Developmental expression of cell recognition molecules in the mushroom body and antennal lobe of the locust Locusta migratoria.

We examined the development of olfactory neuropils in the hemimetabolous insect Locusta migratoria with an emphasis on the mushroom bodies, protocerebral integration centers implicated in memory formation. Using a marker of the cyclic adenosine monophosphate (cAMP) signaling cascade and lipophilic dye labeling, we obtained new insights into mushroom body organization by resolving previously unrecognized accessory lobelets arising from Class III Kenyon cells. We utilized antibodies against axonal guidance cues, such as the cell surface glycoproteins Semaphorin 1a (Sema 1a) and Fasciclin I (Fas I), as embryonic markers to compile a comprehensive atlas of mushroom body development. During embryogenesis, all neuropils of the olfactory pathway transiently expressed Sema 1a. The immunoreactivity was particularly strong in developing mushroom bodies. During late embryonic stages, Sema 1a expression in the mushroom bodies became restricted to a subset of Kenyon cells in the core region of the peduncle. Sema 1a was differentially sorted to the Kenyon cell axons and absent in the dendrites. In contrast to Drosophila, locust mushroom bodies and antennal lobes expressed Fas I, but not Fas II. While Fas I immunoreactivity was widely distributed in the midbrain during embryogenesis, labeling persisted into adulthood only in the mushroom bodies and antennal lobes. Kenyon cells proliferated throughout the larval stages. Their neurites retained the embryonic expression pattern of Sema 1a and Fas I, suggesting a role for these molecules in developmental mushroom body plasticity. Our study serves as an initial step toward functional analyses of Sema 1a and Fas I expression during locust mushroom body formation.

Neurexins and neuroligins: recent insights from invertebrates.

During brain development, each neuron must find and synapse with the correct pre- and postsynaptic partners. The complexity of these connections and the relatively large distances some neurons must send their axons to find the correct partners makes studying brain development one of the most challenging, and yet fascinating disciplines in biology. Furthermore, once the initial connections have been made, the neurons constantly remodel their dendritic and axonal arbours in response to changing demands. Neurexin and neuroligin are two cell adhesion molecules identified as important regulators of this process. The importance of these genes in the development and modulation of synaptic connectivity is emphasised by the observation that mutations in these genes in humans have been associated with cognitive disorders such as Autism spectrum disorders, Tourette syndrome and Schizophrenia. The present review will discuss recent advances in our understanding of the role of these genes in synaptic development and modulation, and in particular, we will focus on recent work in invertebrate models, and how these results relate to studies in mammals.

Altered expression of nectin-like adhesion molecules in the peripheral nerve after sciatic nerve transection.

Following axotomy several processes involving cell-cell interaction occur, such as loss of synapses, axon guidance, and remyelination. Two recently discovered families of cell-cell adhesion molecules, nectins and nectin-like molecules (necls) are involved in such processes in vitro and during development, but their roles in nerve injury have been largely unknown until recently. We have previously shown that axotomized motoneurons increase their expression of nectin-1 and nectin-3 and maintain a high expression of necl-1. We here investigate the expression of potential binding partners for motoneuron nectins and necls in the injured peripheral nerve. In situ hybridization (ISH) revealed a decreased signal for necl-1 mRNA in the injured nerve, whereas no signal for necl-2 was detected before or after injury. The signals for necl-4 and necl-5 mRNA both increased in the injured nerve and necl immunoreactivity displayed a close relation to axon and Schwann cell markers. Finally, signal for mRNA encoding necl-5 increased in axotomized spinal motoneurons. We conclude that peripheral axotomy results in altered expression of several necls in motoneurons and Schwann cells, suggesting involvement of the molecules in regeneration.

The lengthening of a giant protein: when, how, and why?

Subcommissural organ (SCO)-spondin is a giant glycoprotein of more than 5000 amino acids found in Vertebrata, expressed in the central nervous system and constitutive of Reissner's fiber. For the first time, in situ hybridization performed on zebrafish (Danio rerio) embryos shows that the gene encoding this protein is expressed transitionally in the floor plate, the ventral midline of the neural tube, and later in the diencephalic third ventricle roof, the SCO. The modular organization of the protein in Echinodermata (Strongylocentrotus purpuratus), Urochordata (Ciona savignyi and C. intestinalis), and Vertebrata (Teleostei, Amphibia, Aves and Mammalia) is also described. As the thrombospondin type 1 repeat motifs represent an increasingly large part of the protein during Deuterostomia evolution, the duplication mechanisms leading to this complex organization are examined. The functional significance of the particularly well-preserved arrangement of the series of SCO-spondin repeat motifs and thombospondin type 1 repeats is discussed.

Ehi neonatal: Lem, o el premio a la superviviencia / Ehi newborn: Lem, or the prize to the survival

La hipoxia- isquemica es la principal causa de injuria del sistema nerviosos central en el feto y en el recién nacido, situación agravada, en algunas circunstancias, por infección intrauterina y respuesta inflamatoria fetal. La reducción en las cifras de mortalidad ha producido un incremento de morbilidad, la posibilidad de asistir a las secuelas de aquellas lesiones. En el niño pretérmino que sobrevive, el sustrato morfológico más frecuente de parálisis cerebral es la lucoencefalomalacia pereventricular, la cual forma parte de un expectro más amplio. Las secuelas son déficit en la mielinización, la pérdida de volúmen de sustancia blanca con consecuente ventriculomegalia, el compromiso de vías largas relacionado con el déficit motor del cuadro clínico de páralisis cerebral. En este artículo se sitúa a la leucoencefalomalacia periventricular en el expectro de lesiones hipóxico, isquémica del recién nacido, se detallan sus características clínicas y macra-microscópicas, y se comentan los recientes aportes de la fisiopatología celular. El rol principal del glutamato, la teoría de la excototoxicidad, las citoquinas, y la cascada inflamatoria operan a través de ventanas de vulnerabilidad, que exponen a la oligodendroglia como target esencial, y a la apoptosis como un mecanismo importante de lesión cerebral

Ehi neonatal: Lem, o el premio a la superviviencia / Ehi newborn: Lem, or the prize to the survival

La hipoxia- isquemica es la principal causa de injuria del sistema nerviosos central en el feto y en el recién nacido, situación agravada, en algunas circunstancias, por infección intrauterina y respuesta inflamatoria fetal. La reducción en las cifras de mortalidad ha producido un incremento de morbilidad, la posibilidad de asistir a las secuelas de aquellas lesiones. En el niño pretérmino que sobrevive, el sustrato morfológico más frecuente de parálisis cerebral es la lucoencefalomalacia pereventricular, la cual forma parte de un expectro más amplio. Las secuelas son déficit en la mielinización, la pérdida de volúmen de sustancia blanca con consecuente ventriculomegalia, el compromiso de vías largas relacionado con el déficit motor del cuadro clínico de páralisis cerebral. En este artículo se sitúa a la leucoencefalomalacia periventricular en el expectro de lesiones hipóxico, isquémica del recién nacido, se detallan sus características clínicas y macra-microscópicas, y se comentan los recientes aportes de la fisiopatología celular. El rol principal del glutamato, la teoría de la excototoxicidad, las citoquinas, y la cascada inflamatoria operan a través de ventanas de vulnerabilidad, que exponen a la oligodendroglia como target esencial, y a la apoptosis como un mecanismo importante de lesión cerebral

The thrombospondin type 1 repeat (TSR) and neuronal differentiation: roles of SCO-spondin oligopeptides on neuronal cell types and cell lines.

SCO-spondin is a large glycoprotein secreted by ependymal cells of the subcommissural organ. It shares functional domains called thrombospondin type 1 repeats (TSRs) with a number of developmental proteins expressed in the central nervous system, and involved in axonal pathfinding. Also, SCO-spondin is highly conserved in the chordate phylum and its multiple domain organization is probably a chordate innovation. The putative involvement of SCO-spondin in neuron/glia interaction in the course of development is assessed in various cell culture systems. SCO-spondin interferes with several developmental processes, including neuronal survival, neurite extension, neuronal aggregation, and fasciculation. The TSR motifs, and especially the WSGWSSCSVSCG sequence, are most important in these neuronal responses. Integrins and growth factor receptors may cooperate as integrative signals. We discuss the putative involvement of the subcommissural organ/Reissner's fiber complex in developmental events, as a particular extracellular signaling system.

Drosophila dumbfounded: a myoblast attractant essential for fusion.

Aggregation and fusion of myoblasts to form myotubes is essential for myogenesis in many organisms. In Drosophila the formation of syncytial myotubes is seeded by founder myoblasts. Founders fuse with clusters of fusion-competent myoblasts. Here we identify the gene dumbfounded (duf) and show that it is required for myoblast aggregation and fusion. duf encodes a member of the immunoglobulin superfamily of proteins that is an attractant for fusion-competent myoblasts. It is expressed by founder cells and serves to attract clusters of myoblasts from which myotubes form by fusion.

Cell-adhesion proteins of the immunoglobulin superfamily in the nervous system.

The unique groups of cell-adhesion proteins, such as IgSF, play essential parts in the formation and maintenance of the nervous system. Recent crystallographic studies have revealed a possible common structure of cell-adhesion proteins. The IgSF proteins are sub-grouped into simple, complex and mixed types. Accumulating evidence reveals the importance of cell-adhesion proteins in neural morphogenesis, maintenance and regeneration. They play key roles in neuronal migration, neurite outgrowth promotion, neurite fasciculation, pathfinding, target recognition, synaptogenesis and myelination. Mutations of cell-adhesion proteins result in neurological disease; for example, mutations of PO in hereditary neuropathy and mutations of L1 in hereditary hydrocephalus, MASA syndrome and spastic paraplegia type 1. Perspectives of the studies of neural cell-adhesion proteins are discussed.

Cloning of neurotrimin defines a new subfamily of differentially expressed neural cell adhesion molecules.

Previous studies in the laboratory indicated that glycosylphosphatidylinositol (GPI)-anchored proteins may generate diversity of the cell surface of different neuronal populations (Rosen et al., 1992). In this study, we have extended these findings and surveyed the expression of GPI-anchored proteins in the developing rat CNS. In addition to several well characterized GPI-anchored cell adhesion molecules (CAMs), we detected an unidentified broad band of 65 kDa that is the earliest and most abundantly expressed GPI-anchored species in the rat CNS. Purification of this protein band revealed that it is comprised of several related proteins that define a novel subfamily of immunoglobulin-like (Ig) CAMs. One of these proteins is the opiate binding-cell adhesion molecule (OBCAM). We have isolated a cDNA encoding a second member of this family, that we have termed neurotrimin, and present evidence for the existence of additional family members. Like OBCAM, with which it shares extensive sequence identity, neurotrimin contains three immunoglobulin-like domains. Both proteins are encoded by distinct genes that may be clustered on the proximal end of mouse chromosome 9. Characterization of the expression of neurotrimin and OBCAM in the developing CNS by in situ hybridization reveals that these proteins are differentially expressed during development. Neurotrimin is expressed at high levels in several developing projection systems: in neurons of the thalamus, subplate, and lower cortical laminae in the forebrain and in the pontine nucleus, cerebellar granule cells, and Purkinje cells in the hindbrain. Neurotrimin is also expressed at high levels in the olfactory bulb, neural retina, dorsal root ganglia, spinal cord, and in a graded distribution in the basal ganglia and hippocampus. OBCAM has a much more restricted distribution, being expressed at high levels principally in the cortical plate and hippocampus. These results suggest that these proteins, together with other members of this family, provide diversity to the surfaces of different neuronal populations that could be important in the specification of neuronal connectivity.

Tenascin isoforms: possible targets for diagnosis and therapy of cancer and mechanisms regulating their expression.

Functionally different tenascin (TN) isoforms containing varying numbers of III homology repeats are generated by alternative splicing of a single TN primary transcript. It has recently been reported that the larger TN isoform is, in general, more expressed in neoplastic tissues than in the normal tissues from which the tumor originates. This is due, at least in breast lesions, to the high proliferative activity of stromal elements. In fact, TN splicing is cell-cycle dependent, thus offering a viable system to study the molecular mechanisms that regulate alternative splicing and suggesting that cell-cycle dependent modifications in the splicing pattern of primary transcripts (which very likely are not limited to the TN pre-mRNA) may also be a cell-cycle regulatory mechanism. Furthermore, the very high accumulation of the larger TN isoform in neoplasia allows wider diagnostic and therapeutic monoclonal antibodies specific for the larger TN isoforms be considered for a number of tumors.

Glycosylation of neural cell adhesion molecules of the immunoglobulin superfamily.

Cell adhesion molecules (CAMs) are believed to play key roles during morphogenesis. In this review we focus on neural CAMs belonging to the immunoglobulin superfamily. Data concerning distribution, expression pattern, structure and function of these CAMs are accumulating these years. In general, little is known about the importance of glycosylation for the function of these CAMs. The neural cell adhesion molecule, NCAM, is probably the best described CAM, and this molecule exhibits special carbohydrate characteristics, e.g. NCAM is polysialylated. Glycosylation of NCAM seems to be regulated during development and to influence the adhesive function of the molecule. Structure, function and glycosylation of NCAM are described in detail.

Ultrastructural localization of molecular subtypes of immunoreactive neural cell adhesion molecule (NCAM) in the adult rodent striatum.

Neural cell adhesion molecule (NCAM) is a plasma membrane glycoprotein that is thought to mediate adhesion between neuronal elements and play an important role in neural development. Although NCAM has been found in the adult brain, as well as the developing brain, little is known about its function or ultrastructural distribution. A monoclonal antibody which was directed against embryonic (E15-E17) mouse brain and identified 180 and 140 kDa molecular weight forms of NCAM was used to examine the immunohistochemical localization of NCAM in the rodent striatum. Light microscopic results in the adult mouse and rat showed that most NCAM180,140 immunoreactivity was localized to the relatively small population of medium and large-sized aspiny interneurons of the caudate nucleus and to the majority of neurons in the globus pallidus. Ultrastructural analysis revealed that reaction product in aspiny somata was present in discrete, closely spaced patches of cytoplasm along the inner face of the plasma membrane and was also prominent in somatic protrusions which were frequently apposed to synapsing axons. Distal aspiny and pallidal dendrites containing NCAM180,140 received numerous synaptic inputs. Within caudate neuropil NCAM180,140 was also present in spines with thin necks and small spine heads which were postsynaptic to unlabeled axon terminals and in preterminal (unmyelinated) axons and terminal boutons that issued from myelinated bundles and formed asymmetric synapses with unlabeled dendritic spines. This study provides the first evidence in adult brain that NCAM180,140 varies in extent and location within neurons. The heterogeneous distribution of NCAM180,140 in neurons of the basal ganglia may be related to a number of functions such as maintaining or modulating the density and distribution of synaptic inputs and the formation of new contacts on dendritic spines.