Motoneuron development and spinal cord patterning

Dr. Lance-Jones’ research focuses on the question of how patterns of motoneurons and muscles develop in the limb of the vertebrate embryo. The model system used is the avian embryo, and the specific structures studied are the motoneurons of the lumbosacral spinal cord and the thigh muscles of the hindlimb. In an eight-day chick embryo (less than halfway through in ovo development), limb structures are remarkably adult in form, suggesting that important pattern-ing mechanisms operate early. A stereotyped pattern of peripheral nerves is present within the limb, and motoneuron projections from specific spinal cord segments are unique and correct in the eight-day embryo. Further, individual muscles with characteristic patterns of fiber types are readily identifiable.

How and when do motoneurons acquire a target identity? How is the early limb bud populated by muscle cell precursors? How does the early spinal cord acquire differences along its cranio-caudal axis? Trainees in Dr. Lance-Jones’ laboratory have the opportunity to study embryonic patterning at tissue, cell and molecular levels. In vivo embryonic surgery is frequently combined with new techniques for identifying different types of embryonic cells. Such techniques might include long-lasting fluorescent cell markers, monoclonal antibodies, retroviral vectors, and/or gene probes. Currently, laboratory members are specifically looking at the roles of hox genes and paraxial mesoderm in the early regional development of the spinal cord.

Van Swearingen, J.M., and Lance-Jones, C. Slow and fast muscle fibers are preferentially derived from myoblasts migrating into the chick limb bud at different developmental times. Dev. Biol. l70: 321-337, 1995.

Matise, M. and Lance-Jones, C. A critical period for the specification of motoneurons in the chick lumbosacral spinal cord. Development 122: 659-669, 1996.

Lin, J., Saito, T., Anderson, D.J., Lance-Jones, C., Jessell, T.M., and Arber, S. Functionally related motor neuron pool and muscle sensory afferent subtypes defined by coordinate ETS gene expression. Cell 95: 393-407, 1998.

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