RESUMO
Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive rare disease condition in which audiological deficit is also observed. A 4-year-old male child with PMD underwent an audiological evaluation. The results suggested normal middle ear and outer hair cells functioning, with only peak I of the auditory brainstem response present until 30 dBnHL. Further, the cervical vestibular evoked myogenic potential showed delayed latencies with normal amplitudes. In this case report, we attempt to explain the audio-vestibular test results and correlate them with the pathophysiology. This is the first report on the cervical vestibular myogenic potentials in patients with PMD.
Assuntos
Potenciais Evocados Auditivos do Tronco Encefálico , Doença de Pelizaeus-Merzbacher , Potenciais Evocados Miogênicos Vestibulares , Humanos , Masculino , Pré-Escolar , Potenciais Evocados Miogênicos Vestibulares/fisiologia , Doença de Pelizaeus-Merzbacher/diagnóstico , Doença de Pelizaeus-Merzbacher/genética , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Vestíbulo do Labirinto/fisiopatologia , Audiometria de Tons Puros/métodosRESUMO
Pelizaeus-Merzbacher disease (PMD) is caused by mutations in the proteolipid protein 1 (PLP1) gene encoding proteolipid protein (PLP). As a major component of myelin, mutated PLP causes progressive neurodegeneration and eventually death due to severe white matter deficits. Medical care has long been limited to symptomatic treatments, but first-in-class PMD therapies with novel mechanisms now stand poised to enter clinical trials. Here, we review PMD disease mechanisms and outline rationale for therapeutic interventions, including PLP1 suppression, cell transplantation, iron chelation, and intracellular stress modulation. We discuss available preclinical data and their implications on clinical development. With several novel treatments on the horizon, PMD is on the precipice of a new era in the diagnosis and treatment of patients suffering from this debilitating disease.
Assuntos
Proteína Proteolipídica de Mielina , Bainha de Mielina , Doença de Pelizaeus-Merzbacher , Doença de Pelizaeus-Merzbacher/genética , Doença de Pelizaeus-Merzbacher/terapia , Doença de Pelizaeus-Merzbacher/diagnóstico , Doença de Pelizaeus-Merzbacher/patologia , Humanos , Bainha de Mielina/metabolismo , Bainha de Mielina/patologia , Animais , Proteína Proteolipídica de Mielina/genética , Proteína Proteolipídica de Mielina/metabolismo , MutaçãoRESUMO
Claudin-25 (CLDN-25), also known as Claudin containing domain 1, is an uncharacterized claudin family member. It has less conserved amino acid sequences when compared to other claudins. It also has a very broad tissue expression profile and there is currently a lack of functional information from murine knockout models. Here, we report a de novo missense heterozygous variant in CLDN25 (c. 745G>C, p. A249P) found in a patient diagnosed with Pelizaeus-Merzbacher-like leukodystrophy and presenting with symptoms such as delayed motor development, several episodes of tonic absent seizures and generalized dystonia. The variant protein does not localize to the cell-cell borders where it would normally be expected to be expressed. Amino acid position 249 is located 4 amino acids from the C-terminal end of the protein where most claudin family members have a conserved binding motif for the key scaffolding protein ZO-1. However, CLDN-25 does not contain this motif. Here, we show that the C-terminal end of CLDN-25 is required for its junctional localization in a ZO-1 independent manner. The A249P mutant protein as well as a deletion mutant lacking its last 5 C-terminal amino acids also failed to localize to the cell-cell border in vitro. Intriguingly, cellular knockout of CLDN25, in vitro, appeared to increase the integrity of the tight junction between 2 contacting cells, while driving highly unusual increased movement of solutes between cells. We propose that the barrier function of CLDN-25 is akin to a decoy claudin, whereby decreasing its expression in "leaky" epithelial cells and endothelial cells will drive dynamic changes in the adhesion and interaction capacity of cell-cell contact points. While it remains unclear how this de novo CLDN-25 mutant induces leukodystrophy, our findings strongly suggest that this mutation induces haploinsufficiency of CLDN-25. Elucidating the function of this uncharacterized claudin protein will lead to a better understanding of the role of claudin proteins in health and disease.
Assuntos
Claudinas , Doença de Pelizaeus-Merzbacher , Humanos , Claudinas/genética , Claudinas/metabolismo , Doença de Pelizaeus-Merzbacher/genética , Doença de Pelizaeus-Merzbacher/metabolismo , Mutação com Perda de Função , Masculino , Mutação de Sentido Incorreto , Feminino , Animais , Sequência de AminoácidosRESUMO
Leukodystrophies, a group of rare demyelinating disorders, mainly affect the CNS. Clinical presentation of different types of leukodystrophies can be nonspecific, and thus, imaging techniques like MRI can be used for a more definitive diagnosis. These diseases are characterized as cerebral lesions with characteristic demyelinating patterns which can be used as differentiating tools. In this review, we talk about these MRI study findings for each leukodystrophy, associated genetics, blood work that can help in differentiation, emerging diagnostics, and a follow-up imaging strategy. The leukodystrophies discussed in this paper include X-linked adrenoleukodystrophy, metachromatic leukodystrophy, Krabbe's disease, Pelizaeus-Merzbacher disease, Alexander's disease, Canavan disease, and Aicardi-Goutières Syndrome.
Assuntos
Adrenoleucodistrofia , Leucodistrofia de Células Globoides , Leucodistrofia Metacromática , Doenças Neurodegenerativas , Doença de Pelizaeus-Merzbacher , Humanos , Leucodistrofia Metacromática/diagnóstico por imagem , Leucodistrofia Metacromática/patologia , Leucodistrofia de Células Globoides/diagnóstico por imagem , Leucodistrofia de Células Globoides/patologia , Adrenoleucodistrofia/diagnóstico por imagem , Adrenoleucodistrofia/genéticaRESUMO
Human brain organoids can serve as models to study myelination, a process orchestrated by oligodendrocytes. Real-time imaging provides new insights on the communication of oligodendrocytes with neurons as well as demyelination processes in patient derived organoids. PLP1, a prominent myelin protein within the central nervous system, is associated with demyelinating diseases, such as Pelizaeus-Merzbacher. In this study, we generated a stable PLP1-Citrine reporter line (fPLP1) in human induced pluripotent stem cells (iPSCs) by CRISPR/Cas9 editing. fPLP1 facilitates visualization of PLP1 expression in living brain organoids, allowing time-lapse imaging of pre-myelinating and myelinating oligodendrocytes.
Assuntos
Células-Tronco Pluripotentes Induzidas , Doença de Pelizaeus-Merzbacher , Humanos , Proteína Proteolipídica de Mielina , Células-Tronco Pluripotentes Induzidas/metabolismo , Bainha de Mielina/metabolismo , Oligodendroglia/metabolismoRESUMO
BACKGROUND: Two preclinical studies using mouse models of Pelizeaus-Merzbacher disease (PMD) have revealed the potential therapeutic effects of curcumin. In this study, we examined the effects of curcumin in patients with PMD. METHODS: We conducted a study administering an open-label oral bioavailable form of curcumin in nine patients genetically confirmed to have PMD (five to 20 years; mean 11 years) for 12 months (low doses for two months followed by high doses for 10 months). We evaluated changes in clinical symptoms as the primary end point using two scales, Gross Motor Function Measure (GMFM) and the PMD Functional Disability Score (PMD-FDS). The level of myelination by brain magnetic resonance imaging (MRI) and the electrophysiological state by auditory brainstem response (ABR) were evaluated as secondary end points. The safety and tolerability of oral curcumin were also examined. RESULTS: Increase in GMFM and PMD-FDS were noted in five and three patients, respectively, but overall, no statistically significant improvement was demonstrated. We found no clear improvement in their brain MRI or ABR. No adverse events associated with oral administration of curcumin were observed. CONCLUSIONS: Although we failed to demonstrate any significant therapeutic effects of curcumin after 12 months, its tolerability and safety were confirmed. This study does not exclude the possibility of therapeutic effects of curcumin, and a trial of longer duration should be considered to compare the natural history of the disease with the effects of curcumin.
Assuntos
Curcumina , Doença de Pelizaeus-Merzbacher , Animais , Camundongos , Humanos , Doença de Pelizaeus-Merzbacher/diagnóstico por imagem , Doença de Pelizaeus-Merzbacher/tratamento farmacológico , Doença de Pelizaeus-Merzbacher/genética , Curcumina/farmacologia , Curcumina/uso terapêutico , Encéfalo/patologia , Imageamento por Ressonância Magnética , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Proteína Proteolipídica de MielinaRESUMO
Genetic alterations in the PLP1 gene, i.e. point mutations and duplications, are associated with demyelinating disease Pelizaeus-Merzbacher. Here, we describe the generation of a human iPSC line harboring a PLP1 variant in codon 33 which leads to an amino acid change from cysteine to tyrosine. The established PLP1C33Y iPSC line enables the study of PMD pathophysiology by investigating various cell types and -characteristics in our developed protocol for bioengineered neuronal organoids (BENOs)1.
Assuntos
Células-Tronco Pluripotentes Induzidas , Doença de Pelizaeus-Merzbacher , Humanos , Doença de Pelizaeus-Merzbacher/genética , Proteína Proteolipídica de Mielina/genética , Células-Tronco Pluripotentes Induzidas/metabolismo , Edição de Genes , Sistemas CRISPR-Cas/genética , Mutação/genéticaRESUMO
OBJECTIVE: Xq chromosome duplication with complex rearrangements is generally acknowledged to be associated with neurodevelopmental disorders, such as Pelizaeus-Merzbacher disease (PMD) and MECP2 duplication syndrome. For couples who required a PGT-M (pre-implantation genetic testing for monogenic disease) for these disorders, junction-specific PCR is useful to directly detect pathogenic variants. Therefore, pre-clinical workup for PGT-M requires the identification of the junction of duplicated segments in PMD and MECP2 duplication syndrome, which is generally difficult. METHODS: In this report, we used nanopore long-read sequencing targeting the X chromosome using an adaptive sampling method to identify breakpoint junctions in disease-causing triplications. RESULTS: By long-read sequencing, we successfully identified breakpoint junctions in one PMD case with PLP1 triplication and in another MECP2 triplication case in a single sequencing run. Surprisingly, the duplicated region involving MECP2 was inserted 45 Mb proximal to the original position. This inserted region was confirmed by FISH analysis. With the help of precise mapping of the pathogenic variant, we successfully re-established STR haplotyping for PGT-M and avoided any potential misinterpretation of the pathogenic allele due to recombination. CONCLUSION: Long-read sequencing with adaptive sampling in a PGT-M pre-clinical workup is a beneficial method for identifying junctions of chromosomal complex structural rearrangements.
Assuntos
Sequenciamento por Nanoporos , Doença de Pelizaeus-Merzbacher , Diagnóstico Pré-Implantação , Feminino , Gravidez , Humanos , Proteína Proteolipídica de Mielina/genética , Duplicação Gênica , Testes Genéticos/métodos , Doença de Pelizaeus-Merzbacher/genética , Cromossomos , Diagnóstico Pré-Implantação/métodosRESUMO
Pelizaeus-Merzbacher disease is a rare X-linked leukodystrophy accompanied by central nervous system hypomyelination with a spectrum of clinical phenotypes. This is the first survey of caregivers of individuals with Pelizaeus-Merzbacher disease to investigate the presenting symptoms, path to diagnosis, identity and impact of most bothersome symptoms, and needs that future treatment should address. One hundred participants completed the survey. Results from this survey demonstrate that the majority of Pelizaeus-Merzbacher disease symptoms manifest before 2 years of age and commonly include deficits in gross and fine motor skills, speech, and communication. Caregivers rated difficulty crawling, standing, or walking as the most bothersome symptoms due to Pelizaeus-Merzbacher disease, with constipation and difficulty with sleep, manual dexterity, and speech and communication rated nearly as high. The most important treatment goals for caregivers were improved mobility and communication. The survey findings present a caregiver perspective of the impact of symptoms in Pelizaeus-Merzbacher disease and provide helpful guidance to affected families, physicians, and drug developers on the often-long path to diagnosis and the unmet medical needs of this patient population.
Assuntos
Doenças Desmielinizantes , Doenças por Armazenamento dos Lisossomos , Doença de Pelizaeus-Merzbacher , Humanos , Doença de Pelizaeus-Merzbacher/diagnóstico , Doença de Pelizaeus-Merzbacher/genética , Cuidadores , MutaçãoRESUMO
BACKGROUND: Clinical and genetic features were analyzed in five pedigrees with Pelizaeus-Merzbacher-like disease (PMLD) to provide bases for genetic counseling and prenatal diagnosis. CONCLUSIONS: Six patients from five pedigrees were diagnosed with PMLD based on their clinical data. Six GJC2 novel mutations were found in this study, expanding the spectrum of GJC2 mutations. This is the second group of GJC2 mutations reported from six Chinese patients with PMLD. METHODS: Clinical data including medical history, physical signs, and auxiliary examinations were collected from six patients and their family numbers in five pedigrees with PMLD. Polymerase chain reaction and sequence analysis were used to amplify GJC2 and PLP1 alterations, while multiplex ligation-dependent probe amplification (MLPA) was performed to detect PLP1 dosage changes. The gene mutations were diagnosed for further analysis of the genetic features. RESULTS: A total of seven GJC2 mutations were identified in these patients, including two novel missense mutations (c.217C>T, p.Pro73Ser; c.1199C>A, p.Ala400Glu), one nonsense mutation (c.735C>A, p.Cys245X), three novel frameshift mutations (c.579delC, p.Gly193fsX17 and c.1296_1297insG, p.Gly433fsX59; c.689delG, p.Gly230AlafsX241), and one known missense mutation (c.814T>G, p.Tyr272Asp). Compound heterozygotes were found for P1-3, while homozygotes were found for P4-6 that were inherited from their parents with normal phenotypes except for P5 and P6, respectively. The c.814T>G (p.Tyr272Asp) mutation in P5 was de novo. A c.1199C>A (p.Ala400Glu) homozygous mutation in GJC2 was identified in P6. A heterozygous variation was found in his father and the wild type was seen in his mother.
Assuntos
Conexinas , Doenças Desmielinizantes , Doenças Desmielinizantes Hereditárias do Sistema Nervoso Central , Doença de Pelizaeus-Merzbacher , Humanos , População do Leste Asiático , Doenças Desmielinizantes Hereditárias do Sistema Nervoso Central/genética , Mutação , Mutação de Sentido Incorreto , Doença de Pelizaeus-Merzbacher/genética , Conexinas/genéticaRESUMO
BACKGROUND: The clinical spectrum of Pelizaeus-Merzbacher disease (PMD), a common hypomyelinating leukodystrophy, ranges between severe neonatal onset and a relatively stable presentation with later onset and mainly lower limb spasticity. In view of emerging treatment options and in order to grade severity and progression, we developed a PMD myelination score. METHODS: Myelination was scored in 15 anatomic sites (items) on conventional T2-and T1w images in controls (n = 328) and 28 PMD patients (53 MRI; n = 5 connatal, n = 3 transitional, n = 10 classic, n = 3 intermediate, n = 2 PLP0, n = 3 SPG2, n = 2 female). Items included in the score were selected based on interrater variability, practicability of scoring and importance of scoring items for discrimination between patients and controls and between patient subgroups. Bicaudate ratio, maximal sagittal pons diameter, and visual assessment of midsagittal corpus callosum were separately recorded. RESULTS: The resulting myelination score consisting of 8 T2-and 5 T1-items differentiates patients and controls as well as patient subgroups at first MRI. There was very little myelin and early loss in severely affected connatal and transitional patients, more, though still severely deficient myelin in classic PMD, ongoing myelination during childhood in classic and intermediate PMD. Atrophy, present in 50% of patients, increased with age at imaging. CONCLUSIONS: The proposed myelination score allows stratification of PMD patients and standardized assessment of follow-up. Loss of myelin in severely affected and PLP0 patients and progressing myelination in classic and intermediate PMD must be considered when evaluating treatment efficacy.
Assuntos
Doença de Pelizaeus-Merzbacher , Recém-Nascido , Humanos , Feminino , Proteína Proteolipídica de Mielina/genética , Mutação , Imageamento por Ressonância Magnética , Corpo Caloso/diagnóstico por imagemRESUMO
Hypomyelinating leukodystrophies comprise a subclass of genetic disorders with deficient myelination of the CNS white matter. Here we report four unrelated families with a hypomyelinating leukodystrophy phenotype harbouring variants in TMEM163 (NM_030923.5). The initial clinical presentation resembled Pelizaeus-Merzbacher disease with congenital nystagmus, hypotonia, delayed global development and neuroimaging findings suggestive of significant and diffuse hypomyelination. Genomic testing identified three distinct heterozygous missense variants in TMEM163 with two unrelated individuals sharing the same de novo variant. TMEM163 is highly expressed in the CNS particularly in newly myelinating oligodendrocytes and was recently revealed to function as a zinc efflux transporter. All the variants identified lie in highly conserved residues in the cytoplasmic domain of the protein, and functional in vitro analysis of the mutant protein demonstrated significant impairment in the ability to efflux zinc out of the cell. Expression of the mutant proteins in an oligodendroglial cell line resulted in substantially reduced mRNA expression of key myelin genes, reduced branching and increased cell death. Our findings indicate that variants in TMEM163 cause a hypomyelinating leukodystrophy and uncover a novel role for zinc homeostasis in oligodendrocyte development and myelin formation.
Assuntos
Doença de Pelizaeus-Merzbacher , Humanos , Doença de Pelizaeus-Merzbacher/genética , Mutação de Sentido Incorreto , Bainha de Mielina/metabolismo , Zinco/metabolismo , Proteínas de Membrana/genéticaRESUMO
Oligodendrocytes, the myelinating cells of the central nervous system, possess great potential for disease modeling and cell transplantation-based therapies for leukodystrophies. However, caveats to oligodendrocyte differentiation protocols ( Ehrlich et al., 2017; Wang et al., 2013; Douvaras and Fossati, 2015) from human embryonic stem and induced pluripotent stem cells (iPSCs), which include slow and inefficient differentiation, and tumorigenic potential of contaminating undifferentiated pluripotent cells, are major bottlenecks towards their translational utility. Here, we report the rapid generation of human oligodendrocytes by direct lineage conversion of human dermal fibroblasts (HDFs). We show that the combination of the four transcription factors OLIG2, SOX10, ASCL1 and NKX2.2 is sufficient to convert HDFs to induced oligodendrocyte precursor cells (iOPCs). iOPCs resemble human primary and iPSC-derived OPCs based on morphology and transcriptomic analysis. Importantly, iOPCs can differentiate into mature myelinating oligodendrocytes in vitro and in vivo. Finally, iOPCs derived from patients with Pelizaeus Merzbacher disease, a hypomyelinating leukodystrophy caused by mutations in the proteolipid protein 1 (PLP1) gene, showed increased cell death compared with iOPCs from healthy donors. Thus, human iOPCs generated by direct lineage conversion represent an attractive new source for human cell-based disease models and potentially myelinating cell grafts.
Assuntos
Células-Tronco Pluripotentes Induzidas , Doença de Pelizaeus-Merzbacher , Diferenciação Celular/fisiologia , Fibroblastos , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Oligodendroglia/metabolismo , Doença de Pelizaeus-Merzbacher/genética , Doença de Pelizaeus-Merzbacher/metabolismo , Doença de Pelizaeus-Merzbacher/terapiaRESUMO
Pelizaeus-Merzbacher-like disease type 1 (PMLD1) is a hypomyelinating disorder arising in patients with mutations in GJC2, encoding Connexin47 (Cx47). PMLD1 causes nystagmus, cerebellar ataxia, spasticity and changes in CNS white matter detected by MRI. At least one mutation (p.I33M) yields a much milder phenotype, spastic paraplegia type 44 (SPG44). Cx47 contributes to gap junction communication channels between oligodendrocytes (OLs), the myelinating cells in the central nervous system (CNS), and between OLs and astrocytes. Prior studies in cell lines have shown that PMLD1 mutants such as p.P87S display defective protein trafficking, intracellular retention in the ER and loss-of-function. Here we show that when expressed in primary OLs, three PMLD1 associated mutants (p.P87S, p.Y269D and p.M283T) show ER retention of Cx47 and evidence of activation of the cellular stress (unfolded protein response, UPR) and apoptotic pathways. On the other hand, the milder SPG44 associated mutation p.I33M shows a wild-type-like subcellular distribution and no activation of the UPR or apoptotic pathways. These studies provide new insight into a potential element of toxic gain of function underlying the mechanism of PMLD1 that should help guide future therapeutic approaches.
Assuntos
Doenças Desmielinizantes , Doenças por Armazenamento dos Lisossomos , Doenças Neurodegenerativas , Doença de Pelizaeus-Merzbacher , Conexinas/genética , Conexinas/metabolismo , Doenças Desmielinizantes/metabolismo , Junções Comunicantes/genética , Junções Comunicantes/metabolismo , Humanos , Doenças por Armazenamento dos Lisossomos/metabolismo , Mutação , Doenças Neurodegenerativas/metabolismo , Doença de Pelizaeus-Merzbacher/genética , Doença de Pelizaeus-Merzbacher/metabolismo , Resposta a Proteínas não Dobradas/genéticaRESUMO
BACKGROUND: The natural history and genotype-phenotype correlation of Pelizaeus-Merzbacher disease (PMD) of Chinese patients has been rarely reported. METHOD: Patients who met the criteria for PMD were enrolled in our study. Genomic analysis was conducted by multiplex ligation probe amplification (MLPA) and Sanger or whole-exome sequencing (WES). Natural history differences and genotype-phenotype correlations were analyzed. RESULT: A total of 111 patients were enrolled in our follow-up study. The median follow-up interval was 53 m (1185). Among PMD patients, developmental delay was the most common sign, and nystagmus and hypotonia were the most common initial symptoms observed. A total of 78.4% of the patients were able to control their head, and 72.1% could speak words. However, few of the patients could stand (9.0%) or walk (4.5%) by themselves. Nystagmus improved in more than half of the patients, and hypotonia sometimes deteriorated to movement disorders. More PLP1 point mutations patients were categorized into severe group, while more patients with PLP1 duplications were categorized into mild group (p < 0.001). Compared to patients in mild groups, those in the severe group had earlier disease onset and had acquired fewer skills at a later age. CONCLUSION: PMD patients have early disease onset with nystagmus and hypotonia followed by decreased nystagmus and movement disorders, such as spasticit. Patients with PLP1 duplication were more likely to be categorized into the mild group, whereas patients with point mutations were more likely to be categorized into the severe group.
Assuntos
Doença de Pelizaeus-Merzbacher , China , Seguimentos , Estudos de Associação Genética , Humanos , Proteína Proteolipídica de Mielina/genética , Doença de Pelizaeus-Merzbacher/diagnóstico , Doença de Pelizaeus-Merzbacher/genéticaRESUMO
Leukodystrophies are a heterogenous group of genetic disorders, characterised by abnormal development of cerebral white matter. Pelizaeus-Merzbacher disease is caused by mutations in PLP1, encoding major myelin-resident protein required for myelin sheath assembly. We report a missense variant p.(Ala109Asp) in MAL as causative for a rare, hypomyelinating leukodystrophy similar to Pelizaeus-Merzbacher disease. MAL encodes a membrane proteolipid that directly interacts with PLP1, ensuring correct distribution during myelin assembly. In contrast to wild-type MAL, mutant MAL was retained in the endoplasmic reticulum but was released following treatment with 4-phenylbutyrate. Proximity-dependent identification of wild-type MAL interactants implicated post-Golgi vesicle-mediated protein transport and protein localisation to membranes, whereas mutant MAL interactants suggested unfolded protein responses. Our results suggest that mislocalisation of MAL affects PLP1 distribution, consistent with known pathomechanisms for hypomyelinating leukodystrophies.
Assuntos
Doenças Neurodegenerativas , Doença de Pelizaeus-Merzbacher , Humanos , Mutação , Mutação de Sentido Incorreto , Proteína Proteolipídica de Mielina/genética , Proteína Proteolipídica de Mielina/metabolismo , Doença de Pelizaeus-Merzbacher/genética , Transporte ProteicoRESUMO
Pelizaeus-Merzbacher-Like Disease 1 is a genetic disorder affecting the central nervous system with an autosomal recessive inheritance pattern. It is a rare genetic disorder that affects the central nervous system. In this report, we demonstrated the clinical and paraclinical features of an Iranian consanguine pedigree with suspected hypomyelinating leukodystrophy, without any defined diagnosis. The proband, a 15-month-old girl, visited the Razi pathobiology and medical genetic laboratory of Karaj, where the study was conducted in 2020. Following whole-exome sequencing analysis of the proband and segregation analysis, a novel pathogenic mutation was discovered. GJC2 (NM_020435.4):c.1096dupG was found to be homozygous in the proband and heterozygous in both parents. This mutation was in the coding region of the protein, which results in D366Gfs*126 (p.Asp366GlyfsTer126). The site of mutation was at the 3' region of the connexin superfamily domain. The frameshift results in a different peptide sequence of the C-terminal and extended protein. Our findings led to the diagnosis of the proband's disease as Pelizaeus-Merzbacher-Like Disease 1 and led to the end of the diagnostic odyssey. We provided effective genetic counseling through the identification of a novel pathogenic mutation in gap junction protein C2 in this family and suggested preimplantation genetic diagnosis for the next pregnancy. Furthermore, our findings confirmed the association of GJC2 mutations with PMLD1. This discovery added to the repertoire of genetic mutations of Pelizaeus-Merzbacher-Like Disease 1. This knowledge could be applied for expanded carrier screening of other families, especially for Iranian consanguine marriages.
Assuntos
Conexinas/genética , Proteínas do Tecido Nervoso/genética , Doença de Pelizaeus-Merzbacher/diagnóstico , Feminino , Humanos , Lactente , Irã (Geográfico) , Mutação/genética , Doença de Pelizaeus-Merzbacher/genética , Sequenciamento do ExomaRESUMO
Autosomal dominant leukodystrophy (ADLD) is an extremely rare and fatal neurodegenerative disease due to the overexpression of the nuclear lamina component Lamin B1. Many aspects of the pathology still remain unrevealed. This work highlights the effect of Lamin B1 accumulation on different cellular functions in an ADLD astrocytic in vitro model. Lamin B1 overexpression induces alterations in cell survival signaling pathways with GSK3ß inactivation, but not the upregulation of ß-catenin targets, therefore resulting in a reduction in astrocyte survival. Moreover, Lamin B1 build up affects proliferation and cell cycle progression with an increase of PPARγ and p27 and a decrease of Cyclin D1. These events are also associated to a reduction in cell viability and an induction of apoptosis. Interestingly, ADLD astrocytes trigger a tentative activation of survival pathways that are ineffective. Finally, astrocytes overexpressing Lamin B1 show increased immunoreactivity for both GFAP and vimentin together with NF-kB phosphorylation and c-Fos increase, suggesting astrocytes reactivity and substantial cellular activation. These data demonstrate that Lamin B1 accumulation is correlated to biochemical, metabolic, and morphologic remodeling, probably related to the induction of a reactive astrocytes phenotype that could be strictly associated to ADLD pathological mechanisms.
Assuntos
Astrócitos/metabolismo , Lamina Tipo B/efeitos adversos , Doenças Neurodegenerativas/fisiopatologia , Doença de Pelizaeus-Merzbacher/fisiopatologia , HumanosRESUMO
Among the hypomyelinating leukodystrophies, Pelizaeus-Merzbacher disease (PMD) is a representative disorder. The disease is caused by different types of PLP1 mutations, among which PLP1 duplication accounts for â¼70% of the mutations. Previous studies have shown that PLP1 duplications lead to PLP1 retention in the endoplasmic reticulum (ER); in parallel, recent studies have demonstrated that PLP1 duplication can also lead to mitochondrial dysfunction. As such, the respective roles and interactions of the ER and mitochondria in the pathogenesis of PLP1 duplication are not clear. In both PLP1 patients' and healthy fibroblasts, we measured mitochondrial respiration with a Seahorse XF Extracellular Analyzer and examined the interactions between the ER and mitochondria with super-resolution microscopy (spinning-disc pinhole-based structured illumination microscopy, SD-SIM). For the first time, we demonstrated that PLP1 duplication mutants had closer ER-mitochondrion interfaces mediated through structural and morphological changes in both the ER and mitochondria-associated membranes (MAMs). These changes in both the ER and mitochondria then led to mitochondrial dysfunction, as reported previously. This work highlights the roles of MAMs in bridging PLP1 expression in the ER and pathogenic dysfunction in mitochondria, providing novel insight into the pathogenicity of mitochondrial dysfunction resulting from PLP1 duplication. These findings suggest that interactions between the ER and mitochondria may underlie pathogenic mechanisms of hypomyelinating leukodystrophies diseases at the organelle level.
Assuntos
Proteína Proteolipídica de Mielina , Doença de Pelizaeus-Merzbacher , Retículo Endoplasmático , Humanos , Mitocôndrias , Mutação , Proteína Proteolipídica de Mielina/genética , Doença de Pelizaeus-Merzbacher/genética , VirulênciaRESUMO
Pelizaeus-Merzbacher disease (PMD) is a severe hypomyelinating disorder of the central nervous system (CNS) linked to mutations in the proteolipid protein-1 (PLP1) gene. Although there are multiple animal models of PMD, few of them fully mimic the human disease. Here, we report three spontaneous cases of male neonatal rhesus macaques with the clinical symptoms of hypomyelinating disease, including intention tremors, progressively worsening motor dysfunction, and nystagmus. These animals demonstrated a paucity of CNS myelination accompanied by reactive astrogliosis, and a lack of PLP1 expression throughout white matter. Genetic analysis revealed that these animals were related to one another and that their parents carried a rare, hemizygous missense variant in exon 5 of the PLP1 gene. These animals therefore represent the first reported non-human primate model of PMD, providing a novel and valuable opportunity for preclinical studies that aim to promote myelination in pediatric hypomyelinating diseases.