Deletion of the calcium-binding protein S100β alters axon initial segment development in the visual cortex.

The axon initial segment (AIS) is a key structure for fine-tuning neuronal excitability. It plays a particularly important role during development across many sensory systems, where it contributes to network refinement and the adjustment of excitability levels. In the visual cortex, the AIS undergoes a significant period of plasticity that helps adjust neuronal excitability during key developmental stages such as eye opening and the onset of binocular vision. This development is tightly regulated by numerous factors, including glial cells. The calcium-binding protein S100β, which is primarily expressed in astrocytes, has previously been implicated in axonal development. We therefore asked whether it might also contribute to the normal development of the AIS in the visual cortex. Here, we characterize the consequences of S100β loss on AIS development and examine its impact on neuronal excitability.