Morsy H, Benkirane M, Cali E, Rocca C, Zhelcheska K, Cipriani V, Galanaki E, Maroofian R, Efthymiou S, Murphy D, O'Driscoll M, Suri M, Banka S, Clayton-Smith J, Wright T, Redman M, Bassetti JA, Nizon M, Cogne B, Jamra RA, Bartolomaeus T, Heruth M, Krey I, Gburek-Augustat J, Wieczorek D, Gattermann F, Mcentagart M, Goldenberg A, Guyant-Marechal L, Garcia-Moreno H, Giunti P, Chabrol B, Bacrot S, Buissonnière R, Magry V, Gowda VK, Srinivasan VM, Melegh B, Szabó A, Sümegi K, Cossée M, Ziff M, Butterfield R, Hunt D, Bird-Lieberman G, Hanna M, Koenig M, Stankewich M, Vandrovcova J, Houlden H; Genomics England Research Consortium. Expanding SPTAN1 monoallelic variant associated disorders: From epileptic encephalopathy to pure spastic paraplegia and ataxia. Genet Med. 2023 Jan;25(1):76-89. doi: 10.1016/j.gim.2022.09.013. Epub 2022 Nov 4. PMID: 36331550; PMCID: PMC10620943.
Abstract
Purpose: Nonerythrocytic αII-spectrin (SPTAN1) variants have been previously associated with intellectual disability and epilepsy. We conducted this study to delineate the phenotypic spectrum of SPTAN1 variants.
Methods: We carried out SPTAN1 gene enrichment analysis in the rare disease component of the 100,000 Genomes Project and screened 100,000 Genomes Project, DECIPHER database, and GeneMatcher to identify individuals with SPTAN1 variants. Functional studies were performed on fibroblasts from 2 patients.
Results: Statistically significant enrichment of rare (minor allele frequency < 1 × 10-5) probably damaging SPTAN1 variants was identified in families with hereditary ataxia (HA) or hereditary spastic paraplegia (HSP) (12/1142 cases vs 52/23,847 controls, p = 2.8 × 10-5). We identified 31 individuals carrying SPTAN1 heterozygous variants or deletions. A total of 10 patients presented with pure or complex HSP/HA. The remaining 21 patients had developmental delay and seizures. Irregular αII-spectrin aggregation was noted in fibroblasts derived from 2 patients with p.(Arg19Trp) and p.(Glu2207del) variants.
Conclusion: We found that SPTAN1 is a genetic cause of neurodevelopmental disorder, which we classified into 3 distinct subgroups. The first comprises developmental epileptic encephalopathy. The second group exhibits milder phenotypes of developmental delay with or without seizures. The final group accounts for patients with pure or complex HSP/HA.
Syrbe S, Harms FL, Parrini E, Montomoli M, Mütze U, Helbig KL, Polster T, Albrecht B, Bernbeck U, van Binsbergen E, Biskup S, Burglen L, Denecke J, Heron B, Heyne HO, Hoffmann GF, Hornemann F, Matsushige T, Matsuura R, Kato M, Korenke GC, Kuechler A, Lämmer C, Merkenschlager A, Mignot C, Ruf S, Nakashima M, Saitsu H, Stamberger H, Pisano T, Tohyama J, Weckhuysen S, Werckx W, Wickert J, Mari F, Verbeek NE, Møller RS, Koeleman B, Matsumoto N, Dobyns WB, Battaglia D, Lemke JR, Kutsche K, Guerrini R. Delineating SPTAN1 associated phenotypes: from isolated epilepsy to encephalopathy with progressive brain atrophy. Brain. 2017 Sep 1;140(9):2322-2336. doi: 10.1093/brain/awx195. PMID: 29050398; PMCID: PMC6248409.
Abstract
De novo in-frame deletions and duplications in the SPTAN1 gene, encoding the non-erythrocyte αII spectrin, have been associated with severe West syndrome with hypomyelination and pontocerebellar atrophy. We aimed at comprehensively delineating the phenotypic spectrum associated with SPTAN1 mutations. Using different molecular genetic techniques, we identified 20 patients with a pathogenic or likely pathogenic SPTAN1 variant and reviewed their clinical, genetic and imaging data. SPTAN1 de novo alterations included seven unique missense variants and nine in-frame deletions/duplications of which 12 were novel. The recurrent three-amino acid duplication p.(Asp2303_Leu2305dup) occurred in five patients. Our patient cohort exhibited a broad spectrum of neurodevelopmental phenotypes, comprising six patients with mild to moderate intellectual disability, with or without epilepsy and behavioural disorders, and 14 patients with infantile epileptic encephalopathy, of which 13 had severe neurodevelopmental impairment and four died in early childhood. Imaging studies suggested that the severity of neurological impairment and epilepsy correlates with that of structural abnormalities as well as the mutation type and location. Out of seven patients harbouring mutations outside the α/β spectrin heterodimerization domain, four had normal brain imaging and three exhibited moderately progressive brain and/or cerebellar atrophy. Twelve of 13 patients with mutations located within the spectrin heterodimer contact site exhibited severe and progressive brain, brainstem and cerebellar atrophy, with hypomyelination in most. We used fibroblasts from five patients to study spectrin aggregate formation by Triton-X extraction and immunocytochemistry followed by fluorescence microscopy. αII/βII aggregates and αII spectrin in the insoluble protein fraction were observed in fibroblasts derived from patients with the mutations p.(Glu2207del), p.(Asp2303_Leu2305dup) and p.(Arg2308_Met2309dup), all falling in the nucleation site of the α/β spectrin heterodimer region. Molecular modelling of the seven SPTAN1 amino acid changes provided preliminary evidence for structural alterations of the A-, B- and/or C-helices within each of the mutated spectrin repeats. We conclude that SPTAN1-related disorders comprise a wide spectrum of neurodevelopmental phenotypes ranging from mild to severe and progressive. Spectrin aggregate formation in fibroblasts with mutations in the α/β heterodimerization domain seems to be associated with a severe neurodegenerative course and suggests that the amino acid stretch from Asp2303 to Met2309 in the α20 repeat is important for α/β spectrin heterodimer formation and/or αII spectrin function.
Van de Vondel L, De Winter J, Beijer D, Coarelli G, Wayand M, Palvadeau R, Pauly MG, Klein K, Rautenberg M, Guillot-Noël L, Deconinck T, Vural A, Ertan S, Dogu O, Uysal H, Brankovic V, Herzog R, Brice A, Durr A, Klebe S, Stock F, Bischoff AT, Rattay TW, Sobrido MJ, De Michele G, De Jonghe P, Klopstock T, Lohmann K, Zanni G, Santorelli FM, Timmerman V, Haack TB, Züchner S; PREPARE Consortium; Schüle R, Stevanin G, Synofzik M, Basak AN, Baets J. De Novo and Dominantly Inherited SPTAN1 Mutations Cause Spastic Paraplegia and Cerebellar Ataxia. Mov Disord. 2022 Jun;37(6):1175-1186. doi: 10.1002/mds.28959. Epub 2022 Feb 12. PMID: 35150594; PMCID: PMC9232883.
Abstract
Background: Pathogenic variants in SPTAN1 have been linked to a remarkably broad phenotypical spectrum. Clinical presentations include epileptic syndromes, intellectual disability, and hereditary motor neuropathy.
Objectives: We investigated the role of SPTAN1 variants in rare neurological disorders such as ataxia and spastic paraplegia.
Methods: We screened 10,000 NGS datasets across two international consortia and one local database, indicative of the level of international collaboration currently required to identify genes causative for rare disease. We performed in silico modeling of the identified SPTAN1 variants.
Results: We describe 22 patients from 14 families with five novel SPTAN1 variants. Of six patients with cerebellar ataxia, four carry a de novo SPTAN1 variant and two show a sporadic inheritance. In this group, one variant (p.Lys2083del) is recurrent in four patients. Two patients have novel de novo missense mutations (p.Arg1098Cys, p.Arg1624Cys) associated with cerebellar ataxia, in one patient accompanied by intellectual disability and epilepsy. We furthermore report a recurrent missense mutation (p.Arg19Trp) in 15 patients with spastic paraplegia from seven families with a dominant inheritance pattern in four and a de novo origin in one case. One further patient carrying a de novo missense mutation (p.Gln2205Pro) has a complex spastic ataxic phenotype. Through protein modeling we show that mutated amino acids are located at crucial interlinking positions, interconnecting the three-helix bundle of a spectrin repeat.
Conclusions: We show that SPTAN1 is a relevant candidate gene for ataxia and spastic paraplegia. We suggest that for the mutations identified in this study, disruption of the interlinking of spectrin helices could be a key feature of the pathomechanism.
Van de Vondel L, De Winter J, Beijer D, Coarelli G, Wayand M, Palvadeau R, Pauly MG, Klein K, Rautenberg M, Guillot-Noël L, Deconinck T, Vural A, Ertan S, Dogu O, Uysal H, Brankovic V, Herzog R, Brice A, Durr A, Klebe S, Stock F, Bischoff AT, Rattay TW, Sobrido MJ, De Michele G, De Jonghe P, Klopstock T, Lohmann K, Zanni G, Santorelli FM, Timmerman V, Haack TB, Züchner S; PREPARE Consortium; Schüle R, Stevanin G, Synofzik M, Basak AN, Baets J. De Novo and Dominantly Inherited SPTAN1 Mutations Cause Spastic Paraplegia and Cerebellar Ataxia. Mov Disord. 2022 Jun;37(6):1175-1186. doi: 10.1002/mds.28959. Epub 2022 Feb 12. PMID: 35150594; PMCID: PMC9232883.
Abstract
Background: Pathogenic variants in SPTAN1 have been linked to a remarkably broad phenotypical spectrum. Clinical presentations include epileptic syndromes, intellectual disability, and hereditary motor neuropathy.
Objectives: We investigated the role of SPTAN1 variants in rare neurological disorders such as ataxia and spastic paraplegia.
Methods: We screened 10,000 NGS datasets across two international consortia and one local database, indicative of the level of international collaboration currently required to identify genes causative for rare disease. We performed in silico modeling of the identified SPTAN1 variants.
Results: We describe 22 patients from 14 families with five novel SPTAN1 variants. Of six patients with cerebellar ataxia, four carry a de novo SPTAN1 variant and two show a sporadic inheritance. In this group, one variant (p.Lys2083del) is recurrent in four patients. Two patients have novel de novo missense mutations (p.Arg1098Cys, p.Arg1624Cys) associated with cerebellar ataxia, in one patient accompanied by intellectual disability and epilepsy. We furthermore report a recurrent missense mutation (p.Arg19Trp) in 15 patients with spastic paraplegia from seven families with a dominant inheritance pattern in four and a de novo origin in one case. One further patient carrying a de novo missense mutation (p.Gln2205Pro) has a complex spastic ataxic phenotype. Through protein modeling we show that mutated amino acids are located at crucial interlinking positions, interconnecting the three-helix bundle of a spectrin repeat.
Conclusions: We show that SPTAN1 is a relevant candidate gene for ataxia and spastic paraplegia. We suggest that for the mutations identified in this study, disruption of the interlinking of spectrin helices could be a key feature of the pathomechanism. © 2022 International Parkinson and Movement Disorder Society.
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