Ventral Zone Research Articles

Interaction between neuropeptide Y immunoreactive neurons and galanin immunoreactive neurons in the brain of the masu salmon, Oncorhynchus masou

We investigated the immunohistochemical localization of neuropeptide Y (NPY) and galanin (GAL) in the brain of the masu salmon Oncorhynchus masou in order to clarify the interaction between these neuropeptide hormones in the brain. NPY-immunoreactive (ir) cell bodies were observed in the ventral and lateral regions of the ventral telencephalon (Vv and Vl, respectively), and in the dorsolateral midbrain tegmentum. NPY-ir fibers were observed throughout the brain, mainly in the ventral telencephalon, hypothalamus, optic tectum, and midbrain. GAL-ir cell bodies were observed in the nucleus preopticus parvicellularis anterioris (PPa) and the ventral zone of the periventricular hypothalamus (Hv). Both GAL-ir and NPY-ir fibers were observed throughout the brain. Furthermore, we examined the interaction between the NPY neurons and GAL neurons by performing double-staining immunohistochemistry. Some GAL-ir fibers were in close contact with the NPY-ir cell bodies in the Vv and Vl. In addition, some NPY-ir fibers were in close contact with the GAL-ir cell bodies in the PPa and Hv. These findings suggest that reciprocal connections exist between the NPY neurons and GAL neurons in the brain of the masu salmon.

Comparative Lipid Composition Study in Farmed and Wild Blackspot Seabream (Pagellus bogaraveo)

During the latest decades, the fish trade has accorded an increasing attention to aquaculture development as a source of marine food products. In this sense, blackspot seabream (<I>Pagellus bogaraveo</I>) has recently attracted a great commercial interest as a farmed product. This work provides a comparative lipid composition study between wild and farmed individuals. For it, three different edible zones (ventral, dorsal and tail white muscles) were considered. From a nutritional point of view, lipid composition of farmed and wild blackspot seabream showed valuable lipid parameters (total polyunsaturated fatty acids, total ω3/total ω6 fatty acid ratio and α-tocopherol values). Comparison between farmed and wild fishes led to a wide number of differences. Thus, farmed fish muscle showed a higher (<I>P</I> < 0.05) total lipid content than its counterpart wild one. In addition, farmed fish showed higher triglyceride contents but lower (<I>P</I> < 0.05) values in the remaining lipid classes and groups studied (phospholipids, sterols and α-tocopherol). Concerning the fatty acid analysis, farmed fish showed a higher (<I>P</I> < 0.05) monounsaturated fatty acids (ventral and tail zones) content but lower for polyunsaturated fatty acids (ventral and tail zones) and total ω3/ total ω6 ratio. No differences (<I>P</I> > 0.05) were detected between both kinds of fish for the saturated fatty acids proportion. For all parameters studied, both farmed and wild fishes provided very little differences (<I>P</I> < 0.05) among the different muscle zones considered, so that an inhomogeneous distribution in the actual species could not be concluded.

Neuroepithelial cells require fucosylated glycans to guide the migration of vagus motor neuron progenitors in the developing zebrafish hindbrain

The molecular mechanisms by which neurons migrate and accumulate to form the neural layers and nuclei remain unclear. The formation of vagus motor nuclei in zebrafish embryos is an ideal model system in which to address this issue because of the transparency of the embryos and the availability of established genetic and molecular biological techniques. To determine the genes required for the formation of the vagus motor nuclei, we performed N-ethyl-N-nitrosourea-based mutant screening using a zebrafish line that expresses green fluorescent protein in the motor neurons. In wild-type embryos, the vagus motor neuron progenitors are born in the ventral ventricular zone, then migrate tangentially in the dorsolateral direction, forming the nuclei. However, in towhead (twd(rw685)) mutant embryos, the vagus motor neuron progenitors stray medially away from the normal migratory pathway and fail to stop in the right location. The twd(rw685) mutant has a defect in the GDP-mannose 4,6 dehydratase (gmds) gene, which encodes a key enzyme in the fucosylation pathway. Levels of fucosylated glycans were markedly and specifically reduced in twd(rw685) mutant embryos. Cell transplantation analysis revealed that GMDS is not essential in the vagus motor neuron progenitors for correct formation of the vagus motor nuclei, but is required in the neuroepithelial cells that surround the progenitors. Together, these findings suggest that fucosylated glycans expressed in neuroepithelial cells are required to guide the migration of vagus motor neuron progenitors.

Peripheral sensory deafferentation affects olfactory bulb neurogenesis in zebrafish

The potential effects of the removal of olfactory input on adult neurogenesis in the olfactory bulb were examined. Olfactory organs of adult zebrafish were permanently and completely ablated by cautery and animals were exposed to bromodeoxyuridine then examined following short (4-hour) or long (3-week) survival periods. Short survival times allowed analysis of cell proliferation in the olfactory bulb. Long survival times permitted investigation of survival of adult-formed cells. Deafferentation did not immediately affect the dividing cells in the bulb but did affect the number of adult-formed cells, some of which expressed a neuronal marker, present in the bulb 3 weeks later. Thus, afferent removal influenced the fate of newly formed cells by impacting subsequent divisions, maturation, or survival of those cells. One week of deafferentation altered the pattern of cell genesis, with a significant increase in the number of dividing cells located in the olfactory bulb and also in the ventral telencephalic proliferation zone. Sham surgery did not impact either proliferation or survival of adult-formed cells in the olfactory bulb, suggesting that the deafferentation effect is specific. Thus, afferent innervation is necessary for normal cell proliferation and maintenance of the olfactory bulb in adult zebrafish.

The origin and migration of the earliest‐developing sensory neurons in the peripheral nervous system of amphioxus

In amphioxus embryos, the early development of the type 1 sensory neurons was followed by Tlx gene expression and scanning electron microscopy. At the early neurula stage, AmphiTlx transcription is first detectable in a ventral zone of epidermis. In later embryos, expression is also seen in differentiating type 1 receptor cells of the peripheral nervous system, in a few cells in the central nervous system (CNS), and in anterior notochord cells. The type 1 receptors originate from the ventral epidermis by delaminating individually into the subepidermal space, where they can conveniently be visualized because of their strong expression of AmphiTlx. Within the subepidermal space, the apex of each delaminated receptor loses its cilium and microvilli whereas the base of the cell extends lamellate pseudopodia on the surface of the deeper tissues. The pseudopodia become oriented toward the dorsal side of the embryo, the direction of cell migration. After reaching the flanks of the embryo, the receptor cell stops migrating, loses its pseudopodia, and produces an axon that extends to the CNS. As the receptor finishes differentiating, it downregulates Tlx expression and evidently re-inserts its perikaryon into the epidermis. The discussion considers the possible homology of the type 1 receptor neurons of amphioxus with migrating lateral line primordia and hair cells of vertebrates.

CDKL5 Expression Is Modulated during Neuronal Development and Its Subcellular Distribution Is Tightly Regulated by the C-terminal Tail

Mutations in the human X-linked cyclin-dependent kinase-like 5 (CDKL5) gene have been identified in patients with Rett syndrome (RTT), West syndrome, and X-linked infantile spasms, sharing the common feature of mental retardation and early seizures. CDKL5 is a rather uncharacterized kinase, but its involvement in RTT seems to be explained by the fact that it works upstream of MeCP2, the main cause of Rett syndrome. To understand the role of this kinase for nervous system functions and to address if molecular mechanisms are involved in regulating its distribution and activity, we studied the ontogeny of CDKL5 expression in developing mouse brains by immunostaining and Western blotting. The expression profile of CDKL5 was compared with that of MeCP2. The two proteins share a general expression profile in the adult mouse brain, but CDKL5 levels appear to be highly modulated at the regional level. Its expression is strongly induced in early postnatal stages, and in the adult brain CDKL5 is present in mature neurons, but not in astroglia. Interestingly, the presence of CDKL5 in the cell nucleus varies at the regional level of the adult brain and is developmentally regulated. CDKL5 shuttles between the cytoplasm and the nucleus and the C-terminal tail is involved in localizing the protein to the cytoplasm in a mechanism depending on active nuclear export. Accordingly, Rett derivatives containing disease-causing truncations of the C terminus are constitutively nuclear, suggesting that they might act as gain of function mutations in this cellular compartment.

Organization of Projection-Specific Interneurons in the Spinal Cord of the Red-Eared Turtle

Using differential retrograde axonal tracing, we identified motoneurons (MNs) and projection-specific interneuron (IN) classes in lumbar segment D9 of the adult red-eared turtle spinal cord. We characterized the distribution of these neurons in the transverse plane, and estimated their numbers and proportions. Different labeling paradigms allowed us to distinguish ipsilateral INs (IINs) from commissural INs (CINs), and to identify IINs and CINs with either ascending (a) axons, descending (d) axons, or axons that bifurcate to both ascend and descend (ad). Local interneurons with axons shorter than 1 segment in length were not studied. We show that most retrogradely labeled INs are located dorsal to the MNs, in the ventral horn, the intermediate zone and the dorsal horn. IINs predominate in the dorsal horn. CINs are located on average more medially than the IINs in the ventral horn and intermediate zone. Within the IIN and CIN populations, aINs and dINs overlap extensively. The adIINs and adCINs make up only a small fraction of the total number of INs and are scattered throughout much of the respective IIN and CIN domains. The proportions of IINs and CINs are about equal, as are the proportions of aIINs versus dIINs, of aCINs versus dCINs, and of adIINs versus adCINs. The findings are compared to the organization of lumbar spinal INs in other vertebrate species.

A Time and a Place for Nkx2-1 in Interneuron Specification and Migration

The homeobox transcription factor, Nkx2-1, plays multiple roles during forebrain development. Using restricted genetic ablation of Nkx2-1, in this issue of Neuron, Butt et al. show that Nkx2-1 in telencephalic progenitors regulates interneuron subtype specification, while Nóbrega-Pereira et al. demonstrate that postmitotic Nkx2-1 regulates migration and sorting of interneurons to the striatum or cortex by controlling the expression of the guidance receptor, Neuropilin-2.

Visual, lateral line, and auditory ascending pathways to the dorsal telencephalic area through the rostrolateral region of the lateral preglomerular nucleus in cyprinids

Fiber connections of the rostrolateral region of the lateral preglomerular nucleus (PGlr) were studied by tract-tracing methods in carp and goldfish. The PGlr receives fibers from the optic tectum, ventrolateral nucleus of semicircular torus, ventromedial thalamic nucleus, medial pretoral nucleus, anterior tuberal nucleus, subglomerular nucleus, and (unexpectedly) also from the retina. Dendritic morphology of tecto-preglomerular neurons suggests that they receive retinal inputs. The PGlr can be further subdivided into dorsal (PGlr-d) and ventral (PGlr-v) zones, both of which are composed of somata and neuropil layers. Retinal and tectal fibers terminate mostly in the neuropil layer of the PGlr-d with the retinal terminals concentrated medially and tectal terminals laterally. Lateral line toral fibers terminate mainly in a lateral portion and ventromedial thalamic fibers in a medial portion of the somata layer of the PGlr-d. Auditory fibers from the medial pretoral nucleus and anterior tuberal nucleus terminate in the PGlr-v. The central nucleus of the semicircular torus also projects sparse fibers to the PGlr-v. The PGlr projects to the lateral, central, and medial parts of the dorsal telencephalic area, and the latter telencephalic part sends descending fibers to the PGlr. Differential distribution patterns of PGlr-d and PGlr-v fibers are noted within the dorsal telencephalic parts, suggesting that different sensory modalities may be represented in distinct regions at least to a certain degree.

Sex-specific crossover patterns in Zebrafish (Danio rerio)

Some species display intersex variation in their rate of meiotic recombination, where recombination is usually suppressed in the heterogametic sex. Although no heteromorphic sex chromosomes have been detected in zebrafish (Danio rerio), genetic analysis has indicated a lower frequency of recombination in males relative to females. Our study of the meiotic recombination pattern in female zebrafish indicates that adult females have only a few meiotic oocytes that are found in groups in the ventral zone of the ovarian surface. We used antibody staining of human mutL homolog 1 (MLH1) protein to mark the sites of putative chiasmata to seek a physical basis for the pattern of recombination and its relative frequency in both sexes. We report that MLH1 foci are found mostly in distal regions of the synaptonemal complexes (SCs) in males, but tend to be more evenly distributed in females. Our cytological analysis yields a ratio of MLH1 foci per chromosome in males versus females of 1:1.55. This lower level of recombination in males is in general agreement with previously published results from linkage map analysis. However, the similar ratio of MLH1 foci per unit length of SCs in both sexes demonstrates a correlation between SC length and the frequency of recombination rather than a mechanism that suppresses recombination in males. Thus, chiasma interference seems to provide similar expression in males and females in agreement with the situation in humans, where oocytes with longer SCs display a higher level of recombination that is not a consequence of more closely spaced crossovers along the SCs.

Makorin-2 Is a Neurogenesis Inhibitor Downstream of Phosphatidylinositol 3-Kinase/Akt (PI3K/Akt) Signal

Makorin-2 belongs to the makorin RING zinc finger gene family, which encodes putative ribonucleoproteins. Here we cloned the Xenopus makorin-2 (mkrn2) and characterized its function in Xenopus neurogenesis. Forced overexpression of mkrn2 produced tadpoles with dorso-posterior deficiencies and small-head/short-tail phenotype, whereas knockdown of mkrn2 by morpholino antisense oligonucleotides induced double axis in tadpoles. In Xenopus animal cap explant assay, mkrn2 inhibited activin, and retinoic acid induced animal cap neuralization, as evident from the suppression of a pan neural marker, neural cell adhesion molecule. Surprisingly, the anti-neurogenic activity of mkrn2 is independent of the two major neurogenesis signaling cascades, BMP-4 and Wnt8 pathways. Instead, mkrn2 works specifically through the phosphatidylinositol 3-kinase (PI3K) and Akt-mediated neurogenesis pathway. Overexpression of mkrn2 completely abrogated constitutively active PI3K- and Akt-induced, but not dominant negative glycogen synthase kinase-3beta (GSK-3beta)-induced, neural cell adhesion molecule expression, indicating that mkrn2 acts downstream of PI3K and Akt and upstream of GSK-3beta. Moreover, mkrn2 up-regulated the mRNA and protein levels of GSK-3beta. These results revealed for the first time the important role of mkrn2 as a new player in PI3K/Akt-mediated neurogenesis during Xenopus embryonic development.

Targeting Inflammatory Demyelinating Lesions to Sites of Wallerian Degeneration

In Theiler’s murine encephalomyelitis virus (TMEV) infection, an animal model for multiple sclerosis (MS), axonal injury precedes inflammatory demyelinating lesions, and the distribution of axonal damage present during the early phase of infection corresponds to regions where subsequent demyelination occurs during the chronic phase. We hypothesized that axonal damage recruits inflammatory cells to sites of Wallerian degeneration, leading to demyelination. Three weeks after TMEV infection, axonal degeneration was induced in the posterior funiculus of mice by injecting the toxic lectin Ricinus communis agglutinin (RCA) I into the sciatic nerve. Neuropathology was examined 1 week after lectin injection. Control mice, infected with TMEV but receiving no RCA I, had inflammatory demyelinating lesions in the anterior/lateral funiculi. Other control mice that received RCA I alone did not develop inflammatory lesions. In contrast, RCA I injection into TMEV-infected mice induced lesions in the posterior funiculus in addition to the anterior/lateral funiculi. We found no differences in lymphoproliferative responses or antibody titers against TMEV among the groups. This suggests that axonal degeneration contributes to the recruitment of inflammatory cells into the central nervous system by altering the local microenvironment. In this scenario, lesions develop from the axon (inside) to the myelin (outside) (Inside-Out model).

Gastrin-releasing peptide mediates light-like resetting of the suprachiasmatic nucleus circadian pacemaker through cAMP response element-binding protein and Per1 activation.

Circadian rhythmicity in the primary mammalian circadian pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus, is maintained by transcriptional and translational feedback loops among circadian clock genes. Photic resetting of the SCN pacemaker involves induction of the clock genes Period1 (Per1) and Period2 (Per2) and communication among distinct cell populations. Gastrin-releasing peptide (GRP) is localized to the SCN ventral retinorecipient zone, from where it may communicate photic resetting signals within the SCN network. Here, we tested the putative role of GRP as an intra-SCN light signal at the behavioral and cellular levels, and we also tested whether GRP actions are dependent on activation of the cAMP response element-binding protein (CREB) pathway and Per1. In vivo microinjections of GRP to the SCN regions of Per1::green fluorescent protein (GFP) mice during the late night induced Per1::GFP throughout the SCN, including a limited population of arginine vasopressin-immunoreactive (AVP-IR) neurons. Blocking spike-mediated communication with tetrodotoxin did not disrupt overall Per1::GFP induction but did reduce induction within AVP-IR neurons. In vitro GRP application resulted in persistent increases in the spike frequency of Per1::GFP-induced neurons. Blocking endogenous Per1 with antisense oligodeoxynucleotides inhibited GRP-induced increases in spike frequency. Furthermore, inhibition of CREB-mediated gene activation with decoy oligonucleotides blocked GRP-induced phase shifts of PER2::luciferase rhythms in SCN slices. Altogether, these results indicate that GRP communicates phase resetting signals within the SCN network via both spike-dependent and spike-independent mechanisms, and that activation of the CREB pathway and Per1 are key steps in mediating downstream events in GRP resetting of SCN neurons.

Hand transcription factors cooperatively regulate development of the distal midline mesenchyme

Hand proteins are evolutionally conserved basic helix–loop–helix (bHLH) transcription factors implicated in development of neural crest-derived tissues, heart and limb. Hand1 is expressed in the distal (ventral) zone of the branchial arches, whereas the Hand2 expression domain extends ventrolaterally to occupy two-thirds of the mandibular arch. To circumvent the early embryonic lethality of Hand1 or Hand2-null embryos and to examine their roles in neural crest development, we generated mice with neural crest-specific deletion of Hand1 and various combinations of mutant alleles of Hand2. Ablation of Hand1 alone in neural crest cells did not affect embryonic development, however, further removing one Hand2 allele or deleting the ventrolateral branchial arch expression of Hand2 led to a novel phenotype presumably due to impaired growth of the distal midline mesenchyme. Although we failed to detect changes in proliferation or apoptosis between the distal mandibular arch of wild-type and Hand1/Hand2 compound mutants at embryonic day (E)10.5, dysregulation of Pax9, Msx2 and Prx2 was observed in the distal mesenchyme at E12.5. In addition, the inter-dental mesenchyme and distal symphysis of Meckel’s cartilage became hypoplastic, resulting in the formation of a single fused lower incisor within the hypoplastic fused mandible. These findings demonstrate the importance of Hand transcription factors in the transcriptional circuitry of craniofacial and tooth development.

Topography of ganglion cells in the retina of the duck (Anas platyrhynchos var. domesticus)

ABSTRACTThe purpose of this study was to define ganglion cell density, size and topography in the retina of the mallard duck. After killing adult mallard ducks (Anas platyrhynchos var. domesticus), their eyes were removed using pentobarbital (30 mg/kg). The retinas were isolated, whole mount specimens were prepared by staining with 0.1% cresyl violet and then fixing the tissues for study. The retinal ganglion cells were counted, mapped and measured. The mean total number of ganglion cells was estimated at approximately 1.7 × 106 and the retinal area centralis had the highest ganglion cell density with 15 820 cells/mm2. The number of ganglion cell bodies was highest in the temporal area, followed by the nasal, dorsal and ventral areas. Ganglion cell size ranged from 56 to 406 μm2. A population of small ganglion cells persisted into the central area just above the optic disc and the largest soma area was in the ventral zone of the retina. This localization of ganglion cells suggests that the quality of vision is not equal in all the areas of the duck retina and the central part may have the highest vision quality as a function of the retinal ganglion cells.

Role of cooperative cell movements and mechano-geometric constrains in patterning of axial rudiments in Xenopus laevis embryos

The role of cooperative cell movements has been explored in establishment of regular segregation of the marginal zone of Xenopus laevis embryos into the main axial rudiments: notochord, somites and neural tissue. For this purpose, the following operations were performed at the late blastula-early gastrula stages: (1) isolation of marginal zones, (2) addition of the ventral zone fragments to the marginal zones, (3) dissection of isolated marginal zones along either ventral (a) or dorsal (b) midlines, (4) immediate retransplantation of excised fragments of the suprablastoporal area to the same places without rotation or after 90 degrees rotation, (5) pi-shaped separation of the suprablastoporal area either anteriorly or posteriorly. In experiments 1, 4, and 5, lateromedial convergent cell movements and differentiation of the axial rudiments were suppressed. In experiments 4 and 5, cell movements were reoriented ventrally, the entire embryo architecture was extensively reconstructed, and the axial rudiments were relocated to the blastopore lateral lips. In experiment 3, convergent cell movements were restored and oriented either towards the presumptive embryo midline (a), or in the perpendicular direction (b). In both cases, well developed axial rudiments elongated perpendicularly to cell convergences were formed. If the areas of axial rudiment formation were curved, mesodermal somites and neural tissue were always located on the convex (stretched) and concave (compressed) sides, respectively. We conclude that no stable prepatterning of the marginal zone takes place until at least the midgastrula stage. This prepatterning requires cooperative cell movements and associated mechano-geometric constrains.

Sperm nucleomorphogenesis in the cephalopod Sepia officinalis

Sperm nucleomorphogenesis in the cephalopod Sepia officinalis is the product of the interaction between perinuclear microtubules and condensing chromatin. This interaction occurs during spermiogenesis and is established through the nuclear membrane. As in other cephalopod species, the perinuclear microtubules are transient structures. In the case of S. officinalis, they begin to appear in the basal area of the early spermatid and progress from there, establishing contact with the external nuclear membrane and follow a defined, but not symmetric, geometry. Thus, the microtubules accumulate preferentially in one area of the nuclear membrane which we refer to here as the “dorsal zone”. Later, the microtubules will be eliminated before the mature spermatid migrates to the epidydimis. The chromatin is condensed within the nucleus following a complex pattern, beginning as fibro-granular structures until forming fibres of approximately 45 nm diameter (patterning phases). From this stage on, an increase in the chemical basicity of DNA-interacting proteins is produced, and chromatin fibres coalesce together, being recruited to the dorsal zone of the membrane, where there is a higher density of microtubules. This last step (condensation phases) allows the chromatin fibres to be arranged parallel to the axis of the elongating nucleus, and more importantly, is deduced to cause a lateral compression of the nucleus. This lateral compression is in fact a recruitment of the ventral zone toward the dorsal zone, which brings about an important reduction in nuclear volume. The detailed observations which comprise this work complement previous studies of spermiogenesis of Sepia and other cephalopods, and will help to better understand the process of cellular morphology implicated in the evolution of sperm nuclear shape in this taxonomic group.

The secreted EGF-Discoidin factor xDel1 is essential for dorsal development of the Xenopus embryo

We show here that a secreted EGF-Discoidin-domain protein, Xenopus Del1 (xDel1), is an essential factor for dorsal development in the early Xenopus embryo. Knockdown of the xDel1 function causes obvious ventralization of the embryo. Conversely, overexpression of xDel1 expands dorsal-marker expression and suppresses ventral-marker expression in the gastrula embryo. Forced expression of xDel1 dorsalizes ventral marginal zone explants, whereas it weakly induces neural differentiation but not mesodermal differentiation in animal caps. The dorsalizing activity of xDel1 is dependent on the Discoidin domains and not on the RGD motif (which is implicated in its angiogenic activity) or EGF repeats. Luciferase assays show that xDel1 attenuates BMP-signaling reporter activity by interfering with the pathway downstream of the BMP receptor. Thus, xDel1 functions as a unique extracellular regulatory factor of DV patterning in early vertebrate embryogenesis.

Formation of the dorsal marginal zone in Xenopus laevis analyzed by time-lapse microscopic magnetic resonance imaging

The dorsal marginal zone (DMZ) of the amphibian embryo is a key embryonic region involved in body axis organization and neural induction. Using time-lapse microscopic magnetic resonance imaging (MRI), we follow the pregastrula movements that lead to the formation of the DMZ of the stage 10 Xenopus embryo. 2D and 3D MRI time-lapse series reveal that pregastrular movements change the tissue architecture of the DMZ at earlier stages and in a different fashion than previously appreciated. Beginning at stage 9, epiboly of the animal cap moves tissue into the dorsal but not into the ventral marginal zone, resulting in an asymmetry between the dorsal and the ventral sides. Time-lapse imaging of labeled blastomeres shows that the animal cap tissue moves into the superficial DMZ overlying the deeper mesendoderm of the DMZ. The shearing of superficial tissue over the deeper mesendoderm creates the radial/vertical arrangement of ectoderm outside of mesendoderm within the DMZ, which is independent of involution and prior to the formation of the dorsal blastoporal lip. This tilting of the DMZ is distinct from, but occurs synchronously with, the vegetal rotation of the vegetal cell mass [R., Winklbauer, M., Schürfeld (1999). “Vegetal rotation, a new gastrulation movement involved in the internalization of the mesoderm and endoderm in Xenopus.” Development. 126, 3703–3713.]. We present a revised model of gastrulation movements in Xenopus laevis.

Developmental Expression of Transferrin Binding Protein in Oligodendrocyte Lineage Cells of the Embryonic Chick Spinal Cord

Oligodendrocytes develop from precursor cells in the neuroepithelium of the ventral ventricular zone. Oligodendrocytes in the different stages of development are characterized by expression of a number of different marker molecules such as myelin genes, growth factors, and specific antigens. We have previously identified that transferrin binding protein (TfBP), a member of heat shock protein 90 families, is a novel avian ER-associated membrane protein that is specifically localized in oligodendrocytes in adult chicken CNS. In this study we describe the developmental expression of TfBP in the embryonic chick spinal cord. A few, distinct, TfBP+ cells appeared at the lateral margin of the subventricular neuroepithelium of the spinal cord at E7. Thereafter, some TfBP+ cells, exhibited a migrative form of unipolar or bipolar shape occurred around E8 in the mantle layer, midway between the neuroepithelium and the marginal layer of the primitive spinal cord. Thereafter, the TfBP+ cells rapidly increased in number as well as their staining intensity, and overall distribution of TfBP+ cells at E15 was comparable to that of a mature spinal cord. Our observations suggest that TfBP is expressed in the subpopulation of oligodendrocyte lineage in the development and a putative role of TfBP in relation to transferrin and iron trafficking is considered.