title: Gene dosage-dependent rescue of HSP neurite defects in SPG4 patients' neurons.
abstract: The hereditary spastic paraplegias (HSPs) are a heterogeneous group of motorneuron diseases characterized by progressive spasticity and paresis of the lower limbs. Mutations in Spastic Gait 4 (SPG4), encoding spastin, are the most frequent cause of HSP. To understand how mutations in SPG4 affect human neurons, we generated human induced pluripotent stem cells (hiPSCs) from fibroblasts of two patients carrying a c.1684C>T nonsense mutation and from two controls. These SPG4 and control hiPSCs were able to differentiate into neurons and glia at comparable efficiency. All known spastin isoforms were reduced in SPG4 neuronal cells. The complexity of SPG4 neurites was decreased, which was paralleled by an imbalance of axonal transport with less retrograde movement. Prominent neurite swellings with disrupted microtubules were present in SPG4 neurons at an ultrastructural level. While some of these swellings contain acetylated and detyrosinated tubulin, these tubulin modifications were unchanged in total cell lysates of SPG4 neurons. Upregulation of another microtubule-severing protein, p60 katanin, may partially compensate for microtubuli dynamics in SPG4 neurons. Overexpression of the M1 or M87 spastin isoforms restored neurite length, branching, numbers of primary neurites and reduced swellings in SPG4 neuronal cells. We conclude that neurite complexity and maintenance in HSP patient-derived neurons are critically sensitive to spastin gene dosage. Our data show that elevation of single spastin isoform levels is sufficient to restore neurite complexity and reduce neurite swellings in patient cells. Furthermore, our human model offers an ideal platform for pharmacological screenings with the goal to restore physiological spastin levels in SPG4 patients.
authors.affiliation: IZKF Junior Research Group and BMBF Research Group Neuroscience, IZKF, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Glückstr. 6, Erlangen 91054, Germany.
authors.forename: Steven
authors.initials: S
authors.lastname: Havlicek
authors.forename: Zacharias
authors.initials: Z
authors.lastname: Kohl
authors.forename: Himanshu K
authors.initials: HK
authors.lastname: Mishra
authors.forename: Iryna
authors.initials: I
authors.lastname: Prots
authors.forename: Esther
authors.initials: E
authors.lastname: Eberhardt
authors.forename: Naime
authors.initials: N
authors.lastname: Denguir
authors.forename: Holger
authors.initials: H
authors.lastname: Wend
authors.forename: Sonja
authors.initials: S
authors.lastname: Plötz
authors.forename: Leah
authors.initials: L
authors.lastname: Boyer
authors.forename: Maria C N
authors.initials: MC
authors.lastname: Marchetto
authors.forename: Stefan
authors.initials: S
authors.lastname: Aigner
authors.forename: Heinrich
authors.initials: H
authors.lastname: Sticht
authors.forename: Teja W
authors.initials: TW
authors.lastname: Groemer
authors.forename: Ute
authors.initials: U
authors.lastname: Hehr
authors.forename: Angelika
authors.initials: A
authors.lastname: Lampert
authors.forename: Ursula
authors.initials: U
authors.lastname: Schlötzer-Schrehardt
authors.forename: Jürgen
authors.initials: J
authors.lastname: Winkler
authors.forename: Fred H
authors.initials: FH
authors.lastname: Gage
authors.forename: Beate
authors.initials: B
authors.lastname: Winner
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D001370:Axonal Transport; D048430:Cell Shape; D002478:Cells, Cultured; D005260:Female; D018628:Gene Dosage; D015870:Gene Expression; D015316:Genetic Therapy; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000502:physiology; D008297:Male; D008870:Microtubules / Q000378:metabolism; D008875:Middle Aged; D016501:Neurites / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015419:Spastic Paraplegia, Hereditary / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D000074181:Spastin
chemical_list: D020033:Protein Isoforms; D000251:Adenosine Triphosphatases; D000074181:Spastin; C400283:SPAST protein, human