Kathryn W. Tosney

      Muscle Differentiation and Morphogenesis

As with our studies of axon guidance, studies addressing the determination and morphogenesis of the myotome begin with surgical approaches to define phenomena and then analyze their cellular and molecular mechanisms.

A study in progress shows that the dermatome is a bipotential precursor, able to generate either dermis or myotomal cells, and that local interactions control cell fate.

A second study shows that intercostal muscle precursors arise at both limb and thoracic levels, but normally develop only at thoracic levels. Analysis shows that, at limb levels, these muscle precursors preferentially die. Embryonic surgeries reveal that limb buds induce apoptosis. Interactions inducing apoptosis thus control the spatial development of an entire muscle group.

shows a scanning electron micrograph cut through the limb bud level of a chick embryo. Dermatomes are the epithelial tissue at the top, on either side of the central neural tube. The developing myotome is a thin line of cells lying just below the dermatome.


  • Tosney KW . Life and death at the dermatome boundary: the limb induces apoptosis of hypaxial muscle precursors (in preparation).
  • Tosney KW. CAPs: Centers of Active Progenitors (CAPs) in the dermatome generate myotome populations in a stereotyped spatial-temporal array. (in preparation)
  • Schroeter S and Tosney KW (1991). Spatial and temporal patterns of muscle cleavage in the chick thigh and their value as criteria for homology. Am. J. Embryol. 191: 325-350.
  • Schroeter S and Tosney KW (1991). Ultrastructural and morphometric analysis of the separation of two thigh muscles in the chick. Am. J. Anat. 191: 351-386.
  • Grim M, Nensa K, Christ B, Jacob HJ, and Tosney KW (1989). A hierarchy of determining factors controls motoneuron innervation. Experimental studies on the development of the plantaris muscle in avian chimeras. Anat. Embryol. 180:179-189.