysis shows that at each retinal location, human ON and OFF ChAT cells differentiate, form their separate synaptic layers, and establish non-random mosaics at about the same time. However, unlike in the adult fovea, ChAT immunostaining is initially robust in both ON and OFF populations, up until at least mid-gestation. ChAT expression in the OFF layer in the fovea is therefore significantly reduced after mid-gestation. OFF ChAT cells in the human fovea and in the retinal periphery thus follow distinct maturational paths.

The GABAergic system in the retina of neonate and adult Octodon degus, studied by immunohistochemistry and electroretinography

In the vertebrate retina, gamma-aminobutyric acid (GABA) mediates inhibitory processes that shape the visual response and is also thought to have neurotrophic functions during retinal development. To investigate the role of GABAergic signaling at the beginning of visual experience, we used immunohistochemistry to compare the distribution of GABA, the two isoforms of glutamic acid decarboxylase GAD65/67, and the GABA receptor types A, B, and C, in neonate versus adult Octodon degus, a native South American rodent with diurnal-crepuscular activity and a high cone-to-rod ratio. In parallel, we used electroretinography to evaluate retinal functionality and to test the contribution of fast GABAergic transmission to light responses at both developmental stages. Neonate O. degus opened their eyes on postnatal day (P)0 and displayed an adult-like retinal morphology at this time. GABA, its biosynthetic sources, and receptors had a similar cellular distribution in neonates and adults, but labeling of the outer plexiform layer and of certain amacrine and ganglion cells was more conspicuous at P0. In neonates, retinal sensitivity was 10 times lower than in adults, responses to ultraviolet light could not be detected, and oscillatory potentials were reduced or absent. Blockade of GABA(A/C) receptors by bicuculline and TPMPA had no noticeable effect in neonates, while it significantly altered the electroretinogram response in adults.

CONCLUSION

In spite of modest differences regarding retinal morphology and GABAergic expression, overall light response properties and GABAergic signaling are undeveloped in neonate O. degus compared to adults, suggesting that full retinal functionality requires a period of neural refinement under visual experience.

Expression patterns of calretinin, calbindin and parvalbumin and their colocalization in neurons during development of Macaca monkey retina

The developmental expression of calbindin (CalB), calretinin (CaR) and parvalbumin (PV) was followed in Macaca monkey retina using single and double immunolabeling to identify which proteins provide distinctive labels for specific cell types and to clarify the role of these proteins during development. Ganglion cells (GC) expressed PV at fetal day (Fd)55 and CaR and CalB by Fd85. CaR was downregulated after birth. Separate subsets of amacrine (AM) cells expressed CaR and CalB at Fd65-70. After Fd115, many CaR+ AM coexpressed CalB. After Fd120 a few AM expressed PV and these added CaR and CalB after birth. A subset of horizontal cells (HZ) expressed CaR and CalB at Fd70. Slightly later all HZ express PV and CaR while the early subset is CalB+/PV+/CaR+. CaR downregulates in all HZ after birth. The DB3 cone bipolar cells (BP) under the HZ label for CalB by Fd90-110 while a probable OFF BP cell body just above the AM layer becomes CaR+ near birth with labeling increasing after birth. All cones outside of the fovea label for CalB by Fd125. Foveal cones, rods, most BP and Müller glia do not label for these proteins at any age. The complex patterns of up- and down-regulation found in Macaca retina are similar to previous reports of expression in human retina, but in many instances are quite different than earlier reports of CaR, CalB and PV expression patterns in monkey central visual centers. This makes it highly likely that each protein plays a specific but undetermined role(s) in each visual center, and that its expression is controlled at a given stage of retinal development by multiple intrinsic and extrinsic factors.

Voronoi analysis uncovers relationship between mosaics of normally placed and displaced amacrine cells in the thraira retina

Although neuronal dynamics is to a high extent a function of synapse strength, the spatial distribution of neurons is also known to play an important role, which is evidenced by the topographical organization of the main stations of the visual system: retina, lateral geniculate nucleus, and cortex. The coexisting systems of normally placed and displaced amacrine cells in the vertebrate retina provide interesting examples of retinotopic spatial organization. However, it is not clear whether these two systems are spatially interrelated or not. The current work applies two mathematical-computational methods-a new method involving Voronoi diagrams for local density quantification and a more traditional approach, the Ripley K function-in order to characterize the mosaics of normally placed and displaced amacrine cells in the retina of Hoplias malabaricus and search for possible spatial relationships between these two types of mosaics. The results obtained by the Voronoi local density analysis suggest that the two systems of amacrine cells are spatially interrelated through nearly constant local density ratios.

Calcium-binding protein distribution in the retina of strepsirhine and haplorhine primates

Calcium-binding proteins are involved in numerous functional roles in the retina and are widely distributed in almost all retinal neurons. The present study aimed to characterize the distribution of the calcium-binding proteins calbindin, calretinin, parvalbumin and recoverin in relation to retinal cell types in a strepsirhine primate (mouse lemur, Microcebus) in comparison with primate species of the three main haplorhine lineages (marmoset, macaque and human), as well as a rodent (gerbil, Taterillus). The main findings show that whereas the recoverin antibody labels both rod and cone photoreceptors in all species, calbindin consistently labels cones, but not rods, in the haplorhine primates marmoset, macaque and human, but none of the photoreceptors in the mouse lemur. Marmoset and macaque also show a distinct label of cone outer segments with calretinin. Depending on the species, bipolar cells express calbindin and/or recoverin, while amacrine, horizontal and ganglion cells are labeled to varying degrees with calbindin, calretinin and parvalbumin. Haplorhine and strepsirhine primates clearly differ in the expression of calcium-binding protein expression in horizontal cells. In all haplorhine species, horizontal cells are densely labeled with parvalbumin whereas in mouse lemur horizontal cells express calbindin but not parvalbumin. Several characteristics of the calcium-binding immunostaining in the retina of the mouse lemur are similar to those observed in the rodent, and distinguish this species from the diurnal haphorhine primates. These differences may be related to adaptations of retinal structure and function to the nocturnal niche, since nocturnal strepsirhine and haphorhine (Tarsius and Aotus) primates share some features of calcium-binding expression.

Immunocytochemical development of the guinea pig retina

The aim of the present study was to establish the neurochemical profile of amacrine and horizontal cells during ontogeny in the guinea pig, a precocial species where significant retinal development occurs prenatally as opposed to altricial species where development largely occurs postnatally. The expression of neurochemical markers of horizontal cells and specific amacrine cell populations was investigated from 20 days of gestation (dg, term approximately 67 dg) to adulthood. Amacrine cell populations were identified immunohistochemically using antibodies to gamma-amino-butyric acid, cholineacetyltransferase, calbindin, calretinin, neuronal nitric oxide synthetase and tyrosine hydroxylase; horizontal cells were labelled with calbindin. All markers were present at 30 dg and had attained their mature (adult) laminar distribution and expression by 60 dg. Horizontal cells appeared in their final location at 30 dg with amacrine cell populations appearing in their final locations by 45 dg. Thus, in the guinea pig retina, the amacrine and horizontal cell populations investigated in this study are fully mature prior to birth.

Characterization of calbindin-positive cones in primates

The aim of this study is to characterize calbindin-positive photoreceptors and their opsin content in the retina of nocturnal prosimians (Microcebus murinus), New World monkeys (Callithrix jacchus), Old World monkeys (Macaca fascicularis), and humans. To identify the calbindin and opsin content of cones, combined multiple labeling with different fluorescent probes, antibodies directed against calbindin, short, and mid-long wavelength opsins, and lectin peanut agglutinin cytochemistry were used. With the exception of Microcebus, calbindin is present in the cones of all primates but is absent from rods. The distribution of calbindin is similar in human and macaque cones, with dense label in the inner segment, cell body, axon and cone pedicle. Cones in marmoset also show dense staining in the cell body, axon and pedicle but only light label in the inner segment. Primate cone outer segments do not contain calbindin. In the primates studied, three patterns of calbindin and opsin localization are observed. In macaque and marmoset all short and mid-long wavelength cones contain calbindin. In humans, all mid-long wavelength cones contain calbindin whereas all short wavelength cones are devoid of calbindin as confirmed by confocal microscopy. In the nocturnal prosimian Microcebus none of the mid-long or short wavelength cones contain calbindin. In addition to primates, calbindin is absent in cones of other nocturnal species but is present in cones of diurnal species suggesting a difference in the role of calbindin possibly related to the adaptational states or other photoreceptor properties.

Distribution of the calcium-binding proteins parvalbumin, calbindin D-28k and calretinin in the retina of two teleosts

Using monoclonal antibodies against parvalbumin (PV) and calbindin (CB), and a polyclonal antiserum against calretinin (CR), the expression patterns of these proteins in the retina of the tench and rainbow trout were studied at light microscopic level in in toto preparations and radial sections. Parvalbumin was present in subpopulations of small amacrine cells in both species, but these cells were more abundant and had a clear centre-periphery gradient distribution in the tench. Using the McAB 300 monoclonal antibody against CB, glial cells such as Müller cells, astrocytes in the nerve fibre layer, and sparse large cells close to the entrance of the optic nerve were observed in both species. Moreover, this antibody strongly labelled H1 horizontal cells and their thick axon terminals in the tench retina, whereas only a small population of amacrine cells was stained in the trout. Calretinin was expressed in different types of ganglion cells and numerous neurones located in the inner plexiform layer in both species, but was more abundant and more strongly stained in the trout retina, where some bipolar cells were easily distinguishable. A comparison to current results in other vertebrate species is offered.

Evidence that the bifunctional redox factor / AP endonuclease Ref-1 is an anti-apoptotic protein associated with differentiation in the developing retina

Retinal cell differentiation leads to resistance to apoptosis induced by inhibition of protein synthesis, suggesting the accumulation of anti-apoptotic proteins. The redox factor/AP endonuclease Ref-1 (APE, APEX, HAP1) affects both DNA repair and the activity of various transcription factors, and controls sensitivity to genotoxic insults. We studied the expression of Ref-1 in the retina and brain of developing rats. Ref-1 immunoreactivity increased progressively within the nucleus of differentiating retinal cells, whereas it decreased in the developing hippocampal formation. During both natural and experimentally-induced cell death, Ref-1 disappeared from the nucleus of apoptotic cells. Degradation of Ref-1 in axotomized ganglion cells preceded the morphological characteristics of apoptosis. The sensitivity to apoptosis triggered by either thapsigargin or okadaic acid was the highest in photoreceptors, that contain the least Ref-1 among differentiated retinal cells. In both these differentiated cell types, inhibition of protein synthesis prevented the loss of Ref-1 and rescued the neurons. The data suggest that Ref-1 is an anti-apoptotic protein associated with cell differentiation in the retina.

Spatiotemporal patterns of ontogenetic expression of parvalbumin in the superior colliculi of rats and rabbits

We have examined the development of parvalbumin immunoreactivity in the superior colliculi (SC) of the perinatal and mature rats and rabbits. In mature animals, parvalbumin-expressing cells (PECs) and neuropil in the retinorecipient layers were distributed in a continuous single band extending throughout the entire extent of the colliculus, whereas those in the intermediate layers formed distinct, radially oriented patches. Parvalbumin was expressed for the first time on postconceptional day 34 (PCD 34, postnatal day 12) and PCD 42 (postnatal day 11) in the SC of rat and rabbit, respectively. During ensuing development, both the thickness of the parvalbumin-expressing band in the retinorecipient layers and the numbers of PECs in this band gradually increased, reaching adultlike values by PCD 44 and PCD 50 in the rat and rabbit, respectively. In the rat, monocular eye enucleations on PCD 23 resulted in approximately 55% reduction in the number of PECs in the retinorecipient layers of the contralateral colliculi examined on PCD 44 or PCD 50. Unilateral ablations of the entire visual cortex on PCD 23 (before the first corticotectal fibers from visual cortices reach the SC) or on PCD 28 (when about half of the corticotectal fibers have reached colliculus) resulted in, respectively, approximately 55% and approximately 25% relative reduction in the number of PECs in the retinorecipient layers of the ipsilateral colliculi examined on PCD 44 or PCD 50. We conclude that the ontogenetic expression of parvalbumin in most of PECs in the retinorecipient collicular layers is induced by the activity of the contralateral retinotectal and/or the activity of the ipsilateral corticotectal afferents.

Prenatal development of nicotinamide adenine dinucleotide phosphate-diaphorase activity in the human hippocampal formation

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry was used to study the development of the neurons metabolizing nitric oxide in the prenatal human hippocampal formation. Strongly reactive non-pyramidal neurons appeared in small numbers in the subplate at 15 weeks, and rapidly increased in this layer, as well as the cortical plate-derived layers between 17 and 24 weeks. The marginal zone also had a few NADPH-d cells at 15 weeks. The pattern of these darkly reactive cells stabilized by 28 weeks, with the somata distributed mostly at the border of the cortex and white matter in the entorhinal cortex and subiculum, or the alveus in Ammon's horn. Moderately stained non-pyramidal neurons appeared in the dentate gyrus by 17 weeks, and increased in this region and Ammon's horn up to 28 weeks. Small, lightly reactive non-pyramidal neurons were first seen by 32 weeks and increased in number by term. They were mainly distributed in layers II/III of the entorhinal cortex and stratum pyramidale of the subiculum and Ammon's horn. NADPH-d positive fibers in the marginal zone were mostly thin and developed between 20 and 28 weeks. In other cortical layers, thick processes from the darkly stained NADPH-d neurons appeared first, then fine fibers appeared more numerous, especially after 28 weeks. NADPH-d processes that arose from non-pyramidal cells were frequently apposed to blood vessels, including those in the hippocampal fissure. In addition, NADPH-d reactivity was also present in pyramidal and granule cells, but this staining was most pronounced between 15 and 24 weeks. The results show three types of distinctly stained NADPH-d interneurons in the fetal human hippocampal formation with different developmental courses and morphology. Also, hippocampal principal neurons transiently express NADPH-d at early fetal ages. Our data correlated with other findings suggest that nitric oxide may play a role in neuronal development in the hippocampal formation by modulating neuronal differentiation and maturation, and regulating blood supply.