Spinal muscular atrophy

Autosomal-recessive proximal spinal muscular atrophy (Werdnig-Hoffmann, Kugelberg-Welander) is caused by mutation of the SMN1 gene, and the clinical severity correlates with the number of copies of a nearly identical gene, SMN2. The SMN protein plays a critical role in spliceosome assembly and may have other cellular functions, such as mRNA transport. Cell culture and animal models have helped to define the disease mechanism and to identify targets for therapeutic intervention. The main focus for developing treatment has been to increase SMN levels, and accomplishing this with small molecules, oligonucleotides, and gene replacement has been quite. An oligonucleotide, nusinersen, was recently approved for treatment in patients, and confirmatory studies of other agents are now under way.

Systemic Delivery of MicroRNA Using Recombinant Adeno-associated Virus Serotype 9 to Treat Neuromuscular Diseases in Rodents

RNA interference via the endogenous miRNA pathway regulates gene expression by controlling protein synthesis through post-transcriptional gene silencing. In recent years, miRNA-mediated gene regulation has shown potential for treatment of neurological disorders caused by a toxic gain of function mechanism. However, efficient delivery to target tissues has limited its application. Here we used a transgenic mouse model for spinal and bulbar muscular atrophy (SBMA), a neuromuscular disease caused by polyglutamine expansion in the androgen receptor (AR), to test gene silencing by a newly identified AR-targeting miRNA, miR-298. We overexpressed miR-298 using a recombinant adeno-associated virus (rAAV) serotype 9 vector to facilitate transduction of non-dividing cells. A single tail-vein injection in SBMA mice induced sustained and widespread overexpression of miR-298 in skeletal muscle and motor neurons and resulted in amelioration of the neuromuscular phenotype in the mice.

Nucleocytoplasmic transport defect in a North American patient with ALS8

Amyotrophic lateral sclerosis 8 (ALS8) is a rare progressive neurodegenerative disease resulting from mutation in the gene for vesicle-associated membrane protein-associated protein B. We evaluated a North American patient using exome sequencing, and identified a P56S mutation. The disease protein had similar subcellular localization and expression levels in the patient and control fibroblasts. Patient fibroblasts showed increased basal endoplasmic reticulum stress and dysfunction of nucleocytoplasmic transport as evidenced by impaired Ran trafficking. This finding extends the identification of ALS8 into North America, and indicates a cellular defect similar to other forms of hereditary motor neuron disease.

Senataxin Mutation Reveals How R-Loops Promote Transcription by Blocking DNA Methylation at Gene Promoters

R-loops are three-stranded nucleic acid structures found abundantly and yet often viewed as by-products of transcription. Studying cells from patients with a motor neuron disease (amyotrophic lateral sclerosis 4 [ALS4]) caused by a mutation in senataxin, we uncovered how R-loops promote transcription. In ALS4 patients, the senataxin mutation depletes R-loops with a consequent effect on gene expression. With fewer R-loops in ALS4 cells, the expression of BAMBI, a negative regulator of transforming growth factor β (TGF-β), is reduced; that then leads to the activation of the TGF-β pathway. We uncovered that genome-wide R-loops influence promoter methylation of over 1,200 human genes. DNA methyl-transferase 1 favors binding to double-stranded DNA over R-loops. Thus, in forming R-loops, nascent RNA blocks DNA methylation and promotes further transcription. Hence, our results show that nucleic acid structures, in addition to sequences, influence the binding and activity of regulatory proteins.

Adenylyl cyclase activating polypeptide reduces phosphorylation and toxicity of the polyglutamine-expanded androgen receptor in spinobulbar muscular atrophy

Spinobulbar muscular atrophy (SBMA) is an X-linked neuromuscular disease caused by polyglutamine (polyQ) expansion in the androgen receptor (AR) gene. SBMA belongs to the family of polyQ diseases, which are fatal neurodegenerative disorders mainly caused by protein-mediated toxic gain-of-function mechanisms and characterized by deposition of misfolded proteins in the form of aggregates. The neurotoxicity of the polyQ proteins can be modified by phosphorylation at specific sites, thereby providing the rationale for the development of disease-specific treatments. We sought to identify signaling pathways that modulate polyQ-AR phosphorylation for therapy development. We report that cyclin-dependent kinase 2 (CDK2) phosphorylates polyQ-AR specifically at Ser⁹⁶ Phosphorylation of polyQ-AR by CDK2 increased protein stabilization and toxicity and is negatively regulated by the adenylyl cyclase (AC)/protein kinase A (PKA) signaling pathway. To translate these findings into therapy, we developed an analog of pituitary adenylyl cyclase activating polypeptide (PACAP), a potent activator of the AC/PKA pathway. Chronic intranasal administration of the PACAP analog to knock-in SBMA mice reduced Ser⁹⁶ phosphorylation, promoted polyQ-AR degradation, and ameliorated disease outcome. These results provide proof of principle that noninvasive therapy based on the use of PACAP analogs is a therapeutic option for SBMA.

Nonalcoholic fatty liver disease in spinal and bulbar muscular atrophy

Objective:

To determine the prevalence and features of fatty liver disease in spinal and bulbar muscular atrophy (SBMA).

Methods:

Two groups of participants with SBMA were evaluated. In the first group, 22 participants with SBMA underwent laboratory analysis and liver imaging. In the second group, 14 participants with SBMA were compared to 13 female carriers and 23 controls. Liver biopsies were done in 4 participants with SBMA.

Results:

Evidence of fatty liver disease was detected by magnetic resonance spectroscopy in all participants with SBMA in the first group, with an average dome intrahepatic triacylglycerol of 27% (range 6%–66%, ref ≤5.5%). Liver dome magnetic resonance spectroscopy measurements were significantly increased in participants with SBMA in the second group relative to age- and sex-matched controls, with average disease and male control measurements of 17% and 3%, respectively. Liver biopsies were consistent with simple steatosis in 2 participants and nonalcoholic steatohepatitis in 2 others.

Conclusions:

We observed evidence of nonalcoholic liver disease in nearly all of the participants with SBMA evaluated. These observations expand the phenotypic spectrum of the disease and provide a potential biomarker that can be monitored in future studies.

Patient-identified impact of symptoms in spinal and bulbar muscular atrophy

INTRODUCTION

The effects of spinal bulbar muscular atrophy (SBMA) on quality of life (QoL) are not well understood. This study describes symptoms from the patient's perspective and the impact these symptoms have on QoL.

METHODS

We conducted open-ended interviews with 21 adult men with genetically confirmed SBMA. Using a qualitative framework technique, we coded and analyzed interviews to identify symptoms and resulting themes.

RESULTS

From these interviews, 729 quotations were extracted. We identified 200 SBMA-specific symptoms and 20 symptomatic themes. Weakness was mentioned by all interviewees. Symptoms within the domain of mental health and the specific themes of emotional issues and psychological impact were also frequently mentioned.

DISCUSSION

Numerous symptoms affect QoL for patients with SBMA. We identified previously unrecognized symptoms that are important to address in enhancing clinical care for patients with SBMA and in developing tools to evaluate efficacy in future clinical trials. Muscle Nerve 57: 40-44, 2018.

Respiratory magnetic resonance imaging biomarkers in Duchenne muscular dystrophy

OBJECTIVE

To examine the diaphragm and chest wall dynamics with cine breathing magnetic resonance imaging (MRI) in ambulatory boys with Duchenne muscular dystrophy (DMD) without respiratory symptoms and controls.

METHODS

In 11 DMD boys and 15 controls, cine MRI of maximal breathing was recorded for 10 sec. The lung segmentations were done by an automated pipeline based on a Holistically-Nested Network model (HNN method). Lung areas, diaphragm, and chest wall motion were measured throughout the breathing cycle.

RESULTS

The HNN method reliably identified the contours of the lung and the diaphragm in every frame of each dataset (~180 frames) within seconds. The lung areas at maximal inspiration and expiration were reduced in DMD patients relative to controls (P = 0.02 and <0.01, respectively). The change in the lung area between inspiration and expiration correlated with percent predicted forced vital capacity (FVC) in patients (r_s  = 0.75, P = 0.03) and was not significantly different between groups. The diaphragm position, length, contractility, and motion were not significantly different between groups. Chest wall motion was reduced in patients compared to controls (P < 0.01).

INTERPRETATION

Cine breathing MRI allows independent and reliable assessment of the diaphragm and chest wall dynamics during the breathing cycle in DMD patients and controls. The MRI data indicate that ambulatory DMD patients breathe at lower lung volumes than controls when their FVC is in the normal range. The diaphragm moves normally, whereas chest wall motion is reduced in these boys with DMD.

Skeletal muscle water T2 as a biomarker of disease status and exercise effects in patients with Duchenne muscular dystrophy

The purpose of this study was to examine exercise effects on muscle water T₂ in patients with Duchenne muscular dystrophy (DMD). In 12 DMD subjects and 19 controls, lower leg muscle fat (%) was measured by Dixon and muscle water T₂ and R₂ (1/T₂) by the tri-exponential model. Muscle water R₂ was measured again at 3 hours after an ankle dorsiflexion exercise. The muscle fat fraction was higher in DMD participants than in controls (p < .001) except in the tibialis posterior muscle. Muscle water T₂ was measured independent of the degree of fatty degeneration in DMD muscle. At baseline, muscle water T₂ was higher in all but the extensor digitorum longus muscles of DMD participants than controls (p < .001). DMD participants had a lower muscle torque (p < .001) and exerted less power (p < .01) during exercise than controls. Nevertheless, muscle water R₂ decreased (T₂ increased) after exercise from baseline in DMD subjects and controls with greater changes in the target muscles of the exercise than in ankle plantarflexor muscles. Skeletal muscle water T₂ is a sensitive biomarker of the disease status in DMD and of the exercise response in DMD patients and controls.

A novel mutation in KIF5A in a Malian family with spastic paraplegia and sensory loss

Hereditary spastic paraplegias (HSPs) are well‐characterized disorders but rarely reported in Africa. We evaluated a Malian family in which three individuals had HSP and distal muscle atrophy and sensory loss. HSP panel testing identified a novel heterozygous missense mutation in KIF5A (c.1086G>C, p.Lys362Asn) that segregated with the disease (SPG10). Lys362 is highly conserved across species and Lys362Asn is predicted to be damaging. This study shows that HSPs are present in sub‐Saharan Africa, although likely underdiagnosed. Increasing efficiency and decreasing costs of DNA sequencing will make it more feasible to diagnose HSPs in developing countries.

ML372 blocks SMN ubiquitination and improves spinal muscular atrophy pathology in mice

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease and one of the leading inherited causes of infant mortality. SMA results from insufficient levels of the survival motor neuron (SMN) protein, and studies in animal models of the disease have shown that increasing SMN protein levels ameliorates the disease phenotype. Our group previously identified and optimized a new series of small molecules, with good potency and toxicity profiles and reasonable pharmacokinetics, that were able to increase SMN protein levels in SMA patient-derived cells. We show here that ML372, a representative of this series, almost doubles the half-life of residual SMN protein expressed from the SMN2 locus by blocking its ubiquitination and subsequent degradation by the proteasome. ML372 increased SMN protein levels in muscle, spinal cord, and brain tissue of SMA mice. Importantly, ML372 treatment improved the righting reflex and extended survival of a severe mouse model of SMA. These results demonstrate that slowing SMN degradation by selectively inhibiting its ubiquitination can improve the motor phenotype and lifespan of SMA model mice.

Upper arm and cardiac magnetic resonance imaging in Duchenne muscular dystrophy

We analyzed quantitative maps of T₁ and T₂ relaxation times and muscle fat fraction measurements in magnetic resonance imaging of the upper arm skeletal muscles and heart in ambulatory boys with Duchenne muscular dystrophy and age‐range‐matched healthy volunteer boys. The cardiac‐optimized sequences detected fatty infiltration and edema in the upper arm skeletal muscles but not the myocardium in these Duchenne muscular dystrophy boys who had normal ejection fraction. Imaging the heart and skeletal muscle using the same magnetic resonance imaging methods during a single scan may be useful in assessing relative disease status and therapeutic response in clinical trials of Duchenne muscular dystrophy.

The polyglutamine-expanded androgen receptor responsible for spinal and bulbar muscular atrophy inhibits the APC/C(Cdh1) ubiquitin ligase complex

Polyglutamine expansion in the androgen receptor (AR) causes spinal and bulbar muscular atrophy (SBMA), an X-linked neuromuscular disease that is fully manifest only in males. It has been suggested that proteins with expanded polyglutamine tracts impair ubiquitin-dependent proteolysis due to their propensity to aggregate, but recent studies indicate that the overall activity of the ubiquitin-proteasome system is preserved in SBMA models. Here we report that AR selectively interferes with the function of the ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C), which, together with its substrate adaptor Cdh1, is critical for cell cycle arrest and neuronal architecture. We show that both wild-type and mutant AR physically interact with the APC/C^Cdh1 complex in a ligand-dependent fashion without being targeted for proteasomal degradation. Inhibition of APC/C^Cdh1 by mutant but not wild-type AR in PC12 cells results in enhanced neurite outgrowth which is typically followed by rapid neurite retraction and mitotic entry. Our data indicate a role of AR in neuronal differentiation through regulation of APC/C^Cdh1 and suggest abnormal cell cycle reactivation as a pathogenic mechanism in SBMA.

A small-molecule Nrf1 and Nrf2 activator mitigates polyglutamine toxicity in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA, also known as Kennedy's disease) is one of nine neurodegenerative disorders that are caused by expansion of polyglutamine-encoding CAG repeats. Intracellular accumulation of abnormal proteins in these diseases, a pathological hallmark, is associated with defects in protein homeostasis. Enhancement of the cellular proteostasis capacity with small molecules has therefore emerged as a promising approach to treatment. Here, we characterize a novel curcumin analog, ASC-JM17, as an activator of central pathways controlling protein folding, degradation and oxidative stress resistance. ASC-JM17 acts on Nrf1, Nrf2 and Hsf1 to increase the expression of proteasome subunits, antioxidant enzymes and molecular chaperones. We show that ASC-JM17 ameliorates toxicity of the mutant androgen receptor (AR) responsible for SBMA in cell, fly and mouse models. Knockdown of the Drosophila Nrf1 and Nrf2 ortholog cap 'n' collar isoform-C, but not Hsf1, blocks the protective effect of ASC-JM17 on mutant AR-induced eye degeneration in flies. Our observations indicate that activation of the Nrf1/Nrf2 pathway is a viable option for pharmacological intervention in SBMA and potentially other polyglutamine diseases.

Sexual Reassignment Fails to Prevent Kennedy's Disease

Spinal and bulbar muscular atrophy is caused by polyglutamine expansion in the androgen receptor. As an X-linked disease dependent on androgens, symptoms and findings are only fully manifest in males. Here we describe a 40-year-old male-to-female transgender SBMA patient who developed full disease manifestations despite undetectable levels of androgens. We used cell culture and animal models to show that spironolactone, the anti-androgen she had taken for 15 years, promotes nuclear localization and toxicity of the mutant protein, which may explain the disease manifestations in this patient.

Genetics and genomic medicine in Mali: challenges and future perspectives

Genetics and genomic medicine in Mali: challenges and future perspectives.

Mifepristone-inducible transgene expression in neural progenitor cells in vitro and in vivo

Numerous gene and cell therapy strategies are being developed for the treatment of neurodegenerative disorders. Many of these strategies use constitutive expression of therapeutic transgenic proteins, and although functional in animal models of disease, this method is less likely to provide adequate flexibility for delivering therapy to humans. Ligand-inducible gene expression systems may be more appropriate for these conditions, especially within the central nervous system (CNS). Mifepristone's ability to cross the blood-brain barrier makes it an especially attractive ligand for this purpose. We describe the production of a mifepristone-inducible vector system for regulated expression of transgenes within the CNS. Our inducible system used a lentivirus-based vector platform for the ex vivo production of mifepristone-inducible murine neural progenitor cells that express our transgenes of interest. These cells were processed through a series of selection steps to ensure that the cells exhibited appropriate transgene expression in a dose-dependent and temporally controlled manner with minimal background activity. Inducible cells were then transplanted into the brains of rodents, where they exhibited appropriate mifepristone-inducible expression. These studies detail a strategy for regulated expression in the CNS for use in the development of safe and efficient gene therapy for neurological disorders.

CNS uptake of bortezomib is enhanced by P-glycoprotein inhibition: implications for spinal muscular atrophy

The development of therapeutics for neurological disorders is constrained by limited access to the central nervous system (CNS). ATP-binding cassette (ABC) transporters, particularly P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), are expressed on the luminal surface of capillaries in the CNS and transport drugs out of the endothelium back into the blood against the concentration gradient. Survival motor neuron (SMN) protein, which is deficient in spinal muscular atrophy (SMA), is a target of the ubiquitin proteasome system. Inhibiting the proteasome in a rodent model of SMA with bortezomib increases SMN protein levels in peripheral tissues but not the CNS, because bortezomib has poor CNS penetrance. We sought to determine if we could inhibit SMN degradation in the CNS of SMA mice with a combination of bortezomib and the ABC transporter inhibitor tariquidar. In cultured cells we show that bortezomib is a substrate of P-gp. Mass spectrometry analysis demonstrated that intraperitoneal co-administration of tariquidar increased the CNS penetrance of bortezomib, and reduced proteasome activity in the brain and spinal cord. This correlated with increased SMN protein levels and improved survival and motor function of SMA mice. These findings show that CNS penetrance of treatment for this neurological disorder can be improved by inhibiting drug efflux at the blood-brain barrier.

Does the survival motor neuron copy number variation play a role in the onset and severity of sporadic amyotrophic lateral sclerosis in Malians?

Introduction

Spinal muscular atrophy (SMA) and sporadic amyotrophic lateral sclerosis (SALS) are both motor neuron disorders. SMA results from the deletion of the survival motor neuron (SMN) 1 gene. High or low SMN1 copy number and the absence of SMN2 have been reported as risk factors for the development or severity of SALS.

Objective

To investigate the role of SMN gene copy number in the onset and severity of SALS in Malians.

Material and Methods

We determined the SMN1 and SMN2 copy number in genomic DNA samples from 391 Malian adult volunteers, 120 Yoruba from Nigeria, 120 Luyha from Kenya and 74 U.S. Caucasians using a Taqman quantitative PCR assay. We evaluated the SALS risk based on the estimated SMA protein level using the Veldink formula (SMN1 copy number + 0.2 ∗ SMN2 copy number). We also characterized the disease natural history in 15 ALS patients at the teaching hospital of Point G, Bamako, Mali.

Results

We found that 131 of 391 (33.5%) had an estimated SMN protein expression of ≤ 2.2; 60 out of 391 (15.3%) had an estimated SMN protein expression < 2 and would be at risk of ALS and the disease onset was as early as 16 years old. All 15 patients were male and some were physically handicapped within 1-2 years in the disease course.

Conclusion

Because of the short survival time of our patients, family histories and sample DNA for testing were not done. However, our results show that sporadic ALS is of earlier onset and shorter survival time as compared to patients elsewhere. We plan to establish a network of neurologists and researchers for early screening of ALS.

Spinal and Bulbar Muscular Atrophy

Spinal and bulbar muscular atrophy, or Kennedy disease, is a slowly progressive X-linked neuromuscular disease caused by a trinucleotide (CAG) repeat expansion in the androgen receptor gene. Affected males typically develop weakness in their mid-40s as well as evidence of androgen insensitivity with reduced fertility and gynecomastia. Diagnosis is often delayed because of decreased awareness of the disease, although genetic testing allows for direct diagnosis. Therapeutic strategies to block the toxicity of the mutant androgen receptor have been unsuccessful thus far, and evaluation of additional candidate therapies is underway.

The polyglutamine-expanded androgen receptor has increased DNA binding and reduced transcriptional activity

Expansion of a polyglutamine-encoding trinucleotide CAG repeat in the androgen receptor (AR) to more than 37 repeats is responsible for the X-linked neuromuscular disease spinal and bulbar muscular atrophy (SBMA). Here we evaluated the effect of polyglutamine length on AR function in Xenopus oocytes. This allowed us to correlate the nuclear AR concentration to its capacity for specific DNA binding and transcription activation in vivo. AR variants with polyglutamine tracts containing either 25 or 64 residues were expressed in Xenopus oocytes by cytoplasmic injection of the corresponding mRNAs. The intranuclear AR concentration was monitored in isolated nuclei and related to specific DNA binding as well as transcriptional induction from the hormone response element in the mouse mammary tumor virus (MMTV) promoter. The expanded AR with 64 glutamines had increased capacity for specific DNA binding and a reduced capacity for transcriptional induction as related to its DNA binding activity. The possible mechanism behind these polyglutamine-induced alterations in AR function is discussed.

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Spinal bulbular muscular atrophy is caused by a polyQ expanded androgen receptor.

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Function of AR with expanded polyQ tract was analyzed in Xenopus oocytes.

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AR with expanded polyQ tract has increased DNA binding but reduced gene activation.

A randomized controlled trial of exercise in spinal and bulbar muscular atrophy

Objective

To determine the safety and efficacy of a home-based functional exercise program in spinal and bulbar muscular atrophy (SBMA).

Methods

Subjects were randomly assigned to participate in 12 weeks of either functional exercises (intervention) or a stretching program (control) at the National Institutes of Health in Bethesda, MD. A total of 54 subjects enrolled, and 50 completed the study with 24 in the functional exercise group and 26 in the stretching control group. The primary outcome measure was the Adult Myopathy Assessment Tool (AMAT) total score, and secondary measures included total activity by accelerometry, muscle strength, balance, timed up and go, sit-to-stand test, health-related quality of life, creatine kinase, and insulin-like growth factor-1.

Results

Functional exercise was well tolerated but did not lead to significant group differences in the primary outcome measure or any of the secondary measures. The functional exercise did not produce significantly more adverse events than stretching, and was not perceived to be difficult. To determine whether a subset of the subjects may have benefited, we divided them into high and low functioning based on baseline AMAT scores and performed a post hoc subgroup analysis. Low-functioning individuals receiving the intervention increased AMAT functional subscale scores compared to the control group.

Interpretation

Although these trial results indicate that functional exercise had no significant effect on total AMAT scores or on mobility, strength, balance, and quality of life, post hoc findings indicate that low-functioning men with SBMA may respond better to functional exercises, and this warrants further investigation with appropriate exercise intensity.

Mutation in CPT1C Associated With Pure Autosomal Dominant Spastic Paraplegia

IMPORTANCE

The family of genes implicated in hereditary spastic paraplegias (HSPs) is quickly expanding, mostly owing to the widespread availability of next-generation DNA sequencing methods. Nevertheless, a genetic diagnosis remains unavailable for many patients.

OBJECTIVE

To identify the genetic cause for a novel form of pure autosomal dominant HSP.

DESIGN, SETTING, AND PARTICIPANTS

We examined and followed up with a family presenting to a tertiary referral center for evaluation of HSP for a decade until August 2014. Whole-exome sequencing was performed in 4 patients from the same family and was integrated with linkage analysis. Sanger sequencing was used to confirm the presence of the candidate variant in the remaining affected and unaffected members of the family and screen the additional patients with HSP. Five affected and 6 unaffected participants from a 3-generation family with pure adult-onset autosomal dominant HSP of unknown genetic origin were included. Additionally, 163 unrelated participants with pure HSP of unknown genetic cause were screened.

MAIN OUTCOME AND MEASURE

Mutation in the neuronal isoform of carnitine palmitoyl-transferase (CPT1C) gene.

RESULTS

We identified the nucleotide substitution c.109C>T in exon 3 of CPT1C, which determined the base substitution of an evolutionarily conserved Cys residue for an Arg in the gene product. This variant strictly cosegregated with the disease phenotype and was absent in online single-nucleotide polymorphism databases and in 712 additional exomes of control participants. We showed that CPT1C, which localizes to the endoplasmic reticulum, is expressed in motor neurons and interacts with atlastin-1, an endoplasmic reticulum protein encoded by the ATL1 gene known to be mutated in pure HSPs. The mutation, as indicated by nuclear magnetic resonance spectroscopy studies, alters the protein conformation and reduces the mean (SD) number (213.0 [46.99] vs 81.9 [14.2]; P < .01) and size (0.29 [0.01] vs 0.26 [0.01]; P < .05) of lipid droplets on overexpression in cells. We also observed a reduction of mean (SD) lipid droplets in primary cortical neurons isolated from Cpt1c-/- mice as compared with wild-type mice (1.0 [0.12] vs 0.44 [0.05]; P < .001), suggesting a dominant negative mechanism for the mutation.

CONCLUSIONS AND RELEVANCE

This study expands the genetics of autosomal dominant HSP and is the first, to our knowledge, to link mutation in CPT1C with a human disease. The association of the CPT1C mutation with changes in lipid droplet biogenesis supports a role for altered lipid-mediated signal transduction in HSP pathogenesis.

A functional scale for spinal and bulbar muscular atrophy: Cross-sectional and longitudinal study

We aimed to develop, validate, and evaluate a disease-specific outcome measure for SBMA: the Spinal and Bulbar Muscular Atrophy Functional Rating Scale (SBMAFRS). We examined the Japanese version (SBMAFRS-J) in 80 Japanese SBMA subjects to evaluate its validity and reliability. We then assessed this scale longitudinally in 41 additional SBMA subjects. The English version (SBMAFRS-E) was also tested in 15 US subjects. The total score of the SBMAFRS-J was distributed normally without an extreme ceiling or floor effect. For SBMAFRS-J, the high intra- and inter-rater agreement was confirmed (intra-class correlation coefficients [ICCs] 0.910 and 0.797, respectively), and internal consistency was satisfactory (Cronbach's alpha 0.700-0.822). In addition, SBMAFRS-J demonstrated concurrent, convergent, and discriminant validity, except for the respiratory subscale. The inter-rater reliability and internal consistency of SBMAFRS-E were also satisfactory. Longitudinally, SBMAFRS-J showed a higher sensitivity to disease progression than the existing clinical measures. In conclusion, we developed and validated a disease-specific functional rating scale for SBMA in both Japanese and English versions, although it needs to be re-assessed in interventional studies with a larger sample size including English speaking subjects.