Myoblasts are aligned with collagen fibrils in regenerating frog tadpole tails.

Myoblasts in the regenerating frog tadpole tail differentiate from mesenchymal cells that lie next to the basement membrane of the epidermis of the tail. As these cells elongate and form myotubes, they orientate uniformly in the longitudinal axis of the tail. The collagen fibrils of the basement membrane adjacent to the myogenic cells are also orientated in the tail axis just prior to and during the time when the myogenic cells are elongating. This has been demonstrated by transmission electron microscopy of thin sections, by differential interference contrast microscopy of isolated basement membranes, and by scanning electron microscopy of the inner surface of the basement membrane. Since elongating myoblasts are in contact with the longitudinally orientated fibrils, the latter could provide directional cues to the elongating myoblasts. This proposition is supported by the finding that isolated basement membranes readily orientate cells that are cultured upon their inner surfaces.