What cellular changes and molecular signals underlie changes in TSC number?
The loss of TSCs that occurred when junctions shrank could be attributable to cell death or to the migration of TSCs away from the junction. Similarly, the increase in TSC number that occurred as junctions enlarged could result from division of TSCs at the junction or from Schwann cell migration onto the junction from the nerve. TSC death has been observed after denervation, but only in neonates (Trachtenberg and Thompson, 1996), and TSCs migrate from endplates at long times after denervation of adult muscle (Reynolds and Woolf, 1992). Both cell division and migration participate in the addition of TSCs during early postnatal development (Love and Thompson, 1998). At present, we cannot distinguish among these possibilities for TSC addition and loss in the adult. We did not observe apoptotic TSC profiles or cells migrating from junctions after castration, nor did we observe mitotic TSCs or cells migrating onto junctions after testosterone treatment. However, given the small numbers of c
