Novel mutations in spastin gene and absence of correlation with age at onset of symptoms. (2000 Nov)
novel mutations in spastin gene and absence of correlation with age at onset of symptoms . autosomal dominant hereditary spastic paraplegia is genetically heterogeneous , with at least five loci identified by linkage analysis . recently , mutations in spastin were identified in SPG4 , the most common locus for dominant hereditary spastic paraplegia that was previously mapped to chromosome 2p22 . We identified five novel mutations in the spastin gene in five families with SPG4 mutations from north america and tunisia and showed the absence of correlation between the predicted mutant spastin protein and age at onset of symptoms .

Analysis and mapping of cacnb4 , chrna1 , kcnj3 , scn2a and SPG4 , physiological candidate genes for porcine congenital … (2007 Sep)
analysis and mapping of cacnb4 , chrna1 , kcnj3 , scn2a and SPG4 , physiological candidate genes for porcine congenital progressive ataxia and spastic paresis . The cause of porcine congenital progressive ataxia and spastic paresis ( CPA ) is unknown . This severe neuropathy manifests shortly after birth and is lethal . The disease is inherited as a single autosomal recessive allele , designated cpa . In a previous study , we demonstrated close linkage of cpa to microsatellite sw902 on porcine chromosome 3 ( SSC3 ) , which corresponds syntenically to human chromosome 2 . This latter chromosome contains ion channel genes ( Ca ( 2 ) , K ( ) and Na ( ) ) , a cholinergic receptor gene and the spastin ( SPG4 ) gene , which cause human epilepsy and ataxia when mutated . We mapped porcine cacnb4 , kcnj3 , scn2a and chrna1 to ssc15 and SPG4 to SSC3 with the INRA minnesota porcine radiation hybrid panel ( imprh ) and we sequenced the entire open reading frames of cacnb4 and SPG4 without finding any differences between healthy and affected piglets . An anti epileptic drug treatment with ethosuximide did not change the severity of the disease , and pigs with CPA did not exhibit the corticospinal tract axonal degeneration found in humans suffering from hereditary spastic paraplegia , which is associated with mutations in SPG4 . For all these reasons , the hypothesis that cacnb4 , chrna1 , kcnj3 , scn2a or …

Spastin subcellular localization is regulated through usage of different translation start sites and active export from the nucleus. (2005 Sep)
spastin subcellular localization is regulated through usage of different translation start sites and active export from the nucleus . Most cases of autosomal dominant hereditary spastic paraplegia are linked to mutations in SPG4 encoding spastin , a protein involved in microtubule dynamics and membrane trafficking . In pyramidal neurons of the motor cortex and in immortalized motor neurons , spastin is localized to the synaptic terminals and growth cones . however , in other neurons and in proliferating cells spastin is prevalently nuclear . The mechanisms that determine targeting of spastin to the nucleus or the cytoplasm are unknown . We show here that the SPG4 mRNA is able to direct synthesis of two spastin isoforms , 68 and 60 kDa , respectively , through usage of two different translational start sites . Both isoforms are imported into the nucleus , but the 68 kDa isoform contains two nuclear export signals that efficiently drive export to the cytoplasm . nuclear export is leptomycin B sensitive . The cytoplasmic 68 kDa spastin isoform is more abundant in the brain and the spinal cord than in other tissues . Our data indicate that spastin function is modulated through usage of alternative translational start sites and active nuclear import and export , and open new perspectives for the pathogenesis of hereditary spastic paraplegia .

Autosomal dominant hereditary spastic paraplegia : report of a large italian family with r581x spastin mutation. (2007 Aug)
autosomal dominant hereditary spastic paraplegia : report of a large italian family with r581x spastin mutation . We describe a large kindred with a typical pure form of autosomal dominant hereditary spastic paraplegia ( adhsp ) . On the basis of maximum LOD score of 1 . 94 at theta ( max ) 0 with marker d2s367 , we obtained suggestive evidence for linkage of adhsp to SPG4 locus . denaturing high performance liquid chromatography ( dhplc ) and direct sequence analysis allowed us to identify a nonsense mutation ( 1741 C T ) in exon 17 of the spastin gene . This transition , carried by all the affected family members and two apparently healthy individuals , lead to truncation of the last 36 amino acids in the C terminus of the protein . these results confirm the existence of mutation in the SPG4 gene with a reduced penetrance , indicating that other genetic or environmental factors are required to trigger full blown disease .

Mutation analysis of the spastin gene ( SPG4 ) in patients in germany with autosomal dominant hereditary spastic paraplegia. (2002 Jul)
mutation analysis of the spastin gene ( SPG4 ) in patients in germany with autosomal dominant hereditary spastic paraplegia . hereditary spastic paraplegias ( HSP ) comprise a genetically and clinically heterogeneous group of neurodegenerative disorders characterized by progressive spasticity and hyperreflexia of the lower limbs . autosomal dominant hereditary spastic paraplegia 4 linked to chromosome 2p ( SPG4 ) is the most common form of autosomal dominant hereditary spastic paraplegia . It is caused by mutations in the SPG4 gene encoding spastin , a member of the AAA protein family of atpases . In this study the spastin gene of HSP patients from 161 apparently unrelated families in germany was analyzed . The authors identified mutations in 27 out of the 161 HSP families ; 23 of these mutations have not been described before and only one mutation was found in two families . among the detected mutations are 14 frameshift , four nonsense , and four missense mutations , one large deletion spanning several exons , as well as four mutations that affect splicing . Most of the novel mutations are located in the conserved AAA cassette encoding region of the spastin gene . The relative frequency of spastin gene mutations in an unselected group of german HSP patients is approximately 17 . frameshift mutations account for the majority of SPG4 mutations in this population . The proportion of splice mutations is considerably lower than reported elsewhere .

Transcranial magnetic stimulation study in hereditary spastic paraparesis. (2003 May)
transcranial magnetic stimulation study in hereditary spastic paraparesis . The motor evoked potentials and the cortical excitability by transcranial magnetic stimulation ( TMS ) were studied in a family with chromosome 2p linked ( due to mutations in spastin ) and in a family with chromosome 16q linked ( due to mutations in paraplegin ) hereditary spastic paraparesis ( HSP ) , in order to evaluate the utility of these techniques in identifying the subgroups of the disease . central motor conduction time and motor treshold to TMS were abnormal in some members of both families ; the intracortical inhibition was reduced only in the affected members of the family with chromosome 2p linked HSP , even though the neurological symptoms were sometimes similar and also when clinical features reflecting cortical dysfunction were absent . The motor cortex is differentially involved in the often clinically indistinguishable forms of HSP , and TMS may help in the differential diagnosis .

Unexpected pathogenic mechanism of a novel mutation in the coding sequence of SPG4 ( spastin ). (2006 Feb)
unexpected pathogenic mechanism of a novel mutation in the coding sequence of SPG4 ( spastin ) . The authors report a nucleotide substitution ( c . 1216a G ) in SPG4 ( spastin ) causing hereditary spastic paraplegia . This apparent missense mutation in the atpase domain confers aberrant , in frame splicing and results in destabilization of mutated transcript . mutated protein is deficient in microtubule severing activity but , unlike neighboring mutations , shows regular subcellular localization . The authors data point to haploinsufficiency rather than a dominant negative effect as the disease causing mechanism for this mutation .

Identification and expression analysis of spastin gene mutations in hereditary spastic paraplegia. (2001 Apr)
identification and expression analysis of spastin gene mutations in hereditary spastic paraplegia . Pure hereditary spastic paraplegia ( SPG ) type 4 is the most common form of autosomal dominant hereditary SPG , a neurodegenerative disease characterized primarily by hyperreflexia and progressive spasticity of the lower limbs . It is caused by mutations in the gene encoding spastin , a member of the AAA family of atpases . We have screened the spastin gene for mutations in 15 families consistent with linkage to the spastin gene locus , SPG4 , and have identified 11 mutations , 10 of which are novel . Five of the mutations identified are in noninvariant splice junction sequences . reverse transcription PCR analysis of mRNA from patients shows that each of these five mutations results in aberrant splicing . One mutation was found to be leaky , or partially penetrant ; that is , the mutant allele produced both mutant ( skipped exon ) and wild type ( full length ) transcripts . This phenomenon was reproduced in in vitro splicing experiments , with a minigene splicing vector construct only in the context of the endogenous splice junctions flanking the splice junctions of the skipped exon . In the absence of endogenous splice junctions , only mutant transcript was detected . The existence of at least one leaky mutation suggests that relatively small differences in the level of wild type spastin expression can have significant functional consequences . This may account , at least in …

A missense mutation in the coiled coil domain of the kif5a gene and late onset hereditary spastic paraplegia. (2006 Feb)
A missense mutation in the coiled coil domain of the kif5a gene and late onset hereditary spastic paraplegia . background : To our knowledge , up to now , only 2 mutations in the kif5a gene , a member of the kinesin superfamily , have been identified as the molecular cause of early onset autosomal dominant hereditary spastic paraparesis ( adhsp ) . objective : To assess the genetic defect in a family with late onset adhsp . patients AND methods : Only the proband agreed to undergo complete neurological testing and mutational analysis . The proband was screened for mutations in the spastin , atlastin , nipa1 , and kif5a genes , either by denaturing high performance liquid chromatography or sequence analysis . results : The history of the family was consistent with adhsp characterized by late onset of the disease . mutational analysis results were negative for the spastin , atlastin , and nipa1 genes but identified a missense mutation ( c . 1082c T ) in the coiled coil coding region of the kif5a gene . conclusions : This finding enlarges the phenotypic spectrum of adhsp linked to kif5a and enhances the role of that gene in the epidemiology of this disease . We propose that the kif5a gene should be routinely analyzed in patients with hereditary spastic paraplegia negative for spastin and atlastin mutations .

Spg20 is mutated in troyer syndrome , an hereditary spastic paraplegia. (2002 Jul)
spg20 is mutated in troyer syndrome , an hereditary spastic paraplegia . troyer syndrome ( TRS ) is an autosomal recessive complicated hereditary spastic paraplegia ( HSP ) that occurs with high frequency in the Old order amish . We report mapping of the TRS locus to chromosome 13q12 . 3 and identify a frameshift mutation in spg20 , encoding spartin . comparative sequence analysis indicates that spartin shares similarity with molecules involved in endosomal trafficking and with spastin , a molecule implicated in microtubule interaction that is commonly mutated in HSP .

The hereditary spastic paraplegia protein spastin interacts with the escrt III complex associated endosomal protein chmp1b. (2004 Dec)
The hereditary spastic paraplegia protein spastin interacts with the escrt III complex associated endosomal protein chmp1b . Pure hereditary spastic paraplegia is characterized by length dependent degeneration of the distal ends of long axons . mutations in spastin are the most common cause of the condition . We set out to investigate the function of spastin using a yeast two hybrid approach to identify interacting proteins . using full length spastin as bait , we identified chmp1b , a protein associated with the escrt ( endosomal sorting complex required for transport ) III complex , as a binding partner . several different approaches confirmed the physiological relevance of the interaction in mammalian cells . epitope tagged chmp1b and spastin showed clear cytoplasmic co localization in Cos 7 and PC12 cells . chmp1b and spastin interacted specifically in vitro and in vivo in beta lactamase protein fragment complementation assays , and spastin co immunoprecipitated with chmp1b . The interaction was mediated by a region of spastin lying between residues 80 and 196 and containing a microtubule interacting and trafficking domain . expression of epitope tagged chmp1b in mammalian cells prevented the development of the abnormal microtubule phenotype associated with expression of atpase defective spastin . these data point to a role for spastin in intracellular membrane traffic events and provide further evidence to support the emerging recognition that defects in intracellular membrane traffic are a significant cause of motor neuron pathology .

The microtubule severing protein spastin is essential for axon outgrowth in the zebrafish embryo. (2006 Sep)
The microtubule severing protein spastin is essential for axon outgrowth in the zebrafish embryo . hereditary spastic paraplegia ( HSP ) is a collection of neurological disorders characterized by developmental failure or degeneration of motor axons in the corticospinal tract and progressive lower limb spasticity . SPG4 mutations are the most common cause of autosomal dominant HSP and spastin ( the SPG4 gene product ) is a microtubule severing protein that shares homology with katanin , the microtubule severing activity of which promotes axon growth in cultured neurons . given the sequence and functional similarity between spastin and katanin , we hypothesized that spastin promotes the dynamic disassembly and remodelling of microtubules required for robust , properly directed motor axon outgrowth . To investigate this hypothesis , we cloned the zebrafish spg4 orthologue and used morpholino antisense oligonucleotides directed against the translation start site and the intron 7 8 splice donor site to knock down spastin function in the developing zebrafish embryo . reduced spg4 function caused dramatic defects in motor axon outgrowth without affecting the events driving the initial specification of motor neurones . other neuronal subtypes also exhibited a requirement for spg4 function , since spg4 knock down caused both widespread defects in neuronal connectivity and extensive CNS specific apoptosis . Our results reveal a critical requirement for spastin to promote axonal outgrowth during embryonic development , and they validate the zebrafish embryo as a novel model system to dissect the pathogenetic mechanisms underlying HSP . taken together …

Spg3a mutation screening in english families with early onset autosomal dominant hereditary spastic paraplegia. (2003 Nov)
spg3a mutation screening in english families with early onset autosomal dominant hereditary spastic paraplegia . mutations in the spg3a gene encoding the novel gtpase atlastin have recently been implicated in causing autosomal dominant hereditary spastic paraplegia ( adhsp ) in six unrelated families . The phenotype of affected individuals in all cases has been of an early onset uncomplicated form of the disease . One particular missense mutation , r239c , in exon 7 of spg3a has been identified in three of these families . We performed mutation screening by direct sequencing of all 14 exons and flanking sequences of the spg3a gene in affected individuals from 12 unrelated english families , all with an early onset uncomplicated adhsp in whom spastin mutations had previously been excluded . The r239c mutation was found to co segregate with the disease in one english adhsp family confirming a widespread prevalence for this commonly occurring mutation . No additional spg3a mutations were identified in the remaining 11 families suggesting that even within this specific sub set of early onset uncomplicated adhsp patients atlastin mutations are relatively rare .

Identification of nuclear localisation sequences in spastin ( SPG4 ) using a novel tetra GFP reporter system. (2004 May)
identification of nuclear localisation sequences in spastin ( SPG4 ) using a novel tetra GFP reporter system . mutations in the human spastin gene ( SPG4 ) cause the most prevalent form of autosomal dominant hereditary spastic paraplegia ( HSP ) , a neurodegenerative disorder characterised by progressive weakness and spasticity of the lower limbs . We address the question of intracellular localisation of spastin . using polyclonal antibodies against N terminal spastin sequences , we find that the native protein is localised in both the perinuclear cytoplasm and the nucleus . To identify structural motifs within the protein that can explain entry into the nucleus , we developed a reporter system to test nuclear localisation sequence ( NLS ) functionality based on four in frame fused copies of green fluorescent protein . using this novel tool we demonstrate that spastin carries two NLSs located in exons 1 and 6 . Both are independently functional in mediating nuclear entry .

Spastin , a new AAA protein , is altered in the most frequent form of autosomal dominant spastic paraplegia. (1999 Dec)
spastin , a new AAA protein , is altered in the most frequent form of autosomal dominant spastic paraplegia . autosomal dominant hereditary spastic paraplegia ( AD HSP ) is a genetically heterogeneous neurodegenerative disorder characterized by progressive spasticity of the lower limbs . among the four loci causing AD HSP identified so far , the SPG4 locus at chromosome 2p2 1p22 has been shown to account for 40 50 of all AD HSP families . using a positional cloning strategy based on obtaining sequence of the entire SPG4 interval , we identified a candidate gene encoding a new member of the AAA protein family , which we named spastin . sequence analysis of this gene in seven SPG4 linked pedigrees revealed several DNA modifications , including missense , nonsense and splice site mutations . Both SPG4 and its mouse orthologue were shown to be expressed early and ubiquitously in fetal and adult tissues . The sequence homologies and putative subcellular localization of spastin suggest that this atpase is involved in the assembly or function of nuclear protein complexes .

Clinical features of hereditary spastic paraplegia due to spastin mutation. (2006 Jul)
clinical features of hereditary spastic paraplegia due to spastin mutation . background : mutations in the spastin gene are the commonest cause of hereditary spastic paraparesis ( HSP ) , accounting for up to 40 of autosomal dominant cases . The phenotype associated with HSP due to mutation in the spastin gene ( SPG4 ) tends to be pure HSP . objective : To characterize in more detail the genetic and phenotypic characteristics of SPG4 by examining a large cohort of patients with HSP . methods : The authors identified patients who tested positive for spastin mutation using a direct sequencing approach of all exons . results : The authors identified spastin mutations in 53 patients . twenty seven of the mutations identified were novel . The phenotype in the majority of patients was of pure HSP . In one individual , a complicated phenotype with progressive bulbar dysfunction and respiratory insufficiency was observed . evidence of lower motor neuron dysfunction in a subgroup of SPG4 patients was identified . The missense changes S44L and P45Q were identified in patients with other spastin mutations and seemed to be exerting a phenotype modifying effect . conclusion : these findings add to the number of spastin mutations identified and demonstrate the importance of screening the whole gene , given the possibility of double mutations and intragenic modifiers . The identification of the complicated phenotypes has important implications for identifying the phenotype of patients in whom spastin screening should be considered . The …

Isoform specific increase of spastin stability by N terminal missense variants including intragenic modifiers of SPG4 hereditary spastic paraplegia. (2007 Nov)
isoform specific increase of spastin stability by N terminal missense variants including intragenic modifiers of SPG4 hereditary spastic paraplegia . hereditary spastic paraplegia ( HSP ) is a neurodegenerative disorder selectively affecting axons of spinal cord motoneurons . classical mutations in the most frequent HSP gene spast ( spastin protein ) act through haploinsufficiency by abolishing the activity of a C terminal atpase domain or by interfering with expression from the affected allele . N terminal missense variants have been suggested to represent rare polymorphisms , to cause unusually mild phenotypes , and to aggravate the effect of a classical mutation . We confirm these associations for p . S44L but do not detect two other variants ( p . E43Q ; p . P45Q ) in HSP patients and controls . We show that neither of several disease mechanisms associated with classical spast mutations applies to the N terminal variants . instead , all three alterations enhance the stability of one of two alternative spastin isoforms . their phenotypic effect may thus not be mediated by haploinsufficiency but by increasing isoform competition for interacting proteins , substrates or oligomerization partners .

Spectrum of SPG4 mutations in autosomal dominant spastic paraplegia. (2000 Apr)
spectrum of SPG4 mutations in autosomal dominant spastic paraplegia . autosomal dominant hereditary spastic paraplegia ( AD HSP ) is a group of genetically heterogeneous neurodegenerative disorders characterized by pro gressive spasticity of the lower limbs . Five AD HSP loci have been mapped to chromosomes 14q , 2p , 15q , 8q and 12q . The SPG4 locus at 2p21 p22 has been shown to account for approximately 40 of all AD HSP families . SPG4 encoding spastin , a putative nuclear AAA protein , has recently been identified . Here , sequence analysis of the 17 exons of SPG4 in 87 unrelated AD HSP patients has resulted in the detection of 34 novel mutations . these SPG4 mutations are scattered along the coding region of the gene and include all types of DNA modification including missense ( 28 ) , nonsense ( 15 ) and splice site point ( 26 . 5 ) mutations as well as deletions ( 23 ) and insertions ( 7 . 5 ) . The clinical analysis of the 238 mutation carriers revealed a high proportion of both asymptomatic carriers ( 14 / 238 ) and patients unaware of symptoms ( 45 / 238 ) , and permitted the redefinition of this frequent form of AD HSP .

Hereditary spastic paraplegia : clinical genetic study of 15 families. (2004 Jun)
hereditary spastic paraplegia : clinical genetic study of 15 families . background : autosomal dominant hereditary spastic paraplegia ( adhsp ) is mainly caused by mutations in the SPG4 gene , which encodes a new member of the AAA ( adenosine triphosphatases associated with diverse cellular activities ) protein family ( spastin ) . accumulation of genotype phenotype correlation is important for better understanding of SPG4 linked hereditary spastic paraplegia . objectives : To perform a clinical and genetic study of families with adhsp and to perform the functional analysis of the founder mutation discovered in the SPG4 gene . design : genetic and clinical study . patients fifteen unrelated families with adhsp originating from southern scotland . MAIN outcome measures : clinical assessment , linkage analysis , haplotype study , expression of mutant spastin protein in cultured cells . results : Nine families with adhsp were linked to the SPG4 locus at 2p21 p24 . sequence analysis of spg4showed a novel n386s mutation in all 9 of these families . expression of mutant spastin showed aberrant distribution in cultured cells . haplotype analysis suggested the existence of a common founder . clinical examination of the affected members carrying the mutation showed phenotypic variations including broad range of age at onset and disease duration and additional neurologic features such as mental retardation . magnetic resonance imaging demonstrated unique features , including thin corpus callosum and atrophy of the cerebellum in 2 patients . linkage and sequence analyses showed no evidence …

Exon deletions of SPG4 are a frequent cause of hereditary spastic paraplegia. (2007 Apr)
Exon deletions of SPG4 are a frequent cause of hereditary spastic paraplegia . background : point mutations in SPG4 , the gene encoding spastin , are a frequent cause of autosomal dominant hereditary spastic paraplegia ( AD HSP ) . however , standard methods for genetic analyses fail to detect exonic microdeletions . methods : 121 mutation negative probands were screened for rearrangements in SPG4 by multiplex ligation dependent probe amplification . results : 24 patients with 16 different heterozygotic exon deletions in SPG4 ( 20 ) were identified , ranging from one exon to the whole coding sequence . comparison with 78 patients with point mutations showed a similar clinical picture but an earlier age at onset . conclusions : Exon deletions in SPG4 are as frequent as point mutations , and SPG4 is responsible for 40 of AD HSP .