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PubMed1977

Adhesion among neural cells of the chick embryo. II. Purification and characterization of a cell adhesion molecule from neural retina.

The aggregation of cells from dissociated neural retinas of chick embryos can be inhibited by antibodies prepared against whole retinal cells. In order to identify the antigens involved, substances released by retinal tissues in culture were tested for their ability to neutralize specifically the inhibition by antibody of cell adhesion. Using this assay, three active polypeptides from the culture supernatant were purified 500-fold by gel filtration and polyacrylamide gel electrophoresis. Rabbit antibodies prepared against these purified supernatant activities inhibited cell adhesion and reacted only with the three polypeptides. Immunoprecipitation by the specific antibodies of 3H-labeled proteins from a detergent extract of embryonic retinal cell membranes yielded a polypeptide having a Mr of 140,000 in sodium dodecyl sulfate. This precipitation was inhibited in the presence of the three culture supernatant polypeptides that had activity, suggesting that they contained antigenic determinants in common with the 140,000 Mr surface component. They therefore represent all or parts of this cell surface molecule that were released into solution during tissue culture. The data are consistent with the hypothesis that the 140,000 Mr polypeptide is intimately involved in initial adhesion among neural cells.

Animals↗
PubMed2026

Proteomic patterns according to ejection fraction: an EMPEROR-programme analysis.

AIMS: Left ventricular ejection fraction (LVEF) has been incorporated as an inclusion criterion in HF trials. Patient's characteristics, event risk, and treatment response vary according to LVEF. A better understanding of the biological processes across LVEF is warranted. To study proteomic biomarker expression across LVEF using data from the EMPEROR-Programme. METHODS: Two thousand two hundred and fifty-four patients who had proteomic measurements available using 1134 proteins overlapping between the Explore 1536 and 3072 Olink® platforms were included. Main analyses were performed within the EMPEROR-Preserved dataset due to differences in entry criteria between EMPEROR-Preserved and EMPEROR-Reduced with higher entry N-terminal pro B-type natriuretic peptide (NT-proBNP) levels that varied by LVEF cut-offs in the latter. Protein concentrations were compared using ordinal logistic regression across LVEF categories: 41%-49%, 50%-59%, and ≥60%. The resulting β-coefficient indicates the change in the log-odds for the outcome of being in a lower LVEF category for every NPX unit in log2 scale. Analyses were adjusted for covariates and a false-discovery-rate (FDR) correction was applied. RESULTS: A total of 297 proteins exhibited a trend of expression across LVEF categories in EMPEROR-Preserved after adjustment for potential confounders and correction for test multiplicity. Of these, the top 10 proteins were: NT-pro BNP (β = 0.18, 95% CI 0.09-0.27), Wnt inhibitory factor-1 (β = 0.40, 95% CI 0.19-0.61), sialomucin core protein 24 (β = 0.48, 95% CI 0.22-0.74), phospholipid transfer protein (β = 0.38, 95% CI 0.17-0.59), natriuretic peptides B (β = 0.13, 95% CI 0.06-0.20), intercellular adhesion molecule 5 (β = 0.31, 95% CI 0.14-0.49), neural cell adhesion molecule 2 (β = 0.45, 95% CI 0.19-0.70), neural cell adhesion molecule L1-like protein (β = 0.45, 95% CI 0.19-0.71), interactor protein for cytohesin exchange factors 1 (β = 0.12, 95% CI 0.05-0.19), and 3-ketoacyl-CoA thiolase, peroxisomal (β = 0.17, 95% CI 0.07-0.26). The correlation between these proteins and LVEF was generally weak (Rho ≤0.2). CONCLUSIONS: Within EMPEROR-Preserved, the top differentially expressed circulating proteins suggest that pathways related to natriuretic peptides, cell-adhesion, and clonal haematopoiesis are overexpressed at mildly-reduced ejection fraction, but none of the proteins passed the 5%FDR cut-off, and the correlation between circulating proteins and LVEF was weak. These findings suggest that circulating proteins may not be a good discriminant of ejection fraction.

Humans↗
PubMed2026

Thalamic NRXN1-mediated input to human cortical progenitors drives excitatory neurogenesis.

The human cerebral cortex develops through coordinated signals from within the cortex and from other brain regions, including the thalamus. However, how thalamic neuronal projections influence early human cortical development remains less well-understood. In this study, we fused cortical and thalamic organoids to investigate how thalamic input shapes the maturation of human cortical cells. Using single-nuclei RNA-sequencing and cellular imaging, we found that thalamic input increases the production of cortical excitatory neurons. We identify neurexin-1 (NRXN1) as a mediator of physical contact between thalamic axons and cortical outer radial glia. Genetic knockout of thalamic NRXN1 reduced these contacts and attenuated the production of upper-layer excitatory neurons. These findings reveal a mechanism by which thalamic input regulates human cortical progenitors and shapes excitatory neuron production during development.

Animals↗
PubMed1978

Adhesion among neural cells of the chick embryo. III. Relationship of the surface molecule CAM to cell adhesion and the development of histotypic patterns.

We have previously identified a molecule (named cell adhesion molecule [CAM]) that is involved in the in vitro aggregation of neural cells from chick embryos. In the present report, specific anti-CAM antibodies have been used to demonstrated that CAM is localized in neural tissues, and is associated with the plasma membrane of retinal cells and neurites. Furthermore, it has been shown by antibody absorption techniques that the decreased adhesiveness of cultured retinal cells obtained originally from older embryos is correlated with a decrease in the density or accessibility of cell adhesion molecules on the surface of these cells. The central role of CAM in neural cell aggregation has been established by the observation that anti-CAM Fab' fragments inhibit adhesion between neural cells in a variety of assays. To investigate the function of CAM and cell adhesion in developing tissues, aggregates of retinal cells that are capable of forming histotypic patterns in vitro were cultured in the presence and absence of anti-CAM Fab'. The Fab' was found to inhibit sorting out of cell bodies and neurites and to decrease the number of membrane-membrane contacts, suggesting that CAM is associated with cell-cell, cell-neurite, and neurite-neurite interactions.

Animals↗
PubMed2026

Integrative Genomic and Functional Investigation of the Multi-Layered Genetic Architecture Between Anorexia Nervosa and Bone Loss.

OBJECTIVE: Bone loss is a severe and often irreversible complication of anorexia nervosa (AN), yet the genetic mechanisms underlying this comorbidity remain underexplored. This study focuses on constructing a comprehensive genetic architecture between AN and estimated calcaneal bone mineral density (eBMD). METHOD: We applied an integrative framework incorporating genetic correlation, pleiotropic association, and causal inference across single-variant, multi-variant, and gene expression levels. Functional validation was conducted in vitro to investigate the biological role of the key candidate gene. RESULTS: Local genetic correlation analysis identified significant signals at 8p21.2 and 10q26.3, despite the lack of significant global correlation. Mendelian randomization analysis pointed to a suggestive negative causal effect of genetically predisposed AN on eBMD. Extensive pleiotropic signals were detected, particularly at 3p21.31 and 10q26.3, loci enriched with genes associated with both traits. Notably, we identified a novel pleiotropic signal near NCAM1 at 11q23.2, which was supported by multi-layered genetic evidence and confirmed through in vitro functional experiments. NCAM1, a well-established neural-associated gene, promoted osteoclastic differentiation and bone resorption when overexpressed in osteoclast precursor cells, indicating that NCAM1 possesses distinct functional roles in both neural and skeletal tissues. DISCUSSION: This study constructs a comprehensive genetic architecture underlying AN and eBMD and highlights NCAM1 as a key pleiotropic gene.

anorexia nervosa↗
PubMed1978

Adhesion among neural cells of the chick embryo. IV. Role of the cell surface molecule CAM in the formation of neurite bundles in cultures of spinal ganglia.

The cell adhesion molecule (CAM) is involved in adhesion among embryonic retinal and brain cells and has been detected in a variety of neural tissues. This paper describes the use of spinal ganglion cultures and specific anti-CAM antibodies to determine the distribution of CAM on plasma membranes of nerve processes, and to assess the results of perturbation of its function during the growth of neurites from ganglia. The results indicate that CAM is distributed over the entire surface of nerve processes, and that specific anti-CAM Fab' fragments alter the morphology of neurite outgrowth. In particular, it was observed that anti-CAM inhibits formation of nerve bundles, so that the ganglion becomes surrounded by a tangled net of fine processes. Growth cone functions, such as neurite elongation, motility, and attachment to the substratum, did not appear to be affected by the antibody. These studies suggest that one of the major functions of CAM is to mediate side-to-side adhesion between neurites to form fascicles, and raise the possibility that this molecule serves a key role in embryogenesis of nerve tissues.

Animals↗
PubMed1977

Adhesion among neural cells of the chick embryo. I. An immunological assay for molecules involved in cell-cell binding.

An immunologically based method for the quantitative assay of molecules involved in cell adhesion is described. Three observations served as a basis for this assay: (a) cells obtained by trypsinization of retinal tissue aggregated rapidly, provided they had been allowed to recover in culture from the dissociation process; (b) treatment of chick retinal cells with Fab' fragments from rabbit antibodies against these cells prevented their aggregation; and (c) incubation of these antibody fragments with antigens released by retinal cells in culture neutralized their ability to inhibit aggregation. The amount of neutralizing antigen was determined by measuring the rates of cell aggregation in the presence and absence of antibody and antigen using a particle counter. Although adhesion was inhibited by anti-retinal cell antibodies, it was not affected by lectins or anti-carbohydrate antibodies that also were bound to the cell surface. Together, the results suggest that the inhibition involved blockade or inactivation of particular cell surface molecules and that the retinal cell antigens capable of neutralizing the antibodies represented these molecules or their fragments. In the accompanying paper, we describe the use of this assay for the purification from culture supernatants of a cell surface molecule involved in cell to cell adhesion.

Animals↗
PubMed1977

Adhesion among neural cells of the chick embryo.

Cell-cell binding of both retinal and brain cells of the chick embryo varied as a function of developmental age, brain cells acquiring their binding properties at an earlier time than retinal cells. Brain and retinal cells of the appropriate age bound as well to each other as to themselves. Antibodies prepared against a molecule released by retinal cells in culture were able to inhibit cell-cell binding between homologous and heterologous pairs of retinal and brain cells. These results suggest that the molecular mechanism of cell-cell binding is the same in these 2 tissues. Analysis of cell surface proteins precipitated by these antibodies suggest that one of the molecules involved in adhesion has a molecular weight of 150,000, and may be derived from a larger precursor. The possible mechanisms of cell-cell binding are discussed in terms of the properties of this molecule.

Animals↗
PubMed1975

Purification and characterization of the retina-specific cell-aggregating factor.

The tissue-specific, cell-aggregating component of embryonic neural retina cells was purified from the retina cell-aggregating factor and characterized as a glycoprotein. Its molecular weight in solution is in the range of 50,000, and it contains 10-15% carbohydrate. The amino-acid and carbohydrate compositions have been determined. The glycoprotein is produced by embryonic neural retina cells in primary monolayered cultures and is released into the medium. Its tissue-specific, cell-aggregating effect requires integrity of the polypeptide portion, but not of the carbohydrate portion. We suggest that the isolated molecule is a specific determinant of the embryonic retina cell-surface and that it is involved in mediating self-recognition and selective adhesiveness of these cells.

Amino Acids↗
PubMed1977

Biochemical investigations of retinotectal adhesive specificity.

The preferential adhesion of chick neural retina cells to surfaces of intact optic tecta has been investigated biochemically. The study uses a collection assay in which single cells from either dorsal or ventral halves of neural retain adhere preferentially to ventral or dorsal halves of optic tecta respectively. The data presented support the following conclusions: (a) The adhesion of ventral retina to dorsal tecta seems to depend on proteins located on ventral retina and on terminal beta-N-acetylgalactosamine residues on dorsal tecta. (b) The adhesion of dorsal retina to ventral tecta seems to depend on proteins located on ventral tecta and on terminal beta- N-acetylgalactosamine residues on dorsal retina. (c) A double gradient model for retinotectal adhesion along the dorsoventral axis is consistent with the data presented. The model utilizes only two complementary molecules. The molecule suggested to be concentrated dorsally in both retina and tectum seems to require terminal beta-N-acetylgalactosamine residues for adhesion. Its activity is not affected by protease. A molecule fitting these qualifications, the ganglioside GM(2), could not be detected in a gradient, but lecithin vesicles containing GM(2) adhered preferentially to ventral tectal surfaces. The second molecule, concentrated ventrally in both retina and tectum, is a protein and seems capable of binding terminal beta-N- acetylgalactosamine residues. One enzyme, UDP-galactose:GM(2) galactosyltransferase, has been found to be more concentrated in ventral retina than dorsal, but only by 30 percent.

Acetylgalactosamine↗
PubMed1975

A molecular approach to retinotectal specificity.

An assay is described to examine the hypothesis that retinal neurons adhere preferentially to that part of the optic tectum near theri normal synaptic termini. The method measures the adherence of isotopically labelled cell bodies from either the dorsal or ventral half of the neural retina of chick embryos to dorsal and ventral tectum halves. When a labelled cell suspension is prepared from a dorsal half-retina, more cells adhere to the ventral half of the tectum. When the cells are from the ventral part of the retina, more bind to the dorsal half of the tectum. This preferential adhesion mimics the retinotectal projection found in vivo and supports an interpretation of neuronal specificity dependent on cell surface adhesive properties. Molecular mokels are presented that utilize glycosyltransferases and their substrates as the basis for adhesive recognition. Two of these models suggest that quantitative changes in the distribution of transferases and their substrates determine retinotectal specificity. The third proposes qualitative variations in these molecules across the retina and tectum.

Animals↗
PubMed1978

In vitro studies on neural specificity.

The migration of the retinal ganglionic axons through the optic nerve, over the tectal surface, and into the tectum to synapse correctly with brain neurons has been one of the most studied paradigms of neural specificity. Through the use of dissected tecta from the developing chick embryo, dissociated retinal cells can make the same choices in vitro that the ganglion cell termini make in vivo. That is, cells from the dorsal retina prefer to adhere to ventral tectum fragments and vice versa, in accord with the final map of the retina on the tectum. This assay has been used to analyze the biochemical components on the cell and tectal surfaces that might account for the recognition observed. Also, the assay has made it clear that virtually all the retinal cells can distinguish between dorsal and ventral tectal fragments, even though the cells of the retina that normally synapse with the tectum make up not more than 5% of the total population of the retina. One reason for this may be that, although only the retinal ganglion cells send their processes into the brain, these processes use all of the retina initially to get to the fundus of the retina, where the optic nerve begins. The vast majority of the retinal cells may possess surface recognition molecules not for finding the tectum but for serving as substrates for the few retinal cells whose axons must first leave the retina before finding the correct tectal locus.

Animals↗