Developmental Regulation of MicroRNA Expression in Schwann Cells

Abstract

Schwann cell differentiation and subsequent myelination of the peripheral nervous system require the action of several transcription factors, including Sox10, which is vital at multiple stages of development. The transition from immature to myelinating Schwann cell is also regulated posttranscriptionally and depends upon Dicer-mediated processing of microRNAs (miRNAs). Although specific miRNA targets have begun to be identified, the mechanisms establishing the dynamic regulation of miRNA expression have not been elucidated. We performed expression profiling studies and identified 225 miRNAs differentially expressed during peripheral myelination. A subset of 9 miRNAs is positively regulated by Sox10, including miR-338 which has been implicated in oligodendrocyte maturation. In vivo chromatin immunoprecipitation (ChIP) of sciatic nerve cells revealed a Sox10 binding site upstream of an alternate promoter within the Aatk gene, which hosts miR-338. Sox10 occupied this site in spinal cord ChIP experiments, suggesting a similar regulatory mechanism in oligodendrocytes. Cancer profiling studies have identified clusters of miRNAs that regulate proliferation, termed “oncomirs.” In Schwann cells, the expression of many of these proproliferative miRNAs was reduced in the absence of Sox10. Finally, Schwann cells with reduced Sox10 and oncomir expression have an increase in the CDK inhibitor p21 and a concomitant reduction in cell proliferation.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.06270-11.

ACKNOWLEDGMENTS

We thank Marie Adams and Eric Cabot at the UW Biotechnology Center for Illumina library preparation and data analysis. We also thank Yuerong Zhu for performing peak analysis of ChIP-Seq data. We thank Holly Hung for her assistance with sciatic nerve dissections and Erin Jones and Sung-Wook Jang for contributing Sox10 siRNA Affymetrix data. We thank Richard Quarles for providing the S16 cell line and Ian Duncan for providing the CG4 cell line. We also thank John Luecke for his assistance with the HTG miRNA microarrays.

This work was supported by a grant from the National Institutes of Health (RO1HD41590) and its ARRA supplement (HD041590-09S1) to J.S. and by a core grant to the Waisman Center from the National Institute of Child Health and Human Development (P30 HD03352).