Pleiotropic biological effects of the neural cell adhesion molecule (NCAM)

Neural crest derivatives and neuroendocrine cells in the gut of anencephalic and fetuses without congenital defects

BACKGROUND

The enteric nervous system (ENS), a component of the peripheral nervous system in the intestinal walls, regulates motility, secretion, absorption, and blood flow. Neural crest (NC) migration, fundamental for ENS development, may be altered by central nervous system development alterations, such as neural tube defects (NTD). Intestinal innervation anomalies have been correlated to NTD. We aim to describe the ENS on a fetus with NTD and fetuses without congenital defects (FWCD).

CASES

Two male and four female FWCD, 18-20 weeks-gestation (WG), and a 25 WG female anencephalic fetus. Samples from the pancreatoduodenal groove, jejunum, cecum, rectum, and appendix were analyzed by immunohistochemistry. Nervous plexuses were marked with Neuron-specific enolase and S-100; enteric glial cells with CD56; neuroendocrine cells with chromogranin and synaptophysin, and interstitial cells of Cajal (ICC) with CD117.

RESULTS AND CONCLUSION

The anencephalic fetus presented a rudimentary brainstem with a cerebellum. Partial frontal, temporal, and occipital bones were found. A large atrial septal defect, an enlarged kidney with a duplex collecting system and a single adrenal gland were found. NSE, S100, and CD56, showed the presence of the myenteric and submucous plexuses of the ENS; scarce interplexus reactivity may indicate inadequate development. Pancreatic and gut neuroendocrine cells, identified with chromogranin and CD56, showed that the enteroendocrine system is present. Findings on FWCD using these markers are consistent with literature descriptions. Vagal NC migration appears to be unaffected despite the presence of anencephaly, although maturation of the ENS may be altered.

Costimulation of T cell receptor-triggered IL-2 production by Jurkat T cells via fibroblast growth factor receptor 1 upon its engagement by CD56

Recent studies have demonstrated that neural cell adhesion molecule (NCAM) is involved in multiple adhesive interactions with several different classes of ligands on the cell surface and in the extracellular matrix. One of these ligands is fibroblast growth factor receptor (FGFR) that is expressed on neural cells. While it is known that CD56 is a molecular isoform of NCAM expressed on human NK cells and a subset of T cells, it remains poorly characterized, with its ligand unidentified. Therefore, we were prompted to examine if CD56 molecules on NK cells interact with FGFR expressed on T cells. We demonstrate that ligation of FGFR1 beta on J.C2-14 Jurkat T cells by CD56 on fixed NK-92 cells costimulates TCR/CD3-triggered IL-2 production. CD56-binding mAbs inhibited the costimulatory effect of NK-92 cells in 50-75%. Flow cytometric analysis and cell adhesion assays showed that FGFR1 beta/Fc and FGFR2 beta/Fc chimeric proteins bind to NK-92 cells. The binding of FGFR1 beta/Fc protein to CD56 molecules was verified by immunoprecipitation of CD56 with anti-CD56 mAb followed by Western blotting with FGFR1 beta/Fc. These findings suggest that ligation of FGFR1 by CD56 may contribute to the interaction between NK cells and T cells that we have postulated in our previous studies.

The molecular biology of axon guidance

Neuronal growth cones navigate over long distances along specific pathways to find their correct targets. The mechanisms and molecules that direct this pathfinding are the topics of this review. Growth cones appear to be guided by at least four different mechanisms: contact attraction, chemoattraction, contact repulsion, and chemorepulsion. Evidence is accumulating that these mechanisms act simultaneously and in a coordinated manner to direct pathfinding and that they are mediated by mechanistically and evolutionarily conserved ligand-receptor systems.

The neural cell adhesion molecule and synaptic plasticity

Highly stereotyped patterns of neuronal connections are laid down during the development of the nervous system via a range of activity independent and activity dependent mechanisms. Whereas the coarse hard-wiring of the nervous system appears to rely on molecular recognition events between the neuron, its pathway, and its target, the establishment of precisely patterned functional circuits is thought to be driven by neuronal activity. In this review we discuss the role that the neuronal cell adhesion molecule (NCAM) plays in morphological plasticity. Recent studies on NCAM and its probable species homologue in Aplysia (apCAM) suggests that an individual CAM can function to both promote synaptic plasticity and maintain the structure of the synapse. In the adult brain, changes between stability and plasticity are likely to underlie dynamic morphological changes in synaptic structures associated with learning and memory. In this review we use NCAM as an example to illustrate mechanisms that can change the function of an individual CAM from a molecule that promotes plasticity to one that does not. We also discuss evidence that NCAM promotes plasticity by activating a conventional signal transduction cascade, rather than by modulating adhesion per se. Finally, we consider the evidence that supports a role for NCAM in learning and memory.

Brain development and multiple molecular species of proteoglycan

The occurrence of multiple proteoglycan species is a characteristic of the brain. The structural features of individually characterized proteoglycans in the brain are first introduced in brief, then some examples are shown that suggest a relationship between multiple proteoglycans and the many distinct cell types and neural circuits in the brain. Typical experiments demonstrated the neuronal-activity-dependent expression of neural proteoglycans during the critical developmental period of some functional systems such as the visual and vibrissal barrel systems. In addition, the binding properties of neural proteoglycans to other cell surface molecules are discussed in conjunction with their involvement in cell-cell and cell-substratum interactions. This review also covers other potential functions of proteoglycans not only in the development and maintenance of the brain but also in the pathogenesis of Alzheimer's disease. Proteoglycans are really coming of age in neuroscience.

Expression of adhesion molecules by endovascular trophoblast and decidual endothelial cells: implications for vascular invasion during implantation

During the process of implantation, maternal spiral arteries within the decidua are invaded by trophoblast cells that adhere to and migrate along the luminal surface of the vascular endothelial cells. This phenomenon resembles the events that occur during the migration of neutrophils into an acute inflammatory site, therefore it is possible that similar mechanisms are involved. Indeed, previous observations have shown that endovascular trophoblast expresses the blood group-related antigen sialyl Le(x). In this study, we show, by immunohistology, the expression of both E- and P-selectin by vascular endothelial cells only in the decidua basalis and not in decidua parietalis. In contrast, ICAM-1 is expressed by all vascular endothelium throughout the decidua. Expression of VCAM-1 is variable at the implantation site, and is not expressed by vascular endothelial cells in decidua parietalis. Interestingly, we demonstrate the strong expression of a polysialylated form of NCAM by endovascular trophoblast. Our data suggests that vascular invasion by trophoblast is regulated by the expression of appropriate adhesion molecules which permit interaction between endovascular trophoblast and decidual endothelial cells.

Neuronal migration in cerebellar microcultures is inhibited by antibodies against a neurite outgrowth domain of laminin

The functional role of laminin in neuronal migration was investigated by using polyclonal antibodies or their divalent (Fab')2 fragments to a neurite outgrowth promoting domain of the B2 chain of laminin in a cerebellar microculture system widely recognized as a model for neuronal migration. We show here that these antibodies or their (Fab')2 fragments totally inhibit migration of the mouse cerebellar granule cells along the glial and other neuronal cell processes. Antibodies to native laminin or other control antibodies have no inhibitory effect. Immunocytochemical analysis of the cerebellar microcultures indicates that the functional role of these antibodies may relate to the fact that the punctate deposits of laminin and its neurite outgrowth promoting domain accumulate in between the migrating neurons and the glial cells. These data provide the first direct evidence for the functional role of laminin and its neurite outgrowth domain in neuronal migration in the mammals. They further suggest that a neuronal cell surface contact with the extracellular deposits of a neurite outgrowth domain of the B2 chain of laminin may mediate neuronal-glial interactions.