Showing papers by "Betty Soliven published in 2016"

S1P1 deletion in oligodendroglial lineage cells: Effect on differentiation and myelination.

Abstract: Sphingosine 1-phosphate (S1P) receptors are G protein-coupled receptors expressed by many cell types, including cells of oligodendrocyte (OLG) lineage. We had previously shown that targeted deletion of S1P1 in OLG lineage cells did not result in obvious clinical phenotype or altered number of OLGs at 3 months, but there were subtle abnormalities in myelin. In this study, we examined the role of S1P1 in developmental myelination and cell survival, focusing on age 3 weeks. We found that S1P1 deficiency led to delayed differentiation of OLG progenitors (OPCs) into OLGs that is independent of p38 phosphorylation. This was accompanied by decreased levels of myelin basic protein (MBP) but not of myelin-OLG glycoprotein (MOG), and slight decrease in myelin thickness in the corpus callosum of S1P1 conditional knockout (CKO) mice. S1P1 -deficient OLGs exhibited slower process extension, which was associated with attenuated phosphorylation of extracellular signal regulated kinases (ERKs) and p21-activated kinases (PAKs), and with upregulation of tropomodulin1. Basal levels of pAkt were not affected, though expectedly, no response to a selective S1P1 agonist SEW2871 was observed. S1P1 -deficient OLGs did not exhibit increased cell death in response to cuprizone, tumor necrosis factor-α, or deprivation of nutrients and growth factors. We conclude that S1P1 signaling regulates OLG development, morphological maturation and early myelination.

Regulatory T and B lymphocytes in a spontaneous autoimmune polyneuropathy.

Abstract: B7-2(-/-) non-obese diabetic (NOD) mice develop a spontaneous autoimmune polyneuropathy (SAP) that mimics the progressive form of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). In this study, we focused on the role of regulatory T cells (Tregs ) and regulatory B cells (Bregs ) in SAP. We found that deletion of B7-2 in female NOD mice led to a lower frequency and number of Tregs and Bregs in spleens and lymph nodes. Tregs but not Bregs suppressed antigen-stimulated splenocyte proliferation, whereas Bregs inhibited the T helper type 1 (Th1) cytokine response. Both Tregs and Bregs induced an increase in CD4(+) interleukin (IL)-10(+) cells, although less effectively in the absence of B7-2. Adoptive transfer studies revealed that Tregs , but not Bregs , suppressed SAP, while Bregs attenuated disease severity when given prior to symptom onset. B cell deficiency in B cell-deficient (muMT)/B7-2(-/-) NOD mice prevented the development of SAP, which would indicate that the pathogenic role of B cells predominates over its regulatory role in this model. We conclude that Bregs and Tregs control the immunopathogenesis and progression of SAP in a non-redundant fashion, and that therapies aimed at expansion of Bregs and Tregs may be an effective approach in autoimmune neuropathies.

Adenomatous polyposis coli regulates radial axonal sorting and myelination in the PNS

Abstract: The tumor suppressor protein adenomatous polyposis coli (APC) is multifunctional - it participates in the canonical Wnt/β-catenin signal transduction pathway as well as modulating cytoskeleton function. Although APC is expressed by Schwann cells, the role that it plays in these cells and in the myelination of the peripheral nervous system (PNS) is unknown. Therefore, we used the Cre-lox approach to generate a mouse model in which APC expression is specifically eliminated from Schwann cells. These mice display hindlimb weakness and impaired axonal conduction in sciatic nerves. Detailed morphological analyses revealed that APC loss delays radial axonal sorting and PNS myelination. Furthermore, APC loss delays Schwann cell differentiation in vivo, which correlates with persistent activation of the Wnt signaling pathway and results in perturbed extension of Schwann cell processes and disrupted lamellipodia formation. In addition, APC-deficient Schwann cells display a transient diminution of proliferative capacity. Our data indicate that APC is required by Schwann cells for their timely differentiation to mature, myelinating cells and plays a crucial role in radial axonal sorting and PNS myelination.