The expression of alpha-internexin and peripherin in the developing mouse pineal gland

The mammalian pineal gland contains pinealocytes, interstitial glial cells, perivascular macrophages, neurons and neuron-like cells. The neuronal identity of neurons and neuron-like cells was an enigma. alpha-Internexin and peripherin are specific neuronal intermediate filament proteins and are expressed differentially in the CNS and PNS. We investigated the development of immunoreactivity and expression patterns of mRNAs for alpha-internexin and peripherin in the mouse pineal gland to determine the neuronal identity of these cells. Both alpha-internexin- and peripherin-immunoreactive cells were readily visualized only after birth. Both proteins were at the highest level on the postnatal day 7 (P7), rapidly declined at P14, and obtained their adult level at P21. Both protein and mRNA of alpha-internexin are expressed in some cells and nerve processes, but not all, of adult mouse pineal gland. Less number of peripherin immunoreactive or RNA-expressing cells and nerve processes were identified. Accumulations of alpha-internexin and peripherin proteins were also found in the cells from the aged pineal gland (P360). We concluded that some cells in the developing mouse pineal gland may differentiated into neurons and neuron-like cells expressing both alpha-internexin and/or peripherin only postnatally, and these cells possess dual properties of CNS and PNS neurons in nature. We suggested that they may act as interneurons between the pinealocyte and the distal neurons innervating the pinealocytes, or form a local circuitry with pinealocytes to play a role of paracrine regulatory function on the pinealocytes.

Directional asymmetry of the zebrafish epithalamus guides dorsoventral innervation of the midbrain target

The zebrafish epithalamus, consisting of the pineal complex and flanking dorsal habenular nuclei, provides a valuable model for exploring how left-right differences could arise in the vertebrate brain. The parapineal lies to the left of the pineal and the left habenula is larger, has expanded dense neuropil, and distinct patterns of gene expression from the right habenula. Under the influence of Nodal signaling, positioning of the parapineal sets the direction of habenular asymmetry and thereby determines the left-right origin of habenular projections onto the midbrain target, the interpeduncular nucleus (IPN). In zebrafish with parapineal reversal, neurons from the left habenula project to a more limited ventral IPN region where right habenular axons would normally project. Conversely, efferents from the right habenula adopt a more extensive dorsoventral IPN projection pattern typical of left habenular neurons. Three members of the leftover-related KCTD (potassium channel tetramerization domain containing) gene family are expressed differently by the left and right habenula, in patterns that define asymmetric subnuclei. Molecular asymmetry extends to protein levels in habenular efferents, providing additional evidence that left and right axons terminate within different dorsoventral regions of the midbrain target. Laser-mediated ablation of the parapineal disrupts habenular asymmetry and consequently alters the dorsoventral distribution of innervating axons. The results demonstrate that laterality of the dorsal forebrain influences the formation of midbrain connections and their molecular properties.

Knockdown of cone-specific kinase GRK7 in larval zebrafish leads to impaired cone response recovery and delayed dark adaptation

Phosphorylation of rhodopsin by rhodopsin kinase GRK1 is an important desensitization mechanism in scotopic vision. For cone vision GRK1 is not essential. However, cone opsin is phosphorylated following light stimulation. In cone-dominant animals as well as in humans, but not in rodents, GRK7, a cone-specific homolog of GRK1, has been identified in cone outer segments. To investigate the function of GRK7 in vivo, we cloned two orthologs of grk7 in zebrafish and knocked down gene expression of grk7a in zebrafish larvae by morpholino antisense nucleotides. Photoresponse recovery in Grk7a-deficient larvae was delayed in electroretinographic measurements, and temporal contrast sensitivity was reduced, particularly under bright-light conditions. These results show that function of a cone-specific kinase is essential for cone vision in the zebrafish retina and argue that pigment bleaching and spontaneous decay alone are not sufficient for light adaptation and rapid cone response inactivation.

GABAergic system of the pineal organ of an elasmobranch (Scyliorhinus canicula): a developmental immunocytochemical study

The present immunocytochemical study provides evidence of a previously unrecognized, rich, gamma-aminobutyric acid (GABA)-ergic innervation of the pineal organ in the dogfish (Scyliorhinus canicula). In this elasmobranch, the pineal primordium is initially detected at embryonic stage 24 and grows to form a long pineal tube by stage 28. Glutamic acid decarboxylase (GAD)-immunoreactive (-ir) fibers were first observed at stage 26, and by stage 28, thin GAD-ir fibers were detectable at the base of the pineal neuroepithelium. In pre-hatchling embryos, most fibers gave rise to GAD-ir boutons that were localized in the basal region of the neuroepithelium, although a smaller number of labeled terminals ascended to the pineal lumen. A few pale GAD-ir perikarya were observed within the pineal organ of stage 29 embryos, but GAD-ir perikarya were not observed at other developing stages or in adults. In contrast, GABA immunocytochemistry revealed the presence of GABAergic perikarya and fibers in the pineal organ of late stage embryos and adults. Although high densities of GABAergic cells were observed in the paracommissural pretectum, posterior tubercle, and tegmentum of dogfish embryos (regions previously demonstrated to contain pinealopetal cells), the presence of GABA-ir perikarya in the pineal organ strongly suggests that the rich GABAergic innervation of the elasmobranch pineal organ is intrinsic. This contrasts with the central origin of GABAergic fibers in the pineal gland of some mammals.

Embryonic development of the bovine pineal gland (Bos taurus) during prenatal life (30 to 135 days of gestation)

The ontogenesis of the pineal gland of 30 bovine embryos (Bos taurus) has been analysed from 30 until 135 days of gestation by means of optical microscopy and immunohistochemical techniques. For this study, the specimens were grouped into three stages in accordance with the most relevant histological characteristics: Stage 1 (30 to 64 days of prenatal development); Stage 2 (70 to 90 days) and Stage 3 (106 to 135 days). In the cow, it is from 30 days of gestation that the first glandular outline becomes differentiated from the diencephalic ependyma of the third ventricle. This differentiation includes the phenomena of proliferation and multiplication of the ependymal cells that form the epithelium of the pineal outline in development. At 82 days of intrauterine life, in the interior of the pineal parenchyma, we witnessed some incipient pseudoglandular structures that at 135 days were well differentiated. The pineal parenchyma displays a cytology made up of two cellular types of structurally distinct characteristics: pinealoblasts and interstitial cells. Both cellular types begin differentiation at 70 days of embryonic development, the pinealoblasts being greater in number than the interstitial cells. The glandular stroma is formed from the capsular, trabecular and the perivascular connective tissue, filling the interparenchymal space. A dense network of capillaries, which drive across the trabecular connective tissue towards the central glandular zone where their density increases and their calibre is reduced, complete the glandular structure. GFAP positive cells were observed in the embryonic pineal parenchyma in stage 3. At 135 days of gestation, NPY positive fibers entered the pineal gland through the pineal capsule occupying a perivascular localization. Morphological studies of this nature are vital for future use as parameters, indicative of the functional activity of the bovine pineal gland during embryonic development.

The "third eye"-- a new concept of trans-differentiation of pineal gland into median eye in amphibian tadpoles of Bufo melanostictus

Median third eye was found to develop from transplanted pineal gland of external gill stage tadpoles in the recipient 5 toe stage tadpoles of Bufo melanostictus. Pineal gland along with a bit part of brain tissue of the donor external gill stage tadpole was cut out and transplanted into a pit made between two lateral eyes of 5 toe stage recipient tadpoles. Half of the operated tadpoles were treated with vitamin A (15 IU/ml.) for 15 days. Median "third eye" was found to develop in the both untreated and vitamin A treated tadpoles. However, vitamin A increased the percentage of the development of median eyes. Morphological and histological study revealed that newly transformed median eyes were similar to that of normal functional eyes. A stalk like structure developed which connects the median eye to the brain. The median third eye could not develop when pineal gland of 5 toe stage mature tadpole was transplanted into the tadpole of the same age.

Functional development of the zebrafish pineal gland: light-induced expression of period2 is required for onset of the circadian clock

In zebrafish, the pineal gland is a photoreceptive organ that contains an intrinsic circadian oscillator and exhibits rhythmic arylalkylamine-N-acetyltransferase (zfaanat2) mRNA expression. In the present study, we investigated the role of light and of a clock gene, zperiod2 (zper2), in the development of this rhythm. Analysis of zfaanat2 mRNA expression in the pineal gland of 3-day-old zebrafish embryos after exposure to different photoperiodic regimes indicated that light is required for proper development of the circadian clock-controlled rhythmic expression of zfaanat2, and that a 1-h light pulse is sufficient to initiate this rhythm. Analysis of zper2 mRNA expression in zebrafish embryos exposed to different photoperiodic regimes indicated that zper2 expression is transiently up-regulated by light but is not regulated by the circadian oscillator. To establish the association between light-induced zper2 expression and light-induced clock-controlled zfaanat2 rhythm, zPer2 knock-down experiments were performed. The zfaanat2 mRNA rhythm, induced by a 1-h light pulse, was abolished in zPer2 knock-down embryos. These experiments indicated that light-induced zper2 expression is crucial for establishment of the clock-controlled zfaanat2 rhythm in the zebrafish pineal gland.

Development of the circadian melatonin rhythm and the effect of PACAP on melatonin release in the embryonic chicken pineal gland. An in vitro study

Pituitary adenylate cyclase activating polypeptide (PACAP) has been shown to participate in modulation of circadian rhythm and to stimulate melatonin (MT) secretion in both the rat and chicken pineal glands. In contrast to mammals, the main regulator of circadian rhythm in birds is the pineal gland, which begins its rhythmic MT production already during embryonic life. In the present study, we investigated the development of MT secretion in explanted embryonic chicken pineals and their responsiveness to PACAP in a perifusion system. Our results show that: (1) the circadian clock and/or the intracellular signal transduction system connecting the clock to MT synthesizing apparatus develop between the embryonic days 16-18 (E16-18), even in vitro. (2) Exposure of the embryonic chicken pineal gland to PACAP induces transitory increase in MT secretion but does not induce visible phase shift in the circadian rhythm. (3) Cyclic AMP (cAMP) efflux also responds to PACAP at or before day E13 in embryonic chicken pineal gland in vitro.

Transition from embryonic to adult transcription pattern of serotonin N-acetyltransferase gene in avian pineal gland

The study reports the change of transcription pattern of serotonin N-acetyltransferase gene and melatonin receptor genes during ontogenesis of the avian pineal gland. The RT-PCR technique was used to investigate the expression of the arylalkylamine N-acetyltransferase (AA-NAT) and melatonin receptor genes during development of the pineal glands isolated from Japanese quail (Coturnix coturnix japonica) embryos incubated from 3 days on until hatching (17 days), and in some organs (pineal, brain hemisphere, eye, leg, heart) of the 3-day-old quail embryo. It was shown that two phases of AA-NAT expression are observed during pineal gland development. The first, embryonic-type phase, lasts from the beginning until 7-10 days of incubation, and is marked by the presence of two RT-PCR products for AA-NAT: the shorter mature form without intron (238 bp), and the longer form (323 bp) containing an unprocessed intron of 85 bp. The second, adult-type phase is characterized by the presence of a single mature transcript, containing no intron; it starts from 7 to 10 days of incubation and lasts until hatching and in the adult pineal. The duration of this transition time from the embryonic to the adult transcription pattern in the quail pineal gland from 7 to 10 days of incubation we attribute to asynchronic embryo development, because quail chicks usually hatch between the 16th and 19th day of incubation. Analysis of the AA-NAT protein sequences for chick and quail (GeneBank accession no. U 46 502 and AF 007 068, respectively) revealed their perfect homology with the part of protein read from the sequence present in the adult-type phase of the pineal gland (the RT-PCR product of 238 bp). The presence of the intron (in the 323 bp RT-PCR product, accession no. AY 197 460) in the embryonic-phase of the pineal gland changes the reading frame of the mRNA sequence and the hypothetical resulting protein loses its homology with the chick and quail AA-NAT enzyme starting with 105th amino acid of the complete chick AA-NAT protein comprising 205 amino acids (accession no. U 46 502). In the whole embryos at stages 1-8 (according to the Hamburger-Hamilton classification) both RT-PCR products with and without intron were consistently found, and individual tissues from 3-day-old embryos also produced two AA-NAT products, i.e., the expression was of the embryonic-type. At the time of transition from the embryonic to the adult AA-NAT transcription pattern, in 7-11-day-old embryos, all three melatonin receptor transcripts (mel-1a, mel-1b, and mel-1c) were observed in the pineals, without consistent modifications of the band intensity. In the adult pineal, a single mature AA-NAT transcript was present as well as all three melatonin receptor transcripts, usually with preferential expression of the mel-1a band. The transition time from the embryonic to adult AA-NAT expression pattern coincides well with the acquisition of functional activity and the appearance of melatonin synthesis in the embryonic pineal reported for chicken, as related to quail. We suggest that the change in transcription pattern of the AA-NAT gene may reflect another, still unknown mechanism of regulating AA-NAT activity during ontogenesis, at the level of mRNA processing, whose specificity (or not) for embryonic development we wish to establish in the future.

Parapineal specific expression of gfi1 in the zebrafish epithalamus

We describe the isolation of zebrafish growth factor independent 1 (gfi1) and present an analysis of its pattern of expression during early development. As with its murine homologue, gfi1 expression is detected in the ganglion cells of the neural retina and in developing hair cells of the ear. In keeping with a role in the development of sensory hair cells, gfi1 is also expressed in neuromasts of the anterior and posterior lateral line system. Finally, gfi1 is expressed in the developing epithalamus in the dorsal diencephalon where its transcription is restricted to the parapineal.

The 5' flanking sequence of the human retGC1 gene acquires a photoreceptor cell restricted activity pattern over the course of retinal development

PURPOSE

Specific mutations of the retinal guanylyl cyclase-1 (retGC1) gene have been linked to Leber congenital amaurosis type 1 (LCA1) and cone-rod dystrophies in humans, diseases that are amenable to treatments using molecular based therapies. As a step towards developing a therapeutic transgene for LCA1, we analyzed the cell specific and developmental activity profiles of fragments of the human retGC1 5' flanking region in vivo.

METHODS

We generated self inactivating lentiviral vector constructs carrying three different fragments of the human retGC1 promoter fused to a nuclear localized beta-galactosidase reporter gene (nlacZ). The transgenes were packaged into lentiviral vectors, which were then used to transduce retinal progenitor cells of the developing chick. We monitored the expression of nlacZ in the retina over the course of development and in the retina, brain and pineal gland just prior to hatching.

RESULTS

A 1.8 kb fragment of the retGC1 5' flanking region upstream of Exon 2 was capable of targeting nlacZ expression to photoreceptor cells in vivo and its activity was augmented by the presence of intron 1. We also demonstrated that the cell specific activity of this fragment arises, at least in part, by silencing expression in non-photoreceptor cells during the final stages of retinal development.

CONCLUSIONS

We have identified a human retGC1 promoter fragment that exhibits photoreceptor cell specific activity in vivo. Our results suggest that an element located in the proximal promoter may play a role in silencing expression of this gene in non-photoreceptor cells, thereby by shaping the restricted expression pattern of GC1 in the retina.

Time of origin of the rat pineal gland cells. A bromodeoxyuridine immunohistochemical study

The immunohistochemical detection of bromodeoxyuridine (BrdU) was used to study the time of origin of the cells in the pineal gland of the rat. A study was made involving 17 groups of 4 rats each, administered with a single dose of bromodeoxyuridine (BrdU, 25 mg/kg) in 7 phases of the embryonic period (E15 to E21) and in 10 postnatal phases (between P0 and P30), followed by determination in each rat of the number of visible immune-labeled cells in the pineal gland 60 days after birth. The results show that approximately 60% of the pineal cells underwent the last division(s) prior to differentiation in the prenatal period between E18 and E21. The rest of the pineal cells originated after birth, particularly in the first 5 postnatal days.

Evolution of photosensory pineal organs in new light: the fate of neuroendocrine photoreceptors

Pineal evolution is envisaged as a gradual transformation of pinealocytes (a gradual regression of pinealocyte sensory capacity within a particular cell line), the so-called sensory cell line of the pineal organ. In most non-mammals the pineal organ is a directly photosensory organ, while the pineal organ of mammals (epiphysis cerebri) is a non-sensory neuroendocrine organ under photoperiod control. The phylogenetic transformation of the pineal organ is reflected in the morphology and physiology of the main parenchymal cell type, the pinealocyte. In anamniotes, pinealocytes with retinal cone photoreceptor-like characteristics predominate, whereas in sauropsids so-called rudimentary photoreceptors predominate. These have well-developed secretory characteristics, and have been interpreted as intermediaries between the anamniote pineal photoreceptors and the mammalian non-sensory pinealocytes. We have re-examined the original studies on which the gradual transformation hypothesis of pineal evolution is based, and found that the evidence for this model of pineal evolution is ambiguous. In the light of recent advances in the understanding of neural development mechanisms, we propose a new hypothesis of pineal evolution, in which the old notion 'gradual regression within the sensory cell line' should be replaced with 'changes in fate restriction within the neural lineage of the pineal field'.

Otx2 homeobox gene controls retinal photoreceptor cell fate and pineal gland development

Understanding the molecular mechanisms by which distinct cell fate is determined during organogenesis is a central issue in development and disease. Here, using conditional gene ablation in mice, we show that the transcription factor Otx2 is essential for retinal photoreceptor cell fate determination and development of the pineal gland. Otx2-deficiency converted differentiating photoreceptor cells to amacrine-like neurons and led to a total lack of pinealocytes in the pineal gland. We also found that Otx2 transactivates the cone-rod homeobox gene Crx, which is required for terminal differentiation and maintenance of photoreceptor cells. Furthermore, retroviral gene transfer of Otx2 steers retinal progenitor cells toward becoming photoreceptors. Thus, Otx2 is a key regulatory gene for the cell fate determination of retinal photoreceptor cells. Our results reveal the key molecular steps required for photoreceptor cell-fate determination and pinealocyte development.

Ontogeny of circadian clock gene expression in the pineal and the suprachiasmatic nucleus of chick embryo

Avian circadian rhythms are regulated by a multiple oscillatory system consisting of the pineal, the suprachiasmatic nucleus (SCN) and the eye. In the present study, ontogeny of circadian clock in the pineal and the SCN of chick embryo was examined using Per2 expression as a marker. A daily rhythmicity of Per2 expression was first detectable at embryonic day (ED) 18 in the pineal and at ED 16 in the SCN under light-dark (LD) cycles. The amplitude of the rhythmicity increased during the development. In contrast, little expression was observed during the development in constant darkness. These results suggest that although circadian clock matures by the end of the embryonic life in chicken, LD cycles are required for the expression of the Per2.

Effects of gonadal steroids on pineal morphogenesis and cell differentiation of the embryonic quail studied under cell culture conditions

Receptors for gonadal steroid hormones have been localized in the pineal glands of several vertebrate species. No studies, however, have reported on pineal morphogenesis and cell differentiation following hormonal application in vitro during avian embryonic development. Hormonal regulation of embryonic development is crucial in all vertebrate classes. Although gonadal hormones are known to affect organogenesis in avian embryos and chicks, we wanted to investigate whether gonadal steroids (testosterone and estradiol) have any effect on the morphogenesis and cell differentiation of the avian pineal gland. The steroid hormones had a stimulatory influence on pineal morphogenesis in vitro as evidenced from the radial arrangement of colony-forming cells and the subsequent formation of a follicular-like structure under dispersed-cell culture condition. Administration of testosterone in culture medium significantly promoted the numbers of cells that were positively stained for arginine vasopressin and tyrosine hydroxylase, while estradiol showed only a slight effect. Both of the two steroid hormones significantly decreased the numbers of cells positively stained for serotonin and melatonin. Melatonin released in the culture medium decreased in content within the 24 h following steroid treatment (supported by low immunoreactivity in cultured cells and low level released to the medium). These results clearly suggest active roles of gonadal steroid hormones on embryonic pineal morphogenesis and cell differentiation and its physiological activity as they do in adult animals.

Ash1a and Neurogenin1 function downstream of Floating head to regulate epiphysial neurogenesis

The homeodomain transcription factor Floating head (Flh) is required for the generation of neurones in the zebrafish epiphysis. It regulates expression of two basic helix loop helix (bHLH) transcription factor encoding genes, ash1a (achaete/scute homologue 1a) and neurogenin1 (ngn1), in epiphysial neural progenitors. We show that ash1a and ngn1 function in parallel redundant pathways to regulate neurogenesis downstream of flh. Comparison of the epiphysial phenotypes of flh mutant and of ash1a/ngn1 double morphants reveals that reduced expression of ash1a and ngn1 can account for most of the neurogenesis defects in the flh-mutant epiphysis but also shows that Flh has additional activities. Furthermore, different cell populations show different requirements for ash1a and ngn1 within the epiphysis. These populations do not simply correspond to the two described epiphysial cell types: photoreceptors and projection neurones. These results suggest that the genetic pathways that involve ash1a and ngn1 are common to both neuronal types.

Arterial vascularization of the pineal gland in the fetus of Zavot-bred cattle

This study aimed at revealing arterial vascularization of the pineal gland of the Zavot-bred foetus. Twenty foetuses, regardless of their sex, at the age of 2-7 months were used. Coloured-latex was injected by way of both the right and left common carotid arteries. Then, dissection was performed and vessels nourishing the pineal gland were documented. The pineal gland is vascularized by a number of 2-5 central rami. A small vessel arising from each of the central rami in two foetuses (10%) was shown anastomosing with a branch of the cranial cerebral artery, which advances in cranio-caudal direction in the callosal groove. Hence, anastomoses were observed between several sub-branches of each caudal cerebral and cranial cerebellar arteries.

Development of rhythmic melatonin secretion from the pineal gland of embryonic mummichog (Fundulus heteroclitus)

The pineal gland of vertebrates produces and secretes the hormone melatonin in response to changes in the light-dark cycle, with high production at night and low production during the day. Melatonin is thought to play an important role in synchronizing daily and/or seasonal physiological, behavioral, and developmental rhythms in vertebrates. In this study, the functional development of the pineal melatonin-generating system was examined in the mummichog, Fundulus heteroclitus, an euryhaline teleost. In this species, the pineal gland contains an endogenous oscillator, ultimately responsible for timing the melatonin rhythm. Oocytes from gravid females were collected and fertilized in vitro from sperm collected from mature males. Skull caps containing attached pineal glands were obtained from F. heteroclitus embryos at different embryonic stages and placed in static or perfusion culture under various photoperiodic regimes. Rhythmic melatonin secretion from pineal glands of embryonic F. heteroclitus embryos exposed to a 12L:12D cycle in static culture was observed at five days post-fertilization. The ontogeny of circadian-controlled melatonin production from F. heteroclitus pineal glands exposed to constant darkness for five days was also seen at day five post-fertilization. These data show that early development of the pineal melatonin-generating system in this teleost occurs prior to hatching. Pre-hatching development of the melatonin-generating system may confer some selective advantage in this species in its interactions with the environment.

Developmental expression of zebrafish emx1 during early embryogenesis

Emx family homeobox genes, Emx1 and Emx2, play an essential role in rostral brain development in mammalian embryos. Here we report a zebrafish emx family gene, emx1, which is more similar to the mouse Emx1 gene than the previously reported zebrafish emx1 gene; we propose to rename that gene emx3. The expression of emx1 is first detected around the 10-somite stage in the pineal gland (epiphysis) primodium in the developing anterior brain and in the pronephric primodium within the intermediate mesoderm. emx1 expression in the epiphysis has not been reported in other species. Expression in the epiphysis is suppressed at 23 h post-fertilization (hpf) in the floating head (flh) mutant, in which development of the epiphysis is impaired. Subsequently, emx1 is expressed in the telencephalon, as reported in mammals, and can be detected in the olfactory placode and in a small group of cells in the forebrain at 25 hpf. In the mesoderm, emx1 expression is gradually concentrated in the posterior pronephric duct during somitogenesis, and becomes expressed predominantly in the urogenital opening at 25 hpf. Thus, emx1 displays a unique expression pattern that is distinct from the patterns of emx2 and emx3.

Pineal-specific expression of green fluorescent protein under the control of the serotonin-N-acetyltransferase gene regulatory regions in transgenic zebrafish

Zebrafish serotonin-N-acetyltransferase-2 (zfAANAT-2) mRNA is exclusively expressed in the pineal gland (epiphysis) at the embryonic stage. Here, we have initiated an effort to study the mechanisms underlying tissue-specific expression of this gene. DNA constructs were prepared in which green fluorescent protein (GFP) is driven by regulatory regions of the zfAANAT-2 gene. In vivo transient expression analysis in zebrafish embryos indicated that in addition to the 5'-flanking region, a regulatory sequence in the 3'-flanking region is required for pineal-specific expression. This finding led to an effort to produce transgenic lines expressing GFP under the control of the 5' and 3' regulatory regions of the zfAANAT-2 gene. Embryos transiently expressing GFP were raised to maturity and tested for germ cell transmission of the transgene. Three transgenic lines were produced in which GFP fluorescence in the pineal was detected starting 1 to 2 days after fertilization. One line was crossed with mindbomb and floating head mutants that cause abnormal development of the pineal and an elevation or reduction of zfAANAT-2 mRNA levels, respectively. Homozygous mutant transgenic embryos exhibited similar effects on GFP expression in the pineal gland. These observations indicate that the transgenic lines described here will be useful in studying the development of the pineal gland and the mechanisms that determine pineal-specific gene expression in the zebrafish. Published 2002 Wiley-Liss, Inc.

Role of tissue interaction between pineal primordium and neighboring tissues in avian pineal morphogenesis studied by intraocular transplantation

Tissue interactions play an essential role in organogenesis during embryonic development. However, virtually no attempts have been made to study the role of tissue interaction in pineal development. In the present study we examined the inductive role of the epidermis and mesenchyme in the morphogenesis of quail pineal glands. The pineal rudiment is first observed at embryonic day 2 (E2: 2 days of incubation) at the dorsal midline of the diencephalon as a short semi-spherical protrusion. Electron microscopic observations revealed that no mesenchymal cells are found between the epidermis and the distal end of the E2 pineal primordium but that a thin layer of mesenchymal cells separate the epidermis from the pineal primordium at E3. Small pieces containing pineal rudiment were cut off from E2 or E3 embryos. They were treated with enzymes to eliminate the epidermis and/or mesenchyme, grafted into E5 chicken eyes, and cultured there for 1 week. When E3 pineal rudiment was treated with Dispase to remove the epidermis, the pineal gland developed normally. When the rudiment was further treated with collagenase to remove the surrounding mesenchymal cells, a multi-follicular structure was still formed, but to a lesser extent than when rudiments were treated with Dispase alone. When E2 quail pineal rudiment with the epidermis was grafted without any treatment, a multi-follicular structure developed which morphologically resembled embryonic pineal organs. When the epidermis was removed from E2 rudiments by Dispase, a single large vesicular structure was formed. These results suggest that the overlying epidermis and/or mesenchymal cells play some inductive role in the initial pineal development, while the mesenchymal tissue plays an important role in pineal follicular formation later during development. Since only a few experimental studies have been done to examine pineal morphogenesis, the present study provides fundamental insights into avian pineal development.

Morphometric analysis of photoreceptive, neuronal and endocrinal cell differentiation of avian pineal cells: an in vitro immunohistochemical study on the developmental transition from neuronal to photo-endocrinal property

Little is known about the developmental origin, determination and differentiation of different pineal immunoreactive cells in the avian group, and an experimental establishment is then required to explain the differentiation of cell types (i.e. photosensory, neural and secretory types). The present in vitro study suggests that the avian pineal organ is made up of multiple types of cells with different immunoreactivity at the ontogenic state (from embryonic day 9 to day 14), before it acquires the final photoendocrinal nature of the mature state. The morphometric analysis suggests that the developmental changes in the morphology of the quail pinealocytes appear to represent a condensed expression of the phylogenic development in the ontogeny. Several types of immunoreactive cells from a neuronal line were suppressed with maturation of developing pineal glands, while other cell types such as photoreceptive and endocrinal lines became more prominent. The melatonin level in the culture medium presented a high value up to 72 hr of culture, followed by a decrease as well as dampening of the level at the end of the culture possibly because the cultures were maintained in dark. The results of the present study, a combined analysis of morphometry and RIA, open a new line for research into the pineal development and cell differentiation.

Ultrastructural and immunocytochemical characterization of interstitial cells in pre- and postnatal developing sheep pineal gland

Pineal gland interstitial cells from 32 sheep embryos (from day 54 of gestation until birth) and 18 sheep (from 1 month to >2 years) were analysed using ultrastructural and immunohistochemical techniques. From day 98 of gestation and throughout postnatal development, a second cell type was observed in addition to pinealocytes; these cells displayed uniform ultrastructural features similar to those of CNS astrocytes. Ultrastructural homogeneity was not matched by the results of histochemical and immunohistochemical analysis. Expression of phosphotungstic acid hematoxylin, glial fibrillary acidic protein and vimentin indicates that the second cell population in the developing ovine pineal gland is, in fact, a combination of glial-astrocyte cells at varying stages of maturity. Pineal interstitial cells started to show signs of functional activity evident in vascular tropism; such activity, evident from around day 98 of gestation, appeared to relate to the exchange of substances between the pineal parenchyma and blood vessels and, though it continued throughout postnatal development, was most evident in animals slaughtered between 9 months and 2 years of age (group II). Morphologically, functional activity in interstitial cells in this age-group was apparent in: 1, formation of specific contact sites between interstitial cells and nerve fibres in the perivascular space; and 2, the presence of numerous gap junctions between the bulbous endings of cytoplasmic processes.

CNTF is specifically expressed in developing rat pineal gland and eyes

Ciliary neurotrophic factor (CNTF) attracts considerable attention because it supports survival and differentiation of various types of neurons and glial cells in vitro. Although CNTF functions as a moderate neurotrophic factor in mature motor neurons, its role in embryonic development remains unknown. Here, we found a specific CNTF expression in the rat pineal gland and eyes during embryonic development. In vitro, neonatal rat pineal extract including CNTF supported the survival of neonatal sympathetic neurons, which innervate pineal glands immediately after birth.