Genetic analysis of IRF2BPL in a Taiwanese dystonia cohort: The genotype and phenotype correlation.

OBJECTIVE: IRF2BPL mutation has been associated with a rare neurodevelopmental disorder with abnormal movements, including dystonia. However, the role of IRF2BPL in dystonia remains elusive. We aimed to investigate IRF2BPL mutations in a Taiwanese dystonia cohort. METHODS: A total of 300 unrelated patients with molecularly unassigned isolated (n = 256) or combined dystonia (n = 44) were enrolled between January 2015 and July 2023. The IRF2BPL variants were analyzed based on whole exome sequencing. The in silico prediction of the identified potential pathogenic variant was performed to predict its pathogenicity. We also compared the clinical and genetic features to previous literature reports. RESULTS: We identified one adolescent patient carrying a de novo heterozygous pathogenic variant of IRF2BPL, c.379C>T (p.Gln127Ter), who presented with generalized dystonia, developmental regression, and epilepsy (0.33% of our dystonia cohort). This variant resides within the polyglutamine (poly Q) domain before the first PEST sequence block of the IRF2BPL protein, remarkably truncating the protein structure. Combined with other patients with IRF2BPL mutations in the literature (n = 60), patients with variants in the poly Q domain have a higher rate of nonsense mutations (p < 0.001) and epilepsy (p = 0.008) than patients with variants in other domains. Furthermore, as our index patient, carriers with substitutions before the first PEST sequence block have significantly older age of onset (p < 0.01) and higher non-epilepsy symptoms, including generalized dystonia (p = 0.003), and ataxia (p = 0.003). INTERPRETATION: IRF2BPL mutation is a rare cause of dystonia in our population. Mutations in different domains of IRF2BPL exhibit different phenotypes.

Generation of a human induced pluripotent stem cell line NTUHi004-A from a patient with Leigh syndrome harboring a homozygous missense mutation c.836 T > G (p.Met279Arg) in NDUFAF5 gene.

Leigh syndrome is a rare autosomal recessive disorder showcasing a diverse range of neurological symptoms. Classical Leigh syndrome is associated with mitochondrial complex I deficiency, primarily resulting from biallelic mutations in the NDUFAF5 gene, encoding the NADH:ubiquinone oxidoreductase complex assembly factor 5. Using the Sendai virus delivery system, we generated an induced pluripotent stem cell line from peripheral blood mononuclear cells of a 47-years-old female patient who carried a homozygous NDUFAF5 c.836 T > G (p.Met279Arg) mutation. This cellular model serves as a tool for investigating the underlying pathogenic mechanisms and for the development of potential treatments for Leigh syndrome.

Phenotypic Heterogeneity in Patients with Mutations in the Mitochondrial Complex I Assembly Gene NDUFAF5.

BACKGROUND: Rare mutations in NADH:ubiquinone oxidoreductase complex assembly factor 5 (NDUFAF5) are linked to Leigh syndrome. OBJECTIVE: We aimed to describe clinical characteristics and functional findings in a patient cohort with NDUFAF5 mutations. METHODS: Patients with biallelic NDUFAF5 mutations were recruited from multi-centers in Taiwan. Clinical, laboratory, radiological, and follow-up features were recorded and mitochondrial assays were performed in patients' skin fibroblasts. RESULTS: Nine patients from seven unrelated pedigrees were enrolled, eight homozygous for c.836 T > G (p.Met279Arg) in NDUFAF5 and one compound heterozygous for p.Met279Arg. Onset age had a bimodal distribution. The early-onset group (age <3 years) presented with psychomotor delay, seizure, respiratory failure, and hyponatremia. The late-onset group (age ≥5 years) presented with normal development, but slowly progressive dystonia. Combing 25 previously described patients, the p.Met279Arg variant was exclusively identified in Chinese ancestry. Compared with other groups, patients with late-onset homozygous p.Met279Arg were older at onset (P = 0.008), had less developmental delay (P = 0.01), less hyponatremia (P = 0.01), and better prognosis with preserved ambulatory function into early adulthood (P = 0.01). Bilateral basal ganglia necrosis was a common radiological feature, but brainstem and spinal cord involvement was more common with early-onset patients (P = 0.02). A modifier gene analysis showed higher concomitant mutation burden in early-versus late-onset p.Met279Arg homozygous cases (P = 0.04), consistent with more impaired mitochondrial function in fibroblasts from an early-onset case than a late-onset patient. CONCLUSIONS: The p.Met279Arg variant is a common mutation in our population with phenotypic heterogeneity and divergent prognosis based on age at onset. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Diagnostic Challenges of Neuromuscular Disorders after Whole Exome Sequencing.

BACKGROUND: Whole-exome sequencing (WES) facilitates the diagnosis of hereditary neuromuscular disorders. To achieve an accurate diagnosis, physicians should interpret the genetic report carefully along with clinical information and examinations. We described our experience with (1) clinical validation in patients with variants found using WES and (2) a diagnostic approach for those with negative findings from WES. METHODS: WES was performed on patients with the clinical impression of hereditary neuromuscular disorders. Information on clinical manifestations, neurological examination, electrodiagnostic studies, histopathology of muscle and nerve, and laboratory tests were collected. RESULTS: Forty-one patients (Male/Female: 18/23, age of onset: 34.5±15.9) accepted WES and were categorized into four scenarios: (1) patients with a positive WES result, (2) patients with an inconclusive WES result but supporting clinical data, (3) negative findings from WES, but a final diagnosis after further work-up, and (4) undetermined etiology from WES and in further work-ups. The yield rate of the initial WES was 63.4% (26/41). Among these, seventeen patients had positive WES result, while the other nine patients had inconclusive WES result but supporting clinical data. Notably, in the fifteen patients with negative findings from WES, four patients (26.7%) achieved a diagnosis after further workup: tumor-induced osteomalacia, metabolic myopathy with pathogenic variants in mitochondrial DNA, microsatellite expansion disease, and vasculitis-related neuropathy. The etiologies remained undetermined in eleven patients (myopathy: 7, neuropathy: 4) after WES and further workup. CONCLUSIONS: It is essential to design genotype-guided molecular studies to correlate the identified variants with their clinical features. For patients who had negative findings from WES, acquired diseases, mitochondrial DNA disorders and microsatellite expansion diseases should be considered.

Genetic analysis of IMPDH2 gene in Taiwanese patients with isolated or combined dystonia.

The inosine monophosphate dehydrogenase gene (IMPDH2) was recently reported as a novel gene associated with autosomal dominantly inherited dystonia. We investigated 245 Taiwanese patients with molecularly unassigned isolated or combined dystonia without features of neurodevelopmental disorders and found none had pathogenic variants. Our findings suggest that IMPDH2 may not play a major role in dystonia.

Concomitant Sympathetic and Parasympathetic Dysfunction after Acute Ischemic Stroke.

PURPOSE: Autonomic dysfunction is an underrecognized complication of acute ischemic stroke. The cortical regulation of sympathetic activation is predominantly lateralized to the right hemisphere and parasympathetic activation to the left hemisphere. However, prior evidence is lacking regarding ischemic lesions in unilateral hemisphere that concomitantly cause sympathetic and parasympathetic dysfunction. CASE REPORT: We present the case of a 73-year-old woman with acute ischemic stroke in the left middle cerebral artery territory, whose neurological symptoms improved significantly after thrombolysis and endovascular thrombectomy. She presented residual scattered small infarctions involving the left insula and lateral parietal cortex. However, she experienced obvious autonomic symptoms that included orthostatic hypotension, which is indicative of sympathetic dysfunction, and micturition difficulty with exaggerated reflex tachycardia, indicative of parasympathetic dysfunction. The sympathetic and parasympathetic functions sequentially resolved on days 10 and 20 after stroke onset, respectively. CONCLUSION: The case revealed insight into the phenomenon and recovery course of concurrent sympathetic and parasympathetic dysfunction associated with ischemic lesions in the left hemisphere.

Leukoencephalopathy with Brainstem and Spinal Cord Involvement and Lactate Elevation: A Novel DARS2 Mutation and Intra-Familial Heterogeneity.

BACKGROUND: Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is characterized by slowly progressive spastic gait, cerebellar symptoms, and posterior cord dysfunction. DARS2, which encodes mitochondrial aspartyl tRNA synthase, is associated with the rare disease. CASES: The proband had gait disturbance since age 56, while her younger brother had the gait problem since his 20s and needed cane-assistance at age 45. Both cases showed typical demyelinating features of LBSL on the magnetic resonance imaging (MRI) involving the periventricular white matter, brainstem, cerebellum and spinal cord. Sequencing of both cases showed compound heterozygous mutations: c.228-16C>A and c.508C>T in DARS2. The c.228-16C>A is a common mutation in splicing site of intron 2, which causes alternative splicing defect of exon 3, while the c.508C>T at the exon 6 is novel. Our patients are unique in the relative late onset and the apparent difference in disease progression. LITERATURE REVIEW: Literatures from PubMed were reviewed. Five families showed intra-familial heterogeneity on age at onset or clinical severity. CONCLUSION: We identified a family of LBSL with compound heterozygous mutations, and c.508C>T at the exon 6 is a novel one. Clinical heterogeneity was observed in the family and other literatures. Further research for underlying mechanism is required.

Determination of immunosuppressive drugs in human urine and serum by surface-assisted laser desorption/ionization mass spectrometry with dispersive liquid-liquid microextraction.

A rapid and sensitive method for the determination of immunosuppressive drugs through surface-assisted laser desorption/ionization mass spectrometric detection (SALDI/MS) was developed. Colloidal Pd and α-cyano-4-hydroxycinnamic acid (CHCA) were used as the SALDI co-matrix. To eliminate interference and enhance the sensitivity, dispersive liquid-liquid microextraction (DLLME) was employed to extract the immunosuppressive drugs from the aqueous solutions. Under optimal extraction and detection conditions, calibration curves for cyclosporine and everolimus in aqueous solutions were linear over a concentration range from 0.01 to 1.20 µM. For sirolimus, the linear concentration range of the calibration curve was from 0.05 to 2.00 µM. The limits of detection (LODs) were calculated to be 3, 3, and 14 nM for cyclosporine, everolimus, and sirolimus, respectively. The enrichment factors of DLLME were calculated to be 108, 122, and 101 for cyclosporine, everolimus, and sirolimus, respectively. This novel method was successfully applied for the determination of immunosuppressive drugs in human urine and serum samples.

Detection of posaconazole by surface-assisted laser desorption/ionization mass spectrometry with dispersive liquid-liquid microextraction.

A simple, rapid, and sensitive method for the detection of posaconazole using dispersive liquid-liquid microextraction (DLLME) coupled to surface-assisted laser desorption/ionization mass spectrometric detection (SALDI/MS) was developed. After the DLLME, posaconazole was detected using SALDI/MS with colloidal gold and α-cyano-4-hydroxycinnamic acid (CHCA) as the co-matrix. Under optimal extraction and detection conditions, the calibration curve, which ranged from 1.0 to 100.0 nM for posaconazole, was observed to be linear. The limit of detection (LOD) at a signal-to-noise ratio of 3 was 0.3 nM for posaconazole. This novel method was successfully applied to the determination of posaconazole in human urine samples.