Neural Ganglia Transcriptome and Peptidome Associated with Sexual Maturation in Female Pacific Abalone (Haliotis discus hannai)

Genetic information of reproduction and growth is essential for sustainable molluscan fisheries and aquaculture management. However, there is limited knowledge regarding the reproductive activity of the commercially important Pacific abalone Haliotisdiscushannai. We performed de novo transcriptome sequencing of the ganglia in sexually immature and mature female Pacific abalone to better understand the sexual maturation process and the underlying molecular mechanisms. Of the ~305 million high-quality clean reads, 76,684 transcripts were de novo-assembled with an average length of 741 bp, 28.54% of which were annotated and classified according to Gene Ontology terms. There were 256 differentially expressed genes between the immature and mature abalone. Tandem mass spectrometry analysis, as compared to the predicted-peptide database of abalone ganglia transcriptome unigenes, identified 42 neuropeptide precursors, including 29 validated by peptidomic analyses. Label-free quantification revealed differential occurrences of 18 neuropeptide families between immature and mature abalone, including achatin, FMRFamide, crustacean cardioactive peptide, and pedal peptide A and B that were significantly more frequent at the mature stage. These results represent the first significant contribution to both maturation-related transcriptomic and peptidomic resources of the Pacific abalone ganglia and provide insight into the roles of various neuropeptides in reproductive regulation in marine gastropods.

Molecular cloning and functional expression of the 5-HT7 receptor in Chinese mitten crab (Eriocheir sinensis)

Serotonin (5-HT) regulates numerous physiological functions and processes, such as light adaptation, food intake and ovarian maturation, and plays the role through 5-HT receptors. To our knowledge, this is the first study to isolate and characterize the serotonin receptor 7 (5-HT₇ receptor) cDNA encoded in Eriocheir sinensis, an economically important aquaculture species in China, by performing rapid-amplification of cDNA ends. The full-length of 5-HT₇ receptor gene cDNA is 2328 bp and encodes a polypeptide with 590 amino acids that are highly homologous with other crustaceans 5-HT₇ receptor genes. Analysis of the deduced amino acid sequence of the 5-HT₇, including 7 transmembrane domains and some common features of G protein-coupled receptors (GPCRs), indicated that 5-HT₇ receptor was a member of GPCRs family. A gene expression analysis of the 5-HT₇ receptor by RT-PCR revealed that the 5-HT₇ receptor transcripts were widely distributed in various tissues, in which high expression levels were observed in the cranial ganglia, thoracic ganglia and intestines. Further study about the effects of photoperiods on the 5-HT₇ expression in the tissues showed that a significantly increasing expression of the 5-HT₇ receptor was observed in the thoracic ganglia induced by constant light. In addition, in the eyestalks, the expression levels of 5-HT₇ mRNA in constant darkness and constant light were lower than control treatment. Then, the expression levels of the 5-HT₇ receptor in three feeding statuses displayed that there were significantly increasing expressions in the hepatopancreas and intestines after feeding, compared with before feeding and during the feeding period. Finally, the 5-HT₇ mRNA expression levels in stage III and stage IV were higher than the levels in stage I of ovarian development. Our experimental results showed that the 5-HT₇ receptor structurally belongs to GPCRs, and the thoracic ganglia and eyestalks are the important tissues of the 5-HT₇ receptor for light adaptation. The 5-HT₇ receptor may also be involved in the physiological regulation of the hepatopancreas and intestines after ingestion in E. sinensis. In addition, the 5-HT₇ receptor is involved in the process of ovarian maturation. The study provided a foundation for further research of light adaptation, digestive functions and ovarian maturation of the 5-HT₇ receptor in Decapoda.

The allometry of the central nervous system during the postembryonic development of the spider Eratigena atrica

During ontogenesis, the size of a spider body, tissues and organs increases dramatically. The aim of the study was to estimate changes in the central nervous system of postembryonic stages of Eratigena atrica and compare them with the literature data on species differing in behavioural traits. Allometric analysis involved evaluation of histological slides embedded in paraffin and stained with hematoxylin and eosin. The reduced major axis regression (RMA) was applied to find allometric relationships between the volumes of the particular parts of the body. All the measured parts of the central nervous system (CNS) were negatively allometrically related to the volume of the prosoma, showing that the increment of the CNS was lower than that of the entire body. The growth of the brain was negatively allometrically related to the growth of the CNS but the increment of the subesophageal ganglion was greater than that of the CNS, exhibiting a positive allometry. Within both these structures, the increase in neuropil volume was greater than the growth of the cortex (cell body rind). Thus, in postembryonic development, the share of the subesophageal ganglion and neuropil in the total volume of the CNS increased, whereas that of the brain and cortex decreased. The mode of the CNS development in E. atrica is similar to that observed in other arthropods, including Argiope aurantia, a spider of different ecology and behaviour.

Prediction of a neuropeptidome for the eyestalk ganglia of the lobster Homarus americanus using a tissue-specific de novo assembled transcriptome

In silico transcriptome mining is a powerful tool for crustacean peptidome prediction. Using homology-based BLAST searches and a simple bioinformatics workflow, large peptidomes have recently been predicted for a variety of crustaceans, including the lobster, Homarus americanus. Interestingly, no in silico studies have been conducted on the eyestalk ganglia (lamina ganglionaris, medulla externa, medulla interna and medulla terminalis) of the lobster, although the eyestalk is the location of a major neuroendocrine complex, i.e., the X-organ-sinus gland system. Here, an H. americanus eyestalk ganglia-specific transcriptome was produced using the de novo assembler Trinity. This transcriptome was generated from 130,973,220 Illumina reads and consists of 147,542 unique contigs. Eighty-nine neuropeptide-encoding transcripts were identified from this dataset, allowing for the deduction of 62 distinct pre/preprohormones. Two hundred sixty-two neuropeptides were predicted from this set of precursors; the peptides include members of the adipokinetic hormone-corazonin-like peptide, allatostatin A, allatostatin B, allatostatin C, bursicon α, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone (CHH), CHH precursor-related peptide, diuretic hormone 31, diuretic hormone 44, eclosion hormone, elevenin, FMRFamide-like peptide, glycoprotein hormone α2, glycoprotein hormone β5, GSEFLamide, intocin, leucokinin, molt-inhibiting hormone, myosuppressin, neuroparsin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, pyrokinin, red pigment concentrating hormone, RYamide, short neuropeptide F, SIFamide, sulfakinin, tachykinin-related peptide and trissin families. The predicted peptides expand the H. americanus eyestalk ganglia neuropeptidome approximately 7-fold, and include 78 peptides new to the lobster. The transcriptome and predicted neuropeptidome described here provide new resources for investigating peptidergic signaling within/from the lobster eyestalk ganglia.

Development of Calbindin- and Calretinin-Immunopositive Neurons in the Enteric Ganglia of Rats

Calbindin D28 K (CB) and calretinin (CR) are the members of the EF-hand family of calcium-binding proteins that are expressed in neurons and nerve fibers of the enteric nervous system. CB and CR are expressed differentially in neuronal subpopulations throughout the central and peripheral nervous systems and their expression has been used to selectively target specific cell types and isolate neuronal networks. The present study presents an immunohistochemical analysis of CB and CR in the enteric ganglia of small intestine in rats of different ages (newborn, 10-day-old, 20-day-old, 30-day-old, 60-day-old, 1-year-old, and 2-year-old). The data obtained suggest a number of age-dependent changes in CB and CR expression in the myenteric and submucous plexuses. In the myenteric plexus, the lowest percentage of CB-immunoreactive (IR) and CR-IR neurons was observed at birth, after which the number of IR cells increased in the first 10 days of life. In the submucous plexus, CB-IR and CR-IR neurons were observed from 10-day-old onwards. The percentage of CR-IR and CB-IR neurons increased in the first 2 months and in the first 20 days, respectively. In all animals, the majority of the IR neurons colocalized CR and CB. From the moment of birth, the mean of the cross-sectional area of the CB-IR and CR-IR neuronal profiles was larger than that of CB- and CR-negative cells.

Crustacean hyperglycemic hormones of two cold water crab species, Chionoecetes opilio and C. japonicus: isolation of cDNA sequences and localization of CHH neuropeptide in eyestalk ganglia

Crustacean hyperglycemic hormone (CHH) is primarily known for its prototypical function in hyperglycemia which is induced by the release of CHH. The CHH release takes place as an adaptive response to the energy demands of the animals experiencing stressful environmental, physiological or behavioral conditions. Although >63 decapod CHH nucleotide sequences are known (GenBank), the majority of them is garnered from the species inhabiting shallow and warm water. In order to understand the adaptive role of CHH in Chionoecetes opilio and Chionoecetes japonicus inhabiting deep water environments, we first aimed for the isolation of the full-length cDNA sequence of CHH from the eyestalk ganglia of C. opilio (ChoCHH) and C. japonicus (ChjCHH) using degenerate PCR and 5' and 3' RACE. Cho- and ChjCHH cDNA sequences are identical in 5' UTR and ORF with 100% sequence identity of the putative 138aa of preproCHHs. The length of 3' UTR ChjCHH cDNA sequence is 39 nucleotides shorter than that of ChoCHH. This is the first report in decapod crustaceans that two different species have the identical sequence of CHH. ChoCHH expression increases during embryogenesis of C. opilio and is significantly higher in adult males and females. C. japonicus males have slightly higher ChjCHH expression than C. opilio males, but no statistical difference. In both species, the immunostaining intensity of CHH is stronger in the sinus gland than that of X-organ cells. Future studies will enable us to gain better understanding of the comparative metabolic physiology and endocrinology of cold, deep water species of Chionoecetes spp.

Ex vivo neurogenesis within enteric ganglia occurs in a PTEN dependent manner

A population of multipotent stem cells capable of differentiating into neurons and glia has been isolated from adult intestine in humans and rodents. While these cells may provide a pool of stem cells for neurogenesis in the enteric nervous system (ENS), such a function has been difficult to demonstrate in vivo. An extensive study by Joseph et al. involving 108 rats and 51 mice submitted to various insults demonstrated neuronal uptake of thymidine analog BrdU in only 1 rat. Here we introduce a novel approach to study neurogenesis in the ENS using an ex vivo organotypic tissue culturing system. Culturing longitudinal muscle and myenteric plexus tissue, we show that the enteric nervous system has tremendous replicative capacity with the majority of neural crest cells demonstrating EdU uptake by 48 hours. EdU⁺ cells express both neuronal and glial markers. Proliferation appears dependent on the PTEN/PI3K/Akt pathway with decreased PTEN mRNA expression and increased PTEN phosphorylation (inactivation) corresponding to increased Akt activity and proliferation. Inhibition of PTEN with bpV(phen) augments proliferation while LY294002, a PI3K inhibitor, blocks it. These data suggest that the ENS is capable of neurogenesis in a PTEN dependent manner.

Postnatal development of the mucosal plexus in the porcine small and large intestine

Knowledge regarding the foetal and postnatal development of the enteric nervous system is crucial for the understanding of congenital disorders. While lot of information exists regarding the myenteric and submucosal plexuses, the development of the mucosal plexus has not been previously studied. The mucosal innervation seems to play an important role in the local reflex activity of the gut. In this study, we examined the development of enteric mucosal innervation in the pig at various ages of life. Small and large bowel paraffin-embedded specimens were stained with PGP 9.5 and neurofilament protein in three piglets from six age groups (60 and 90 days gestation, newborn, 4 and 12 weeks old, and adult pigs). Small and large bowel demonstrated identical innervation patterns. Myenteric and submucosal plexuses were stained with PGP 9.5 at 60 days gestation. However, the mucosal staining was first noted clearly at the newborn period. By 4 weeks, PGP 9.5 staining was noted in small amounts within the mucosa. Inner proprial and villous fibres were seen ahead in time to the subepithelial fibres. Both inner proprial and villous staining became quiet prominent by 12 weeks of age and remained unchanged into adulthood. However, the subepithelial fibres appear to increase in adulthood. This study demonstrates for the first time that enteric mucosal innervation first appears only at birth. The immaturity of the mucosa generated reflex activity, and secretory functions may have implication in the management of functional intestinal obstruction in the premature infant.

Homology of arthropod anterior appendages revealed by Hox gene expression in a sea spider

Arthropod head segments offer a paradigm for understanding the diversification of form during evolution, as a variety of morphologically diverse appendages have arisen from them. There has been long-running controversy, however, concerning which head appendages are homologous among arthropods, and from which ancestral arrangement they have been derived. This controversy has recently been rekindled by the proposition that the probable ancestral arrangement, with appendages on the first head segment, has not been lost in all extant arthropods as previously thought, but has been retained in the pycnogonids, or sea spiders. This proposal was based on the neuroanatomical analysis of larvae from the sea spider Anoplodactylus sp., and suggested that the most anterior pair of appendages, the chelifores, are innervated from the first part of the brain, the protocerebrum. Our examination of Hox gene expression in another sea spider, Endeis spinosa, refutes this hypothesis. The anterior boundaries of Hox gene expression domains place the chelifore appendages as clearly belonging to the second head segment, innervated from the second part of the brain, the deutocerebrum. The deutocerebrum must have been secondarily displaced towards the protocerebrum in pycnogonid ancestors. As anterior-most appendages are also deutocerebral in the other two arthropod groups, the Euchelicerata and the Mandibulata, we conclude that the protocerebral appendages have been lost in all extant arthropods.

Biotinidase reveals the morphogenetic sequence in cochlea and cochlear nucleus of mice

Hearing loss affects children with biotinidase deficiency, an inherited metabolic disorder in the recycling of biotin. The deficit appears shortly after birth during development of the auditory system. Using a mouse model, we sought to discover where and when biotinidase is expressed in the normal development of the cochlea and cochlear nucleus. In the process, we reconstructed the normal morphogenetic sequences of the constituent cells. Immunolabeling for biotinidase was localized to neurons and other cells of the adult and immature mouse, including the embryonic precursors of these regions dating from the stage of the otocyst. Its distribution was compared to the particular morphological changes occurring at each developmental stage. Biotinidase was localized in cells and their processes at the critical stages in their proliferation, migration, structural differentiation, and innervation, covering the entire span of their development. The prevalence of immunostaining peaked in the adult animal, including hair cells and ganglion cells of the cochlea and neurons of the cochlear nucleus. The findings suggest that biotinidase plays a role in the normal development of the auditory system. Besides the pattern of localization of biotinidase, this study provides the first systematic account of each developmental stage in a mammalian auditory system.

Regional differences in nitrergic neuronal density in the developing porcine urinary bladder

Nitric oxide (NO) is involved in normal bladder physiology by regulating local arteriolar tone and smooth muscle relaxation and modulating the production of extracellular matrix proteins in vitro. Little information is available regarding the nitrergic innervation of the bladder during development. In this study we investigated the changes in density and morphology of the intramural nitrergic neurons of the porcine urinary bladder during development using whole-mount preparation. Bladder specimens were obtained from porcine foetuses of gestational age 60 days (n=5) and 90 days (n=5) and from newborn piglets (n=5) after perfusion fixation. Bladders were divided into base, body, and dome. Whole-mount preparation using NADPH-diaphorase (NADPH-d) histochemistry was used to visualize nitrergic innervation of the urinary bladders and to measure density of NADPH-positive ganglia (including single neurons), number of NADPH-d positive neurons per ganglion, and size of individual neurons. One-way ANOVA and chi-square tests were used for statistical analysis with a p-value <0.05 considered statistically significant. NADPH-d positive ganglia were numerous in the muscular layer of all three age groups. At E60, ganglion density was significantly higher in the body (mean 880/cm(2)) than in the dome (397/cm(2)) or the base (676/cm(2)). The ganglion density significantly decreased with age. The number of NADPH-d positive neurons per ganglion increased significantly between E90 and birth (p<0.01). A marked increase in the size of individual neurons over time was also seen (p<0.001), predominantly due to an increase in cytoplasm. Our data on whole-mount preparations demonstrate that significant maturation in nitrergic neuronal density and morphology occurs in the porcine urinary bladder, at least until birth.

Blocked MAP kinase activity selectively enhances neurotrophic growth responses

Bone morphogenetic proteins (BMPs) 4 and 6 as well as MEK inhibitors PD98059 and U0126 potentiate neurotrophin 3 (NT3)- and neurturin (NTN)-induced neurite outgrowth and survival of peripheral neurons from the E9 chicken embryo. Preexposure to BMP4 or PD98059 was sufficient to prime the potentiation of subsequently added NT3. Phosphorylation of Erk2, induced by NT3, was reduced by MEK inhibition but unaffected by BMP signaling. Real-time PCR showed that neither BMP stimulation nor MEK inhibition increased Trk receptor expression and that the BMP-induced genes Smad6 and Id1 were not upregulated by PD98059. In contrast, both MEK inhibition and BMP signaling suppressed transcription of the serum-response element (SRE)-driven Egr1 gene. A reporter assay using NGF-stimulated PC12 cells demonstrated that MEK/Erk/Elk-driven transcriptional activity was inhibited by Smad1/5 and by PD98059. Thus, suppression of SRE-controlled transcription represents a likely convergence point for pathways regulating neurotrophic responses.

[Age-dependent changes of morphometric and histochemical characteristics of neurocytes in different ganglia of albino rats]

The aim of this study was to obtain the normative data on the age-dependent transformation of morphometric and histochemical characteristics of neurocytes in different ganglia in albino rats. Cell cross-sectional area, activities of cholinesterase (demonstrated with thioacetic acid method) monoamine oxidase (demonstrated with Glenner method) were measured in neurocytes of stellate, spinal, trigeminal and gastric ganglia in rats aged 2 to 360 days. Measurements were made with the help of "Bioscan" videoanalyzer. Informational analysis was used for the evaluation of the degree of maturation of neurocyte systems. General features, age- and organ-related peculiarities of morphometric and enzyme-histochemical characteristics were established for neurocytes of different ganglia, as well as a heterochronism of their definitive state attainment. The time of stabilization for neurocytes of stellate and I thoracic spinal ganglia was the age of 60 days, for those of trigeminal ganglion and intramural gastric ganglia -90 and 120 days, respectively. By this time, neurocyte systems turned from a determined state into a probabilistic-determined one, this transformation being considered as a population stabilization.

Dlx2 progenitor migration in wild type and Nkx2.1 mutant telencephalon

The transcription factor Dlx2 is expressed widely throughout the ventral telencephalon. We have examined the in vitro and in vivo migration of Dlx2 progenitors originating from the different ganglionic eminences of both wild type and Nkx2.1 mutant animals. By examining the expression of tauLacZ targeted into the Dlx2 locus we were able to visualize the distribution of cells expressing this gene at both embryonic and postnatal stages. This analysis suggested that Dlx2-expressing cells traverse a number of characteristic migratory routes to populate both cortical and subcortical regions. We also examined how these patterns of migration were affected in Nkx2.1 mutant animals. In these mutants, the early but not late populations of Dlx2-expressing cells originating in the ventral telencephalon that migrate to the cortex are lost. This recovery may be, at least in part, a result of the late migration of Dlx2 progenitors from the caudal ganglionic eminences (CGE), which, based on our previous work, does not appear to require Nkx2.1 gene function.

Turning teratocarcinoma cells into neurons: rapid differentiation of NT-2 cells in floating spheres

Cells from the human teratocarcinoma line NTera-2 can be induced to terminally differentiate into postmitotic neurons when treated with retinoic acid. However, this differentiation process is rather time consuming as it takes between 42 and 54 days. Here, we propose a modified differentiation protocol which reduces the time needed for differentiation considerably without compromising the quantity of the neurons obtained. The introduction of a proliferation step as free floating cell spheres cuts the total time needed to obtain high yields of purified NT-2 neurons to about 24-28 days. The cells obtained show neuronal morphology and migrate to form ganglion-like cell conglomerates. Differentiated cells express neuronal polarity markers such as the cytoskeleton associated proteins MAP2 and Tau. Moreover, the generation of neurons in sphere cultures induced immunoreactivity to the ELAV-like neuronal RNA-binding proteins HuC/D, which have been implicated in mechanisms of nerve cell differentiation.

Hypobranchial placodes in Xenopus laevis give rise to hypobranchial ganglia, a novel type of cranial ganglia

Recently, a novel type of neurogenic placode was described in anurans. These hypobranchial placodes were recognized as ectodermal thickenings situated ventral to the second and third pharyngeal pouch that give rise to neurons of unknown fate. Here, the development of hypobranchial placodes in Xenopus laevis is described in more detail using in situ hybridization and immunohistochemistry for various placodal ( Six1, Eya1) and neurogenic ( NGNR-1, NeuroD, Delta-1, Hu, acetylated tubulin) markers. Moreover, the fate of hypobranchial placodes was determined by analyzing tadpoles that had received orthotopic grafts of ventral branchial arch ectoderm at embryonic stages from donor embryos injected with the lineage tracer green fluorescent protein. The neurogenic epibranchial and hypobranchial placodes are shown to develop in certain subregions of a broader branchial placodal area as defined by Six1 and Eya1 expression, viz., adjacent to the dorsal and ventral tip of the pharyngeal pouches, respectively. Grafting experiments show that each of the two hypobranchial placodes gives rise to a small and previously undescribed hypobranchial ganglion (identified by its immunoreactivity for the neuron-specific Hu protein) of unknown function located in the ventral branchial arch region. No contributions of hypobranchial placodes to any other ganglia (including cardiac ganglia and the ganglia of branchiomeric nerves located dorsal to pharyngeal pouches) were found.

Expression of the mouse Macf2 gene during inner ear development

Plakins, a family of linker proteins that connect cytoskeletal elements to cellular junctions and the extracellular matrix, are primarily responsible for the mechanical properties of cells and tissues. They include desmoplakin, envoplakin, plectin, dystonin/BPAG1, and Kakapo. Mutations in plakins cause several skin, muscular and neurological disorders. Macrophins are a recently discovered subfamily of plakins with binding domains for actin, intermediate filaments and microtubules. Characteristic features of macrophins include variable actin binding domains, a central rod domain containing both plectin and spectrin repeats, and a C-terminus containing EF hands and GAS2/GAR22 domain. We have examined expression of mouse Macf2, encoding macrophin-2, in adult tissues and in the developing, neonatal, and mature inner ear by in situ hybridization. Northern blot analysis identified three large tissue-specific Macf2 transcripts: a 16-kb mRNA in skeletal muscle and heart, a 15-kb mRNA in brain, and a 9-kb mRNA in RNA from ovary plus uterus. In situ hybridization of the developing mouse inner ear indicated that Macf2 is expressed in the otocyst at day 12.5, in the sensory epithelium by embryonic day 16.5, and in both inner and outer hair cells by day 16.5. Macf2 is expressed in the bodies of both sensory and motor neurons in the central and peripheral nervous system, including the auditory pathway. The Macf2 protein could be involved in the regulation of cytoskeletal connections to cellular junctions and play an important structural role in organs, such as the inner ear, that are subjected to strong mechanical forces.

Cochlear abnormalities in insulin-like growth factor-1 mouse mutants

Insulin-like growth factor 1 (IGF-1) modulates inner ear cell proliferation, differentiation and survival in culture. Its function in human hearing was first evidenced by a report of a boy with a homozygous deletion of the Igf-1 gene, who showed severe sensorineural deafness [Woods et al., New Engl. J. Med. 335 (1996) 1363-1367]. To better understand the in vivo role of IGF-1 during inner ear differentiation and maturation, we studied the cochleae of Igf-1 gene knockout mice by performing morphometric stereological analyses, immunohistochemistry and electron microscopy on postnatal days 5 (P5), P8 and P20. At P20, but not at P5, the volumes of the cochlea and cochlear ganglion were significantly reduced in mutant mice, although the reduction was less severe than whole body dwarfism. A significant decrease in the number and average size of auditory neurons was also evident at P20. IGF-1-deficient cochlear neurons showed increased apoptosis, along with altered expression of neurofilament 200 kDa and vimentin. The eighth nerve, the cochlear ganglion and the fibers innervating the sensory cells of the organ of Corti of the P20 mouse mutants presented increased expression of vimentin, whereas the expression of neurofilament was decreased. In addition, the myelin sheath was severely affected in ganglion neurons. In conclusion, IGF-1 deficit in mice severely affects postnatal survival, differentiation and maturation of the cochlear ganglion cells.

NOGO mRNA expression in adult and fetal human and rat nervous tissue and in weight drop injury

Nogo is a myelin-associated protein known to inhibit growth of neurites. In order to understand possible physiological roles of Nogo, we performed in situ hybridization using rat and human probes complementary to a Nogo-A-specific sequence and a sequence shared by all known Nogo transcripts recognizing nogo-A, -B, and -C. We studied the cellular distribution of nogo-mRNA in fetal and adult human and rat tissues, with a focus on the spinal cord and ganglia. Rat mRNA expression was also studied in a spinal cord weight-drop model and in animals exposed to kainic acid. In human fetal tissue, nogo-A was strongly expressed in the ventral two-thirds of the spinal cord, the dorsal root ganglia, and autonomic ganglia. Similarly, nogo-A mRNA expression was observed in the adult human spinal cord and ganglia. High levels of nogo-A message were observed in neurons, such as motor neurons and sensory ganglia neurons. The distribution of nogo message in rats resembled that seen in human tissues. Thus, nogo mRNA was expressed in neurons and oligodendrocytes, but not astrocytes or Schwann cells. In addition, expression of nogo-A mRNA was observed in human and rat developing muscle tissue. High level of nogo-mRNA were also expressed in the rat trigeminal ganglion and trigeminal pontine nucleus. In fetal rats the adrenal gland and cell clusters in the liver were positive for the nogo-ABC pan-probe, but negative for the nogo-A probe. While neurons in the adult rat brain were generally positive, very prominent nogo-A mRNA and nogo-ABC mRNA signals were obtained from neurons of the hippocampus, piriform cortex, the red nucleus, and the oculomotor nucleus. Nogo-A mRNA expression was markedly reduced in the epicenter of a lesion in the spinal cord of adult rats 6 and 24 h after a weight-drop injury, while no perifocal upregulation of nogo mRNA was seen. No obvious change of nogo expression was detected in kainic acid exposed animals. In conclusion our in situ hybridization study has demonstrated widespread expression of nogo mRNA in the fetal, developing and adult nervous system of rat and man. In addition to oligodendroglial cells, high levels of nogo-A mRNA expression were found in neurons, raising important questions about the function of neuronal nogo mRNA. No obvious regulation of nogo was detected following injury.

The central nervous system, its cellular organisation and development, in the tadpole larva of the ascidian Ciona intestinalis

From its numerical composition, the central nervous system (CNS) of the ascidian larva is one of the simplest known nervous systems having a chordate plan. Fewer than 350 cells together constitute a caudal nerve cord, an interposed visceral ganglion containing motor circuits for swimming and, rostrally, an expanded sensory vesicle containing major sensory and interneuron regions of the CNS. Some cells are ependymal, with ciliated surfaces lining the neural canal, while others are clearly either sensory receptors or motoneurons, but most are distinguishable only on cytological grounds. Although reassignments between categories are still being made, there is evidence for determinancy of total cell number. We have made three-dimensional cell maps either from serial semithin sections, or from confocal image stacks of whole-mounted embryos and larvae stained with nuclear markers. Comparisons between the maps of neural tubes in embryos of successive ages, that is, between cells in one map and their progeny in older maps, enable us to follow the line of mitotic descent through successive maps, at least for the caudal neural tube. Details are clear for the lateral cell rows in the neural tube, at least until the latter contains approximately 320 cells, and somewhat for the dorsal cell row, but the ventral row is more complex. In the hatched larva, serial-EM reconstructions of the visceral ganglion reveal two ventrolateral fibre bundles at the caudalmost end, each of 10-12 axons. These tracts include at least five pairs of presumed motor axons running into the caudal nerve cord. Two pairs of axons decussate. Complementing this vertebrate feature in the CNS of the larval form of Ciona, we confirm that synapses form upon the somata and dendrites of its neurons, and that its motor tracts are ventral.

Developmental changes in membrane properties of chemoreceptor afferent neurons of the rat petrosal ganglia

Carotid body chemoreceptors increase their responsiveness to hypoxia in the postnatal period, but the mechanism for this increase is unresolved. The purpose of the present study was to examine developmental changes in cellular characteristics of chemoreceptor afferent neurons in the petrosal ganglia with the underlying hypothesis that developmental changes occur and may account for the developmental increase in chemoreceptor responsiveness. Chemoreceptor complexes (carotid body, sinus nerve, glossopharyngeal nerve, and petrosal ganglia) were harvested from rats, aged 3-40 days, and intracellular recordings were obtained from petrosal ganglion neurons using sharp electrode impalement. All chemoreceptor neurons across ages were C fibers with conduction velocities <1 m/s and generated repetitive action potentials with depolarization. Resting membrane potential was -61.3 +/- 0.9 (SE) mV (n = 78) and input resistance was 108 +/- 6 MOmega and did not significantly change with age. Cell capacitance was 32.4 +/- 1.7 pF and did not change with age. Rheobase averaged 0.21 +/- 0.02 nA and slightly increased with age. Action potentials were followed by an afterhyperpolarization of 12.4 +/- 0.6 mV and time constant 6.9 +/- 0.5 ms; only the time constant decreased with age. These results, obtained in rat, demonstrate electrophysiologic characteristics which differ substantially from that previously described in cat chemoreceptor neurons. In general developmental changes in cell characteristics are small and are unlikely to account for the developmental increase in chemoreceptor responsiveness with age.

Developmental expression of the CaM kinase II isoforms: ubiquitous gamma- and delta-CaM kinase II are the early isoforms and most abundant in the developing nervous system

CaM kinase II constitutes a family of multifunctional protein kinases that play a major role in Ca2+-mediated signal transduction. As a first step in understanding their possible function in mouse development we characterized the expression patterns of all CaM kinase II isoforms (alpha, beta, gamma and delta) starting in prenatal development. Remarkably, only the ubiquitous gamma- and delta-CaM kinase II are expressed during early development. Their distribution suggests a special role in the developing nervous system and in mature excitable tissues. Additionally, we describe the murine betaM-CaM kinase II, a variant of the 'brain-specific' beta-CaM kinase II, which is highly expressed in skeletal muscle.

Zebrafish semaphorin Z1a collapses specific growth cones and alters their pathway in vivo

The semaphorin/collapsin gene family encodes secreted and transmembrane proteins several of which can repulse growth cones. Although the in vitro activity of Semaphorin III/D/Collapsin 1 is clear, recent analyses of two different strains of semaphorin III/D/collapsin 1 knockout mice have generated conflicting findings. In order to clarify the in vivo action of this molecule, we analyzed sema Z1a, a zebrafish homolog of semaphorin III/D/collapsin 1. The expression pattern of sema Z1a suggested that it delimited the pathway of the growth cones of a specific set of sensory neurons, the posterior ganglion of the lateral line, in zebrafish. To examine the in vivo action of this molecule, we analyzed (1) the pathways followed by lateral line growth cones in mutants in which the expression of sema Z1a is altered in an interesting way, (2) response of lateral line growth cones to exogenous Sema Z1a in living embryos, and (3) the pathway followed by lateral line growth cones when Sema Z1a is misexpressed by cells along their normal route. The results suggest that a repulsive action of Sema Z1a helps guide the growth cones of the lateral line along their normal pathway.

The developmental expression of choline acetyltransferase (ChAT) and the neuropeptide VIP in chick sympathetic neurons: evidence for different regulatory events in cholinergic differentiation

Cholinergic properties in chick sympathetic neurons are detectable early during development of paravertebral ganglia and mature after target contact. The cholinergic marker choline acetyltransferase (ChAT) is first detectable at embryonic day 6 and its expression partly overlaps with that of the noradrenergic marker tyrosine hydroxylase (TH). At late embryonic stages, when sympathetic neurons have established target contact, ganglia consist of two major neuronal populations, TH-positive noradrenergic neurons and cholinergic neurons that at this stage express vasoactive intestinal peptide (VIP) in addition to ChAT. The maturation of sympathetic neurons is paralleled by changes in their response to the neurokine ciliary neurotrophic factor (CNTF). These findings suggest that expression of neurotransmitter properties is controlled differentially before and during target innervation.