Peri-centrosomal positioning of the mammalian Golgi apparatus is known to involve microtubule-based motility, but its importance for cellular physiology is a major unanswered question. Here, we identify golgin-160 and GMAP210 as proteins required for centripetal motility of Golgi membranes. In the absence of either golgin, peri-centrosomal positioning of the Golgi apparatus was disrupted while the cytoskeleton remained intact. Although secretion persisted with normal kinetics, it was evenly distributed in response to wounding rather than directed to the wound edge. Strikingly, these cells also completely failed to polarize. Further, directionally persistent cell migration was inhibited such that wound closure was impaired. These findings not only reveal novel roles for golgin-160 and GMAP210 in conferring membrane motility but also indicate that Golgi positioning has an active role in directed secretion, cell polarity, and wound healing.

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Summary A deletion or duplication in the 16p11.2 region is associated with neurodevelopmental disorders including autism spectrum disorder and schizophrenia. In addition to clinical characteristics, carriers of the 16p11.2 copy number variant (CNV) manifest opposing neuroanatomical phenotypes, e.g. macrocephaly in deletion carriers (16pdel) and microcephaly in duplication carriers (16pdup). Using fibroblasts obtained from 16pdel and 16pdup carriers, we generated induced pluripotent stem cells (iPSCs) and differentiated them into neurons to identify causal cellular mechanisms underlying neurobiological phenotypes. Our study revealed increased soma size and dendrite length in 16pdel neurons and reduced neuronal size and dendrite length in 16pdup neurons. Functional properties of iPSC-derived neurons corroborated aspects of these contrasting morphological differences that may underlie brain size. Interestingly, both 16pdel and 16pdup neurons displayed reduced synaptic density, suggesting that distinct mechanisms may underlie brain size and neuronal connectivity at this locus.

SUMMARY Abnormalities in dendritic spines are manifestations of several neurodevelopmental and psychiatric diseases. TAOK2 is one of the genes in the 16p11.2 locus, copy number variations of which are associated with autism and schizophrenia. Here, we show that the kinase activity of the serine/threonine kinase encoded by TAOK2 is required for spine maturation. TAOK2 depletion results in unstable dendritic protrusions, mislocalized shaft-synapses, and loss of compartmentalization of NMDA receptor-mediated calcium influx. Using chemical-genetics and mass spectrometry, we identified several TAOK2 phosphorylation targets. We show that TAOK2 directly phosphorylates the cytoskeletal GTPase Septin7, at an evolutionary conserved residue. This phosphorylation induces translocation of Septin7 to the spine, where it associates with and stabilizes the scaffolding protein PSD95, promoting dendritic spine maturation. This study provides a mechanistic basis for postsynaptic stability and compartmentalization via TAOK2-Sept7 signaling, with implications toward understanding the potential role of TAOK2 in neurological deficits associated with the 16p11.2 region.