Performance assessment of a fully automated electro-chemiluminescence immunoassay system for serum S100B protein.

The altered expression levels of S100 proteins can lead to four different categories of diseases: diseases of the heart and of the central nervous system, inflammatory disorders and cancer. Various studies have shown the lack of harmonization of the results obtained with different methods, mainly due to different performances and measurements of S100B. The purpose of this work was to compare quantitatively the fully automated Elecsys® immunoassay with the reference immunoenzimatic method CanAg® EIA for serum S100B protein. In the study serum samples were analyzed of 161 patients: 85 females (aged 22-83 years) and 76 males (aged 16-90 years), affected by oncological and non-oncological pathologies. Passing–Bablok regression was used to analyze the comparison between the assays; it showed a strong interassay correlation: r = 0.9350 (95% CI =0.9122 – 0.9520), with an intercept of 0.02063 (95% CI=-0.02850 – 0.01400) and a slope of 1.1125 (95% CI=1.0200 – 1.2417). Elecsys® S100 assay should be preferred to CanAg® S100 for better standardization, good reliability and precision but also with the aim to reduce costs and obtain results in a shorter time.

Neurobehavioral studies, in transgenic F3/CONTACTIN (C57BL/6J × CBA) mice, on cognitive and anxiety aspects during late-adolescential period.

OBJECTIVE: Besides than in the control of developmental events, axonal adhesive glycoproteins may be also involved in functions requiring fine organization and connectivity of the nervous tissue. We previously demonstrated morphological alterations and functional cerebellar deficits in transgenic mice (TAG/F3 mice) ectopically expressing the F3/Contactin axonal glycoprotein under the control of a selected regulatory region from the Transient Axonal Glycoprotein (TAG-1) gene. In the present study, the hippocampal function was explored by evaluating the ability of TAG/F3 mice to encode spatial and non-spatial relationships between discrete stimuli and to analyze an anxiety-related behavior. MATERIALS AND METHODS: To the first end, mice were placed in an "open-Field" containing five objects and, after three sessions of habituation (S2-S4), their reactivity to objects displacement (S5-S4) and object substitution (S7-S6) was examined.To the second end, mice were placed in the "elevated zero maze", a standard test to explore the anxiety-related behavior, in order to study, in transgenic mice, the effects of F3 misexpression on emotional reactivity by measuring the avoidance of the unsheltered open sectors. RESULTS: Statistical evaluations of reactivity to object novelty, TAG-F3 mice showed a lower DO exploration with respect to wild-type mice and, regarding DOs, TAG/F3 mice interacted less than wild-type mice, showing an impaired spatial change response. Furthermore, the number of HDIPS in transgenic TAG/F3 mice resulted significantly lower with respect to the controls (wild type). CONCLUSIONS: These results indicate that the coordinated expression of axonal adhesive glycoproteins may be relevant for the functional maturation of the hippocampus.

Characterization and role of Helix contactin-related proteins in cultured Helix pomatia neurons.

We report on the structural and functional properties of the Helix contactin-related proteins (HCRPs), a family of closely related glycoproteins previously identified in the nervous system of the land snail Helix pomatia through antibodies against the mouse F3/contactin glycoprotein. We focus on HCRP1 and HCRP2, soluble FNIII domains-containing proteins of 90 and 45 kD bearing consensus motifs for both N- and O-glycosylation. Using the anti-HCRPs serum, we find secreted HCRPs in Helix nervous tissue isotonic extracts and in culture medium conditioned by Helix ganglia. In addition, we demonstrate expression of HCRPs on neuronal soma and on neurite extensions. Functionally, in Helix neurons, the antisense HCRP2 mRNA counteracts neurite elongation, and the recombinant HCRP2 protein exerts a strong positive effect on neurite growth when used as substrate. These data point to HCRPs as novel neurite growth-promoting molecules expressed in invertebrate nervous tissue.

Transgenic models for studying expression and function of axonal adhesive glycoproteins.

In this study, by using two transgenic models, we address the general topic of the significance of axonal glycoproteins regulated expression in nervous tissue maturation. The immunoglobulin superfamily components F3/Contactin (F3) and TAG-1 are used as the molecular models in this respect. First, a minigene including the relevant regulatory sequences of the F3 gene, deduced by a previous in vitro study, has been fused to an EGFP (Enhanced Green Fluorescent Protein) reporter and expressed in transgenic mice, which provided information about the profile of F3 gene developmental activation. In a complementary model, transgenic mice have been generated which express the F3 cDNA under control of a selected regulatory region from the TAG-1 gene. While leading to ectopic expression of F3, this perturbed neuronal precursor proliferation and differentiation. The arising effects were even stronger than those coming from the overall suppression of the F3 or, respectively, TAG-1 genes, thus supporting the hypothesis that the mechanisms underlying axonal glycoprotein regulated expression are themselves endowed with a key significance in neural development.

Transgenic mice expressing F3/contactin from the transient axonal glycoprotein promoter undergo developmentally regulated deficits of the cerebellar function.

We have shown that transgenic transient axonal glycoprotein (TAG)/F3 mice, in which the mouse axonal glycoprotein F3/contactin was misexpressed from a regulatory region of the gene encoding the transient axonal glycoprotein TAG-1, exhibit a transient disruption of cerebellar granule and Purkinje cell development [Development 130 (2003) 29]. In the present study we explore the neurobehavioural consequences of this mutation. We report on assays of reproductive parameters (gestation length, litter size and offspring viability) and on somatic and neurobehavioural end-points (sensorimotor development, homing performance, motor activity, motor coordination and motor learning). Compared with wild-type littermates, TAG/F3 mice display delayed sensorimotor development, reduced exploratory activity and impaired motor activity, motor coordination and motor learning. The latter parameters, in particular, were affected also in adult mice, despite the apparent recovery of cerebellar morphology, suggesting that subtle changes of neuronal circuitry persist in these animals after development is complete. These behavioural deficits indicate that the finely coordinated expression of immunoglobulin-like cell adhesion molecules such as TAG-1 and F3/contactin is of key relevance to the functional, as well as morphological maturation of the cerebellum.

Alternative promoters drive the expression of the gene encoding the mouse axonal glycoprotein F3/contactin.

F3/Contactin is a neuronal glycoprotein which mediates axonal growth control via complex interactions with a number of cell surface or matrix components. As part of this developmental role, its expression undergoes differential regulation during the maturation of definite neuronal populations within the central and peripheral nervous tissue. To elucidate the underlying molecular mechanisms we study here the organization of the regulatory region of the mouse F3/Contactin gene. We show that this region displays peculiar features in that it spans more than 80 kb, bears very large introns and includes four untranslated exons which undergo complex splicing events leading to 11 potential arrangements of the F3/Contactin mRNA 5' end. Within this region we identify three alternative neurospecific promoters which, as deduced from the developmental profile of the associated 5' exons (A1,C1,0), drive two different patterns of F3/Contactin gene expression. The activity of the A1 exon-associated promoter displays only minor developmental changes and is likely to contribute to the basal level of the F3/Contactin gene expression; by contrast, the activities of the exon C1- and exon 0-associated promoters are significantly upregulated at the end of the first postnatal week. The data indicate that differential regulation of the F3/Contactin expression during development may depend upon alternative utilization of distinct promoter elements and may involve complex splicing events of the 5' untranslated exons. Several consensuses for homeogene transcription factors are scattered within the identified regulatory region, in agreement with the general assumption of homeotic gene regulation of neural morphoregulatory molecules.

Regional distribution and cell type-specific expression of the mouse F3 axonal glycoprotein: a developmental study.

The expression of the mouse axonal adhesive glycoprotein F3 and of its mRNA was studied on sections of mouse cerebellar cortex, cerebral cortex, hippocampus, and olfactory bulb from postnatal days 0 (P0) to 30 (P30). In cerebellar cortex, a differential expression of F3 in granule versus Purkinje neurons was observed. F3 was highly expressed during migration of and initial axonal growth from cerebellar granule cells. The molecule was then downregulated on cell bodies and remained expressed, although at low levels, on their axonal extensions. On Purkinje cells, F3 was strongly expressed on cell bodies and processes at the beginning of the second postnatal week; by P16 it was restricted to neurites of Purkinje cells subpopulations. In the cerebral cortex, the molecule was highly expressed on migrating neurons at P0; by P16, it was found essentially within the neuropil with a diffuse pattern. In the hippocampal formation, where F3 was expressed on both pyramidal and granule neurons, a clear shift from the cell bodies to neurite extensions was observed on P3. In the olfactory pathway, F3 was expressed mainly on olfactory nerve fibers, mitral cells, and the synaptic glomeruli from P0 to P3, with a sharp decline from P11 to P16. As a whole, the data show that F3 protein expression is regulated at the regional, cellular, and subcellular levels and suggest that, in different regions, it can be proposed as a reliable neuronal differentiation marker.

Regulated expression of the cell adhesion glycoprotein F3 in adult hypothalamic magnocellular neurons.

F3, a glycoprotein of the immunoglobulin superfamily implicated in axonal growth, occurs in oxytocin (OT)-secreting and vasopressin (AVP)-secreting neurons of the adult hypothalamo-neurohypophysial system (HNS) whose axons undergo morphological changes in response to stimulation. Immunocytochemistry and immunoblot analysis showed that during basal conditions of HNS secretion, there are higher levels of this glycosylphosphatidyl inositol-anchored protein in the neurohypophysis, where their axons terminate, than in the hypothalamic nuclei containing their somata. Physiological stimulation (lactation, osmotic challenge) reversed this pattern and resulted in upregulation of F3 expression, paralleling that of OT and AVP under these conditions. In situ hybridization revealed that F3 expression in the hypothalamus is restricted to its magnocellular neurons and demonstrated a more than threefold increase in F3 mRNA levels in response to stimulation. Confocal and electron microscopy localized F3 in secretory granules in all neuronal compartments, a localization confirmed by detection of F3 immunoreactivity in granule-enriched fractions obtained by sucrose density gradient fractionation of rat neurohypophyses. F3 was not visible on any cell surface in the magnocellular nuclei. In contrast, in the neurohypophysis, it was present not only in secretory granules but also on the surface of axon terminals and glia and in extracellular spaces. Taken together, our observations reveal that the cell adhesion glycoprotein F3 is colocalized with neurohypophysial peptides in secretory granules. It follows, therefore, the regulated pathway of secretion in HNS neurons to be released by exocytosis at their axon terminals in the neurohypophysis, where it may intervene in activity-dependent structural axonal plasticity.

Functional organization of the promoter region of the mouse F3 axonal glycoprotein gene.

F3 is a developmentally regulated adhesive glycoprotein expressed by subpopulations of central and peripheral neurons which mediates neurite growth and fasciculation via cis- and trans-interactions with cell-surface or matrix components. We previously reported on the characterization of the F3 gene 5' flanking region in which we identified promoter and enhancer elements. Here, we report on the functional organization of the F3 gene regulatory regions. We show that the F3 promoter is built of linearly arranged positive and negative elements scattered through the 5' flanking region of the F3 gene and the 1st exon (exon 0). Neural- and cell type-specific expression of F3 appears to be governed by elements located in the most proximal promoter region which includes a neural-specific enhancer. In retardation assays, all these cis-acting elements bind nuclear proteins, three of which interact with the identified enhancer element while a single species interacts with sequences located within exon 0. Some of these proteins are also specifically expressed within the brain, indicating that they could correspond to neural-specific trans-acting factors. Elements located immediately upstream of the cell type-specific enhancer and within exon 0 are responsible for regulation of F3 expression by cAMP and retinoic acid.

Expression of the immunoglobulin superfamily cell adhesion molecule F3 by oligodendrocyte-lineage cells.

We have analysed the expression of glycosylphosphatidylinositol (GPI)-anchored proteins by oligodendrocyte-lineage cells. Biosynthetic labeling of mouse oligodendroglial primary cultures and an oligodendroglial precursor cell line demonstrated that these cells synthesise a variety of different GPI-anchored proteins. GPI-anchored proteins were isolated as a bulk preparation from the precursor cell line, and the individual proteins separated by 2D gel electrophoresis and analysed by microsequencing after tryptic digestion of the separated components. One of the most prominent GPI-anchored proteins synthesised by the cell line was identified as the cell adhesion molecule F3, previously thought to be exclusively expressed by neurons. Western blotting and immunoprecipitation with several polyclonal sera confirmed the expression of F3 by oligodendrocyte-lineage cells and demonstrated the presence of F3 in myelin. Double staining with a panel of oligodendrocyte-specific antibodies and anti-F3 antibodies of cerebellar cultures, as well as oligodendrocytes isolated by panning, showed a colocalization of F3 with oligodendrocyte markers. Oligodendrocyte F3 is shown to be susceptible to phosphatidylinositol-phospholipase C (PI-PLC) cleavage, similar to neuronal F3. Northern blots demonstrated that the oligodendroglial F3 mRNA is the same size as the neuronal message; however, no F3 mRNA could be detected in cortical astrocytes and an astrocytic cell line. Thus, in addition to the expression by neurons, the cell-type specificity of F3 expression must be extended to oligodendroglial cells, underscoring the importance of this Ig superfamily member in the nervous system.

Use of chimeric F3-NCAM molecules to explore the properties of VASE exon in modulating polysialylation and neurite outgrowth.

Differential splicing of VASE exon in the fourth immunoglobulin (Ig) domain and attachment to the fifth Ig domain of alpha 2-8 linked sialic acid (PSA) both dramatically change, in opposite manner, Neural Cell Adhesion Molecule (NCAM) functional properties. Reciprocal patterns of VASE and PSA expression suggest that they might be mutually exclusive. Here, we tested whether informations conferring polysialylation reside in NCAM-Ig domains 4 and 5 and the influence of the VASE exon encoded sequence on this process. We also examined if the VASE sequence was still able to inhibit neurite outgrowth when presented out of its normal NCAM context. Constructs have been prepared encoding NCAM-Ig domains 4 (with or without the VASE exon) and 5 fused to the F3 molecule. Stable clones expressing the chimeric molecules or wild type F3 were then obtained in the AtT-20 cell line. Although the chimeric molecules were expressed on the cell surface none of them was bearing PSA. Thus, polysialylation cannot be conferred to proteins by addition of the NCAM-Ig domains 4 and 5 modular motif and in this molecular context, the VASE sequence is not influencing the process. These chimeric molecules, either expressed at the surface of RIN or COS cells or presented as soluble forms, were examined for their effect on neurite outgrowth. In all cases, the length of neurites of sensory neurons was significantly reduced when grown in presence of the VASE containing chimera by comparison with the chimera without VASE or wild type F3. When neurons from NCAM knock-out mice were used for the assay, the VASE inhibition could not be detected. Thus VASE is able to act as a modular motif and NCAM expressed on neurons participates in transducing its effect.

Characterization of the 5' and promoter regions of the gene encoding the mouse neuronal cell adhesion molecule F3.

F3 is a 135 kDa neuronal cell surface adhesive glycoprotein belonging to the immunoglobulin supergene family (IgSF) which mediates heterophilic contact formation among neural cells and is involved in the control of neurite growth. F3 expression is regulated, during critical developmental periods, on neuronal subpopulations thus suggesting that control of F3 gene expression could be of morphogenetic relevance. To shed light on the mechanism involved in the control of F3 gene expression we isolated clones covering about 50 kilobases of the F3 gene which also included the promoter region. The study of F3 gene exon/intron organization revealed that, like other neural IgSF molecules, each of the first two F3 C2 domains is encoded by two exons while the N-terminus, the signal peptide and the 5' untranslated region are each encoded by distinct exons. A single transcription start site was identified, surrounded by a short 114 bp sequence able to direct reporter gene expression in both F3-expressing and -non-expressing cells. In addition, a cell type-specific enhancer, only active in F3-expressing cells, was found immediately upstream to it. Structural analysis of the promoter region revealed consensus sequences for binding transcription factors involved in cell type-specific and/or developmental regulations. Most of them are homeobox containing transcription factors thus suggesting that regulation of F3 gene expression could be part of a large developmental program.

Different domains of the F3 neuronal adhesion molecule are involved in adhesion and neurite outgrowth promotion.

The mouse F3 cell surface protein is preferentially expressed on axons of subpopulations of neurons and is anchored to the membrane by a glycosyl-phosphatidylinositol group. It consists of six immunoglobulin-like domains and four fibronectin type III homologous repeats, and can be found both in membrane-anchored and soluble forms. We have previously established that F3 fulfills the operational criteria of a cell adhesion molecule when anchored to the plasma membrane and that its soluble form stimulates neurite initiation and neurite outgrowth. To further characterize F3-mediated adhesion and to investigate whether adhesion and neurite outgrowth promoting activities are displayed by different parts of the molecule, we (i) selected F3 transfected CHO cells expressing increasing levels of F3 at their surface and (ii) prepared transfectants expressing an F3 molecule with its fibronectin type III repeats deleted. We show that the F3 molecule mediates divalent-cation-independent, temperature-dependent binding. The levels of aggregation of F3 transfectants are proportional to the level of F3 expression. Transfectants expressing F3 deleted of the fibronectin type III repeats lose their adhesive properties; conversely, cells expressing wild-type F3 and treated with collagenase, specifically removing the immunoglobulin-like domains, are still able to aggregate. Therefore, in this model adhesion site(s) mapped to the fibronectin type III repeats. By contrast, transfectants expressing deleted F3, as well as the soluble forms of this F3 deleted molecule, were able to stimulate neurite outgrowth of sensory neurons similarly to wild-type F3. Our data indicate that F3 is a multifunctional molecule and that adhesion and neurite outgrowth promoting properties are expressed by distinct and independent domains.

Functional studies and cellular distribution of the F3 GPI-anchored adhesion molecule.

Many adhesion molecules of the immunoglobulin superfamily expressed in the nervous system are attached to the neuronal membrane by a glycan-phosphatidylinositol. Using neuronal glycoprotein F3 as a model we will discuss how this lipid modification might confer on molecules specific properties which may be particularly well suited to a role in modulating neuronal interactions. In particular, the following data dealing with the question of how the glycosylphosphatidylinositol (GPI) anchor influences the function, transport and localization of this molecule will be presented. 1) When anchored to the plasma membrane, F3 fulfills the operational criteria of an adhesion molecule while its soluble form is able to stimulate neurite outgrowth of sensory neurons in culture. 2) In the hypothalamo-hypophyseal system, immunoblot analysis indicates that there is more F3 in the neurohypophysis where secretory axons terminate than in the hypothalamic nuclei where the molecule is synthesized. In addition, GPI-linked forms predominate in the nuclei while there are mainly soluble forms in the neurohypophysis, suggesting that there is conversion of the GPI-bearing form to the soluble form during axonal transport. 3) In the cerebellum, F3 is polarized to the tips of the axons of granule cells, the major neuronal population in this system, as an indication that indeed GPI might be a signal for targeting molecules to axons. However, some neurons such as Golgi cells express F3 over all their surface.

The F3/11 cell adhesion molecule mediates the repulsion of neurons by the extracellular matrix glycoprotein J1-160/180.

The oligodendrocyte-derived extracellular matrix protein J1-160/180 displays repellent substrate properties toward neurons. In a search for neuronal ligands mediating the response to J1-160/180, we have identified the F3/11 cell surface protein, a glyco-phosphatidylinositol-anchored member of the immunoglobulin superfamily. F3/11 mediates the initial recognition between a J1-160/180 substrate and cerebellar neurons or F3-transfected CHO cells. In cerebellar neurons, the F3/11-J1-160/180 interaction induces a repulsion consisting of the loss of substrate adhesion with time in culture and inhibition of neurite outgrowth. Antibody blocking experiments show that the avoidance response of neurites at J1-160/180 substrate borders is also mediated by F3/11. Active cell-cell and cell-substrate repulsion is considered a major mechanism governing the extent and directionality of axonal growth, but the ligand-receptor interactions involved have remained unknown. Our results show that F3/11 mediates the neuronal response to the repellent molecule J1-160/180 and may thus be involved in signal transduction leading to cell repulsion.

A soluble form of the F3 neuronal cell adhesion molecule promotes neurite outgrowth.

The F3 molecule is a member of the immunoglobulin superfamily anchored to membranes by a glycane-phosphatidylinositol, and is predominantly expressed on subsets of axons of the central and peripheral nervous system. In a previous paper (Gennarini, G., P. Durbec, A. Boned, G. Rougon, and C. Goridis. 1991. Neuron. 6:595-606), we have established that F3 fulfills the operational definition of a cell adhesion molecule and that it stimulates neurite outgrowth when presented to sensory neurons as a surface component of transfected CHO cells. In the present study the question as to whether soluble forms of F3 would be functionally active was addressed in vitro on cultures of mouse dorsal root ganglion neurons. We observed that preparations enriched in soluble F3 had no effect on neuron attachment but enhanced neurite initiation and neurite outgrowth in a dose-dependent manner. By contrast, soluble NCAM-120 does not have any measurable effect on these phenomena. Addition of anti-F3 monovalent antibodies reduced the number of process-bearing neurons and the neuritic output per neuron to control values. Addition of cerebrospinal fluid, a natural source of soluble F3, also stimulated neurite extension, and this effect was partially blocked by anti-F3 antibodies. Our results suggest that the soluble forms of adhesive proteins with neurite outgrowth-promoting properties could act at a distance from their site of release in a way reminiscent of growth and trophic factors.

Expression and release of phosphatidylinositol anchored cell surface molecules by a cell line derived from sensory neurons.

Early postnatal mouse dorsal root ganglion neurons were found to express several glycosylphosphatidylinositol-anchored (GPI) molecules from the immunoglobulin superfamily (neural cell adhesion molecule 120 kD isoform, F3, Thy1) whose expression is developmentally regulated. A hybrid cell line (ND26), made by fusing postmitotic rat dorsal root ganglion (DRG) neurons with the mouse neuroblastoma N18Tg2, could be induced to differentiate by manipulating the composition of the culture medium and expressed similar GPI molecules to DRG neurons. We used this model system to investigate the metabolism of GPI-anchored molecules. We found that neural cell adhesion molecule 120 Kd isoform expression decreased upon differentiation, whereas the level of F3 and Thy1 increased, suggesting a role in neurite outgrowth processes. The ratio of molecules cleavable by exogenous phosphatidylinositol phospholipase C (PI-PLC) was similar for all the GPI-anchored molecules, which could mean that cell-specific modifications of the basic anchoring structure determine the level of potentially releasable molecules. Measurements of spontaneous release indicated that this reflected the overall level of expression of these molecules by the ND26 cell line. Finally, we observed an effect of dibutyryl cAMP on the level of expression of F3 and Thy1 but not of N-CAM. However, we could not detect any significant effect of nerve growth factor (NGF) either on the level of expression or on the amount of spontaneously released molecules.

F3/F11 cell surface molecule expression in the developing mouse cerebellum is polarized at synaptic sites and within granule cells.

The distribution of the F3/F11 neuronal cell surface molecule was investigated in the developing and adult mouse cerebellum by immunocytochemistry at the light and electron microscopic levels. F3/F11 was confined to subsets of neuronal types, since the Purkinje cell body and dendritic arborization as well as the stellate cells were not immunoreactive. In the young developing cerebellum, the granule cell axons strongly express F3/F11 as soon as they begin to grow, consistent with a functional role in promoting directional outgrowth of neuronal processes. In 10-d-old and adult cerebella, the granule cell bodies and dendrites were not immunoreactive whereas the parallel fibers, which are the granule cell axons, were labeled including in their presynaptic varicosities. By contrast, dendrites, cell bodies, and axons of Golgi cells were labeled by anti-F3 antibodies. Hence, F3/F11 can either be expressed throughout the cell or be polarized to the axons. This raises the question of how segregation of the glypiated F3/F11 molecule between different subcellular compartments depending on the type of neuron is achieved. F3/F11 was found to be present at three types of synaptic sites, suggesting that it might play a role in the formation and maintenance of synapses. However, in each type of synpase, F3/F11 was present at only the pre- or postsynaptic site, never at both: the parallel fiber varicosities contained F3/F11 whereas the postsynaptic compartment in contact, that is, the Purkinje cell dendritic spines, did not. The granule cell dendrites were unlabeled while the mossy fiber terminals contacting them were immunoreactive, and finally, the Golgi cell dendrites and dendritic spines were labeled while the presynaptic compartment contacting them was not. If F3/F11 functions as an adhesion molecule in vivo as indicated by in vitro assays, F3/F11-mediated adhesion is likely to be heterophilic.

Transfected F3/F11 neuronal cell surface protein mediates intercellular adhesion and promotes neurite outgrowth.

The mouse neuronal F3 glycoprotein and its chicken homolog F11 belong to a subclass of proteins of the immunoglobulin superfamily with preferential localization on axons and neurites. We have transfected F3 cDNA into CHO cells. Biochemical analysis establishes that the cDNA we have cloned codes for a 130 kd phosphatidylinositol-anchored polypeptide. F3-expressing transfectants exhibited enhanced self-adhesive properties, aggregating with faster kinetics and forming larger aggregates than F3-negative control cells. When used as a culture substrate for sensory neurons, F3-transfected cells showed a markedly enhanced ability to promote neurite outgrowth compared with nontransfected cells. The results support the idea that F3/F11 and other closely similar proteins function as cell adhesion molecules that play a role in axonal growth and guidance.