title: Compound heterozygosity in the SPG4 gene causes hereditary spastic paraplegia.
abstract: The SPG4 gene is frequently mutated in autosomal dominant form of hereditary spastic paraplegia (HSP). We report that the compound heterozygous sequence variants S44L, a known polymorphism, and c.1687G>A, a novel mutation in SPG4 cause a severe form of HSP in a patient. The family members carrying solely c.1687G>A mutation are asymptomatic for HSP. The reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed that the c.1687G>A mutation is a splice site mutation and causes skipping of the exon 15 of spastin. Furthermore, quantification of RT-PCR products by sequencing and quantification of allele-specific expression by pyrosequencing assay revealed that c.1687G>A is a leaky or hypomorphic splice site mutation. At the protein level, c.1687G>A mutation in SPG4 leads to E563K substitution. In ex vivo study, about 10% of cells expressing E563K mutant spastin showed filamentous expression pattern, suggesting a hypomorphic effect at the protein level. Collectively, our results suggest that S44L in association with c.1687G>A (E563K) drops the functional level of spastin below a threshold limit sufficient to manifest HSP.
authors.affiliation: Institute of Human Genetics, University of Goettingen, Goettingen, Germany.
authors.forename: D V K
authors.initials: DV
authors.lastname: Pantakani
authors.forename: U
authors.initials: U
authors.lastname: Zechner
authors.forename: L
authors.initials: L
authors.lastname: Arygriou
authors.forename: S
authors.initials: S
authors.lastname: Pauli
authors.forename: S M
authors.initials: SM
authors.lastname: Sauter
authors.forename: A U
authors.initials: AU
authors.lastname: Mannan
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D000483:Alleles; D019943:Amino Acid Substitution; D001483:Base Sequence; D019295:Computational Biology; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D005858:Germany; D006367:HeLa Cells; D006579:Heterozygote; D006801:Humans; D042541:Intracellular Space; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010375:Pedigree; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D021381:Protein Transport; D022821:RNA Splice Sites / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015419:Spastic Paraplegia, Hereditary / Q000235:genetics*; D000074181:Spastin; D044465:White People / Q000235:genetics
chemical_list: D022821:RNA Splice Sites; D012333:RNA, Messenger; D000251:Adenosine Triphosphatases; D000074181:Spastin; C400283:SPAST protein, human