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Polysialylated NCAM expression during motor axon outgrowth and myogenesis in the fetal rat
Author(s) -
Allan Douglas W.,
Greer John J.
Publication year - 1998
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19980216)391:3<275::aid-cne1>3.0.co;2-z
Subject(s) - biology , myogenesis , neural cell adhesion molecule , neuroscience , axon , axon guidance , motor neuron , neurite , expression (computer science) , microbiology and biotechnology , anatomy , myocyte , genetics , cell , spinal cord , cell adhesion , in vitro , computer science , programming language
Polysialylation of the neural cell adhesion molecule (NCAM) converts it into an anti‐adhesive molecule, attenuating intercellular adhesion and repelling apposed membranes. Previous studies have demonstrated that interaxonal repulsion, or defasciculation, induced by polysialylated NCAM (PSA‐NCAM) expressed along outgrowing chick motor axons promotes intramuscular branching and facilitates differential guidance of segregating axonal populations. In the present study, we have examined the expression of PSA‐NCAM in a developing mammalian motor system during axonal outgrowth, separation of distinct axonal populations, and intramuscular branching. Furthermore, we provide the first clear demonstration of the spatiotemporal modulation of PSA‐NCAM expression on myotubes during each stage of myogenesis. Immunohistochemical labelling was used to compare the spatiotemporal pattern of PSA‐NCAM expression with those of total‐NCAM, the cell adhesion molecule L1, and growth associated protein (GAP‐43) during development of the phrenic nerve and diaphragm of fetal rats (embryonic days, E11–E19). During segregation of phrenic and brachial axonal populations at the brachial plexus (E12.5–E13), PSA‐NCAM expression was restricted to phrenics, being absent from brachial motoneurons. Both populations labelled equivalently for NCAM, L1, and GAP‐43. We postulate that PSA‐NCAM may be a component of the molecular machinery that specifically guides phrenic motoneuron growth at the brachial plexus. During diaphragmatic morphogenesis, PSA‐NCAM expression: (i) remained high within the phrenic nerve throughout intramuscular branching; (ii) was transiently up‐regulated on myotubes during myotube separation associated with primary and secondary myogenesis; (iii) was restricted to those regions of primary and secondary myotube membranes, which were juxtaposed and about to separate. These data suggest a role for PSA‐NCAM in the guidance of specific subsets of mammalian motoneurons and in intramuscular branching, and demonstrate an intimate correlation between PSA‐NCAM expression and myotube separation. J. Comp. Neurol. 391:275–292, 1998. © 1998 Wiley‐Liss, Inc.