199th ENMC international workshop: FHL1 related myopathies, June 7-9, 2013, Naarden, The Netherlands

New Clinical Phenotype in a Child Presenting With an FHL1 Mutation

There is a range of phenotypes associated with pathogenic variants in the FHL1 gene, including X-linked dominant scapuloperoneal myopathy, X-linked myopathy with postural muscle atrophy, reducing body myopathy, Emery-Dreifuss muscular dystrophy, rigid-spine syndrome, and hypertrophic cardiomyopathy. This gene encodes the four-and-a-half LIM domain protein 1 which is highly expressed in skeletal and cardiac muscle. The function of this protein includes influencing cellular architecture, myoblast differentiation, mechanotransduction, and skeletal muscle fiber size. We report a case of a 6-year-old boy with a novel FHL1 gene mutation who presented to the neuromuscular clinic for evaluation of stiffness, joint contractures, and mild proximal weakness. Symptoms first noted in the newborn period have been slowly progressive. The child's presentation has not been described before and represents a new clinical phenotype within the spectrum of FHL1-related disorders.

Anti-FHL1 autoantibodies in adult patients with myositis: a longitudinal follow-up analysis

OBJECTIVES

To determine prevalence and clinical associations of anti-Four-and-a-half-LIM-domain 1 (FHL1) autoantibodies in patients with idiopathic inflammatory myopathies (IIM) and to evaluate autoantibody levels over time.

METHODS

Sera at the time of diagnosis from patients with IIM (n = 449), autoimmune disease controls (DC, n = 130), neuromuscular diseases (NMDs, n = 16) and healthy controls (HC, n = 100) were analysed for anti-FHL1 autoantibodies by enzyme-linked immunosorbent assay (ELISA). Patients with IIM FHL1+ and FHL1- were included in a longitudinal analysis. Serum levels were correlated to disease activity.

RESULTS

Autoantibodies to FHL1 were more frequent in patients with IIM (122/449, 27%) compared with DC (autoimmune DC and NMD, 13/146, 9%, P < 0.001) and HC (3/100.3%, P < 0.001). Anti-FHL1 levels were higher in IIM [median (IQR)=0.62 (0.15-1.04)] in comparison with DC [0.22 (0.08-0.58)], HC [0.35 (0.23-0.47)] and NMD [0.48 (0.36-0.80)] P < 0.001. Anti-FHL1+ patients with IIM were younger at the time of diagnosis compared with the anti-FHL1- group (P = 0.05) and were seronegative for other autoantibodies in 25%.In the first follow-up, anti-FHL1+ sample 20/33 (60%) positive at baseline had turned negative for anti-FHL1 autoantibodies. Anti-FHL1 autoantibodies rarely appeared after initiating treatment. Anti-FHL1 autoantibody levels correlated with CK (r = 0.62, P= 0.01), disease activity measured using the Myositis Disease Activity Assessment Tool (MYOACT) (n = 14, P = 0.004) and inversely with Manual Muscle Test-8 (r = -0.59, P = 0.02) at baseline.

CONCLUSION

Anti-FHL1 autoantibodies were present in 27% of patients with IIM; of these, 25% were negative for other autoantibodies. Other autoimmune diseases had lower frequencies and levels. Anti-FHL1 levels often decreased with immunosuppressive treatment, correlated with disease activity measures at diagnosis and rarely appeared after start of treatment.

FHL1 promotes chikungunya and o'nyong-nyong virus infection and pathogenesis with implications for alphavirus vaccine design

Arthritogenic alphaviruses are positive-strand RNA viruses that cause debilitating musculoskeletal diseases affecting millions worldwide. A recent discovery identified the four-and-a-half-LIM domain protein 1 splice variant A (FHL1A) as a crucial host factor interacting with the hypervariable domain (HVD) of chikungunya virus (CHIKV) nonstructural protein 3 (nsP3). Here, we show that acute and chronic chikungunya disease in humans correlates with elevated levels of FHL1. We generated FHL1-/- mice, which when infected with CHIKV or o'nyong-nyong virus (ONNV) displayed reduced arthritis and myositis, fewer immune infiltrates, and reduced proinflammatory cytokine/chemokine outputs, compared to infected wild-type (WT) mice. Interestingly, disease signs were comparable in FHL1-/- and WT mice infected with arthritogenic alphaviruses Ross River virus (RRV) or Mayaro virus (MAYV). This aligns with pull-down assay data, which showed the ability of CHIKV and ONNV nsP3 to interact with FHL1, while RRV and MAYV nsP3s did not. We engineered a CHIKV mutant unable to bind FHL1 (CHIKV-ΔFHL1), which was avirulent in vivo. Following inoculation with CHIKV-ΔFHL1, mice were protected from disease upon challenge with CHIKV and ONNV, and viraemia was significantly reduced in RRV- and MAYV-challenged mice. Targeting FHL1-binding as an approach to vaccine design could lead to breakthroughs in mitigating alphaviral disease.

Identification of novel FHL1 mutations associated with X-linked scapuloperoneal myopathy in unrelated Chinese patients

Mutations in the FHL1 gene can be associated with a variety of X-linked myopathies and cardiomyopathies, among which X-linked dominant scapuloperoneal myopathy is a rare phenotype. We collected the clinical data of two unrelated Chinese patients with X-linked scapuloperoneal myopathy and analyzed their clinical, pathological, muscle imaging, and genetic features. Both patients were characterized by scapular winging, bilateral Achilles tendon contractures, and weakness in shoulder-girdle and peroneal muscles. Muscle biopsy revealed myopathic changes, and no reducing bodies were found. Muscle magnetic resonance imaging was dominated by fatty infiltration, with minor edema-like findings. Genetic analysis revealed two novel mutations in the FHL1 gene: c.380T > C (p.F127S) and c.802C > T (p.Q268*), which were located in the LIM2 domain and the C-terminal sequence, respectively. To our knowledge, this is the first report of X-linked scapuloperoneal myopathy in the Chinese population. Our findings broadened the genetic and ethnic spectrum of FHL1-related disorders and proposed to look for variants in the FHL1 gene when scapuloperoneal myopathy is observed in the clinical work.

Autoantibodies against Four-and-a-Half-LIM Domain 1 (FHL1) in Inflammatory Myopathies: Results from an Australian Single-Center Cohort

Objectives

To determine the prevalence and associations of autoantibodies targeting a muscle-specific autoantigen, four-and-a-half-LIM-domain 1 (FHL1), in South Australian patients with histologically-confirmed idiopathic inflammatory myopathies (IIM) and in patients with SSc.

Material and methods

Sera from patients with IIM (n = 267) from the South Australian Myositis Database (SAMD), SSc (n = 174) from the Australian Scleroderma Cohort Study (ASCS) and healthy controls (HC, n = 100) were analysed for anti-FHL1 autoantibodies by Enzyme-Linked ImmunoSorbent Assay (ELISA).

Results

Autoantibodies to FHL1 were more frequent in patients with IIM (37/267, 13.8%) compared with SSc (12/174, 7%) (P < 0.02) and HC (2/100, 2%) (P < 0.001). The most common IIM subtypes among FHL1⁺ IIM patients were (32%) and IBM (2/37, 32%). No statistically significant differences in muscular or extra-muscular manifestations of IIM were found when comparing patients who were anti-FHL1⁺ with their anti-FHL1^– counterparts. In 29/37 (78%) anti-FHL1⁺ patients, no myositis-specific autoantibodies (MSA) were present. In FHL1⁺ muscle biopsies, there was less frequent infiltration by CD45⁺ cells (P = 0.04). There was a trend for HLA alleles DRB1*07 and DRB1*15 to be more frequent in anti-FHL1⁺ compared with anti-FHL1^– patients (9/25 vs 19/113, P = 0.09 and 8/25 vs 15/114, P = 0.09, respectively).

Conclusions

We report a substantial prevalence (13.8%) of anti-FHL1 autoantibodies in a large cohort of patients with histologically confirmed IIM; 75% of these cases did not have a detectable myositis-specific autoantibody. Anti-FHL1 autoantibodies were also detected in a subgroup of patients with SSc (7%), indicating that anti-FHL1 autoantibodies may not be myositis-specific. The trend towards an HLA-DR association might indicate a specific immune response to the FHL1 protein.

Reducing body myopathy associated with the LIM2 p.(His123Arg) FHL1 variant

Reducing body myopathy (RBM) is a rare muscle disorder, with marked presence of characteristic intracytoplasmic aggregates in affected muscle fibers. RBM is associated with FHL1 gene mutations. Clinical presentations of RBM have ranged from early fatal to adult onset progressive muscle weakness. We present herein the clinical, electrodiagnostic, and muscle biopsy findings of a 17-year-old female with progressive muscle weakness and contracture. Muscle biopsy showed atrophic fibers that contained menadione nitroblue tetrazolium (NBT) positive reducing bodies. Genetic testing revealed a variant of uncertain significance in the FHL1 gene at a position known to be pathogenic when substituted by other amino acids (p.His123Arg). This variant was later reclassified as pathogenic.

FHL1-related myopathy may not be classified by reducing bodies in muscle biopsy

FHL1-related myopathies, including reducing body myopathy (RBM), X-linked scapulo-axio-peroneal myopathy, rigid spine syndrome, X-linked myopathy with postural muscle atrophy (XMPMA), X-linked Emery-Dreifuss muscular dystrophy and hypertrophic cardiomyopathy, are clinically and pathologically heterogeneous disorders caused by FHL1 gene mutations. According to previous reports, the first three types are myopathies with reducing bodies observed in biopsies, and the last three are myopathies without reducing bodies. We report four FHL1-related myopathy patients, including an XMPMA patient and a RBM family with three patients. Clinical information, muscle biopsies, electromyograms and genetic testing were obtained. Muscle weakness and atrophy, spinal rigidity, and joint contracture were present in the RBM family. The XMPMA patient showed a pseudoathletic appearance with muscle weakness and atrophy, spinal rigidity and deformity. The index patient of the RBM family underwent two muscle biopsies to find reducing bodies. Interestingly, these muscle biopsies revealed reducing bodies and rimmed vacuoles not only in the RBM family but also in the XMPMA patient. Next-generation sequencing identified a reported single missense mutation c.448 C>T (p. C150R) in the RBM family and a novel mutation c.814T>C (p. S272P) in the XMPMA patient. Therefore, FHL1-related myopathies overlap substantially and may not be simply classified into subtypes depending on reducing bodies. Biopsies of additional affected muscles can aid in finding reducing bodies. We report the first XMPMA patient with a novel FHL1 mutation and reducing bodies in a muscle biopsy in China.

Role of Zebrafish fhl1A in Satellite Cell and Skeletal Muscle Development

Background:

Four-and-a-half LIM domains protein 1 (FHL1) mutations are associated with human myopathies. However, the function of this protein in skeletal development remains unclear.

Methods:

Whole-mount in situ hybridization and embryo immunostaining were performed.

Results:

Zebrafish Fhl1A is the homologue of human FHL1. We showed that fhl1A knockdown causes defective skeletal muscle development, while injection with fhl1A mRNA largely recovered the muscle development in these fhl1A morphants. We also demonstrated that fhl1A knockdown decreases the number of satellite cells. This decrease in satellite cells and the emergence of skeletal muscle abnormalities were associated with alterations in the gene expression of myoD, pax7, mef2ca and skMLCK. We also demonstrated that fhl1A expression and retinoic acid (RA) signalling caused similar skeletal muscle development phenotypes. Moreover, when treated with exogenous RA, endogenous fhl1A expression in skeletal muscles was robust. When treated with DEAB, an RA signalling inhibitor which inhibits the activity of retinaldehyde dehydrogenase, fhl1A was downregulated.

Conclusion:

fhl1A functions as an activator in regulating the number of satellite cells and in skeletal muscle development. The role of fhl1A in skeletal myogenesis is regulated by RA signaling.

Concurrent positive anti-3-hydroxy-3-methylglutaryl-coenzyme a reductase antibody with reducing body myopathy: Possible double trouble

Anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase myopathy is less common in children but has been associated with more favorable prognosis than adult patients after immunotherapies. We report anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody positivity in a 6-year-old boy with progressive muscle weakness, scoliosis, spinal rigidity, multiple joint contractures, mild left ventricular hypertrophy, and elevated serum creatine kinase. In contrast to most of previously reported pediatric anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase myopathy, he showed little response to immunotherapies. Muscle biopsy contained changes suggestive of myofiber necrosis and regeneration and reducing bodies. The diagnosis of reducing body myopathy was later confirmed by reported c.368A>G (p.His123Arg) mutation in the FHL1 gene. Although the level of association between these two conditions is still inconclusive, this is the first report of concurrent positive anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody with reducing body myopathy emphasizing the possibility of co-occurrence of immune mediated necrotizing myopathy and muscular dystrophy and importance of comprehensive diagnostic investigations in unusual cases.

Aggresome-Autophagy Involvement in a Sarcopenic Patient with Rigid Spine Syndrome and a p.C150R Mutation in FHL1 Gene

The four-and-half LIM domain protein 1 (FHL1) is highly expressed in skeletal and cardiac muscle. Mutations of the FHL1 gene have been associated with diverse chronic myopathies including reducing body myopathy, rigid spine syndrome (RSS), and Emery–Dreifuss muscular dystrophy. We investigated a family with a mutation (p.C150R) in the second LIM domain of FHL1. In this family, a brother and a sister were affected by RSS, and their mother had mild lower limbs weakness. The 34-year-old female had an early and progressive rigidity of the cervical spine and severe respiratory insufficiency. Muscle mass evaluated by DXA was markedly reduced, while fat mass was increased to 40%. CT scan showed an almost complete substitution of muscle by fibro-adipose tissue. Muscle biopsy showed accumulation of FHL1 throughout the cytoplasm and around myonuclei into multiprotein aggregates with aggresome/autophagy features as indicated by ubiquitin, p62, and LC3 labeling. DNA deposits, not associated with nuclear lamina components and histones, were also detected in the aggregates, suggesting nuclear degradation. Ultrastructural analysis showed the presence of dysmorphic nuclei, accumulation of tubulofilamentous and granular material, and perinuclear accumulation of autophagic vacuoles. These data point to involvement of the aggresome–autophagy pathway in the pathophysiological mechanism underlying the muscle pathology of FHL1 C150R mutation.