Three novel spastin ( SPG4 ) mutations in families with autosomal dominant hereditary spastic paraplegia. (2002 Aug)
three novel spastin ( SPG4 ) mutations in families with autosomal dominant hereditary spastic paraplegia . hereditary spastic paraplegia ( HSP ) is a clinically and genetically heterogeneous condition , characterised principally by progressive spasticity of the lower limbs . forty percent of autosomal dominant ( AD ) pedigrees show linkage to the SPG4 locus on chromosome 2 , which encodes spastin , an atpase associated with diverse cellular activities ( AAA ) protein . We have performed a clinical and genetic study of three AD HSP families linked to SPG4 . sequencing revealed three novel causative mutations . Two of the mutations were located in exon 5 ( a 1 base pair ( bp ) insertion and a 5 bp deletion ) , resulting in frameshift and premature termination of translation , with the predicted protein lacking the entire AAA functional domain . The 5 bp deletion was associated with a later onset and mild cerebellar features . The third mutation was a 3 bp deletion in exon 9 , resulting in the loss of a highly conserved phenylalanine residue within the AAA cassette and an apparently milder phenotype . This is the first example of a deletion of an amino acid in spastin .

Recent advances in hereditary spastic paraplegia. (2001 Jul)
recent advances in hereditary spastic paraplegia . The hereditary spastic paraplegias are a group of rare disorders that are characterized by great clinical and genetic heterogeneity . there has been an exponential increase in the number of HSP loci mapped in recent years , with nine out of the 17 loci reported during the past 2 years . eight loci have now been identified for the autosomal dominant form , and seven of these are associated with pure HSP . spastic paraplegia 4 remains the most frequent locus , and is usually associated with a pure phenotype . although the corresponding spastin gene was only recently identified , over 50 mutations have been described to date , which renders molecular diagnosis difficult . Five loci are known for autosomal recessive HSP , and four of these are associated with complex forms , all with different phenotypes . Two genes have been identified : paraplegin and sacsin . finally , three loci have been identified in X linked HSP , two of which are complex forms . The genes that encode L1 and PLP were the first to be identified in HSP disorders . surprisingly , the five genes encode proteins of different families , making understanding and diagnosis of HSP even more difficult . The discovery of new genes should hopefully help to clarify the pathophysiology of these disorders .

Clinical characteristics and spastin gene mutation analysis on an autosomal dominant kindred with hereditary spastic paraplegia objective : To investigate … (2007 Apr)
clinical characteristics and spastin gene mutation analysis on an autosomal dominant kindred with hereditary spastic paraplegia objective : To investigate the clinical characteristics and analyze spastin gene mutation on a kindred with hereditary spastic paraplegia ( HSP ) . methods : All family members were studied through clinical examinations . The proband and another two patients in this kindred were subjected to electromyography ( EMG ) examinations . The proband was subjected to thoracic MRI examination too . mutation analysis of spastin gene was screened by polymerase chain reaction combined with DNA sequencing in the proband and his father . results : All patients in the kindred manifested as classical HSP . thoracic MRI revealed atrophies of the spinal cord in the proband . No abnormal spastin gene mutation was detected in these two patients . conclusion : This kindred has typical clinical manifestations of HSP . The pathogenesis has no association with mutation of the exons of spastin gene .

Large deletion involving the 5 UTR in the spastin gene caused mild phenotype of autosomal dominant hereditary spastic paraplegia. (2005 Feb)
large deletion involving the 5 UTR in the spastin gene caused mild phenotype of autosomal dominant hereditary spastic paraplegia . hereditary spastic paraplegia ( HSP ) due to mutations in the spastin gene ( SPG4 ) located to 2p22 p21 is the most common form of autosomal dominant ( AD ) HSP . We performed PCR based direct sequencing of SPG4 , followed by a linkage analysis and subsequent southern blot analysis in large japanese kindred where 20 of 33 members were evaluated neurologically , and consequently 6 were affected with HSP . clinical evaluation showed that the mean age at disease onset of the patients was older and the disability was less severe than those of previously reported typical patients with SPG4 mutations . direct sequencing of genomic DNA and RT PCR product did not show a SPG4 mutation despite of a strong linkage to the SPG4 locus at 2p . southern blot analysis suggested a deletion involving the 5 UTR of SPG4 . further sequence analysis confirmed a heterozygous 2307 bp deletion spanning from the 5 UTR to intron 1 of SPG4 . The results suggested that transcription of the mutated allele starts from an authentic initiation site , but lacks an authentic translational start site of exon 1 because of a deficient splice donor site and coding region . The abnormal transcripts may result in rapid RNA decay . The novel refractory mutation we identified widens the spectrum of SPG4 mutations . these findings suggest that structural …

The hereditary spastic paraplegia gene , spastin , regulates microtubule stability to modulate synaptic structure and function. (2004 Jul)
The hereditary spastic paraplegia gene , spastin , regulates microtubule stability to modulate synaptic structure and function . background : hereditary spastic paraplegia ( HSP ) is a devastating neurological disease causing spastic weakness of the lower extremities and eventual axonal degeneration . Over 20 genes have been linked to HSP in humans ; however , mutations in one gene , spastin ( SPG4 ) , are the cause of 40 of all cases . spastin is a member of the atpases associated with diverse cellular activities ( AAA ) protein family , and contains a microtubule interacting and organelle transport ( MIT ) domain . previous work in cell culture has proposed a role for spastin in regulating microtubules . results : employing drosophila transgenic methods for overexpression and RNA interference ( RNAi ) , we have investigated the role of spastin in vivo . We show that drosophila spastin ( D spastin ) is enriched in axons and synaptic connections . At neuromuscular junctions ( NMJ ) , dspastin RNAi causes morphological undergrowth and reduced synaptic area . moreover , dspastin overexpression reduces synaptic strength , whereas dspastin RNAi elevates synaptic currents . By using antibodies against posttranslationally modified alpha tubulin , we find that dspastin regulates microtubule stability . functional synaptic defects caused by dspastin RNAi and overexpression were pharmacologically alleviated by agents that destabilize and stabilize microtubules , respectively . conclusions : Loss of dspastin in drosophila causes an aberrantly stabilized microtubule cytoskeleton in neurons and …

Interaction of two hereditary spastic paraplegia gene products , spastin and atlastin , suggests a common pathway for axonal maintenance. (2006 Jul)
interaction of two hereditary spastic paraplegia gene products , spastin and atlastin , suggests a common pathway for axonal maintenance . hereditary spastic paraplegia ( HSP ) is a neurodegenerative disorder that is characterized by retrograde axonal degeneration that primarily affects long spinal neurons . The disease is clinically heterogeneous , and there are 20 genetic loci identified . Here , we show a physical interaction between spastin and atlastin , two autosomal dominant HSP gene products . spastin encodes a microtubule ( MT ) severing AAA atpase ( atpase associated with various activities ) , and atlastin encodes a golgi localized integral membrane protein gtpase . atlastin does not regulate the enzymatic activity of spastin . We also identified a clinical mutation in atlastin outside of the gtpase domain that prevents interaction with spastin in cells . therefore , we hypothesize that failure of appropriate interaction between these two HSP gene products may be pathogenetically relevant . these data indicate that at least a subset of HSP genes may define a cellular biological pathway that is important in axonal maintenance .

Spastic paraplegia caused by a novel mutation in the spastin gene ( 1207c G , p361r ) clinical features of … (2008 Feb)
spastic paraplegia caused by a novel mutation in the spastin gene ( 1207c G , p361r ) clinical features of a patient without family history A 52 year old man with no apparent family history of neurodegenerative diseases developed gait disturbance at age 47 . neurological examination at aged 52 revealed spastic paraplegia , generalized hyperreflexia , decreased of vibration sense in the lower limbs , and pollakisuria . ocular symptoms , deafness , cerebellar ataxia , extrapyramidal signs , mental deterioration , dementia , peripheral neuropathy , retinal pigment degeneration , ichthyosis and syndactyly were absent . MRI of the brain was normal . A pure form of hereditary spastic paraplegia was diagnosed . genetic analysis revealed a novel missense mutation in the spastin gene ( 1207c G , p361r ) . The clinical features of this patient were consistent with those of patient with the pure form of SPG4 . Gene analysis should be considered for patients with spastic paraplegia even in the absence of any family history .

Prenatal diagnosis of autosomal dominant hereditary spastic paraplegia ( SPG4 ) using direct mutation detection. (2004 May)
prenatal diagnosis of autosomal dominant hereditary spastic paraplegia ( SPG4 ) using direct mutation detection . objective : To present a report on prenatal diagnosis using direct SPG4 gene analysis in a family with autosomal dominant hereditary spastic paraplegia ( AD HSP ) . methods : genetic linkage and haplotype analysis were previously carried out with chromosome 2p markers . DNA was obtained from affected individuals , the affected father , the mother , and fetal DNA from an ongoing pregnancy by chorionic villus sampling ( CVS ) in the first trimester . The spastin gene ( SPG4 ) was completely sequenced . results : A novel 832insgdelaa frameshift mutation , predicted to cause loss of functional protein , was identified in the affected father and in the fetal DNA . conclusions : This is the first report on direct prenatal diagnosis of chromosome 2p linked AD HSP ( SPG4 ) . In addition , we report a novel SPG4 combined small insertion / deletion mutation in exon 5 , which may be the first SPG4 mutational hot spot .

Neurophysiological findings in SPG4 patients differ from other types of spastic paraplegia. (2003 May)
neurophysiological findings in SPG4 patients differ from other types of spastic paraplegia . The authors examined 12 families with autosomal dominant hereditary spastic paraplegia for phenotypic characteristics predicting the underlying genotype . They found no clinical differences between patients with or without mutations in the spastin gene ( SPG4 ) . motor evoked potentials and nerve conduction studies were almost normal in those with SPG4 . In contrast , non SPG4 families had prolonged central motor conduction times or marked peripheral neuropathy , or both .

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 .

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 .

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 .

Structural basis of microtubule severing by the hereditary spastic paraplegia protein spastin. (2008 Jan)
structural basis of microtubule severing by the hereditary spastic paraplegia protein spastin . spastin , the most common locus for mutations in hereditary spastic paraplegias , and katanin are related microtubule severing AAA atpases involved in constructing neuronal and non centrosomal microtubule arrays and in segregating chromosomes . The mechanism by which spastin and katanin break and destabilize microtubules is unknown , in part owing to the lack of structural information on these enzymes . Here we report the X ray crystal structure of the drosophila spastin AAA domain and provide a model for the active spastin hexamer generated using small angle X ray scattering combined with atomic docking . The spastin hexamer forms a ring with a prominent central pore and six radiating arms that may dock onto the microtubule . helices unique to the microtubule severing AAA atpases surround the entrances to the pore on either side of the ring , and three highly conserved loops line the pore lumen . mutagenesis reveals essential roles for these structural elements in the severing reaction . peptide and antibody inhibition experiments further show that spastin may dismantle microtubules by recognizing specific features in the carboxy terminal tail of tubulin . collectively , our data support a model in which spastin pulls the C terminus of tubulin through its central pore , generating a mechanical force that destabilizes tubulin tubulin interactions within the microtubule lattice . Our work also provides insights into the structural defects in spastin that arise from mutations …

High frequency of partial spast deletions in autosomal dominant hereditary spastic paraplegia. (2006 Dec)
High frequency of partial spast deletions in autosomal dominant hereditary spastic paraplegia . background : hereditary spastic paraplegia ( HSP ) is a genetically heterogeneous neurodegenerative disease . The most frequent cause of autosomal dominant HSP is mutation of spast ( SPG4 locus ) , but additional pedigrees remain mutation negative by conventional screening despite linkage to SPG4 . objective : To determine the frequency of genomic copy number aberrations of spast in autosomal dominant HSP . methods : We developed and validated a multiplex ligation dependent probe amplification assay targeting spast and spg3a , another gene frequently involved in autosomal dominant HSP . In a multicenter study we subsequently investigated 65 index patients with autosomal dominant HSP , all of whom had previously been screened negative for spast mutations . independent secondary samples , additional family members , and cDNA were analyzed to confirm positive findings . results : aberrant MLPA profiles were identified in 12 cases ( 18 ) . They exclusively affect spast , represent deletions , segregate with the disease , and are largely pedigree specific . internal spast deletions entail expression of correspondingly shortened transcripts , which vary in stability . Age at onset in spast deletion carriers does not differ from that associated with other spast mutations . conclusions : partial spast deletions , but not spast amplifications and spg3a copy number aberrations , represent an underestimated cause of autosomal dominant hereditary spastic paraplegia . partial spast deletions are likely to act via haploinsufficiency …

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 C. (2007 Jun)
The C . elegans homologue of the spastic paraplegia protein , spastin , disassembles microtubules . mutations in human spastin ( SPG4 ) cause an autosomal dominant form of hereditary spastic paraplegia . sequence analysis revealed that spastin contains the AAA ( atpases associated with diverse cellular activities ) domain in the C terminal region . recently , it was reported that spastin interacts dynamically with microtubules and displays microtubule severing activity . A plausible caenorhabditis elegans homologue of spastin ( SPAS 1 ) has been identified by homology search and phylogenetic analyses . To understand the function of the spastin homologue , we characterized the spas 1 deletion mutant and analyzed spas 1 expression regulation in C . elegans . SPAS 1 was localized with cytoskeletons at the perinuclear region . We found that microtubules were intensely stained at the centrosomal region in the deletion mutant . furthermore , overexpression of SPAS 1 caused disassembly of microtubule network in cultured cells , while atpase deficient SPAS 1 did not . these results indicate that C . elegans SPAS 1 plays an important role in microtubule dynamics . We also found that two kinds of products were generated from spas 1 by alternative splicing in a developmental stage dependent manner .

Novel spastin ( SPG4 ) mutations in italian patients with hereditary spastic paraplegia. (2006 Jun)
novel spastin ( SPG4 ) mutations in italian patients with hereditary spastic paraplegia . spastic paraplegia type 4 is caused by mutations in the gene that encodes spastin ( SPG4 ) , a member of the AAA protein family . A cohort of 34 unrelated italian patients with pure spastic paraplegia , of which 18 displayed autosomal dominant inheritance and 16 were apparently sporadic , were screened for mutations in the SPG4 gene by denaturing high performance liquid chromatography . We identified a previously reported mutation in a sporadic patient with pure hereditary spastic paraplegia . We also identified eight unrelated patients with pure autosomal dominant hereditary spastic paraplegia carrying five novel mutations in the SPG4 gene ( one missense mutation , c . 1304 C T ; one nonsense mutation , c . 807C A ; two frameshift mutations , c . 1281dupt , c . 1514 1515insata ; and one splicing mutation , c . 1322 2A C ) . The frequency for SPG4 mutations detected in autosomal dominant hereditary spastic paraplegia was 44 . 4 . This study contributes to expand the spectrum of SPG4 mutations in italian population .

Zfyve27 ( spg33 ) , a novel spastin binding protein , is mutated in hereditary spastic paraplegia. (2006 Jul)
zfyve27 ( spg33 ) , a novel spastin binding protein , is mutated in hereditary spastic paraplegia . spastin , the most commonly mutated protein in the autosomal dominant form of hereditary spastic paraplegia ( AD HSP ) has been suggested to be involved in vesicular cargo trafficking ; however , a comprehensive function of spastin has not yet been elucidated . To characterize the molecular function of spastin , we used the yeast two hybrid approach to identify new interacting partners of spastin . Here , we report zfyve27 , a novel member of the FYVE finger family of proteins , as a specific spastin binding protein , and we validate the interaction by both in vivo coimmunoprecipitation and colocalization experiments in mammalian cells . More importantly , we report a german family with AD HSP in which zfyve27 ( spg33 ) is mutated ; furthermore , we demonstrate that the mutated zfyve27 protein shows an aberrant intracellular pattern in its tubular structure and that its interaction with spastin is severely affected . We postulate that this specific mutation in zfyve27 affects neuronal intracellular trafficking in the corticospinal tract , which is consistent with the pathology of HSP .

Hereditary spastic paraplegia with cerebellar ataxia : a complex phenotype associated with a new SPG4 gene mutation. (2005 Jan)
hereditary spastic paraplegia with cerebellar ataxia : a complex phenotype associated with a new SPG4 gene mutation . complex forms of hereditary spastic paraplegia ( HSP ) are rare and usually transmitted in an autosomal recessive pattern . A family of four generations with autosomal dominant hereditary spastic paraplegia ( AD HSP ) and a complex phenotype with variably expressed co existing ataxia , dysarthria , unipolar depression , epilepsy , migraine , and cognitive impairment was investigated . genetic linkage analysis and sequencing of the SPG4 gene was performed and electrophysiologic investigations were carried out in six individuals and positron emission tomography ( PET ) in one patient . The disease was linked to the SPG4 locus on chromosome 2p as previously reported for pure HSP . sequence analysis of the SPG4 ( spastin ) gene identified a novel 1593 C T ( gln490stop ) mutation leading to premature termination of exon 12 with ensuing truncation of the encoded protein . however , the mutation was only identified in those individuals who were clinically affected by a complex phenotype consisting of HSP and cerebellar ataxia . other features noted in this kindred including epilepsy , cognitive impairment , depression , and migraine did not segregate with the HSP phenotype or mutation , and therefore the significance of these features to SPG4 is unclear . electrophysiologic investigation showed increased central conduction time at somatosensory evoked potentials measured from the lower limbs as the only abnormal finding in two affected individuals …

A novel missense mutation ( i344k ) in the spg4gene in a korean family with autosomal dominant hereditary spastic paraplegia. (2002 Aug)
A novel missense mutation ( i344k ) in the spg4gene in a korean family with autosomal dominant hereditary spastic paraplegia . hereditary spastic paraplegia ( HSP ) is a group of clinically and genetically heterogeneous neurodegenerative disorders characterized by slowly progressive spasticity and weakness of the lower extremities . among eight loci linked with autosomal dominant ( AD ) HSP , the SPG4 locus on chromosome 2p22 accounts for about 40 of all patients . recently , mutations in a new member of the AAA protein family , called spastin , have been identified as responsible for SPG4 linked AD HSP . Here , we describe a novel missense mutation ( c . 1031t A ; i344k ) in exon 7 of the SPG4 gene identified in a korean family with typical clinical features of pure AD HSP . The mutation affects the third amino acid of the highly conserved AAA cassette domain , which is the most fore part of the domain altered by a missense mutation reported so far . clinical presentations of affected individuals carrying the i344k mutation were not different from those of pure AD HSP with SPG4 mutations reported previously . however , it is noteworthy that neither urinary dysfunction nor involvement of upper extremities was noticed in this family . To our knowledge , this is the first report of genetically confirmed AD HSP in korea .