Peripheral nervous system plasmalogens regulate Schwann cell differentiation and myelination
Tiago Ferreira da Silva, Jessica Eira, André T. Lopes, Ana R. Malheiro, Vera Sousa, Adrienne Luoma, Robin L. Avila, Ronald J.A. Wanders, Wilhelm W. Just, Daniel A. Kirschner, Mónica M. Sousa, Pedro Brites
Tiago Ferreira da Silva, Jessica Eira, André T. Lopes, Ana R. Malheiro, Vera Sousa, Adrienne Luoma, Robin L. Avila, Ronald J.A. Wanders, Wilhelm W. Just, Daniel A. Kirschner, Mónica M. Sousa, Pedro Brites
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Research Article Neuroscience

Peripheral nervous system plasmalogens regulate Schwann cell differentiation and myelination

Abstract

Rhizomelic chondrodysplasia punctata (RCDP) is a developmental disorder characterized by hypotonia, cataracts, abnormal ossification, impaired motor development, and intellectual disability. The underlying etiology of RCDP is a deficiency in the biosynthesis of ether phospholipids, of which plasmalogens are the most abundant form in nervous tissue and myelin; however, the role of plasmalogens in the peripheral nervous system is poorly defined. Here, we used mouse models of RCDP and analyzed the consequence of plasmalogen deficiency in peripheral nerves. We determined that plasmalogens are crucial for Schwann cell development and differentiation and that plasmalogen defects impaired radial sorting, myelination, and myelin structure. Plasmalogen insufficiency resulted in defective protein kinase B (AKT) phosphorylation and subsequent signaling, causing overt activation of glycogen synthase kinase 3β (GSK3β) in nerves of mutant mice. Treatment with GSK3β inhibitors, lithium, or 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8) restored Schwann cell defects, effectively bypassing plasmalogen deficiency. Our results demonstrate the requirement of plasmalogens for the correct and timely differentiation of Schwann cells and for the process of myelination. In addition, these studies identify a mechanism by which the lack of a membrane phospholipid causes neuropathology, implicating plasmalogens as regulators of membrane and cell signaling.

Authors

Tiago Ferreira da Silva, Jessica Eira, André T. Lopes, Ana R. Malheiro, Vera Sousa, Adrienne Luoma, Robin L. Avila, Ronald J.A. Wanders, Wilhelm W. Just, Daniel A. Kirschner, Mónica M. Sousa, Pedro Brites

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Figure 5

Defects in plasmalogens result in impaired AKT activation and signaling.

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Defects in plasmalogens result in impaired AKT activation and signaling....
(A) Western blot analysis and quantification of AKT phosphorylation (p-AKT) in sciatic nerve lysates of P15 WT and Gnpat-KO mice. *P = 0.018; **P = 0.006. (B–E) Quantification of phosphorylated forms of GSK3β at Ser9 (B), c-RAF at Ser259 (C), PDK1 at Ser241 (D), and PTEN at Ser380 (E) in sciatic nerves from WT and Gnpat-KO mice. *P < 0.02. (F) Density of BrdU-positive cells in nerves from P4 WT and Gnpat-KO mice. *P = 0.020. (G) Western blot analyses of p-AKT and p-ERK1/2 in serum-starved MEFs from WT and Gnpat-KO mice stimulated with 10% FBS. (H and I) Quantification of p-AKT at Ser473 (H) and Thr308 (I) in primary WT and Gnpat-KO Schwann cells after stimulation with NRG1. (J) Western blot analysis of total and p-AKT in cytosolic and membrane fractions of serum-starved MEFs from WT and Gnpat-KO mice stimulated with 10% FBS. Western blot analysis of caveolin 1 (CAV1), GAPDH, and peroxisomal thiolase (ACAA1) used to control membrane fractions and cytosolic fractions and to monitor lack of solubilized organelles in cytosolic fractions, respectively. (K) DRG cocultures from WT and Gnpat-KO mice treated with DMSO (control) or with SC79, stained for neuronal βIII-tubulin (green) and MBP (red). Scale bars: 100 μm. (L) Density of myelin segments in DRG cocultures from WT and Gnpat-KO mice after DMSO and SC79 treatment. *P < 0.002. (M) Length of individual myelin segments in myelinating cocultures. *P < 0.01. Error bars represent SEM in all graphs.