SUMMARY
Topographic projection of afferent terminals into two-dimensional maps in the central nervous system (CNS) is a general strategy used by the nervous system to encode the locations of sensory stimuli. In vertebrates, it is known that while guidance cues are critical for establishing a coarse topographic map, neural activity directs fine-scale topography between adjacent afferent terminals [1–4]. However, the molecular mechanism underlying activity-dependent regulation of fine-scale topography is poorly understood. Molecular analysis of the spatial relationship between adjacent afferent terminals requires reliable localization of the presynaptic terminals of single neurons as well as genetic manipulations with single-cell resolution in vivo. Although both requirements can potentially be met in Drosophila melanogaster [5, 6], no activity-dependent topographic system has been identified in flies [7]. Here we report a topographic system that is shaped by neuronal activity in Drosophila. With this system, we found that topographic separation of the presynaptic terminals of adjacent nociceptive neurons requires different levels of Trim9, an evolutionarily conserved signaling molecule [8–11]. Neural activity regulates Trim9 protein levels to direct fine-scale topography of sensory afferents. This study offers both a novel mechanism by which neural activity directs fine-scale topography of axon terminals and a new system to study this process at single-neuron resolution.
We report the synthesis and characterization of two diphosphine nickel complexes containing 9-borafluorene (PBFlu, 9-(diisopropylphosphino)phenyl-9-borafluorene) and 9,10-dihydroboranthrene (B2P2, 9,10-bis(2-(diisopropylphosphino)phenyl)-9,10-dihydroboranthrene) cores. Metalation of PBFlu and B2P2 with Ni(PPh3)4 leads to the monometallic complexes (PBFlu)Ni(PPh3) and (B2P2)Ni, respectively. Cyclic voltammetry studies show a reversible redox event at ~ 0.1 V and a quasi-reversible event at ca.-3 V versus ferrocene/ferrocenium for (B2P2)Ni while (PBFlu)Ni(PPh3) features no reversible redox events. Electronic structure calculations were performed to provide further insight into the bonding in these complexes.
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