The normal functioning of an animal's limb depends on a highly ordered pattern of connections between motoneurons in the spinal cord and the various muscles of the limb. This pattern is established during development by specific axonal growth. Motoneuron axons normally make a series of pathway choices as they grow from the spinal cord to their target muscle. These choices require axons to recognize and respond appropriately to multiple growth cues associated with cells whose precise location and identity are presently unknown in any vertebrate. A combination of various surgical manipulations and several anatomical techniques will be used to localize and to identify the cell populations which provide the environmental cues to guide growing motor axons to their target muscles. All of the experiments will be done on chick or quail embryos. The first question is whether the cues for the two axes of the limb are separately located along the nerve pathways. Other experiments will determine whether the presence of muscle cells, the targets of motoneurons, are required for accurate pathfinding, or whether connective tissue cells are sufficient. The final series of experiments will explore the role of presumptive sheath cells, or Schwann cells, in assuring normal innervation of limb muscles. An increased knowledge of the location and cellular identity of guidance cues used by growing axons during normal development should aid efforts to understand neuromuscular disorders as well as to promote specific regrowth of adult nervous tissue following damage due either to disease or injury.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS025340-02
Application #
3410597
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1987-02-01
Project End
1990-01-31
Budget Start
1988-02-01
Budget End
1989-01-31
Support Year
2
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Bryn Mawr College
Department
Type
Schools of Arts and Sciences
DUNS #
City
Bryn Mawr
State
PA
Country
United States
Zip Code
19010
Hollyday, M (1995) Chick wing innervation. I. Time course of innervation and early differentiation of the peripheral nerve pattern. J Comp Neurol 357:242-53
Hollyday, M; Morgan-Carr, M (1995) Chick wing innervation. II. Morphology of motor and sensory axons and their growth cones during early development. J Comp Neurol 357:254-71
Ferns, M J; Hollyday, M (1995) Chick wing innervation. III. Formation of axon collaterals in developing peripheral nerves. J Comp Neurol 357:272-80
Gutman, C R; Ajmera, M K; Hollyday, M (1993) Organization of motor pools supplying axial muscles in the chicken. Brain Res 609:129-36
Ferns, M J; Hollyday, M (1993) Motor innervation of dorsoventrally reversed wings in chick/quail chimeric embryos. J Neurosci 13:2463-76
Carpenter, E M; Hollyday, M (1992) The location and distribution of neural crest-derived Schwann cells in developing peripheral nerves in the chick forelimb. Dev Biol 150:144-59
Carpenter, E M; Hollyday, M (1992) The distribution of neural crest-derived Schwann cells from subsets of brachial spinal segments into the peripheral nerves innervating the chick forelimb. Dev Biol 150:160-70
Phelan, K A; Hollyday, M (1991) Embryonic development and survival of brachial motoneurons projecting to muscleless chick wings. J Comp Neurol 311:313-20
Prasad, A; Hollyday, M (1991) Development and migration of avian sympathetic preganglionic neurons. J Comp Neurol 307:237-58
Hollyday, M (1990) Specificity of initial axonal projections to embryonic chick wing. J Comp Neurol 302:589-602

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