Mitochondrial Membrane Protein-associated Neurodegeneration Research Articles

Mitochondrial membrane protein-associated neurodegeneration presenting with pure motor neuropathy: A rare case report and review of the literature

Abstract Neurodegeneration with brain iron accumulation is a collective term for neurodegenerative disorders characterized by excessive deposition of iron in the brain, especially in the globus pallidus and substantia nigra. Mitochondrial membrane protein-associated neurodegeneration mainly affects the pyramidal and extrapyramidal systems, and patients can present with various manifestations during disease progression, including gait disorder, dystonia, ataxia, swallowing dysfunction, neuropsychiatric abnormalities, cognitive disabilities, optic atrophy, and, sometimes, peripheral neuropathy. We report a patient of mitochondrial membrane protein-associated neurodegeneration with peripheral neuropathy as the predominant symptom.

Mitochondrial Membrane Protein-Associated Neurodegeneration with Brain Iron Accumulation: Diagnosis by MRI

Mitochondrial Membrane Protein-Associated Neurodegeneration with Brain Iron Accumulation: Diagnosis by MRI

Phenotype and natural history of mitochondrial membrane protein-associated neurodegeneration.

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is an ultraorphan neurogenetic disease from the group of neurodegeneration with brain iron accumulation (NBIA) disorders. Here we report cross-sectional and longitudinal data to define the phenotype, to assess disease progression and to estimate sample sizes for clinical trials. We enrolled patients with genetically confirmed MPAN from the Treat Iron-Related Childhood-Onset Neurodegeneration (TIRCON) registry and cohort study, and from additional sites. Linear mixed-effect modelling (LMEM) was used to calculate annual progression rates for the Unified Parkinson's Disease Rating Scale (UPDRS), Barry-Albright Dystonia (BAD) scale, Schwab and England Activities of Daily Living (SE-ADL) scale and the Pediatric Quality of Life Inventory (PedsQL). We investigated 85 MPAN patients cross-sectionally, with functional outcome data collected in 45. Median age at onset was 9 years and the median diagnostic delay was 5 years. The most common findings were gait disturbance (99%), pyramidal involvement (95%), dysarthria (90%), vision disturbances (82%), with all but dysarthria presenting early in the disease course. After 16 years with the disease, 50% of patients were wheelchair dependent. LMEM showed an annual progression rate of 4.5 points in total UPDRS. The total BAD scale score showed no significant progression over time. The SE-ADL scale and the patient- and parent-reported PedsQL showed a decline of 3.9%, 2.14 and 2.05 points, respectively. No patient subpopulations were identified based on longitudinal trajectories. Our cross-sectional results define the order of onset and frequency of symptoms in MPAN, which will inform the diagnostic process, help to shorten diagnostic delay and aid in counselling patients, parents and caregivers. Our longitudinal findings define the natural history of MPAN, reveal the most responsive outcomes and highlight the need for an MPAN-specific rating approach. Our sample size estimations inform the design of upcoming clinical trials.

Generation of two human iPSC lines, HMGUi004-A and FINCBi004-A, from fibroblasts of MPAN patients carrying pathogenic recessive mutations in the gene C19orf12

Mitochondrial membrane Protein-Associated Neurodegeneration (MPAN) is a lethal neurodegenerative disorder caused by mutations in the human gene C19orf12. The molecular mechanisms underlying the disorder are still unclear, and no established therapy is available. Here, we describe the generation and characterization of two human induced pluripotent stem cell (iPSC) lines derived from skin fibroblasts of two MPAN patients carrying homozygous recessive mutations in C19orf12. These iPSC lines represent a useful resource for future investigations on the pathology of MPAN, as well as for the development of successful treatments.

Olfactory status in neurodegeneration with brain iron accumulation disorders.

Olfactory dysfunction has been suggested as a diagnostic and discriminative biomarker in some neurodegenerative disorders. However, there are few studies regarding the olfactory status in rare diseases including neurodegeneration with brain iron accumulation (NBIA) disorders. Genetically-confirmed NBIA patients were enrolled. Neurological and cognitive examinations were conducted according to the Pantothenate Kinase-Associated Neurodegeneration-Disease Rating Scale (PKAN-DRS) and the Mini-Mental State Examination (MMSE) questionnaire, respectively. Olfaction was assessed in three domains of odor threshold (OT), odor discrimination (OD), odor identification (OI), and total sum (TDI) score by the Sniffin' Sticks test. The olfactory scores were compared to a control group and a normative data set. Thirty-seven patients, including 22 PKAN, 6 Kufor Rakeb syndrome, 4 Mitochondrial membrane Protein-Associated Neurodegeneration (MPAN), 5 cases of other 4 subtypes, and 37 controls were enrolled. The mean PKAN-DRS score was 51.83±24.93. Sixteen patients (55.2%) had normal cognition based on MMSE. NBIA patients had significantly lower olfactory scores compared to the controls in TDI and all three subtests, and 60% of them were hyposmic according to the normative data. Including only the cognitively-normal patients, still, OI and TDI scores were significantly lower compared to the controls. The phospholipase A2-Associated Neurodegeneration (PLAN) and MPAN patients had a significantly lower OI score compared to the cognitively-matched PKAN patients. Olfactory impairment as a common finding in various subtypes of NBIA disorder can potentially be considered a discriminative biomarker. Better OI in PKAN compared to PLAN and MPAN patients may be related to the different underlying pathologies.

Autosomal Dominant MPAN: Mosaicism Expands the Clinical Spectrum to Atypical Late-Onset Phenotypes.

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is caused by mutations in the C19orf12 gene. MPAN typically appears in the first two decades of life and presents with progressive dystonia-parkinsonism, lower motor neuron signs, optic atrophy, and abnormal iron deposits predominantly in the basal ganglia. MPAN, initially considered as a strictly autosomal recessive disease (AR), turned out to be also dominantly inherited (AD). Our aim was to better characterize the clinical, molecular, and functional spectra associated with such dominant pathogenic heterozygous C19orf12 variants. We collected clinical, imaging, and molecular information of eight individuals from four AD-MPAN families and obtained brain neuropathology results for one. Functional studies, focused on energy and iron metabolism, were conducted on fibroblasts from AD-MPAN patients, AR-MPAN patients, and controls. We identified four heterozygous C19orf12 variants in eight AD-MPAN patients. Two of them carrying the familial variant in mosaic displayed an atypical late-onset phenotype. Fibroblasts from AD-MPAN showed more severe alterations of iron storage metabolism and autophagy compared to AR-MPAN cells. Our data add strong evidence of the realness of AD-MPAN with identification of novel monoallelic C19orf12 variants, including at the mosaic state. This has implications in diagnosis procedures. We also expand the phenotypic spectrum of MPAN to late onset atypical presentations. Finally, we demonstrate for the first time more drastic abnormalities of iron metabolism and autophagy in AD-MPAN than in AR-MPAN. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A late-onset mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN) case with Parkinsonism

A late-onset mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN) case with Parkinsonism

Identification of Autophagy as a Functional Target Suitable for the Pharmacological Treatment of Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN) In Vitro

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is a relentlessly progressive neurodegenerative disorder caused by mutations in the C19orf12 gene. C19orf12 has been implicated in playing a role in lipid metabolism, mitochondrial function, and autophagy, however, the precise functions remain unknown. To identify new robust cellular targets for small compound treatments, we evaluated reported mitochondrial function alterations, cellular signaling, and autophagy in a large cohort of MPAN patients and control fibroblasts. We found no consistent alteration of mitochondrial functions or cellular signaling messengers in MPAN fibroblasts. In contrast, we found that autophagy initiation is consistently impaired in MPAN fibroblasts and show that C19orf12 expression correlates with the amount of LC3 puncta, an autophagy marker. Finally, we screened 14 different autophagy modulators to test which can restore this autophagy defect. Amongst these compounds, carbamazepine, ABT-737, LY294002, oridonin, and paroxetine could restore LC3 puncta in the MPAN fibroblasts, identifying them as novel potential therapeutic compounds to treat MPAN. In summary, our study confirms a role for C19orf12 in autophagy, proposes LC3 puncta as a functionally robust and consistent readout for testing compounds, and pinpoints potential therapeutic compounds for MPAN.

'Comb Sign': A Novel Appearance of Substantia Nigra in Mitochondrial Membrane Protein-Associated Neurodegeneration.

'Comb Sign': A Novel Appearance of Substantia Nigra in Mitochondrial Membrane Protein-Associated Neurodegeneration.

Нейродегенеративне захворювання з накопиченням заліза в головному мозку дитини, хворої на гемофілію А, ускладнену інгібіторними антитілами

Hemophilia A is an X-linked recessive disorder caused by a deficiency of plasma coagulation FVIII, which may be inherited or arise from a spontaneous mutation. FVIII deficiency leads to a decrease in normal hemostasis and is manifested by spontaneous or induced bleeding. As a result of hemorrhages in the central nervous system, neurological complications are possible. In such cases, doctors should be on the alert so as not to miss another accompanying pathology. Neurodegenerative disease with iron accumulation in the brain is a genetically and clinically heterogeneous group of hereditary progressive disorders of the central nervous system with pronounced iron accumulation in the basal ganglia, which have a specific picture on magnetic resonance imaging of the brain in combination with characteristic clinical signs. Purpose - is to describe a clinical case of a combination of two complex hereditary diseases in a 10-year-old boy, hemophilia A of moderate severity, complicated by an inhibitor, and a progressive neurodegenerative disease with accumulation of iron in the brain, with associated neurodegeneration associated with the protein of the mitochondrial membrane. The publication reports for the first time a clinical case of a combination of two complex hereditary diseases in a 10-year-old boy, confirmed by molecular genetic studies: hemophilia A of moderate severity, complicated by an inhibitor with the detection of a large deletion of exons 23-26 in the gene, and progressive neurodegeneration with brain iron accumulation, with the presence of a pathogenic mutation of the C19orf12 gene, variant c.204_214del (p.Gly69Argfs*10) in a homozygous state, autosomal recessive type of inheritance, Mitochondrial-membrane Protein-Associated Neurodegeneration. Coagulopathy is controlled by prophylactic administration of emicizumab subcutaneously. Neurodegeneration with brain iron accumulation in the child was manifested by: Friedreich's foot, equinus feet, positive Babinski symptom, high tendon reflexes, optic nerve atrophy; partial dysplasia of both eyes; with myopia of both eyes, impaired accommodation, progressively increasing paresthesias in both legs, impaired gait, ataxic gait, coordination difficulties, muscle atrophy of both legs, visual impairment, rapid fatigue with preserved intelligence and mental development. Magnetic resonance imaging of the brain showed a moderate bilateral symmetrical lesion of the globus pallidus. Our report confirms that the use of molecular genetic studies plays an important decisive role in the verification of the disease, often determining its type and possible complications. The research was carried out in accordance with the principles of the Helsinki Declaration. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

A novel p.Ala34Val variant in C19orf12 is associated with neurodegeneration with brain iron accumulation

Loss-of-function mutations in the C19orf12 gene may lead to mitochondrial membrane protein- associated neurodegeneration (MPAN), which is a subtype of neurodegeneration with brain iron accumulation disorders. It is manifest with juvenile-onset spastic paraparesis, dystonia, dysphagia, optic atrophy, decreased cognitive functions, and neuropsychiatric symptoms. Large amounts of iron are accumulated in the globus pallidus and substantia nigra pars reticulata due to abnormal brain iron metabolism. We report a novel C19orf12 (c.101C>T;p.Ala34Val) homozygous mutation in a Turkish man who presented with postural instability, slow gait and anxiety. Neuroimaging showed mild iron deposition in the basal ganglia and cortical atrophy. These results are consistent with the MPAN. This report demonstrates the importance of testing patients with spastic paraplegia, parkinsonism, motor axonal neuropathy, difficulty walking or dysarthria for MPAN.

Juvenile-onset Mitochondrial-membrane Protein-associated Neurodegeneration with Late Diagnosis

Juvenile-onset Mitochondrial-membrane Protein-associated Neurodegeneration with Late Diagnosis

Erratum

Erratum

Two cases with mitochondrial membrane protein-associated neurodegeneration: genetic features and long-term clinical follow-up

ABSTRACT Mitochondrial membrane protein-associated neurodegeneration (MPAN) is a rare neurological disease with childhood or adult onset. It is a subtype of clinically and genetically heterogeneous group of disorders, collectively known as neurodegeneration with brain iron accumulation . MPAN is generally associated with biallelic pathogenic variants in C19orf12. Herein, we describe genetic and clinical findings of two MPAN cases from Turkey. In the first case, we have identified the relatively common pathogenic variant of C19orf12 in the homozygous state, which causes late-onset MPAN. The second case was homozygous for an essential splice-site variation.

Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN): Two Phenotypes-Dystonia and Spastic Paraparesis.

Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN): Two Phenotypes-Dystonia and Spastic Paraparesis.

Mitochondrial Membrane Protein-associated Neurodegeneration: Two Adult Cases with Different Clinical Presentation

Mitochondrial Membrane Protein-associated Neurodegeneration: Two Adult Cases with Different Clinical Presentation

Novel C19orf12 loss-of-function variant leading to neurodegeneration with brain iron accumulation

ABSTRACT Neurodegeneration with brain iron accumulation (NBIA) is a group of inherited disorders characterised by cerebral iron overload mainly in the basal ganglia. Mitochondrial membrane protein-associated neurodegeneration (MPAN) is a form of NBIA caused by pathogenic C19orf12 gene variants. We report on a Romanian patient with MPAN confirmed through exome sequencing, revealing a homozygous nonsense variant in the C19orf12 gene, NM_001031726.3: c.215T>G (p.Leu72*), that co-segregates with disease in tested relatives: the patient`s parents, younger brother and paternal uncle are heterozygous carriers. This is a novel disease-causing variant in the C19orf12 gene and the first reported MPAN case in a Romanian patient.

Consensus clinical management guideline for beta-propeller protein-associated neurodegeneration.

This review provides recommendations for the evaluation and management of individuals with beta-propeller protein-associated neurodegeneration (BPAN). BPAN is one of several neurodegenerative disorders with brain iron accumulation along with pantothenate kinase-associated neurodegeneration, PLA2G6-associated neurodegeneration, mitochondrial membrane protein-associated neurodegeneration, fatty acid hydroxylase-associated neurodegeneration, and COASY protein-associated neurodegeneration. BPAN typically presents with global developmental delay and epilepsy in childhood, which is followed by the onset of dystonia and parkinsonism in mid-adolescence or adulthood. BPAN is an X-linked dominant disorder caused by pathogenic variants in WDR45, resulting in a broad clinical phenotype and imaging spectrum. This review, informed by an evaluation of the literature and expert opinion, discusses the clinical phenotype and progression of the disease, imaging findings, epilepsy features, and genetics, and proposes an approach to the initial evaluation and management of disease manifestations across the life span in individuals with BPAN. What this paper adds The complex epilepsy profile of beta-propeller protein-associated neurodegeneration (BPAN) often resolves in adolescence. The treatment for an individual with BPAN is supportive, with attention to sleep disorders, complex epilepsy, and behavioral problems. Individuals with BPAN have shifting needs throughout their life span requiring multidisciplinary care.

Emerging Disease-Modifying Therapies in Neurodegeneration With Brain Iron Accumulation (NBIA) Disorders.

Neurodegeneration with Brain Iron Accumulation (NBIA) is a heterogeneous group of progressive neurodegenerative diseases characterized by iron deposition in the globus pallidus and the substantia nigra. As of today, 15 distinct monogenetic disease entities have been identified. The four most common forms are pantothenate kinase-associated neurodegeneration (PKAN), phospholipase A2 group VI (PLA2G6)-associated neurodegeneration (PLAN), beta-propeller protein-associated neurodegeneration (BPAN) and mitochondrial membrane protein-associated neurodegeneration (MPAN). Neurodegeneration with Brain Iron Accumulation disorders present with a wide spectrum of clinical symptoms such as movement disorder signs (dystonia, parkinsonism, chorea), pyramidal involvement (e.g., spasticity), speech disorders, cognitive decline, psychomotor retardation, and ocular abnormalities. Treatment remains largely symptomatic but new drugs are in the pipeline. In this review, we discuss the rationale of new compounds, summarize results from clinical trials, provide an overview of important results in cell lines and animal models and discuss the future development of disease-modifying therapies for NBIA disorders. A general mechanistic approach for treatment of NBIA disorders is with iron chelators which bind and remove iron. Few studies investigated the effect of deferiprone in PKAN, including a recent placebo-controlled double-blind multicenter trial, demonstrating radiological improvement with reduction of iron load in the basal ganglia and a trend to slowing of disease progression. Disease-modifying strategies address the specific metabolic pathways of the affected enzyme. Such tailor-made approaches include provision of an alternative substrate (e.g., fosmetpantotenate or 4′-phosphopantetheine for PKAN) in order to bypass the defective enzyme. A recent randomized controlled trial of fosmetpantotenate, however, did not show any significant benefit of the drug as compared to placebo, leading to early termination of the trials' extension phase. 4′-phosphopantetheine showed promising results in animal models and a clinical study in patients is currently underway. Another approach is the activation of other enzyme isoforms using small molecules (e.g., PZ-2891 in PKAN). There are also compounds which counteract downstream cellular effects. For example, deuterated polyunsaturated fatty acids (D-PUFA) may reduce mitochondrial lipid peroxidation in PLAN. In infantile neuroaxonal dystrophy (a subtype of PLAN), desipramine may be repurposed as it blocks ceramide accumulation. Gene replacement therapy is still in a preclinical stage.

Retrospective analysis of 17 patients with mitochondrial membrane protein-associated neurodegeneration diagnosed in Russia

IntroductionMitochondrial membrane protein-associated neurodegeneration (MPAN) is a rare neurological syndrome caused by pathogenic variants in the C19orf12 and is characterized by iron deposition in the basal ganglia and substantia nigra. Only a limited number of cohort studies were published to date and the prevalence of MPAN remains uncertain. MethodsRecruited subjects with MPAN in Russia were diagnosed by whole-exome sequencing or Sanger sequencing of the C19orf12 gene. Data of over 14000 whole exome sequencing analyses was used to calculate the estimated disease frequency. RNA analysis was performed by RT-PCR. QSVanalyzer software was used to quantify the allelic disbalance. ResultsWe describe the clinical and molecular characterizations of 17 patients with MPAN. DNA analysis detected three previously undescribed pathogenic/likely pathogenic variants in the C19orf12 gene. The estimated disease frequency was calculated to be 1:619150. We describe unusual clinical observations in several cases. One patient showed severe neurogenic muscle weakness along with a lack of marked spasticity or optic nerve atrophy. In another mild clinical case with the NM_001031726.3:c.204_214del (p.(Gly69Argfs*10)) variant in a heterozygous state, a marked allelic disbalance was observed on the RNA level with reduced expression level of the wild-type allele. Thus, this case became the first one of a possible regulatory variant causing MPAN. ConclusionWe reported a detailed clinical and molecular characterization of the third-largest MPAN cohort. We expanded the mutational and clinical spectrum of MPAN. Moreover, we calculated the estimated MPAN frequency in the Russian population for the first time.