Muscular and Molecular Pathology Associated with SPATA5 Deficiency in a Child with EHLMRS.

Mutations in the SPATA5 gene are associated with epilepsy, hearing loss and mental retardation syndrome (EHLMRS). While SPATA5 is ubiquitously expressed and is attributed a role within mitochondrial morphogenesis during spermatogenesis, there is only limited knowledge about the associated muscular and molecular pathology. This study reports on a comprehensive workup of muscular pathology, including proteomic profiling and microscopic studies, performed on an 8-year-old girl with typical clinical presentation of EHLMRS, where exome analysis revealed two clinically relevant, compound-heterozygous variants in SPATA5. Proteomic profiling of a quadriceps biopsy showed the dysregulation of 82 proteins, out of which 15 were localized in the mitochondrion, while 19 were associated with diseases presenting with phenotypical overlap to EHLMRS. Histological staining of our patient's muscle biopsy hints towards mitochondrial pathology, while the identification of dysregulated proteins attested to the vulnerability of the cell beyond the mitochondria. Through our study we provide insights into the molecular etiology of EHLMRS and provide further evidence for a muscle pathology associated with SPATA5 deficiency, including a pathological histochemical pattern accompanied by dysregulated protein expression.

GestaltMatcher Database - A global reference for facial phenotypic variability in rare human diseases.

The most important factor that complicates the work of dysmorphologists is the significant phenotypic variability of the human face. Next-Generation Phenotyping (NGP) tools that assist clinicians with recognizing characteristic syndromic patterns are particularly challenged when confronted with patients from populations different from their training data. To that end, we systematically analyzed the impact of genetic ancestry on facial dysmorphism. For that purpose, we established the GestaltMatcher Database (GMDB) as a reference dataset for medical images of patients with rare genetic disorders from around the world. We collected 10,980 frontal facial images - more than a quarter previously unpublished - from 8,346 patients, representing 581 rare disorders. Although the predominant ancestry is still European (67%), data from underrepresented populations have been increased considerably via global collaborations (19% Asian and 7% African). This includes previously unpublished reports for more than 40% of the African patients. The NGP analysis on this diverse dataset revealed characteristic performance differences depending on the composition of training and test sets corresponding to genetic relatedness. For clinical use of NGP, incorporating non-European patients resulted in a profound enhancement of GestaltMatcher performance. The top-5 accuracy rate increased by +11.29%. Importantly, this improvement in delineating the correct disorder from a facial portrait was achieved without decreasing the performance on European patients. By design, GMDB complies with the FAIR principles by rendering the curated medical data findable, accessible, interoperable, and reusable. This means GMDB can also serve as data for training and benchmarking. In summary, our study on facial dysmorphism on a global sample revealed a considerable cross ancestral phenotypic variability confounding NGP that should be counteracted by international efforts for increasing data diversity. GMDB will serve as a vital reference database for clinicians and a transparent training set for advancing NGP technology.

Mutant SPART causes defects in mitochondrial protein import and bioenergetics reversed by Coenzyme Q.

Pathogenic variants in SPART cause Troyer syndrome, characterized by lower extremity spasticity and weakness, short stature and cognitive impairment, and a severe mitochondrial impairment. Herein, we report the identification of a role of Spartin in nuclear-encoded mitochondrial proteins. SPART biallelic missense variants were detected in a 5-year-old boy with short stature, developmental delay and muscle weakness with impaired walking distance. Patient-derived fibroblasts showed an altered mitochondrial network, decreased mitochondrial respiration, increased mitochondrial reactive oxygen species and altered Ca2+ versus control cells. We investigated the mitochondrial import of nuclear-encoded proteins in these fibroblasts and in another cell model carrying a SPART loss-of-function mutation. In both cell models the mitochondrial import was impaired, leading to a significant decrease in different proteins, including two key enzymes involved in CoQ10 (CoQ) synthesis, COQ7 and COQ9, with a severe reduction in CoQ content, versus control cells. CoQ supplementation restored cellular ATP levels to the same extent shown by the re-expression of wild-type SPART, suggesting CoQ treatment as a promising therapeutic approach for patients carrying mutations in SPART.

Neuromuscular Features in XL-MTM Carriers: A Cross-sectional Study in an Unselected Cohort.

BACKGROUND AND OBJECTIVE: X-linked myotubular myopathy (XL-MTM) is an early-onset congenital myopathy characterized by mild to severe muscle weakness in male individuals. The objective was to characterize the clinical spectrum of neuromuscular features in X-linked myotubular myopathy (XL-MTM) carriers. METHODS: We performed a nationwide cross-sectional study focusing on neuromuscular features in an unselected cohort of Dutch XL-MTM carriers. Participants were recruited from neuromuscular centers in the Netherlands and through the Dutch and European patient associations. Genetic results were collected. Carriers were classified based on ambulatory status and muscle weakness. We used a questionnaire focusing on medical and family history and neuromuscular symptoms. In addition, we performed a neurologic examination including manual muscle testing (MMT), timed up and go (TUG) test, and 6-minute walking test (6MWT). RESULTS: We included 21 carriers (20 genetically confirmed and 1 obligate), of whom 11 (52%) carriers were classified as manifesting, with severe (nonambulatory; n = 2), moderate (minimal independent ambulation/assisted ambulation; n = 2), mild (independent ambulation but with limb or axial muscle weakness; n = 3), and minimal (only facial muscle weakness, n = 4) phenotypes. Three of the manifesting carriers (2 severe and 1 moderate) were from families without genetically confirmed male XL-MTM patients. Furthermore, 7 manifesting carriers (1 moderate; 2 mild; and 4 minimal) were not classified as manifesting carriers before participation in our study. Three carriers reported a history of pneumothorax. The obstetric history revealed frequent polyhydramnios (50%) and reduced fetal movements (36%) in pregnancies of affected sons. Muscle weakness was most pronounced in proximal and limb girdle muscles. Other frequently reported signs included (asymmetric) facial weakness (73%), reduced or absent deep tendon reflexes (45%), scoliosis (40%), and ptosis (45%). Ten participants (48%) were classified as nonmanifesting. Manifesting carriers had lower functional testing scores on 6MWT and TUG compared with nonmanifesting carriers. DISCUSSION: This study showed that 52% of an unselected group of XL-MTM carriers has muscle weakness (3 of whom were previously unclassified as manifesting). This corresponds to findings of our recent questionnaire study on self-reported symptoms in XL-MTM carriers. These observations should raise awareness of the neuromuscular manifestations of the XL-MTM carrier state and provide important epidemiologic information required for future clinical trials.

Expansion of the mutational spectrum of BMPER leading to diaphanospondylodysostosis and description of the associated disease process.

BACKGROUND: Diaphanospondylodysostosis (DSD) is a rare congenital, lethal skeletal disorder caused by recessively inherited mutations in the BMPER gene, which encodes the bone morphogenetic protein-binding endothelial cell precursor-derived regulator. The most prominent features of DSD are missing ossification of the axial skeleton, rib abnormalities and thoracic hypoplasia/insufficiency, as well as intralobar nephrogenic rests within the kidneys. METHODS: We report on the case of a 22-month-old patient with DSD where trio-exome sequencing was performed. RESULTS: Genetic testing revealed a homozygous nonsense variant c.1577G>A (p.Trp526*) in the BMPER gene, leading to a premature stop in protein translation. Both parents are asymptomatic carriers for the BMPER variant, which has not been described in the literature before. CONCLUSIONS: Our findings expand the genotypic and phenotypic spectrum of BMPER variants leading to DSD.

Diagnosing X-linked Myotubular Myopathy - A German 20-year Follow Up Experience.

X-linked myotubular myopathy (XLMTM) is a life-threatening rare neuromuscular disease, which is caused by pathogenic variants in the MTM1 gene. It has a large phenotypic heterogeneity, ranging from patients, who are able to walk independently to immobile patients who are only able to bring hand to mouth and depend on a respirator 24 hours a day every day. This suggests that ventilator requirements may not illustrate the full clinical picture of patients with XLMTM. At present, there is no curative therapy available, despite first promising results from ongoing gene therapy studies.In this study, we evaluated in detail the data from 13 German XLMTM patients, which was collected over a period of up to 20 years in our university hospital. We compared it to the international prospective longitudinal natural history study (NHS) data from 45 patients (containing 11 German patients). To highlight the broad phenotypic spectrum of the disease, we additionally focused on the clinical presentation of three cases at a glance.Comparing our data with the above mentioned natural history study, it appears the patients of the present German cohort seem to be more often severely affected, with higher frequency of non-ambulatory patients and patients on ventilation (and for longer time) and a higher proportion of patients needing a percutaneous endoscopic gastrostomy. Another key finding is a potential gap in time between first clinical presentation and final diagnosis, showing a need for patients to be treated in a specialized center for neuromuscular diseases.

Spectrum of Clinical Features in X-Linked Myotubular Myopathy Carriers: An International Questionnaire Study.

OBJECTIVE: To characterize the spectrum of clinical features in a cohort of X-linked myotubular myopathy (XL-MTM) carriers, including prevalence, genetic features, clinical symptoms, and signs, as well as associated disease burden. METHODS: We performed a cross-sectional online questionnaire study among XL-MTM carriers. Participants were recruited from patient associations, medical centers, and registries in the United Kingdom, Germany, and the Netherlands. We used a custom-made questionnaire, the Checklist Individual Strength (CIS), the Frenchay Activities Index (FAI), the Short Form 12 (SF-12) health survey, and the McGill Pain Questionnaire. Carriers were classified as manifesting or nonmanifesting on the basis of self-reported ambulation and muscle weakness. RESULTS: The prevalence of manifesting carriers in this study population (n = 76) was 51%, subdivided into mild (independent ambulation, 39%), moderate (assisted ambulation, 9%), and severe (wheelchair dependent, 3%) phenotypes. In addition to muscle weakness, manifesting carriers frequently reported fatigue (70%) and exercise intolerance (49%). Manifesting carriers scored higher on the overall CIS (p = 0.001), the fatigue subscale (p < 0.001), and least severe pain subscale (p = 0.005) than nonmanifesting carriers. They scored lower on the FAI (p = 0.005) and the physical component of the SF-12 health survey (p < 0.001). CONCLUSIONS: The prevalence of manifesting XL-MTM carriers may be higher than currently assumed, most having a mild phenotype and a wide variety of symptoms. Manifesting carriers are particularly affected by fatigue, limitations of daily activities, pain, and reduced quality of life. Our findings should increase awareness and provide useful information for health care providers and future clinical trials.