Prohibitin 1 regulates mtDNA release and downstream inflammatory responses.

Exposure of mitochondrial DNA (mtDNA) to the cytosol activates innate immune responses. But the mechanisms by which mtDNA crosses the inner mitochondrial membrane are unknown. Here, we found that the inner mitochondrial membrane protein prohibitin 1 (PHB1) plays a critical role in mtDNA release by regulating permeability across the mitochondrial inner membrane. Loss of PHB1 results in alterations in mitochondrial integrity and function. PHB1-deficient macrophages, serum from myeloid-specific PHB1 KO (Phb1MyeKO) mice, and peripheral blood mononuclear cells from neonatal sepsis patients show increased interleukin-1ß (IL-1ß) levels. PHB1 KO mice are also intolerant of lipopolysaccharide shock. Phb1-depleted macrophages show increased cytoplasmic release of mtDNA and inflammatory responses. This process is suppressed by cyclosporine A and VBIT-4, which inhibit the mitochondrial permeability transition pore (mPTP) and VDAC oligomerization. Inflammatory stresses downregulate PHB1 expression levels in macrophages. Under normal physiological conditions, the inner mitochondrial membrane proteins, AFG3L2 and SPG7, are tethered to PHB1 to inhibit mPTP opening. Downregulation of PHB1 results in enhanced interaction between AFG3L2 and SPG7, mPTP opening, mtDNA release, and downstream inflammatory responses.

A novel homozygous HPDL variant in Japanese siblings with autosomal recessive hereditary spastic paraplegia: case report and literature review.

Biallelic variants of 4-hydroxyphenylpyruvate dioxygenase-like (HPDL) gene have been linked to neurodegenerative disorders ranging from severe neonatal encephalopathy to early-onset spastic paraplegia. We identified a novel homozygous variant, c.340G > T (p.Gly114Cys), in the HPDL gene in two siblings with autosomal recessive hereditary spastic paraplegia (HSP). Despite sharing the same likely pathogenic variant, the older sister had pure HSP, whereas her brother had severe and complicated HSP, accompanied by early-onset mental retardation and abnormalities in magnetic resonance imaging. Given the clinical heterogeneity and potential for treatable conditions in HPDL-related diseases, we emphasize the importance of genetic testing for the HPDL gene.

MRI-ARSACS: An Imaging Index for Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) Identification Based on the Multicenter PROSPAX Study.

BACKGROUND: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) and hereditary spastic paraplegia type 7 (SPG7) represent the most common genotypes of spastic ataxia (SPAX). To date, their magnetic resonance imaging (MRI) features have only been described qualitatively, and a pure neuroradiological differential diagnosis between these two conditions is difficult to achieve. OBJECTIVES: To test the performance of MRI measures to discriminate between ARSACS and SPG7 (as an index of common SPAX disease). METHODS: In this prospective multicenter study, 3D-T1-weighted images of 59 ARSACS (35.4 ± 10.3 years, M/F = 33/26) and 78 SPG7 (54.8 ± 10.3 years, M/F = 51/27) patients of the PROSPAX Consortium were analyzed, together with 30 controls (45.9 ± 16.9 years, M/F = 15/15). Different linear and surface measures were evaluated. A receiver operating characteristic analysis was performed, calculating area under the curve (AUC) and corresponding diagnostic accuracy parameters. RESULTS: The pons area proved to be the only metric increased exclusively in ARSACS patients (P = 0.02). Other different measures were reduced in ARSACS and SPG7 compared with controls (all with P ≤ 0.005). A cut-off value equal to 1.67 of the pons-to-superior vermis area ratio proved to have the highest AUC (0.98, diagnostic accuracy 93%, sensitivity 97%) in discriminating between ARSACS and SPG7. CONCLUSIONS: Evaluation of the pons-to-superior vermis area ratio can discriminate ARSACS from other SPAX patients, as exemplified here by SPG7. Hence, we hereby propose this ratio as the Magnetic Resonance Index for the Assessment and Recognition of patients harboring SACS mutations (MRI-ARSACS), a novel diagnostic tool able to identify ARSACS patients and useful for discriminating ARSACS from other SPAX patients undergoing MRI. © 2024 International Parkinson and Movement Disorder Society.

A novel homozygous variant in ATL1 associated with early onset spastic paraplegia 3A: Further evidence for autosomal recessive inheritance.

Spastic paraplegia 3A (SPG3A) has long been considered as an autosomal dominant disorder till the report in 2014 and 2016 of two consanguineous Arabic families, showing that ATL1 mutations may cause autosomal recessive paraplegia. Here, a third report of a consanguineous Arabic family with recessive SPG3A is described. Exome sequencing reveals homozygosity for a novel likely pathogenic ATL1 splice donor variant (c.522+1G>T) in an affected 5-year-old infant whereas the parents, heterozygous carriers, are asymptomatic. The infant's phenotype is consistent with an early onset complicated SPG3A with severe progressive spasticity of the lower limbs and intellectual disability.

Rescue of lysosomal function as therapeutic strategy for SPG15 hereditary spastic paraplegia.

SPG15 is a hereditary spastic paraplegia subtype caused by mutations in Spastizin, a protein encoded by the ZFYVE26 gene. Spastizin is involved in autophagosome maturation and autophagic lysosome reformation and SPG15-related mutations lead to autophagic lysosome reformation defects with lysosome enlargement, free lysosome depletion and autophagosome accumulation. Symptomatic and rehabilitative treatments are the only therapy currently available for patients. Here, we targeted autophagy and lysosomes in SPG15 patient-derived cells by using a library of autophagy-modulating compounds. We identified a rose of compounds affecting intracellular calcium levels, the calcium-calpain pathway or lysosomal functions, which reduced autophagosome accumulation. The six most effective compounds were tested in vivo in a new SPG15 loss of function Drosophila model that mimicked the reported SPG15 phenotype, with autophagosome accumulation, enlarged lysosomes, reduced free lysosomes, autophagic lysosome reformation defects and locomotor deficit. These compounds, namely verapamil, Bay K8644, 2',5'-dideoxyadenosine, trehalose, Small-Molecule Enhancer of Rapamycin 28 and trifluoperazine, improved lysosome biogenesis and function in vivo, demonstrating that lysosomes are a key pharmacological target to rescue SPG15 phenotype. Among the others, the Small-Molecule Enhancer of Rapamycin 28 was the most effective, rescuing both autophagic lysosome reformation defects and locomotor deficit, and could be considered as a potential therapeutic compound for this hereditary spastic paraplegia subtype.

The prodromal phase of hereditary spastic paraplegia type 4: the preSPG4 cohort study.

This cohort study aimed to characterize the prodromal phase of hereditary spastic paraplegia type 4 (SPG4) using biomarkers and clinical signs and symptoms that develop before manifest gait abnormalities. Fifty-six first-degree relatives at risk of developing SPG4 underwent blinded genotyping and standardized phenotyping, including the Spastic Paraplegia Rating Scale (SPRS), complicating symptoms, non-motor affection, Three-Minute Walk, and neurophysiological assessment. Automated MR image analysis was used to compare volumetric properties. CSF of 33 probands was analysed for neurofilament light chain (NfL), tau, and amyloid-ß (Aß). Thirty participants turned out to be SPAST mutation carriers, whereas 26 did not inherit a SPAST mutation. Increased reflexes, ankle clonus, and hip abduction weakness were more frequent in prodromal mutation carriers but were also observed in non-mutation carriers. Only Babinski's sign differentiated reliably between the two groups. Timed walk and non-motor symptoms did not differ between groups. Whereas most mutation carriers had total SPRS scores of 2 points or more, only two non-mutation carriers reached more than 1 point. Motor evoked potentials revealed no differences between mutation and non-mutation carriers. We found NfL but not tau or Aß to rise in CSF of mutation carriers when approaching the time point of predicted disease manifestation. Serum NfL did not differ between groups. Volumetric MRI analyses did not reveal group differences apart from a smaller cingulate gyrus in mutation carriers. This study depicts subtle clinical signs which develop before gait abnormalities in SPG4. Long-term follow-up is needed to study the evolution of SPG4 in the prodromal stage and conversion into manifest disease. NfL in CSF is a promising fluid biomarker that may indicate disease activity in prodromal SPG4 but needs further evaluation in longitudinal studies.

Novel ERLIN2 variant expands the phenotype of Spastic Paraplegia 18.

BACKGROUND: The Brazilian Northeast region is notable for its high prevalence of consanguineous marriages and isolated populations, which has led to a significant prevalence of rare genetic disorders. This study describes the clinical presentation of four affected individuals from the same family, comprising two siblings and their cousins, with ages ranging from 11 to 20 years. METHODS: In a small and isolated community in Northeastern Brazil, affected individuals initially underwent a clinical assessment. Subsequently, written consent was obtained from their legal guardians, and an extensive clinical evaluation was conducted at a medical genetics center. Family data provided the basis for constructing the pedigree, and biological samples (blood or oral swabs) were collected from both affected and unaffected family members. Following informed consent from one patient, Whole Exome Sequencing (WES) was carried out, encompassing exome sequencing, assembly, genotyping, and annotation. A potentially deleterious variant was then singled out for further segregation analysis through Sanger Sequencing, involving both the proband and select family members. RESULTS AND CONCLUSION: These individuals exhibit severe neurodevelopmental delays, encompassing symptoms such as spastic paraplegia, neuropathy, intellectual impairments, and language challenges. Through next-generation sequencing (NGS) techniques, a previously unreported homozygous variant within the ERLIN2 gene linked to spastic paraplegia 18 (SPG18) was identified across all four patients. Also, all patients displayed childhood cataract, expanding the known clinical spectrum of SPG18.

Expanding SPG18 clinical spectrum: autosomal dominant mutation causes complicated hereditary spastic paraplegia in a large family.

BACKGROUND: SPG18 is caused by mutations in the endoplasmic reticulum lipid raft associated 2 (ERLIN2) gene. Autosomal recessive (AR) mutations are usually associated with complicated hereditary spastic paraplegia (HSP), while autosomal dominant (AD) mutations use to cause pure SPG18. AIM: To define the variegate clinical spectrum of the SPG18 and to evaluate a dominant negative effect of erlin2 (encoded by ERLIN2) on oligomerization as causing differences between AR and AD phenotypes. METHODS: In a four-generation pedigree with an AD pattern, a spastic paraplegia multigene panel test was performed. Oligomerization of erlin2 was analyzed with velocity gradient assay in fibroblasts of the proband and healthy subjects. RESULTS: Despite the common p.V168M mutation identified in ERLIN2, a phenoconversion to amyotrophic lateral sclerosis (ALS) was observed in the second generation, pure HSP in the third generation, and a complicated form with psychomotor delay and epilepsy in the fourth generation. Erlin2 oligomerization was found to be normal. DISCUSSION: We report the first AD SPG18 family with a complicated phenotype, and we ruled out a dominant negative effect of V168M on erlin2 oligomerization. Therefore, our data do not support the hypothesis of a relationship between the mode of inheritance and the phenotype, but confirm the multifaceted nature of SPG18 on both genetic and clinical point of view. Clinicians should be aware of the importance of conducting an in-depth clinical evaluation to unmask all the possible manifestations associated to an only apparently pure SPG18 phenotype. We confirm the genotype-phenotype correlation between V168M and ALS emphasizing the value of close follow-up.

Treatment of ZC4H2 Variant-Associated Spastic Paraplegia with Selective Dorsal Rhizotomy and Intensive Postoperative Rehabilitation: A Case Report.

Selective dorsal rhizotomy (SDR) has been used to treat children with spastic cerebral palsy (CP), and its beneficial effect on quality of life and ambulation has been confirmed in long-term follow-up studies. However, the role of SDR in the treatment of spasticity in patients with hereditary spastic paraplegia (HSP) and related disorders is not well-established. Here, we report the first patient with the ZC4H2 variant who underwent SDR to treat spastic paraplegia. Abnormal gait was discovered during a regular checkup at the age of 3 years and 9 months, and she was diagnosed with spastic paraplegia. She was heterozygous for the ZC4H2 variant and underwent SDR at the age of 5 years and 11 months, which alleviated the spasticity. The patient underwent inpatient postoperative rehabilitation for 4 months and continued outpatient physiotherapy after discharge. The Gross Motor Function Measure-88 score and maximum walking speed decreased transiently 1 month postoperatively, but gradually recovered, and continuously improved 6 months postoperatively. SDR and postoperative intensive rehabilitation were effective in improving motor and walking functions up to 6 months after surgery, although long-term follow-up is needed to draw conclusions.

Focused ion beam-scanning electron microscopy links pathological myelin outfoldings to axonal changes in mice lacking Plp1 or Mag.

Healthy myelin sheaths consist of multiple compacted membrane layers closely encasing the underlying axon. The ultrastructure of CNS myelin requires specialized structural myelin proteins, including the transmembrane-tetraspan proteolipid protein (PLP) and the Ig-CAM myelin-associated glycoprotein (MAG). To better understand their functional relevance, we asked to what extent the axon/myelin-units display similar morphological changes if PLP or MAG are lacking. We thus used focused ion beam-scanning electron microscopy (FIB-SEM) to re-investigate axon/myelin-units side-by-side in Plp- and Mag-null mutant mice. By three-dimensional reconstruction and morphometric analyses, pathological myelin outfoldings extend up to 10 µm longitudinally along myelinated axons in both models. More than half of all assessed outfoldings emerge from internodal myelin. Unexpectedly, three-dimensional reconstructions demonstrated that both models displayed complex axonal pathology underneath the myelin outfoldings, including axonal sprouting. Axonal anastomosing was additionally observed in Plp-null mutant mice. Importantly, normal-appearing axon/myelin-units displayed significantly increased axonal diameters in both models according to quantitative assessment of electron micrographs. These results imply that healthy CNS myelin sheaths facilitate normal axonal diameters and shape, a function that is impaired when structural myelin proteins PLP or MAG are lacking.

circRNA-miRNA-mRNA network analysis to explore the pathogenesis of abnormal spermatogenesis due to aberrant m6A methylation.

Many studies have shown that circRNAs and miRNAs play important roles in many different life processes. However, the function of circRNAs in spermatogenesis remains unknown. Here, we aimed to explore the mechanisms whereby circRNA-miRNAs-mRNAs regulate abnormal m6A methylation in GC-1spg spermatogonia. We first reduced m6A methylation in GC-1spg whole cells after knocking down the m6A methyltransferase enzyme, METTL3. Then, we performed circRNA- and miRNA-seq on GC-1spg cells with low m6A methylation and identified 48 and 50 differentially expressed circRNAs and miRNAs, respectively. We also predicted the targets of the differentially expressed miRNAs by using Miranda software and further constructed the differentially expressed circRNA-differentially expressed miRNA-mRNA ceRNA network. GO analysis was performed on the differentially expressed circRNAs and miRNA-targeted mRNAs, and an interaction network between the proteins of interest was constructed using Cytoscape. The final GO analysis showed that the target mRNAs were involved in sperm formation. Therefore, a PPI network was subsequently constructed and 2 hub genes (H2afx and Dnmt3a) were identified. In this study, we constructed a ceRNA network and explored the regulatory roles of circRNAs and miRNAs in the pathogenesis of abnormal spermatogenesis caused by low levels of methylated m6A. Also, we identified two pivotal genes that may be key factors in infertility caused by abnormal m6A methylation. This may provide some ideas for the treatment of infertility resulting from abnormal spermatogenesis.

Copy number variations in SPAST and ATL1 are rare among Brazilians.

Copy number variations (CNV) may represent a significant proportion of SPG4 and SPG3A diagnosis, the most frequent autosomal dominant subtypes of hereditary spastic paraplegias (HSP). We aimed to assess the frequency of CNVs in SPAST and ATL1 and to update the molecular epidemiology of HSP families in southern Brazil. A cohort study that included 95 Brazilian index cases with clinical suspicion of HSP was conducted between April 2011 and September 2022. Multiplex Ligation Dependent Probe Amplification (MLPA) was performed in 41 cases without defined diagnosis by different massive parallel sequencing techniques (MPS). Diagnosis was obtained in 57/95 (60%) index cases, 15/57 (26.3%) being SPG4. Most frequent autosomal recessive HSP subtypes were SPG7 followed by SPG11, SPG76 and cerebrotendinous xanthomatosis. No CNVs in SPAST and ATL1 were found. Copy number variations are rare among SPG4 and SPG3A families in Brazil. Considering the possibility of CNVs detection by specific algorithms with MPS data, we consider that this is likely the most cost-effective approach to investigate CNVs in these genes in low-risk populations, with MLPA being reserved as an orthogonal confirmatory test.

Putative founder effect of Arg338* AP4M1 (SPG50) variant causing severe intellectual disability, epilepsy and spastic paraplegia: Report of three families.

Bi-allelic variants affecting one of the four genes encoding the AP4 subunits are responsible for the "AP4 deficiency syndrome." Core features include hypotonia that progresses to hypertonia and spastic paraplegia, intellectual disability, postnatal microcephaly, epilepsy, and neuroimaging features. Namely, AP4M1 (SPG50) is involved in autosomal recessive spastic paraplegia 50 (MIM#612936). We report on three patients with core features from three unrelated consanguineous families originating from the Middle East. Exome sequencing identified the same homozygous nonsense variant: NM_004722.4(AP4M1):c.1012C>T p.Arg338* (rs146262009). So far, four patients from three other families carrying this homozygous variant have been reported worldwide. We describe their phenotype and compare it to the phenotype of patients with other variants in AP4M1. We construct a shared single-nucleotide polymorphism (SNP) haplotype around AP4M1 in four families and suggest a probable founder effect of Arg338* AP4M1 variant with a common ancestor most likely of Turkish origin.

Plasma Neurofilament Light Chain Is Elevated in Adaptor Protein Complex 4-Related Hereditary Spastic Paraplegia.

BACKGROUND: Adaptor protein complex 4-associated hereditary spastic paraplegia (AP-4-HSP) is caused by pathogenic biallelic variants in AP4B1, AP4M1, AP4E1, and AP4S1. OBJECTIVE: The aim was to explore blood markers of neuroaxonal damage in AP-4-HSP. METHODS: Plasma neurofilament light chain (pNfL) and glial fibrillary acidic protein (GFAP) levels were measured in samples from patients and age- and sex-matched controls (NfL: n = 46 vs. n = 46; GFAP: n = 14 vs. n = 21) using single-molecule array assays. Patients' phenotypes were systematically assessed using the AP-4-HSP natural history study questionnaires, the Spastic Paraplegia Rating Scale, and the SPATAX disability score. RESULTS: pNfL levels increased in AP-4-HSP patients, allowing differentiation from controls (Mann-Whitney U test: P = 3.0e-10; area under the curve = 0.87 with a 95% confidence interval of 0.80-0.94). Phenotypic cluster analyses revealed a subgroup of individuals with severe generalized-onset seizures and developmental stagnation, who showed differentially higher pNfL levels (Mann-Whitney U test between two identified clusters: P = 2.5e-6). Plasma GFAP levels were unchanged in patients with AP-4-HSP. CONCLUSIONS: pNfL is a potential disease marker in AP-4-HSP and can help differentiate between phenotypic subgroups. © 2023 International Parkinson and Movement Disorder Society.

Malnutrition diagnosed by GLIM criteria better predicts long-term outcomes for patients with non-Hodgkin's lymphoma: A prospective multicenter cohort study.

Since Global Leadership Initiative on Malnutrition (GLIM) method was proposed, few studies have applied these new criteria to hematological tumors. In this study, we explored the prevalence of malnutrition according to the GLIM criteria and scored Patient-Generated Subjective Global Assessment (sPG-SGA) and their association with 1-year, 3-year and 5-year mortality among patients with non-Hodgkin's lymphoma (NHL). Malnutrition of all patients were assessed by GLIM criteria and sPG-SGA. Relationship between the malnutrition based on GLIM criteria or sPG-SGA and mortality was investigated by Cox regression analyses. The performance of GLIM criteria was evaluated by assessing the sensitivity, specificity, k-value, receiver operating characteristic (ROC) curve and time-dependent ROC. Of 963 patients with NHL, the prevalence of malnutrition was 38.8% with GLIM criteria, 65.3% with GLIM-omitted NRS-2002 and 53.2% with sPG-SGA. In comparison with sPG-SGA, the sensitivity of GLIM criteria was 61.7%, the specificity was 84.8%, and the agreement was moderate (k = 0.48, p < 0.001). Malnutrition based on GLIM criteria could also predict 3-year and 5-year mortality after adjusting for confounders, except for sPG-SGA (HR = 1.816, 95%CI = 1.274-2.589, p = 0.001 for 3-year mortality; HR = 1.707, 95%CI = 1.223-2.382, p = 0.002 for 5-year mortality). For patients with NHL, GLIM criteria could be applied as an effective replacement to sPG-SGA for nutrition assessment and mortality prediction, especially for predicting long-term prognostic outcomes.

Expanding SPG7 dominant optic atrophy phenotype: Infantile nystagmus and optic atrophy without spastic paraplegia.

Spastic paraplegia is a neurodegenerative disorder characterized by progressive leg weakness and spasticity due to degeneration of corticospinal axons. SPG7 encodes paraplegin, and pathogenic variants in the gene cause hereditary spastic paraplegia as an autosomal recessive trait. Various ophthalmological findings including optic atrophy, ophthalmoplegia, or nystagmus have been reported in patients with spastic paraplegia type 7. We report a 15-year-old male patient with a novel heterozygous variant, c.1224T>G:p.(Asp408Glu) in SPG7 (NM_003119.3) causing early onset isolated optic atrophy and infantile nystagmus prior to the onset of neurological symptoms. Therefore, SPG7 should be considered a cause of infantile nystagmus with optic atrophy.

New cellular imaging-based method to distinguish the SPG4 subtype of hereditary spastic paraplegia.

BACKGROUND AND PURPOSE: Microtubule defects are a common feature in several neurodegenerative disorders, including hereditary spastic paraplegia. The most frequent form of hereditary spastic paraplegia is caused by mutations in the SPG4/SPAST gene, encoding the microtubule severing enzyme spastin. To date, there is no effective therapy available but spastin-enhancing therapeutic approaches are emerging; thus prognostic and predictive biomarkers are urgently required. METHODS: An automated, simple, fast and non-invasive cell imaging-based method was developed to quantify microtubule cytoskeleton organization changes in lymphoblastoid cells and peripheral blood mononuclear cells. RESULTS: It was observed that lymphoblastoid cells and peripheral blood mononuclear cells from individuals affected by SPG4-hereditary spastic paraplegia show a polarized microtubule cytoskeleton organization. In a pilot study on freshly isolated peripheral blood mononuclear cells, our method discriminates SPG4-hereditary spastic paraplegia from healthy donors and other hereditary spastic paraplegia subtypes. In addition, it is shown that our method can detect the effects of spastin protein level changes. CONCLUSIONS: These findings open the possibility of a rapid, non-invasive, inexpensive test useful to recognize SPG4-hereditary spastic paraplegia subtype and evaluate the effects of spastin-enhancing drug in non-neuronal cells.

Movement disorders in hereditary spastic paraplegia (HSP): a systematic review and individual participant data meta-analysis.

BACKGROUND: Hereditary spastic paraplegia (HSP) is a rare genetic disorder associated with mutations in > 80 loci designated SPG (SPastic parapleGia). The phenotypic spectrum of HSP can extend to include other neurologic features, including movement disorders. Our aim was to investigate genotype-phenotype associations in HSP with a focus on movement disorders. METHODS: We performed a systematic review and individual participant data (IPD)-level meta-analysis by retrieving publications from Medline/EMBASE/Web of Science on HSP with a SPG genotype. Studies were included only if individual-level information was accessible and at least one patient with a movement disorder was reported for that genotype. Out of 21,957 hits, 192 manuscripts with a total of 1413 HSP cases were eligible. Data were compared between two HSP groups: manifested with (HSP-MD, n = 767) or without (HSP-nMD, n = 646) a movement disorder. RESULTS: The HSP-MD group had an older age of onset (20.5 ± 16.0 vs. 17.1 ± 14.2 yr, p < 0.001) and less frequent autosomal dominant inheritance (7.6% vs. 30.1%, p < 0.001) compared to HSP-nMD. SPG7 (31.2%) and SPG11 (23.8%) were the most frequent genotypes in the HSP-MD group. HSP-MD with SPG7 had higher frequency of later onset during adulthood (82.9% vs. 8.5%), ataxia (OR = 12.6), extraocular movement disturbances (OR = 3.4) and seizure (OR = 3.7) compared to HSP-MD with SPG11. Conversely, SPG11 mutations were more frequently associated with consanguinity (OR = 4.1), parkinsonism (OR = 7.8), dystonia (OR = 5.4), peripheral neuropathy (OR = 26.9), and cognitive dysfunction (OR = 34.5). CONCLUSION: This systematic IPD-level meta-analysis provides the largest data on genotype-phenotype associations in HSP-MD. Several clinically relevant phenotypic differences were found between various genotypes, which can possibly facilitate diagnosis in resource-limited settings.

An SPG7 mutation as a novel cause of monogenic progressive muscular atrophy.

BACKGROUND: Progressive muscular atrophy (PMA) is a rare adult-onset neurological disease that is characterized by isolated lower motor neuron degeneration. While it is still disputable whether PMA is a subtype of amyotrophic lateral sclerosis (ALS) or an isolated disorder, it is well-established as a clinically defined entity. About 5% of PMA cases are monogenic, and the implicated genes largely overlap with those causing monogenic ALS. CASE DESCRIPTION: Here we describe a 68-year-old female patient with progressive and asymmetric upper-limb weakness throughout an 18-month period, with muscle atrophy, dysphagia and slurring of speech. The lower limbs were unaffected, and there was no sign of upper motor neuron dysfunction. Comprehensive genetic testing for single nucleotide and copy-number variants revealed a pathogenic monoallelic variant c.1529C>T, p.(Ala510Val) in the SPG7 gene. DISCUSSION: Pathogenic biallelic SPG7 variants have been originally associated with hereditary spastic paraplegia, but other phenotypes are nowadays known to be linked to these variants, such as ALS. However, there is no report of this (or any) other SPG7 variant in association with PMA, whether it progressed to ALS or not. In conclusion, we present the first known case of PMA associated with a monoallelic SPG7 mutation.

Dysfunctional neuro-muscular mechanisms explain gradual gait changes in prodromal spastic paraplegia.

BACKGROUND: In Hereditary Spastic Paraplegia (HSP) type 4 (SPG4) a length-dependent axonal degeneration in the cortico-spinal tract leads to progressing symptoms of hyperreflexia, muscle weakness, and spasticity of lower extremities. Even before the manifestation of spastic gait, in the prodromal phase, axonal degeneration leads to subtle gait changes. These gait changes - depicted by digital gait recording - are related to disease severity in prodromal and early-to-moderate manifest SPG4 participants. METHODS: We hypothesize that dysfunctional neuro-muscular mechanisms such as hyperreflexia and muscle weakness explain these disease severity-related gait changes of prodromal and early-to-moderate manifest SPG4 participants. We test our hypothesis in computer simulation with a neuro-muscular model of human walking. We introduce neuro-muscular dysfunction by gradually increasing sensory-motor reflex sensitivity based on increased velocity feedback and gradually increasing muscle weakness by reducing maximum isometric force. RESULTS: By increasing hyperreflexia of plantarflexor and dorsiflexor muscles, we found gradual muscular and kinematic changes in neuro-musculoskeletal simulations that are comparable to subtle gait changes found in prodromal SPG4 participants. CONCLUSIONS: Predicting kinematic changes of prodromal and early-to-moderate manifest SPG4 participants by gradual alterations of sensory-motor reflex sensitivity allows us to link gait as a directly accessible performance marker to emerging neuro-muscular changes for early therapeutic interventions.