Peripheral nerves and Schwann cells have to sustain constant mechanical constraints, caused by developmental growth as well as stretches associated with movements of the limbs and mechanical compressions from daily activities. In Schwann cells, signaling molecules sensitive to stiffness or stretch of the extracellular matrix, such as YAP/TAZ, have been shown to be critical for Schwann cell development and peripheral nerve regeneration. YAP/TAZ have also been suggested to contribute to tumorigenesis, neuropathic pain, and inherited disorders. Yet, the role of mechanosensitive ion channels in myelinating Schwann cells is vastly unexplored. Here we comprehensively assessed the expression of mechanosensitive ion channels in Schwann cells and identified that PIEZO1 and PIEZO2 are among the most abundant mechanosensitive ion channels expressed by Schwann cells. Using classic genetic ablation studies, we show that PIEZO1 is a transient inhibitor of radial and longitudinal myelination in Schwann cells. Contrastingly, we show that PIEZO2 may be required for myelin formation, as the absence of PIEZO2 in Schwann cells delays myelin formation. We found an epistatic relationship between PIEZO1 and PIEZO2, at both the morphological and molecular levels. Finally, we show that PIEZO1 channels affect the regulation of YAP/TAZ activation in Schwann cells. Overall, we present here the first demonstration that PIEZO1 and PIEZO2 contribute to mechanosensation in Schwann cells as well myelin development in the peripheral nervous system.

BackgroundNumerous studies have indicated that myelination is the result of the interplay between extracellular signals and an intricate network of transcription factors. Yet, the identification and characterization of the full repertoire of transcription factors that modulate myelination are still incomplete. CC2D1B is a member of the Lgd/CC2D1 family of proteins highly expressed in myelinating cells in the central and peripheral nervous systems. In addition, the absence of CC2D1B limits myelin formation in vitro. Here we propose to delineate the function of CC2D1B in myelinating cells during developmental myelination in vivo in the central and peripheral nervous systems.MethodsWe used a Cc2d1b constitutive knockout mouse model and then performed morphological analyses on semithin sections of sciatic nerves and electron micrographs of optic nerves. We also performed immunohistological studies on coronal brain sections. All analyses were performed at 30 days of age.ResultsIn the peripheral nervous system, animals ablated for Cc2d1b did not show any myelin thickness difference compared to control animals. In the central nervous system, immunohistological studies did not show any difference in the number of oligodendrocytes or the level of myelin proteins in the cortex, corpus callosum, and striatum. However, optic nerves showed a hypomyelination (0.844 ± 0.022) compared to control animals (0.832 ± 0.016) of large diameter myelinated fibers.ConclusionsWe found that CC2D1B plays a role in developmental myelination in the central nervous system. These results suggest that CC2D1B could contribute to gene regulation during oligodendrocytes myelination in optic nerves.

Starch is a key component in many aspects of daily life. Reversible starch phosphorylation by dikinases and glucan phosphatases is an essential step in plant transitory starch metabolism. Much of the progress of glucan phosphatases has been come from studying the proteins from Arabidopsis thaliana, a model species in plant biology. However, there are several unresolved questions as to how glucan phosphatases bind and locate phosphate groups within the complex starch structure and how we can harness phosphorylation to modify starch yield and properties in plant systems. The overall goal of this project is to expand our understanding of glucan phosphatases on to agriculturally relevant crop species and utilize them to improve starch degradation in vitro and starch yield in vivo. To identify glucan phosphatases from plant and algal species, BLAST searches were performed using the A. thaliana homologs as query sequences. We cloned and overexpressed Starch Excess4 (SEX4) and Like SEX Four 2 (LSF2) from Oryza sativa (rice), Zea mays (corn), and Solanum tuberosum (potato) in E. Coli and purified them to homogeneity using nickel affinity chromatography and size exclusion chromatography. Successful purification of SEX4 and LSF2 has allowed us to obtain functional and structural mechanisms of glucan dephosphorylation in transitory starch degradation.