Development of basket cell axons. (A) original drawing by Santiago Ramon y Cajal of a cerebellar basket cell (B) labeled by Golgi staining demonstrating its characteristic axonal arbors (a), the “pinceaux” formations, around the Purkinje cell body and axon. (B) Basket cell axons synapse preferentially on the Purkinje cell axon initial segment (AIS) under the influence of a gradient of Neurofascin 186, stabilized by Ankyrin G. In Ankyrin G knockout mice, the gradient of Neurofascin is abolished and basket cell axons do not synapse preferentially on the AIS. Abbreviations: ML, molecular layer; PCL, Purkinke cell layer; GCL, granule cell layer. A, Cajal drawing. Original conserved at the Instituto Cajal (CSIC), Madrid (Spain). B is adapted from Huang et al., 2007.