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Ataxia in Patients With Bi-Allelic NFASC Mutations and Absence of Full-Length NF186
Karolinska Univ Hosp, Dept Clin Genet, Stockholm, Sweden;Karolinska Inst, Ctr Mol Med, Dept Mol Med & Surg, Stockholm, Sweden.
Karolinska Inst, Ctr Mol Med, Dept Mol Med & Surg, Stockholm, Sweden;Karolinska Inst, Biomed, Dept Neurosci, Stockholm, Sweden.
Karolinska Inst, Ctr Mol Med, Dept Mol Med & Surg, Stockholm, Sweden.
Karolinska Inst, Biomed, Dept Neurosci, Stockholm, Sweden.
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2019 (Engelska)Ingår i: Frontiers in Genetics, ISSN 1664-8021, E-ISSN 1664-8021, Vol. 10, artikel-id 896Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The etiology of hereditary ataxia syndromes is heterogeneous, and the mechanisms underlying these disorders are often unknown. Here, we utilized exome sequencing in two siblings with progressive ataxia and muscular weakness and identified a novel homozygous splice mutation (c.3020-1G > A) in neurofascin (NFASC). In RNA extracted from fibroblasts, we showed that the mutation resulted in inframe skipping of exon 26, with a deprived expression of the full-length transcript that corresponds to NFASC isoform NF186. To further investigate the disease mechanisms, we reprogrammed fibroblasts from one affected sibling to induced pluripotent stem cells, directed them to neuroepithelial stem cells and finally differentiated to neurons. In early neurogenesis, differentiating cells with selective depletion of the NF186 isoform showed significantly reduced neurite outgrowth as well as fewer emerging neurites. Furthermore, whole-cell patch-clamp recordings of patient-derived neuronal cells revealed a lower threshold for openings, indicating altered Na+ channel kinetics, suggesting a lower threshold for openings as compared to neuronal cells without the NFASC mutation. Taken together, our results suggest that loss of the full-length NFASC isoform NF186 causes perturbed neurogenesis and impaired neuronal biophysical properties resulting in a novel early-onset autosomal recessive ataxia syndrome.

Ort, förlag, år, upplaga, sidor
2019. Vol. 10, artikel-id 896
Nyckelord [en]
neurofascin, neuronal isoform NF186, ataxia, patient-specific induced pluripotent stem cells, neuroepithelial stem cells, neurites
Nationell ämneskategori
Neurovetenskaper
Identifikatorer
URN: urn:nbn:se:uu:diva-395798DOI: 10.3389/fgene.2019.00896ISI: 000487628800001OAI: oai:DiVA.org:uu-395798DiVA, id: diva2:1365629
Forskningsfinansiär
Vetenskapsrådet, 2015-02424Vetenskapsrådet, 2017-03407Vetenskapsrådet, 2017-02936Stiftelsen för strategisk forskning (SSF), IB13-0074HjärnfondenSvenska Sällskapet för Medicinsk Forskning (SSMF)Tillgänglig från: 2019-10-25 Skapad: 2019-10-25 Senast uppdaterad: 2019-12-09Bibliografiskt granskad
Ingår i avhandling
1. Induced pluripotent stem cell (iPSC) modelling for the identification of mechanisms behind neurodevelopmental disorders
Öppna denna publikation i ny flik eller fönster >>Induced pluripotent stem cell (iPSC) modelling for the identification of mechanisms behind neurodevelopmental disorders
2020 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Human induced pluripotent stem cells (iPSCs) have opened new possibilities to recapitulate disease mechanisms and to model disorders in vitro. In the studies presented here, iPSCs were established to model neural differentiation in Down syndrome (DS), caused by trisomy for chromosome 21 (T21); Dravet syndrome (DRS), caused by variants in the SCN1A gene; and an ataxia syndrome, caused by a variant in the NFASC gene. The major aim has been to uncover molecular and cellular mechanisms behind perturbed neurogenesis in the three disorders.

In Paper I, the analysis of transcriptomes and proteomes of the DS iPSC derived neural model revealed several perturbed gene clusters with strong temporal dynamics along neural differentiation, markedly down-regulated mitochondrial genes and a dysregulation of hub proteins. These results predict complex and genome-wide changes in T21 neural cells associated with prolonged cell cycle, reduced cell growth and a perturbed energy metabolism.

In Paper II, it was demonstrated that the transcriptional profile of iPSC based neural model system for DS was enriched for differentially methylated genes and gene families when compared to a corresponding euploid model. The differentially methylated genes were enriched for transcriptional regulation and chromatin structure, suggesting novel mechanistic links between the genomic imbalance caused by T21 and the global transcriptional dysregulation in DS.

 In Paper III, it was shown that DRS patient iPSCs differentiated into GABAergic interneurons exhibit a dysregulated epilepsy gene network as well as an altered expression of genes involved in chromatin remodelling, accompanied by abnormal electrophysiological properties and increased stress sensitivity.

In Paper IV, it was shown that neural iPSCs, established from a patient with an ataxia syndrome and a novel homozygous variant in the NFASC gene, lack a full-length neurofascin-186 important for cell adhesion. The patient derived neural iPSCs showed delayed neuronal differentiation, reduced sprouting, shorter neurites and altered electrophysiology.

The Papers I-IV show that patient derived neural iPSCs enable to identify molecular and cellular mechanisms associated with neuropathogenesis. Besides specific dysregulated pathways and cellular defects in models of three developmental disorders, with shortlists of novel candidate disease biomarkers, the results are consistent with prior data and clinical presentation of patients. The knowledge gained is of paramount importance for translation into clinical settings and a step towards development of novel therapies with the ultimate goal to alleviate symptoms of affected individuals.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2020. s. 63
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1622
Nyckelord
Induced pluripotent stem cells, Neurogenesis, Neural differentiation, Down syndrome, Dravet syndrome, Ataxia
Nationell ämneskategori
Medicin och hälsovetenskap
Forskningsämne
Medicinsk cellbiologi
Identifikatorer
urn:nbn:se:uu:diva-398620 (URN)978-91-513-0833-3 (ISBN)
Disputation
2020-02-07, Room A1:111a, BMC, Husargatan 3, Uppsala, 09:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2020-01-17 Skapad: 2019-12-09 Senast uppdaterad: 2020-03-05

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