Marshall, W. | Search bioRxiv

bioRxiv2018

Electron Cryo-Tomography Provides Insight into Procentriole Architecture and Assembly Mechanism

Centriole is an essential structure with multiple functions in cellular processes. Centriole biogenesis and homeostasis is tightly regulated. Using electron cryo-tomography (cryoET) we present the structure of procentrioles from Chlamydomonas reinhardtii. We identified a set of non-tubulin components attached to the triplet microtubule (MT), many are at the junctions of tubules likely to reinforce the triplet. We describe structure of the A-C linker that bridges neighboring triplets. We find that POC1 is an integral component of the A-C linker. Its conserved WD40 {beta}-propeller domain provides sites for attachment to other A-C linker components. The twist of A-C linker results in an iris diaphragm-like motion of the triplets in the longitudinal direction of procentriole. Finally, we identified two assembly intermediates at the growing ends of procentriole allowing us to propose a model for the procentriole assembly. Our results provide a comprehensive structural framework for understanding the molecular mechanisms underpinning procentriole biogenesis and assembly.

cell biology↗

bioRxiv2017

Role of somatostatin-positive cortical interneurons in the generation of sleep slow waves

Cortical slow waves - the hallmark of NREM sleep - reflect near-synchronous OFF periods in cortical neurons. However, the mechanisms triggering such OFF periods are unclear, as there is little evidence for somatic inhibition. We studied cortical inhibitory interneurons that express somatostatin (SOM), because [~]70% of them are Martinotti cells that target diffusely layer 1 and can block excitatory transmission presynaptically, at glutamatergic terminals, and postsynaptically, at apical dendrites, without inhibiting the soma. In freely moving mice, we show that SOM+ cells can fire immediately before slow waves and their optogenetic stimulation triggers neuronal OFF periods during sleep. Next, we show that chemogenetic activation of SOM+ cells increases slow wave activity (SWA), the slope of individual slow waves, and the duration of NREM sleep; whereas their chemogenetic inhibition decreases SWA and slow wave incidence without changing time spent asleep. By contrast, activation of parvalbumin+ (PV+) cells, the most numerous population of cortical inhibitory neurons, greatly decreases SWA and cortical firing. These results indicate that SOM+ cells, but not PV+ cells, are involved in the generation of sleep slow waves. Whether Martinotti cells are solely responsible for this effect, or are complemented by other classes of inhibitory neurons, remains to be investigated.

neuroscience↗