Genetic background of the hereditary spastic paraplegia phenotypes in Hungary - An analysis of 58 probands

Identification of c.1495C > T mutation in SPAST gene in a family of Han Chinese with hereditary spastic paraplegia

BACKGROUND

Hereditary spastic paraplegia 4 (SPG4) caused by spastin (SPAST) gene mutations accounts for 40-45% of hereditary spastic paraplegia (HSP) cases. To search for more genetic evidences for the pathogenesis of HSP, the SPAST genotype and clinical phenotype of a Chinese Han SPG4 family were analysed in this study.

METHODS

The clinical data of the proband and his family members were collected. Whole genomic DNA was extracted from peripheral blood, and the gene detection and pathogenicity analysis of mutations were conducted using whole-exome sequencing technology. Suspected pathogenic mutations were identified. Verification within this family was conducted by Sanger sequencing.

RESULTS

Eight (4 males and 4 females) of 20 members in 4 generations had SPG4. All patients presented with the high feet arches (pes cavus), the abnormal gait, the active tendon reflexes of the upper limbs, the hyperreflexia of the lower limbs, and the positive ankle clonus and Babinski's signs bilaterally. In the proband, we found a heterozygous mutation c.1495C > T in SPAST gene, which was associated with the autosomal dominant SPG4. Both the daughters and granddaughters of the proband in this family were verified to carry this mutation. The clinical characteristics of the SPG4 patients in this family are in line with the simple type of HSP. Heterozygous c.1495C > T is a pathogenic mutation in this family.

CONCLUSION

In this study, we identified a c.1495C > T mutation in the SPAST gene in a Han Chinese family, enriching the mutation spectrum of SPG4.

Power of NGS-based tests in HSP diagnosis: analysis of massively parallel sequencing in clinical practice

Hereditary spastic paraplegia (HSP) refers to a group of heterogeneous neurological disorders mainly characterized by corticospinal degeneration (pure forms), but sometimes associated with additional neurological and extrapyramidal features (complex HSP). The advent of next-generation sequencing (NGS) has led to huge improvements in knowledge of HSP genetics and made it possible to clarify the genetic etiology of hundreds of "cold cases," accelerating the process of reaching a molecular diagnosis. The different NGS-based strategies currently employed as first-tier approaches most commonly involve the use of targeted resequencing panels and exome sequencing, whereas genome sequencing remains a second-tier approach because of its high costs. The question of which approach is the best is still widely debated, and many factors affect the choice. Here, we aim to analyze the diagnostic power of different NGS techniques applied in HSP, by reviewing 38 selected studies in which different strategies were applied in different-sized cohorts of patients with genetically uncharacterized HSP.

Clinical and genetic characterization of NIPA1 mutations in a Taiwanese cohort with hereditary spastic paraplegia

OBJECTIVE

NIPA1 mutations have been implicated in hereditary spastic paraplegia (HSP) as the cause of spastic paraplegia type 6 (SPG6). The aim of this study was to investigate the clinical and genetic features of SPG6 in a Taiwanese HSP cohort.

METHODS

We screened 242 unrelated Taiwanese patients with HSP for NIPA1 mutations. The clinical features of patients with a NIPA1 mutation were analyzed. Minigene-based splicing assay, RT-PCR analysis on the patients' RNA, and cell-based protein expression study were utilized to assess the effects of the mutations on splicing and protein expression.

RESULTS

Two patients were identified to carry a different heterozygous NIPA1 mutation. The two mutations, c.316G>A and c.316G>C, are located in the 3' end of NIPA1 exon 3 near the exon-intron boundary and putatively lead to the same amino acid substitution, p.G106R. The patient harboring NIPA1 c.316G>A manifested spastic paraplegia, epilepsy and schizophrenia since age 17 years, whereas the individual carrying NIPA1 c.316G>C had pure HSP since age 12 years. We reviewed literature and found that epilepsy was present in multiple individuals with NIPA1 c.316G>A but none with NIPA1 c.316G>C. Functional studies demonstrated that both mutations did not affect splicing, but only the c.316G>A mutation was associated with a significantly reduced NIPA1 protein expression.

INTERPRETATION

SPG6 accounted for 0.8% of HSP cases in the Taiwanese cohort. The NIPA1 c.316G>A and c.316G>C mutations are associated with adolescent-onset complex and pure form HSP, respectively. The different effects on protein expression of the two mutations may be associated with their phenotypic discrepancy.

Clinical and Genetic Features of Chinese Patients With NIPA1-Related Hereditary Spastic Paraplegia Type 6

Background: Mutations in the NIPA1 gene cause hereditary spastic paraplegia (HSP) type 6 (SPG6), which is a rare type of HSP with a frequency of less than 1% in Europe. To date, less than 30 SPG6 families and limited NIPA1 mutations have been reported in different ethnic regions. The clinical features are variable.

Methods: We screened for NIPA1 mutations by whole exome sequencing or next generation sequencing in 35 unrelated Chinese families with HSP. The clinical manifestations were evaluated.

Results: Two variants of NIPA1 were identified in three index patients (3/35, 8.6%), two of whom carried a previously reported common variant c.316G > A (p.G106R), and the third patient harbored a novel likely pathogenic variant c.126C > G (p.N42K). Both variants were de novo in the three index patients. The phenotype was pure HSP in two patients and complicated HSP with epilepsy in the third one.

Conclusion:NIPA1-related HSP is more common in China than it in Europe. Both pure and complicated form of HSP can be found. The variant c.316G > A is a hotspot mutation, and the novel variant c.126C > G expands the mutational spectrum. The phenomenon of de novo mutations in NIPA1 emphasizes the need to consider autosomal dominant HSP-related genes in sporadic patients.

HACE1, GLRX5, and ELP2 gene variant cause spastic paraplegies

Hereditary spastic paraplegias (HSPs) are a clinically and genetically heterogeneous group of conditions that are characterized by lower limb spasticity and weakness. Considering the clinical overlap between metabolic causes, genetic diseases, and autosomal recessive HSP, differentiation between these types can be difficult based solely on their clinical characteristics. This study aimed to investigate the genetic etiology of patients with clinically suspected HSP. The study group was composed of seven Turkish families who each had two affected children and three families who each had a single affected child (17 total patients). The 17 probands (14 males, 3 females) underwent whole exome sequencing. Five typical HSP genes (FA2H, AP4M1, AP4E1, CYP7B1, and MAG) and three genes not previously related to HSP (HACE1, GLRX5, ad ELP2) were identified in 14 probands. Eight novel variants were identified in seven families: c.653 T > C (p.Leu218Pro) in the FA2H gene, c.347G > A (p.Gly116Asp) in the GLRX5 gene, c.2581G > C (p.Ala861Pro) in the HACE1 gene, c.1580G > A (p.Arg527Gln) and c.1189-1G > A in the ELP2 gene, c.10C > T (p.Gln4*) and c.1025 + 1G > A in the AP4M1 gene, c.1291delG (p.Gly431Alafs*3) and c.3250delA (p.Ile1084*) in the AP4E1 gene, and c.475 T > G (p.Cys159Gly) in the MAG gene. The growing use of next-generation sequencing improved diagnosis but also led to the continual identification of new causal genes for neurogenetic diseases associated with lower limb spasticity. The increasing number of HSP genes identified thus far highlights the extreme genetic heterogeneity of these disorders and their clinical and functional overlap with other neurological conditions. Our findings suggest that the HACE1, GLRX5, and ELP2 genes are genetic causes of HSP.

An integrated modelling methodology for estimating global incidence and prevalence of hereditary spastic paraplegia subtypes SPG4, SPG7, SPG11, and SPG15

BACKGROUND

Hereditary spastic paraplegias (HSPs) are progressively debilitating neurodegenerative disorders that follow heterogenous patterns of Mendelian inheritance. Available epidemiological evidence provides limited incidence and prevalence data, especially at the genetic subtype level, preventing a realistic estimation of the true social burden of the disease. The objectives of this study were to (1) review the literature on epidemiology of HSPs; and (2) develop an epidemiological model of the prevalence of HSP, focusing on four common HSP genetic subtypes at the country and region-level.

METHODS

A model was constructed estimating the incidence at birth, survival, and prevalence of four genetic subtypes of HSP based on the most appropriate published literature. The key model parameters were assessed by HSP clinical experts, who provided feedback on the validity of assumptions. A model was then finalized and validated through comparison of outputs against available evidence. The global, regional, and national prevalence and patient pool were calculated per geographic region and per genetic subtype.

RESULTS

The HSP global prevalence was estimated to be 3.6 per 100,000 for all HSP forms, whilst the estimated global prevalence per genetic subtype was 0.90 (SPG4), 0.22 (SPG7), 0.34 (SPG11), and 0.13 (SPG15), respectively. This equates to an estimated 3365 (SPG4) and 872 (SPG11) symptomatic patients, respectively, in the USA.

CONCLUSIONS

This is the first epidemiological model of HSP prevalence at the genetic subtype-level reported at multiple geographic levels. This study offers additional data to better capture the burden of illness due to mutations in common genes causing HSP, that can inform public health policy and healthcare service planning, especially in regions with higher estimated prevalence of HSP.

Hereditary Spastic Paraplegia: An Update

Hereditary spastic paraplegia (HSP) is a rare neurodegenerative disorder with the predominant clinical manifestation of spasticity in the lower extremities. HSP is categorised based on inheritance, the phenotypic characters, and the mode of molecular pathophysiology, with frequent degeneration in the axon of cervical and thoracic spinal cord’s lateral region, comprising the corticospinal routes. The prevalence ranges from 0.1 to 9.6 subjects per 100,000 reported around the globe. Though modern medical interventions help recognize and manage the disorder, the symptomatic measures remain below satisfaction. The present review assimilates the available data on HSP and lists down the chromosomes involved in its pathophysiology and the mutations observed in the respective genes on the chromosomes. It also sheds light on the treatment available along with the oral/intrathecal medications, physical therapies, and surgical interventions. Finally, we have discussed the related diagnostic techniques as well as the linked pharmacogenomics studies under future perspectives.

SPG6 (NIPA1 variant): A report of a case with early-onset complex hereditary spastic paraplegia and brief literature review

SPG6, caused by NIPA1 (nonimprinted in Prader-Willi/Angelman syndrome) gene pathogenic variants, is mainly considered as a pure autosomal dominant hereditary spastic paraplegia (AD-HSP), even if descriptions of complex cases have also been reported. We detected the common c.316G > A, p.(Gly106Arg) pathogenic de novo substitution in a 10-year-old patient with HSP and drug-resistant eyelid myoclonia with absences. In order to assess the significance of this association, we reviewed the literature to find that 25/110 (23%) SPG6 cases are complex, including a heterogeneous spectrum of comorbidities, in which epilepsy is most represented (10%), but also featuring peripheral neuropathy (5.5%), amyotrophic lateral sclerosis (3.6%), memory deficits (3.6%) or cognitive impairment (2.7%), tremor (2.7%) and dystonia (0.9%). From this literature review and our single case experience, two main conclusions can be drawn. First, SPG6 is an AD-HSP with both pure and complex presentation, and frequent occurrence of epilepsy within the spectrum of genetic generalized epilepsies (absences, bilateral tonic-clonic, bilateral tonic-clonic with upper limbs myoclonic seizures and eyelid myoclonia with absences). Second, opposed to previous descriptions, seizures might not always be drug responsive.

The emerging genetic diversity of hereditary spastic paraplegia in Korean patients

Hereditary Spastic Paraplegias (HSP) are a group of rare inherited neurological disorders characterized by progressive loss of corticospinal motor-tract function. Numerous patients with HSP remain undiagnosed despite screening for known genetic causes of HSP. Therefore, identification of novel genetic variations related to HSP is needed. In this study, we identified 88 genetic variants in 54 genes from whole-exome data of 82 clinically well-defined Korean HSP families. Fifty-six percent were known HSP genes, and 44% were composed of putative candidate HSP genes involved in the HSPome and originally reported neuron-related genes, not previously diagnosed in HSP patients. Their inheritance modes were 39, de novo; 33, autosomal dominant; and 10, autosomal recessive. Notably, ALDH18A1 showed the second highest frequency. Fourteen known HSP genes were firstly reported in Koreans, with some of their variants being predictive of HSP-causing protein malfunction. SPAST and REEP1 mutants with unknown function induced neurite abnormality. Further, 54 HSP-related genes were closely linked to the HSP progression-related network. Additionally, the genetic spectrum and variation of known HSP genes differed across ethnic groups. These results expand the genetic spectrum for HSP and may contribute to the accurate diagnosis and treatment for rare HSP.

Clinical and molecular characterization of hereditary spastic paraplegia in a spanish southern region

Spastic paraplegia (SPG) is a syndrome characterised by lower limb spasticity, occurring alone or in association with other neurological manifestations. Despite of the new molecular technologies, many patients remain yet undiagnosed. The purpose of this study was to describe the clinical presentation and molecular characteristics of a cohort of 27 patients from 18 different families with SPG in the south of Spain. We used a targeted next-generation sequencing (NGS) approach to study a proband from each family. Variants in SPG11 gene were the most common cause of SPG in our area. We made a genetic diagnosis in 52% of cases, identified 3 novel variants and reclassified one uncertain variant in SPG11 gene as pathogenic variant. We identified a patient with two truncanting mutation in SPG11 gene and late onset disease and report another missense mutation outside of motor domain of KIF1A gene in a family with pure SPG. Our study contributes to enhance the scientific knowledge of SPG. It is important to note the large group of cases (48%) that were not genetically diagnosed in our cohort. Therefore NGS approach is an efficient diagnostic tool, but it still large the number of non-diagnosed subjects, suggesting further genetic heterogeneity.

Genotype-phenotype associations in hereditary spastic paraplegia: a systematic review and meta-analysis on 13,570 patients

AIMS

The hereditary spastic paraplegias (HSPs) are a heterogeneous group of inherited neurodegenerative disorders. Although, several genotype-phenotype studies have carried out on HSPs, the association between genotypes and clinical phenotypes remain incomplete since most studies are small in size or restricted to a few genes. Accordingly, this study provides the systematic meta-analysis of genotype-phenotype associations in HSP.

METHODS AND RESULTS

We retrieved literature on genotype-phenotype associations in patients with HSP and mutated SPAST, REEP1, ATL1, SPG11, SPG15, SPG7, SPG35, SPG54, SPG5. In total, 147 studies with 13,570 HSP patients were included in our meta-analysis. The frequency of mutations in SPAST (25%) was higher than REEP1 (3%), as well as ATL1 (5%) in AD-HSP patients. As for AR-HSP patients, the rates of mutations in SPG11 (18%), SPG15 (7%) and SPG7 (13%) were higher than SPG5 (5%), as well as SPG35 (8%) and SPG54 (7%). The mean age of AD-HSP onset for ATL1 mutation-positive patients was earlier than patients with SPAST, REEP1 mutations. Also, the tendency toward younger age at AR-HSP onset for SPG35 was higher than other mutated genes. It is noteworthy that the mean age at HSP onset ranged from infancy to adulthood. As for the gender distribution, the male proportion in SPG7-HSP (90%) and REEP1-HSP (78%) was markedly high. The frequency of symptoms was varied among patients with different mutated genes. The rates of LL weakness, superficial sensory abnormalities, neuropathy, and deep sensory impairment were noticeably high in REEP1 mutations carriers. Also, in AR-HSP patients with SPG11 mutations, the presentation of symptoms including pes cavus, Neuropathy, and UL spasticity was higher.

CONCLUSION

Our comprehensive genotype-phenotype assessment of available data displays that the mean age at disease onset and particular sub-phenotypes are associated with specific mutated genes which might be beneficial for a diagnostic procedure and differentiation of the specific mutated genes phenotype among diverse forms of HSP.

Bi-allelic variants in RNF170 are associated with hereditary spastic paraplegia

Alterations of Ca2+ homeostasis have been implicated in a wide range of neurodegenerative diseases. Ca2+ efflux from the endoplasmic reticulum into the cytoplasm is controlled by binding of inositol 1,4,5-trisphosphate to its receptor. Activated inositol 1,4,5-trisphosphate receptors are then rapidly degraded by the endoplasmic reticulum-associated degradation pathway. Mutations in genes encoding the neuronal isoform of the inositol 1,4,5-trisphosphate receptor (ITPR1) and genes involved in inositol 1,4,5-trisphosphate receptor degradation (ERLIN1, ERLIN2) are known to cause hereditary spastic paraplegia (HSP) and cerebellar ataxia. We provide evidence that mutations in the ubiquitin E3 ligase gene RNF170, which targets inositol 1,4,5-trisphosphate receptors for degradation, are the likely cause of autosomal recessive HSP in four unrelated families and functionally evaluate the consequences of mutations in patient fibroblasts, mutant SH-SY5Y cells and by gene knockdown in zebrafish. Our findings highlight inositol 1,4,5-trisphosphate signaling as a candidate key pathway for hereditary spastic paraplegias and cerebellar ataxias and thus prioritize this pathway for therapeutic interventions.

Mutational Spectrum of Spast (Spg4) and Atl1 (Spg3a) Genes In Russian Patients With Hereditary Spastic Paraplegia

Hereditary spastic paraplegia (HSP) comprises a heterogeneous group of neurodegenerative disorders, it share common symptom - of progressive lower spastic paraparesis. The most common autosomal dominant (AD) forms of HSP are SPG4 (SPAST gene) and SPG3 (ATL1 gene). In the current research we investigated for the first time the distribution of pathogenic mutations in SPAST and ATL1 genes within a large cohort of Russian HSP patients (122 probands; 69 famillial cases). We determined the frequencies of genetic abnormalities using Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and Next Generation Sequencing (NGS) of targeted gene panels. As a result, SPG4 was diagnosed in 30.3% (37/122) of HSP cases, where the familial cases represented 37.7% (26/69) of SPG4. In total 31 pathogenic and likely pathogenic variants were detected in SPAST, with 14 new mutations. Among all detected SPAST variants, 29% were gross deletions and duplications. The proportion of SPG3 variants in Russian cohort was 8.2% (10/122) that were all familial cases. All 10 detected ATL1 mutations were missense substitutions, most of which were in the mutational hot spots of 4, 7, 8, 12 exons, with 2 novel mutations. This work will be helpful for the populational genetics of HSP understanding.

An allosteric network in spastin couples multiple activities required for microtubule severing

The AAA+ ATPase spastin remodels microtubule arrays through severing and its mutation is the most common cause of hereditary spastic paraplegias (HSP). Polyglutamylation of the tubulin C-terminal tail recruits spastin to microtubules and modulates severing activity. Here, we present a ~3.2 Å resolution cryo-EM structure of the Drosophila melanogaster spastin hexamer with a polyglutamate peptide bound in its central pore. Two electropositive loops arranged in a double-helical staircase coordinate the substrate sidechains. The structure reveals how concurrent nucleotide and substrate binding organizes the conserved spastin pore loops into an ordered network that is allosterically coupled to oligomerization, and suggests how tubulin tail engagement activates spastin for microtubule disassembly. This allosteric coupling may apply generally in organizing AAA+ protein translocases into their active conformations. We show that this allosteric network is essential for severing and is a hotspot for HSP mutations.

Hereditary spastic paraplegia: from diagnosis to emerging therapeutic approaches

Hereditary spastic paraplegia (HSP) describes a heterogeneous group of genetic neurodegenerative diseases characterised by progressive spasticity of the lower limbs. The pathogenic mechanism, associated clinical features, and imaging abnormalities vary substantially according to the affected gene and differentiating HSP from other genetic diseases associated with spasticity can be challenging. Next generation sequencing-based gene panels are now widely available but have limitations and a molecular diagnosis is not made in most suspected cases. Symptomatic management continues to evolve but with a greater understanding of the pathophysiological basis of individual HSP subtypes there are emerging opportunities to provide targeted molecular therapies and personalised medicine.

Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III

Lipid droplets (LDs) are neutral lipid storage organelles that transfer lipids to various organelles including peroxisomes. Here, we show that the hereditary spastic paraplegia protein M1 Spastin, a membrane-bound AAA ATPase found on LDs, coordinates fatty acid (FA) trafficking from LDs to peroxisomes through two interrelated mechanisms. First, M1 Spastin forms a tethering complex with peroxisomal ABCD1 to promote LD-peroxisome contact formation. Second, M1 Spastin recruits the membrane-shaping ESCRT-III proteins IST1 and CHMP1B to LDs via its MIT domain to facilitate LD-to-peroxisome FA trafficking, possibly through IST1- and CHMP1B-dependent modifications in LD membrane morphology. Furthermore, LD-to-peroxisome FA trafficking mediated by M1 Spastin is required to relieve LDs of lipid peroxidation. M1 Spastin's dual roles in tethering LDs to peroxisomes and in recruiting ESCRT-III components to LD-peroxisome contact sites for FA trafficking may underlie the pathogenesis of diseases associated with defective FA metabolism in LDs and peroxisomes.

[Common forms of hereditary spastic paraplegias]

A group of hereditary spastic paraplegias includes about 80 spastic paraplegia genes (SPG): forms with identified (almost 70) or only mapped (about 10) genes. Methods of next generation sequencing (NGS), along with new SPG discovering, modify knowledge about earlier delineated SPG. Clinical and genetic characteristics of common autosomal dominant (SPG4, SPG3, SPG31) and autosomal recessive (SPG11, SPG7, SPG15) forms are presented.

Next Generation Molecular Diagnosis of Hereditary Spastic Paraplegias: An Italian Cross-Sectional Study

Hereditary spastic paraplegia (HSP) refers to a group of genetically heterogeneous neurodegenerative motor neuron disorders characterized by progressive age-dependent loss of corticospinal motor tract function, lower limb spasticity, and weakness. Recent clinical use of next generation sequencing (NGS) methodologies suggests that they facilitate the diagnostic approach to HSP, but the power of NGS as a first-tier diagnostic procedure is unclear. The larger-than-expected genetic heterogeneity-there are over 80 potential disease-associated genes-and frequent overlap with other clinical conditions affecting the motor system make a molecular diagnosis in HSP cumbersome and time consuming. In a single-center, cross-sectional study, spanning 4 years, 239 subjects with a clinical diagnosis of HSP underwent molecular screening of a large set of genes, using two different customized NGS panels. The latest version of our targeted sequencing panel (SpastiSure3.0) comprises 118 genes known to be associated with HSP. Using an in-house validated bioinformatics pipeline and several in silico tools to predict mutation pathogenicity, we obtained a positive diagnostic yield of 29% (70/239), whereas variants of unknown significance (VUS) were found in 86 patients (36%), and 83 cases remained unsolved. This study is among the largest screenings of consecutive HSP index cases enrolled in real-life clinical-diagnostic settings. Its results corroborate NGS as a modern, first-step procedure for molecular diagnosis of HSP. It also disclosed a significant number of new mutations in ultra-rare genes, expanding the clinical spectrum, and genetic landscape of HSP, at least in Italy.

Mitochondrial dysfunction and autism: comprehensive genetic analyses of children with autism and mtDNA deletion

Background

The etiology of autism spectrum disorders (ASD) is very heterogeneous. Mitochondrial dysfunction has been described in ASD; however, primary mitochondrial disease has been genetically proven in a small subset of patients. The main goal of the present study was to investigate correlations between mitochondrial DNA (mtDNA) changes and alterations of genes associated with mtDNA maintenance or ASD.

Methods

Sixty patients with ASD and sixty healthy individuals were screened for common mtDNA mutations. Next generation sequencing was performed on patients with major mtDNA deletions (mtdel-ASD) using two gene panels to investigate nuclear genes that are associated with ASD or are responsible for mtDNA maintenance. Cohorts of healthy controls, ASD patients without mtDNA alterations, and patients with mitochondrial disorders (non-ASD) harbouring mtDNA deletions served as comparison groups.

Results

MtDNA deletions were confirmed in 16.6% (10/60) of patients with ASD (mtdel-ASD). In 90% of this mtdel-ASD children we found rare SNVs in ASD-associated genes (one of those was pathogenic). In the intergenomic panel of this cohort one likely pathogenic variant was present. In patients with mitochondrial disease in genes responsible for mtDNA maintenance pathogenic mutations and variants of uncertain significance (VUS) were detected more frequently than those found in patients from the mtdel-ASD or other comparison groups. In healthy controls and in patients without a mtDNA deletion, only VUS were detected in both panel.

Conclusions

MtDNA alterations are more common in patients with ASD than in control individuals. MtDNA deletions are not isolated genetic alterations found in ASD; they coexist either with other ASD-associated genetic risk factors or with alterations in genes responsible for intergenomic communication. These findings indicate that mitochondrial dysfunction is not rare in ASD. The occurring mtDNA deletions in ASD may be mostly a consequence of the alterations of the causative culprit genes for autism or genes responsible for mtDNA maintenance, or because of the harmful effect of environmental factors.

Electronic supplementary material

The online version of this article (10.1186/s12993-018-0135-x) contains supplementary material, which is available to authorized users.

Clinical features and genotype-phenotype correlation analysis in patients with ATL1 mutations: A literature reanalysis

Background

The hereditary spastic paraplegias (HSPs) are a group of clinically and genetically heterogeneous disorders. Approximately 10% of the autosomal dominant (AD) HSPs (ADHSPs) have the spastic paraplegia 3A (SPG3A) genotype which is caused by ATL1 gene mutations. Currently there are more than 60 reported ATL1 gene mutations and the genotype-phenotype correlation remains unclear. The study aims to investigate the genotype-phenotype correlation in SPG3A patients.

Methods

We performed a reanalysis of the clinical features and genotype-phenotype correlations in 51 reported studies exhibiting an ATL1 gene mutation.

Results

Most HSPs-SPG3A patients exhibited an early age at onset (AAO) of <10 years old, and showed an autosomal dominant pure spastic paraplegia. We found that 14% of the HSPs-SPG3A patients presented complicated phenotypes, with distal atrophy being the most common complicated symptom. The AAO of each mutation group was not statistically significant (P > 0.05). The mutational spectrum associated with ATL1 gene mutation is wide, and most mutations are missense mutations, but do not involve the functional motif of ATL1 gene encoded atlastin-1 protein.

Conclusions

Our findings indicate that there is no clear genotype-phenotype correlation in HSPs-SPG3A patients. We also find that exons 4, 7, 8 and 12 are mutation hotspots in ATL1 gene.

Electronic supplementary material

The online version of this article (doi:10.1186/s40035-017-0079-3) contains supplementary material, which is available to authorized users.