PMM2
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Congenital disorders of glycosylation (CDG) are a rapidly growing family of genetic diseases with the phosphomannomutase 2 (PMM2)-CDG being the most common form of CDG. Most of these monogenic diseases are autosomal recessive and have multi-systemic manifestations, mainly psychomotor retardation, facial dysmorphisms, characteristic distribution of the fat pads, and variable coagulation abnormalities. The association of fetal hydrops with CDG has been reported, and pericardial effusion was also rarely observed in patients with PMM2-CDG. Here we describe an infant boy with PMM2-CDG. The diagnosis was suspected based on inverted nipples, fat pads, and combined coagulopathy. However, the primary symptom was progressive pericardial effusion leading to patient death at the age of 3 months. Screening for CDG performed by the use of isoelectric focusing of serum transferrin showed a typical PMM2-CDG pattern. Exome sequencing revealed one common pathogenic variant (c.691G > A/p.Val231Met) and one novel variant (c.447 + 3dupA) in the PMM2 gene. Both PMM2 variants were further confirmed by Sanger sequencing in both the proband and the parents' DNA. The novel variant was predicted to result in loss of donor splice site, and the analysis at mRNA level confirmed that it leads to exon five skipping (r.348_447del) and causes premature termination of translation to the protein (p.G117Kfs∗4), therefore is classified as likely pathogenic. Although there is no curative therapy for the PMM2-CDG at the moment, the other supportive care options are available to be offered. The definite diagnosis of PMM2-CDG can also assist in the process of genetic counseling, family planning, and preimplantation genetic diagnosis.
- Publikační typ
- časopisecké články MeSH
- MeSH
- cévní mozková příhoda MeSH
- dítě MeSH
- fosfotransferasy * chemie nedostatek MeSH
- kanálopatie genetika MeSH
- lidé MeSH
- nemoci mozečku diagnostické zobrazování MeSH
- prognóza MeSH
- vápníkové kanály genetika MeSH
- vrozené poruchy glykosylace diagnostické zobrazování genetika patofyziologie MeSH
- Check Tag
- dítě MeSH
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
PMM2-CDG is the most common defect among the congenital disorders of glycosylation. In order to investigate the effect of hypoglycosylation on important cellular pathways, we performed extensive biochemical studies on skin fibroblasts of PMM2-CDG patients. Among others, acylcarnitines, amino acids, lysosomal proteins, organic acids and lipids were measured, which all revealed significant abnormalities. There was an increased expression of acylcarnitines and amino acids associated with increased amounts of calnexin, calreticulin and protein-disulfid-isomerase in combination with intensified amounts of ubiquitinylated proteins. Lysosomal enzyme activities were widely decreased as well as citrate and pyruvate levels indicating mitochondrial dysfunction. Main lipid classes such as phosphatidylethanolamine, cholesterol or alkyl-phosphatidylcholine, as well as minor lipid species like hexosylceramide, lysophosphatidylcholines or phosphatidylglycerol, were abnormal. Biotinidase and catalase activities were severely reduced. In this study we discuss the impact of metabolite abnormalities on the phenotype of PMM2-CDG. In addition, based on our data we propose new and easy-to-implement therapeutic approaches for PMM2-CDG patients.
- MeSH
- aminokyseliny metabolismus MeSH
- fosfotransferasy (fosfomutasy) * genetika MeSH
- glykosylace MeSH
- lidé MeSH
- lipidy MeSH
- vrozené poruchy glykosylace * genetika terapie metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
We report on the largest single dataset of patients with PMM2-CDG enrolled in an ongoing international, multicenter natural history study collecting genetic, clinical, and biological information to evaluate similarities with previous studies, report on novel findings, and, additionally, examine potential genotype/phenotype correlations. A total of 137 participants had complete genotype information, representing 60 unique variants, of which the most common were found to be p.Arg141His in 58.4% (n = 80) of participants, followed by p.Pro113Leu (21.2%, n = 29), and p.Phe119Leu (12.4%, n = 17), consistent with previous studies. Interestingly, six new variants were reported, comprised of five missense variants (p.Pro20Leu, p.Tyr64Ser, p.Phe68Cys, p.Tyr76His, and p.Arg238His) and one frameshift (c.696del p.Ala233Argfs∗100). Patient phenotypes were characterized via the Nijmegen Progression CDG Rating Scale (NPCRS), together with biochemical parameters, the most consistently dysregulated of which were coagulation factors, specifically antithrombin (below normal in 79.5%, 93 of 117), in addition to Factor XI and protein C activity. Patient genotypes were classified based upon the predicted pathogenetic mechanism of disease-associated mutations, of which most were found in the catalysis/activation, folding, or dimerization regions of the PMM2 enzyme. Two different approaches were used to uncover genotype/phenotype relationships. The first characterized genotype only by the predicted pathogenic mechanisms and uncovered associated changes in biochemical parameters, not apparent using only NPCRS, involving catalysis/activation, dimerization, folding, and no protein variants. The second approach characterized genotype by the predicted pathogenic mechanism and/or individual variants when paired with a subset of severe nonfunctioning variants and uncovered correlations with both NPCRS and biochemical parameters, demonstrating that p.Cys241Ser was associated with milder disease, while p.Val231Met, dimerization, and folding variants with more severe disease. Although determining comprehensive genotype/phenotype relationships has previously proven challenging for PMM2-CDG, the larger sample size, plus inclusion of biochemical parameters in the current study, has provided new insights into the interplay of genetics with disease. Trial Registration: NCT03173300.
- MeSH
- dítě MeSH
- dospělí MeSH
- fenotyp MeSH
- fosfotransferasy (fosfomutasy) * genetika chemie MeSH
- genetické asociační studie * MeSH
- genotyp MeSH
- kojenec MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mutace MeSH
- předškolní dítě MeSH
- vrozené poruchy glykosylace * genetika diagnóza MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- kojenec MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- předškolní dítě MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- multicentrická studie MeSH
- pozorovací studie MeSH
PMM2-CDG is the most common congenital disorder of glycosylation (CDG) accounting for almost 65% of known CDG cases affecting N-glycosylation. Abnormalities in N-glycosylation could have a negative impact on many endocrine axes. There is very little known on the effect of impaired N-glycosylation on the hypothalamic-pituitary-adrenal axis function and whether CDG patients are at risk of secondary adrenal insufficiency and decreased adrenal cortisol production. Cortisol and ACTH concentrations were simultaneously measured between 7:44 am to 1 pm in forty-three subjects (20 female, median age 12.8 years, range 0.1 to 48.6 years) participating in an ongoing international, multi-center Natural History study for PMM2-CDG (ClinicalTrials.gov Identifier: NCT03173300). Of the 43 subjects, 11 (25.6%) had cortisol below 5 μg/dl and low to normal ACTH levels, suggestive of secondary adrenal insufficiency. Two of the 11 subjects have confirmed central adrenal insufficiency and are on hydrocortisone replacement and/or stress dosing during illness; 3 had normal and 1 had subnormal cortisol response to ACTH low-dose stimulation test but has not yet been started on therapy; the remaining 5 have upcoming stimulation testing planned. Our findings suggest that patients with PMM2-CDG may be at risk for adrenal insufficiency. Monitoring of morning cortisol and ACTH levels should be part of the standard care in patients with PMM2-CDG.
- MeSH
- adrenální insuficience diagnóza etiologie patofyziologie MeSH
- dítě MeSH
- dospělí MeSH
- fosfotransferasy (fosfomutasy) krev genetika MeSH
- glykosylace MeSH
- kojenec MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- předškolní dítě MeSH
- prospektivní studie MeSH
- rizikové faktory MeSH
- systém hypofýza - nadledviny fyziologie MeSH
- vrozené poruchy glykosylace MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- kojenec MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- předškolní dítě MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- pozorovací studie MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
PURPOSE: PMM2-CDG is the most common congenital disorder of glycosylation (CDG), which presents with either a neurologic or multisystem phenotype. Little is known about the longitudinal evolution. METHODS: We performed data analysis on PMM2-CDG patients' clinical features according to the Nijmegen CDG severity score and laboratory data. Seventy-five patients (28 males) were followed up from 11.0 ± 6.91 years for an average of 7.4 ± 4.5 years. RESULTS: On a group level, there was no significant evolution in overall clinical severity. There was some improvement in mobility and communication, liver and endocrine function, and strabismus and eye movements. Educational achievement and thyroid function worsened in some patients. Overall, the current clinical function, the system-specific involvement, and the current clinical assessment remained unchanged. On follow-up there was improvement of biochemical variables with (near) normalization of activated partial thromboplastin time (aPTT), factor XI, protein C, antithrombin, thyroid stimulating hormone, and liver transaminases. CONCLUSION: PMM2-CDG patients show a spontaneous biochemical improvement and stable clinical course based on the Nijmegen CDG severity score. This information is crucial for the definition of endpoints in clinical trials.
- MeSH
- dítě MeSH
- fenotyp MeSH
- fosfotransferasy (fosfomutasy) nedostatek MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- následné studie MeSH
- předškolní dítě MeSH
- progrese nemoci MeSH
- vrozené poruchy glykosylace epidemiologie patofyziologie MeSH
- Check Tag
- dítě MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- předškolní dítě MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
PMM2-CDG is the most prevalent type of congenital disorders of glycosylation (CDG). It is caused by pathogenic variants in the gene encoding phosphomannomutase 2 (PMM2), which converts mannose-6-phosphate to mannose-1-phosphate and thus activates this saccharide for further glycosylation processes. Defective glycosylation can lead to an abnormal accumulation of unfolded proteins in endoplasmic reticulum (ER) and cause its stress. The ER is a key compartment for glycosylation, and its connection and communication with mitochondria has been described extensively in literature. Their crosstalk is important for cell proliferation, calcium homeostasis, apoptosis, mitochondrial fission regulation, bioenergetics, autophagy, lipid metabolism, inflammasome formation and unfolded protein response. Therefore, in the present study we posed a question, whether defective glycosylation leads to bioenergetic disruption. Our data reveal possible chronic stress in ER and activated unfolded protein response via PERK pathway in PMM2-CDG fibroblasts. Presumably, it leads to bioenergetic reorganization and increased assembly of respiratory chain complexes into supercomplexes together with suppressed glycolysis in PMM2-CDG patient cells. These changes cause alterations in Krebs cycle, which is tightly connected to electron transport system in mitochondria. In summary, we present data showing metabolic adaptation of cells to glycosylation defect caused by various pathogenic variants in PMM2.
Cíl studie: Cílem studie bylo zavést metodu pro stanovení aktivity fosfomanomutázy 2 (PMM2) a kontrolního enzymu fosfo - manoizomerázy (PMI) v izolovaných lymfocytech a kultivovaných kožních fibroblastech a využít ji jako diferenciální diagnos - tický krok v souboru 18 pacientů s podezřením na CDG syndrom typu I. Typ studie: Původní práce. Název a sídlo pracoviště: Klinika dětského a dorostového lékařství, 1. lékařská fakulta Univerzity Karlovy a Všeobecná fakultní nemocnice v Praze. Materiál a metody: Analyzovaný soubor představuje 16 vzorků lymfocytů a 8 linií kultivovaných kožních fibroblastů od 18 pacientů z 15 nepříbuzných rodin, u kterých lékaři vyslovili vysoké podezření na CDG syndrom typu I. Kontrolní skupinu tvořilo 59 vzorků lymfocytů a 29 linií fibroblastů od pacientů, u kterých nebylo prokázáno podezření na metabolickou poruchu. Aktivity PMM2 a PMI byly měřeny spektrofotometricky při 37 °C jako redukce NADP + na NADPH při 340 nm. Výsledky: U PMM2 a PMI nebyly v lymfocytech ani kultivovaných fibroblastech nalezeny statisticky významné rozdíly aktivit v závislosti na věku či pohlaví. Aktivita PMM2 v lymfocytech u kontrolního souboru byla 0,34–2,58 nmol/min/mg (2,5% až 97,5% percentil) a ve fibroblastech 0,44–9,0 nmol/min/mg. Aktivita PMM2 v lymfocytech byla v souboru pacientů nízká (0,02–0,18 nmol/min/mg, mezikvartilové rozpětí, kontroly 0,73-1,42, p<0,001). Aktivita PMM2 ve fibroblastech od pacientů byla také nízká (0,2–0,66 nmol/min/mg; kontroly 1,06–3,17, p<0,001). Poměr PMM2/PMI byl u pacientů významně snížený v obou tkáních (p<0,001). U všech 18 pacientů byla diagnóza PMM2-CDG potvrzena i nálezem mutací v PMM2 genu. Závěr: Měření aktivity PMM2 v lymfocytech nebo kultivovaných fibroblastech umožňuje rychlé stanovení diagnózy PMM2- CDG, nejčastější dědičné poruchy glykosylace typu I
Objective: Aim of study was to establish a method for determining the activity of phosphomannomutase 2 (PMM2) and phosphomannose isomerase (PMI) as a control enzyme in isolated lymphocytes and cultured skin fibroblasts and use it as a differential diagnostic step in a group of 18 patients with suspected CDG syndrome type I. Design: Original paper. Settings: Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague Material and methods: Cohort of samples consists of 16 isolated lymphocytes and 8 cultured skin fibroblasts lines from 18 patients from 15 unrelated families with high clinical suspicion for CDG syndrome type I. Group of controls consisted of 59 lymphocytes and 29 fibroblasts cell lines from disease free patients. Activities PMM2 and PMI were measured spectrophotometrically at 37 °C as the reduction of NADP+ to NADPH at 340 nm. Results: Statistically significant correlation between activity of PMM2 and PMI and age or gender in lymphocytes or cul tured fibroblasts was not found. PMM2 activity in lymphocytes in the control group was from 0.34 to 2.58 nmol/min/mg (2.5% to 97.5% percentile) and in fibroblasts from 0.44 to 9.0 nmol/min/mg. PMM2 activity in lymphocytes in the group of patients was low (0.02-0.18 nmol/min/mg, interquartile range, controls 0.73-1.42 nmol/min/mg, p <0.001). PMM2 activity in fibroblasts from patients was also low (0.2-0.66 nmol/min/mg, controls 1.06-3.17 nmol/min/mg, p<0.001). PMM2 / PMI ratio in patients was significantly decreased in both tissues (p<0.001). The diagnosis of PMM2-CDG was confirmed by finding of mutations in PMM2 gene in all 18 patients. Conclusion: Measurement of PMM2 activity in lymphocytes or cultured fibroblasts allows to quickly diagnose PMM2-CDG, the most common congenital disorder of glycosylation.
- Klíčová slova
- fosfomanomutáza (PMM2),
- MeSH
- fibroblasty MeSH
- glykosylace MeSH
- lidé MeSH
- lymfocyty MeSH
- mannosa-6-fosfátisomerasa * analýza MeSH
- metabolismus sacharidů MeSH
- spektrofotometrie MeSH
- vrozené poruchy glykosylace * diagnóza MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- klinická studie MeSH
Úvod: Deficit fosfomanomutázy 2 (PMM2-CDG) je nejčastějším typem poruch N-glykosylace s popsanými >900 pacienty. Onemocnění je autosomálně recesivně dědičné a biochemickou podstatou je porucha přeměny manóza-6-fosfátu na manóza-1-fosfát (M1P). Onemocnění se projevuje encefalopatií, neuropatií, typickou dysmorfií, atrofií mozečku a koagulopatií. Práce prezentuje výsledky klinických, biochemických a molekulárních vyšetření pacientů diagnostikovaných v ČR. Výsledky: Od roku 2002 bylo v ČR diagnostikováno 22 pacientů z 18 rodin. Dvě děti zemřely v kojeneckém věku. Věk žijících 20 pacientů je v rozpětí 9 měsíců až 29 let (medián 14 let). U všech pacientů je přítomný hypotonický a mozečkový syndrom, strabismus, deformity skeletu, koagulopatie a mentální retardace, která je v pásmu od lehkého až po hluboké postižení. U 94 % pacientů jsme prokázali atrofii mozečku. Typická dysmorfie (atypické rozložení tuku a vpáčení bradavek) byla zjištěna u 82 % dětí. U 9 pacientů se projevila epilepsie a 3 pacienti prodělali iktu podobné příhody. Isoelektrická fokusace transferinu v séru prokázala u všech pacientů zvýšené zastoupení nízkosialovaných forem. Diagnóza byla potvrzena enzymologicky detekcí snížené aktivity PMM2 v lymfocytech či fibroblastech a/nebo molekulárně-geneticky. V našem souboru pacientů bylo zastoupeno 10 mutací v genu PMM2, všichni pacienti jsou složení heterozygoti a 71 % mutovaných alel neslo jednu ze dvou prevalentních patogenních variant (c.422G>A, c.338C>T). Závěr: S ohledem na odhadovanou incidenci PMM2-CDG 1:20 000 se jedná o onemocnění v ČR poddiagnostikované. PMM2-CDG patří do diferenciální diagnostiky všech dětí s atrofií mozečku, a to i bez přítomnosti charakteristických dysmorfických rysů. V plánu je zařazení českých pacientů do prospektivní multicentrické mezinárodní studie hodnotící přirozený průběh onemocnění a eventuálně zařazení do klinické studie s novou experimentální léčebnou molekulou LipoM1P (manóza-1-fosfát inkorporovaná do liposomu).
Introduction: PMM2-CDG is the most common autosomal recessive N-glycosylation disorder with more than 900 patients described worldwide. It is caused by a deficiency of the phosphomannomutase 2 enzyme (PMM2) which catalyzes the second step of the mannose pathway, namely the conversion of mannose-6-phosphate to mannose-1-phosphate. The clinical presentation is characterised by encephalopathy, neuropathy, typical dysmorphism, cerebellar atrophy and coagulopathy. We present the results of clinical, biochemical and molecular analyses in patients diagnosed in the Czech Republic. Results: Since 2002, a total of 22 Czech patients from 18 families with PMM2 deficiency have been diagnosed. The age range of the patients spans from 9 months to 29 years with a median of 14 years, except two patients who died during infancy. Muscle hypotonia, intellectual disability of varying severity, strabismus, ataxia, bone deformities, and coagulopathy were observed in all patients. Cerebellar atrophy was documented in 94% of the investigated patients. The characteristic dysmorphism (inverted nipples and atypical fat pads) were present in 82% of the patients. Nine patients suffered from seizures, and three patients showed transient neurological deterioration after stroke-like episodes. In all the patients, increased amount of hypoglycosylated transferrin was found by isoelectric focusing. The diagnosis of the PMM2-CDG was confirmed at enzymatic and/or at molecular levels. Molecular analyses revealed that all patients are compound heterozygotes for a total of 10 different mutations in PMM2, and that 71% of our patients´ alleles have one of the two most frequent genetic variants (c.422G>A, c.338C>T). Conclusion: The estimated incidence of PMM2-CDG is 1:20,000, suggesting that this disorder is underdiagnosed in the Czech Republic. PMM2-CDG must be considered in differential diagnosis of patients with cerebellar atrophy even if they do not manifest characteristic dysmorphism. We plan to include our patients in a longitudinal international multicenter observational study and potentially the upcoming clinical trial with LipoM1P (lipomised mannose-1-phosphate).
- Klíčová slova
- atrofie mozečku,
- MeSH
- dědičné koagulopatie diagnóza patologie MeSH
- dítě MeSH
- dospělí MeSH
- fosfotransferasy (fosfomutasy) * nedostatek MeSH
- genetické techniky MeSH
- isoelektrická fokusace MeSH
- kojenec MeSH
- lidé MeSH
- mladiství MeSH
- mozeček patologie MeSH
- předškolní dítě MeSH
- retrospektivní studie MeSH
- vrozené poruchy glykosylace * diagnóza komplikace patofyziologie MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- kojenec MeSH
- lidé MeSH
- mladiství MeSH
- mužské pohlaví MeSH
- předškolní dítě MeSH
- ženské pohlaví MeSH
- Publikační typ
- práce podpořená grantem MeSH
- přehledy MeSH
