Determination of dendritic spine morphology by the striatin scaffold protein STRN4 through interaction with the phosphatase PP2A.

Dendritic spines are heterogeneous and exist with various morphologies. Altered spine morphology might underlie the cognitive deficits in neurodevelopmental disorders such as autism, but how different subtypes of dendritic spines are selectively maintained along development is still poorly understood. Spine maturation requires spontaneous activity of N-methyl-d-aspartate (NMDA) receptor and local dendritic protein synthesis. STRN4 (also called zinedin) belongs to the striatin family of scaffold proteins, and some of the potential striatin-interacting proteins are encoded by autism risk genes. Although previous studies have demonstrated their localization in dendritic spines, the function of various striatin family members in the neuron remains unknown. Here, we demonstrate that Strn4 mRNA is present in neuronal dendrites, and the local expression of STRN4 protein depends on NMDA receptor activation. Notably, STRN4 is preferentially expressed in mushroom spines, and STRN4 specifically maintains mushroom spines but not thin spines and filopodia through interaction with the phosphatase PP2A. Our findings have therefore unraveled the local expression of STRN4 as a novel mechanism for the control of dendritic spine morphology.