The SG of a7 Cre:DTA embryos is reduced in size and the majority of cells remaining give rise to mostly peripherinlabeled efferents (see Fig. 5E ). These fibers also appear to be more densely aggregated relative to the a7 GFP control mouse ( Fig. 6A and B) . While peripherin-identified processes still project to the presumptive sensory cells (both IHC and OHC), they were less branched and those that did project to the former OHC target fields often turn and proceed backwards towards the vicinity of IHCs ( Fig. 6C and D) . These results are consistent with the earliest expression of a7 being after major cochlear structures are determined, and there was the expected selective ablation of OHCs and Deiters's cells. The necessity of the presence of the target sensory cell to coordinate the innervation process is also suggested by these findings.