Differential Glycosylation of Tractin and LeechCAM, Two Novel Ig Superfamily Members, Regulates Neurite Extension and Fascicle Formation

By immunoaffinity purification with the mAb Lan3-2, we have identified two novel Ig superfamily members, Tractin and LeechCAM. LeechCAM is an NCAM/FasII/ApCAM homologue, whereas Tractin is a cleaved protein with several unique features that include a PG/YG repeat domain that may be part of or interact with the extracellular matrix. Tractin and LeechCAM are widely expressed neural proteins that are differentially glycosylated in sets and subsets of peripheral sensory neurons that form specific fascicles in the central nervous system. In vivo antibody perturbation of the Lan3-2 glycoepitope demonstrates that it can selectively regulate extension of neurites and filopodia. Thus, these experiments provide evidence that differential glycosylation can confer functional diversity and specificity to widely expressed neural proteins

Establishing a functional brain circuitry: the development of the retino-tectal projection

Topographic matching between pre- and postsynaptic ganglion cell sheets appears to be a typical way in which different regions of the vertebrate brain are interconnected. The visual system provides a well-suited model to study the processes underlying the generation of 'topographic projections' during development. In this review, we will discuss several mechanisms which are possibly involved in the sorting of retinal axon terminals within their target field, the optic tectum. These mechanisms include target recognition by 'cytochemical matching' between axons and target cells, fiber-fiber interactions, and synapse stabilization and elimination based on impulse activity

Protein analysis on two-dimensional polyacrylamide gels in the femtogram range: use of a new sulfur-labeling reagent

An ultrasensitive staining procedure for two-dimensional polyacrylamide gels of protein homogenates has been developed. It combines the use of ultrathin gels and the labeling of proteins by a 35S-labeling reagent

Affinity purification of monospecific antibodies from polyclonal sera as a means for the identification of differentially expressed genes and proteins

The identification and characterization of genes and proteins that are either cell-type specific or exhibit an otherwise spatially or temporally restricted expression pattern is a crucial step toward understanding the complex interactions between the different cell types in an organism. We demonstrate here that monospecific polyclonal antibodies purified from rabbit antisera by a simple Western blotting and reelution technique can be successfully used for the detection of such proteins, as well as the corresponding genes by screening cDNA expression libraries. This strategy is discussed as a supplement to other approaches, such as the generation of tissue-specific monoclonal antibodies and the "subtractive hybridization technique.

Axonal Growth on Solubilized and Reconstituted Matrix from the Embryonic Chicken Retina Inner Limiting Membrane

Basal laminae, thin sheets of extracellular matrix covering the basal side of all neuroepithelia, are strongly supportive for neurite outgrowth in vitro and may provide a permissive environment for growing neurites in vivo. To gain information about the biological activity and composition of in situ-derived basal laminae the inner limiting membranes from embryonic day (E) 7 to E11 chick and quail retinae were isolated. The basal laminae were solubilized with high-molar guanidine hydrochloride or urea, and the solubilized proteins reconstituted by dialysis. The matrix proteins were spotted or dried onto nitrocellulose or polylysine-coated dishes. When explants from retina or from dorsal root ganglia were incubated on the protein spots, neurite extension was very robust, at a level as high as on authentic basal lamina. Extracts from the pigment epithelial basement membrane did not support neurite extension. Western blot analysis showed that the explant from the retinal inner limiting membrane contained predominantly basal lamina-type proteins, such as laminin, collagen type IV and heparan sulphate proteoglycan, whereas the matrix extract from the pigment epithelium contained predominantly mesenchymal-type proteins, like collagen type I and tenascin. JG22, a beta1 integrin antibody that inhibited neurite extension on EHS tumour laminin substrate, had no effect on neurite outgrowth on retinal basal lamina matrix, indicating that embryonic basal laminae contain other or additional growth promoting substrate molecules

Repair strategies for traumatic spinal cord injury, with special emphasis on novel biomaterial-based approaches

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