Figure 1.

CBA-1 fragment of agrin A4B19 delivered by stably transfected rat L6 myoblasts injected into the nerve-free region (es) of denervated soleus muscle increases the level of AChR ɛ-subunit transcripts as observed in Northern blot hybridization. Test muscles were injected with stably transfected cells (L6-agrin); contralateral control muscles were injected with the same number of nontransfected L6 cells. Bar diagrams indicate levels of transcripts (mean ± SEM; n = 4 to 6) upon injection of agrin-secreting cells of one positive L6 clone (es, L6-agrin), relative to those injected with control L6 cells (es, L6-control); bars marked s give data for the muscle segments that contained synapses. Injection of another transfected clone of L6 cells and of transfected C2C12 cells into mouse soleus muscle gave similar results. Injection of L6 control cells or sham injection with saline into an endplate-free region did not affect AChR ɛ-subunit mRNA levels compared with noninjected muscles (data not shown). Levels of actin-specific mRNA are shown for control.