Faithful SGCE imprinting in iPSC-derived cortical neurons: an endogenous cellular model of myoclonus-dystonia

Karen Grütz,Francesca A Carlisle,Philip Seibler,Anne Grünewald,Christine Klein,Ana Westenberger,Katja Lohmann,Anne Weissbach,Derek J Blake

doi:10.1038/srep41156

Karen Grütz, Francesca A Carlisle + Show 7 more

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https://doi.org/10.1038/srep41156

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Abstract

In neuropathology research, induced pluripotent stem cell (iPSC)-derived neurons are considered a tool closely resembling the patient brain. Albeit in respect to epigenetics, this concept has been challenged. We generated iPSC-derived cortical neurons from myoclonus-dystonia patients with mutations (W100G and R102X) in the maternally imprinted ε-sarcoglycan (SGCE) gene and analysed properties such as imprinting, mRNA and protein expression. Comparison of the promoter during reprogramming and differentiation showed tissue-independent differential methylation. DNA sequencing with methylation-specific primers and cDNA analysis in patient neurons indicated selective expression of the mutated paternal SGCE allele. While fibroblasts only expressed the ubiquitous mRNA isoform, brain-specific SGCE mRNA and ε-sarcoglycan protein were detected in iPSC-derived control neurons. However, neuronal protein levels were reduced in both mutants. Our phenotypic characterization highlights the suitability of iPSC-derived cortical neurons with SGCE mutations for myoclonus-dystonia research and, in more general terms, prompts the use of iPSC-derived cellular models to study epigenetic mechanisms impacting on health and disease.

Highlights

Induced pluripotent stem cell technology has greatly advanced our understanding of pathways underlying neurological disorders[1,2]
Results induced pluripotent stem cell (iPSC) from M-D patients with SGCE mutations are efficiently differentiated into cortical neurons
In keeping with the immunofluorescence results, mRNA expression analysis indicated high levels of the pluripotency markers NANOG, GDF3, OCT4, and SOX2 in both patient iPSC lines compared to non-transfected fibroblasts (Fig. 1D)

Summary

Introduction

Induced pluripotent stem cell (iPSC) technology has greatly advanced our understanding of pathways underlying neurological disorders[1,2]. It is of great importance to investigate the utility of iPSC technology to study specific epigenetic-related neurological diseases such as myoclonus-dystonia (M-D). SGCE-associated M-D is inherited in an autosomal-dominant fashion with variable expressivity and incomplete penetrance[5]. The latter is caused by maternal imprinting, an epigenetic phenomenon resulting in selective silencing of the maternal SGCE allele[6,7], a finding that is of translational relevance as it informs genetic counselling of mutation carriers. While wildtype ε-sarcoglycan localizes to the plasma membrane, all missense mutant forms currently analysed were retained intracellularly and degraded by the proteasome in overexpression studies using mammalian cell lines[9]

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