Tract formation and axon fasciculation of molecularly distinct peripheral neuron subpopulations during leech embryogenesis

Johansen, Kristen M.; Kopp, Diane M.; Jellies, John

doi:10.1016/0896-6273(92)90283-j

Cited by 29 publications

(57 citation statements)

References 33 publications

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“…Membrane Tethering of the Cleaved NH 2 -terminal Tractin Fragment-The above studies provide evidence that the NH 2 -terminal fragment of Tractin is constitutively cleaved in the trans-Golgi network although it is known from immunocytochemistry and immunoelectron microscopy that it is localized to the surface of axons (32,33). This raises the question of how it is tethered to the membrane.…”

Section: Biochemical Analysismentioning

confidence: 79%

Proteolytic Cleavage of the Ectodomain of the L1 CAM Family Member Tractin

Zipser³

et al. 2003

Journal of Biological Chemistry

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Tractin is a member of the L1 family of cell adhesion molecules in leech. Immunoblot analysis suggests that Tractin is constitutively cleaved in vivo at a proteolytic site with the sequence RKRRSR. This sequence conforms to the consensus sequence for cleavage by members of the furin family of convertases, and this proteolytic site is shared by a majority of other L1 family members. We provide evidence with furin-specific inhibitor experiments, by site-specific mutagenesis of Tractin constructs expressed in S2 cells, as well as by Tractin expression in furin-deficient LoVo cells that a furin convertase is the likely protease mediating this processing. Cross-immunoprecipitations with Tractin domain-specific antibodies suggest that the resulting NH 2 -and COOH-terminal cleavage fragments interact with each other and that this interaction provides a means for the NH 2 -terminal fragment to be tethered to the membrane. Furthermore, in S2 cell aggregation assays we show that the NH 2 -terminal fragment is necessary for homophilic adhesion and that cells expressing only the transmembrane COOH-terminal fragment are non-adhesive. However, tethering of exogeneously provided Tractin NH 2 -terminal fragment to S2 cells expressing only the COOHterminal fragment can functionally restore the adhesive properties of Tractin.

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Section: Biochemical Analysismentioning

confidence: 79%

Proteolytic Cleavage of the Ectodomain of the L1 CAM Family Member Tractin

Zipser³

et al. 2003

Journal of Biological Chemistry

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“…The epitopes recognized by these monoclonal antibodies (mAbs) are found on the surfaces of sensory afferents, where they are located on the N-linked carbohydrate chains of the 130 kD sensory afferent proteins (Bajt et al, 1990). The epitope recognized by mAb Lan3-2 serves as a carbohydrate marker for the full set of sensory afferents, while epitopes recognized by other mAbs serve as carbohydrate markers for four disjoint subsets of these same sensory afFerents (Zipser et al, 1994;Johansen et al, 1992). The projections of the full set of sensory afferents can be visualized by staining live CNS ganglia with rhodamine-conjugated mAb Lan3-2.…”

Section: The Central and Peripheral Nervous System Of The Leechmentioning

confidence: 99%

Leech photoreceptors project their galectin-containing processes into the optic neuropils where they contact AP cells

et al. 1996

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We characterized a subset of leech sensory afferents, the photoreceptors, in terms of their molecular composition, anatomical distribution, and candidate postsynaptic partners. For reagents, we used an antiserum generated against purified LL35, a 35 kD leech lactose-binding protein (galectin); monoclonal antibody (mAb) Lan3-2, which is specific for a mannose-containing epitope common to the full set of sensory afferents; and dye injections. Photoreceptors differ from other types of sensory afferents by their abundant expression of galectin. However, photoreceptors share in common with other sensory modalities the mannose-containing epitope recognized by mAb Lan3-2. Photoreceptors from a given segment project their axons directly into the CNS ganglion innervating the same segment. They assemble in a target region, the optic neuropil, which is separate from the target regions of other sensory modalities. They also extend their axons as an optic tract into the connective to innervate optic neuropils of other CNS ganglia, thereby providing extensive intersegmental innervation for the 33 CNS ganglia comprising the leech nerve cord. Because of its intimate contact with the optic neuropil, a central neuron, the AP effector cell, is a strong candidate second order visual neuron. In confocal images, the AP cell projects its primary axon for about 100 microns alongside the optic neuropil. In electron micrographs, spines emanating from the axon of the AP cell make contact with vesicle laden nerve terminals of photoreceptors. Leech photoreceptors and their second order visual neurons represent a simple visual system for studying the mechanisms of axonal targeting.

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“…Tractin is expressed on the soma and processes of both peripheral and central neurons as they differentiate and therefore serves as an ideal marker for neuron development and process outgrowth. By labeling the germinal plate of staged leech embryos with this antibody, we show that early in development, in addition to the seven groups of sensillar sensory neurons that have been previously characterized (Johansen et al, 1992;Jellies et al, 1994;, 21 identifiable peripheral neurons are present in each hemisegment. All but two of these neurons are aligned with the major nerves, and since their differentiation precedes extension of axons from the CNS, they are candidates to serve as guides for the formation of common nerve pathways.…”

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confidence: 97%

Development and pathway formation of peripheral neurons during leech embryogenesis

1998

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By labeling the germinal plates of staged leech embryos with monoclonal antibodies to the immunoglobulin superfamily member Tractin, we have documented the distribution and initial development of peripheral neurons in a hirudinid leech. We find, in addition to sensillar and extrasensillar sensory neurons, that there are 21 identifiable peripheral neurons in each hemisegment. These neurons are found in highly stereotyped positions, and all but two of them are associated with the segmental nerves. We show that eight of the peripheral neurons have the characteristic morphology of stretch receptor neurons and that they form a circumferentially distributed grid aligned in such a way that each of five specialized longitudinal muscle fascicles are monitored by at least two stretch receptor cells covering ventral, lateral, and dorsal regions of the body wall. Furthermore, we show that, in contrast to the dorsal posterior nerve, which is pioneered by central projections, the pathways of the three remaining segmental nerves are likely to be pioneered or guided by peripheral neurons.

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Tract formation and axon fasciculation of molecularly distinct peripheral neuron subpopulations during leech embryogenesis

Cited by 29 publications

References 33 publications

Proteolytic Cleavage of the Ectodomain of the L1 CAM Family Member Tractin

Proteolytic Cleavage of the Ectodomain of the L1 CAM Family Member Tractin

Leech photoreceptors project their galectin-containing processes into the optic neuropils where they contact AP cells

Development and pathway formation of peripheral neurons during leech embryogenesis

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