The subcellular localization of the carbohydrate epitope 3-fucosyl-N-acetyllactosamine is different in normal and reactive astrocytes

Identification and validation of a Lewis x glycomimetic peptide

Glycans play important roles in regulating cell recognition and interactions to fine tune development, and synaptic plasticity and regeneration in the adult nervous system. The spatial and temporal expression pattern of Lewis(x) (a terminal trisaccharide epitope characterized by alpha1,3-fucosyl-N-acetyl-lactosamine) in the nervous system indicates an important role of this epitope in neurogenesis and brain development. Localization of Lewis(x) in the proliferative subventricular zone of the developing nervous system and also its expression on stem cells of the adult nervous system suggests a role in neurogenesis and hence regeneration. To provide an alternative tool to elucidate the functional roles of Lewis(x), we screened a random peptide phage library against a Lewis(x)-specific antibody to identify a Lewis(x) glycomimetic peptide. We identified a peptide that specifically bound to the Lewis(x)-specific antibody and this binding could be competed by the Lewis(x) glycan. Different aspects of the Lewis(x) glycomimetic peptide were investigated by introducing it in in vitro assays measuring neurite outgrowth and in in vivo assays to determine its efficacy in regeneration of peripheral nerve and spinal cord after injury in adult mice. In vitro, neurite outgrowth triggered by the Lewis(x-)carrying adhesion molecule CD24 was abolished alike by the Lewis(x) glycan and the glycomimetic peptide, while no influence of the glycomimetic peptide was seen in regeneration. Our results validate the use of Lewis(x) glycomimetic peptide as a functionally equivalent structure to the Lewis(x) glycan.

Neural stem cell heterogeneity demonstrated by molecular phenotyping of clonal neurospheres

Neural stem cells (NSCs) in vitro are able to generate clonal structures, "neurospheres," that exhibit intra-clonal neural cell-lineage diversity; i.e., they contain, in addition to NSCs, neuronal and glial progenitors in different states of differentiation. The present study focuses on a subset of neurospheres derived from fresh clinical specimens of human brain by using an in vitro system that relies on particular growth factors, serum, and anchorage withdrawal. Thirty individual and exemplary cDNA libraries from these neurosphere clones were clustered and rearranged within a panel after characterization of differentially expressed transcripts. The molecular phenotypes that were obtained indicate that clonogenic NSCs in our in vitro system are heterogeneous, with subsets reflecting distinct neural developmental commitments. This approach is useful for the sorting and expansion of NSCs and facilitates the discovery of genes involved in cell proliferation, communication, fate control, and differentiation.

FUT4 and FUT9 genes are expressed early in human embryogenesis

The Le(x) oligosaccharide is expressed in organ buds progressing in mesenchyma, during human embryogenesis. Myeloid-like alpha3-fucosyltransferases are good candidates to synthesize this oligosaccharide. We investigated by Northern analysis all the alpha3-fucosyltransferase gene transcripts and only FUT4 and FUT9 were detected. The enzymes encoded by the FUT4 and FUT9 genes are the first alpha3-fucosyltransferases strongly expressed during the first two months of embryogenesis. The Northern profile of expression of the embryo FUT4 transcripts is similar in size and sequence to the known FUT4 transcripts of 6 kb, 3 kb, and 2.3 kb, but a new FUT9 transcript of 2501 bp, different from the known mouse (2170 bp) and human (3019 bp) transcripts was cloned. FUT3, FUT5, FUT6, and FUT7 were not detected by Northern blot. The FUT3 and FUT6 transcripts start to appear at this stage, but are only detected by reverse transcriptase-PCR analysis. The expression of FUT5 is weaker than FUT3 and FUT6 and the RT-PCR signal is faint and irregular. FUT7 is not detected at all. Using mRNA from 40- to 65-day-old embryos, we have prepared different hexamer and oligo-dT cDNA libraries and cloned, by rapid amplification cDNA ends-PCR, FUT4 and FUT9 alpha3-fucosyltransferase transcripts. The tissue expression of the embryonic FUT9 transcript is closer to that observed for the mouse (brain), than to the known human (stomach) transcripts. The acceptor specificity and the kinetics of the alpha3-fucosyltransferase encoded by this FUT9 transcript are similar to the FUT4 enzyme, except for the utilization of the lac-di-NAc acceptor which is not efficiently transformed by the FUT9 enzyme. Like FUT4, this embryonic FUT9 is N-ethylmaleimide and heat resistant and the corresponding gene was confirmed to be localized in the chromosome band 6q16. Finally, this FUT9 transcript has a single expressed exon as has been observed for most of the other vertebrate alpha2- and alpha3-fucosyltransferases.

Loss of immunoreactivity for glial fibrillary acidic protein (GFAP) in astrocytes as a marker for profound tissue damage in substantia nigra and basal cortical areas after status epilepticus induced by pilocarpine in rat

Status epilepticus induced by pilocarpine in rats induces massive tissue damage comprising neurons and astrocytes (incomplete infarction) in substantia nigra pars reticulata (SNR) and in basal cortical areas (BCTX). Immunohistochemistry with a polyclonal antiserum and a monoclonal antibody to GFAP were used here to study the astroglial damage in these regions. Control sections showed a strong labeling for glial fibrillary acidic protein (GFAP) for both antibodies in SNR and BCTX. At 1 day after induction of seizures, labeling with the polyclonal antibodies showed diffuse increase within the lesioned areas and enhanced staining of astrocytes at the border zones. However, staining with the monoclonal antibody was abolished. At 3 days, labeling with both the polyclonal antiserum and the monoclonal antibody was severely reduced within the damaged regions. Reactive astrocytes in the surround of the infarct showed enhanced labeling with both antibodies. This combination of enhanced labeling with polyclonal antibodies and decreased labeling with the specific monoclonal antibody for GFAP can be taken as indicator for acute glial cell damage in seizures and related experimental conditions.