AAV9-based PMM2 gene replacement augments PMM2 expression and improves glycosylation in primary fibroblasts of patients with phosphomannomutase 2 deficiency (PMM2-CDG).
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SUBMITTER: Zhong M
PROVIDER: S-EPMC10733668 | biostudies-literature | 2024 Mar
REPOSITORIES: biostudies-literature
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AAV9-based <i>PMM2</i> gene replacement augments PMM2 expression and improves glycosylation in primary fibroblasts of patients with phosphomannomutase 2 deficiency (PMM2-CDG).
Zhong M M Balakrishnan B B Guo A J AJ Lai K K
Molecular genetics and metabolism reports 20231216
Inherited deficiency of phosphomannomutase 2 (PMM2) (aka PMM2-CDG) is the most common congenital disorders of glycosylation (CDG) and has no cure. With debilitating morbidity and significant mortality, it is imperative to explore novel, safe, and effective therapies for the disease. Our Proof-of-Concept study showed that AAV9-<i>PMM2</i> infection of patient fibroblasts augmented PMM2 expression and improved glycosylation. Thus, AAV9-<i>PMM2</i> gene replacement is a promising therapeutic strate ...[more]
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Project description:BackgroundPhosphomannomutase deficiency (PMM2-CDG) is the most frequent congenital disorder of glycosylation. The cerebellum is nearly always affected in PMM2-CDG patients, a cerebellar atrophy progression is observed, and cerebellar dysfunction is their main daily functional limitation. Different therapeutic agents are under development, and clinical evaluation of drug candidates will require a standardized score of cerebellar dysfunction. We aim to assess the validity of the International Cooperative Ataxia Rating Scale (ICARS) in children and adolescents with genetically confirmed PMM2-CDG deficiency. We compare ICARS results with the Nijmegen Pediatric CDG Rating Scale (NPCRS), neuroimaging, intelligence quotient (IQ) and molecular data.MethodsOur observational study included 13 PMM2-CDG patients and 21 control subjects. Ethical permissions and informed consents were obtained. Three independent child neurologists rated PMM2-CDG patients and control subjects using the ICARS. A single clinician administered the NPCRS. All patients underwent brain MRI, and the relative diameter of the midsagittal vermis was measured. Psychometric evaluations were available in six patients. The Mann-Whitney U test was used to compare ICARS between patients and controls. To evaluate inter-observer agreement in patients' ICARS ratings, intraclass correlation coefficients (ICC) were calculated. ICARS internal consistency was evaluated using Cronbach's alpha. Spearman's rank correlation coefficient test was used to correlate ICARS with NPCRS, midsagittal vermis relative diameter and IQ.ResultsICARS and ICARS subscores differed between patients and controls (p < 0.001). Interobserver agreement of ICARS was "almost perfect" (ICC = 0.99), with a "good" internal reliability (Cronbach's alpha = 0.72). ICARS was significantly correlated with the total NPCRS score (rs 0.90, p < 0.001). However, there was no agreement regarding categories of severity. Regarding neuroimaging, inverse correlations between ICARS and midsagittal vermis relative diameter (rs -0.85, p = 0.003) and IQ (rs -0.94, p = 0.005) were found. Patients bearing p.E93A, p.C241S or p.R162W mutations presented a milder phenotype.ConclusionsICARS is a reliable instrument for assessment of PMM2-CDG patients, without significant inter-rater variability. Despite our limited sample size, the results show a good correlation between functional cerebellar assessment, IQ and neuroimaging. For the first a correlation between ICARS, neuroimaging and IQ in PMM2-CDG patients has been demonstrated.
| S-EPMC4623922 | biostudies-literature
Project description:BackgroundPMM2-CDG (CDG-Ia) is the most frequent N-glycosylation disorder. While supplying mannose to PMM2-deficient fibroblasts corrects the altered N-glycosylation in vitro, short term therapeutic approaches with mannose supplementation in PMM2-CDG patients have been unsuccessful. Mannose found no further mention in the design of a potential therapy for PMM2-CDG in the past years, as it applies to be ineffective. This retrospective study analyzes the first long term mannose supplementation in 20 PMM2-CDG patients. Mannose was given at a total of 1-2 g mannose/kg b.w./d divided into 5 single doses over a mean time of 57,75 ± 25,85 months. Protein glycosylation, blood mannose concentration and clinical presentation were monitored in everyday clinical practice.ResultsAfter a mean time period of more than 1 year the majority of patients showed significant improvements in protein glycosylation.ConclusionDietary mannose supplementation shows biological effects in PMM2-CDG patients improving glycosylation in the majority of patients. A double-blind randomized study is needed to examine the role of mannose in the design of a therapy for children with PMM2-CDG in more detail.
| S-EPMC7510076 | biostudies-literature
Project description:PMM2-CDG (formerly CDG-1a), the most common type of congenital disorders of glycosylation, is inherited in an autosomal recessive pattern. PMM2-CDG frequently presents in infancy with multisystemic clinical involvement, and it has been diagnosed in over 1000 people worldwide. There have been few natural history studies reporting neurodevelopmental characterization of PMM2-CDG. Thus, a prospective study was conducted that included neurodevelopmental assessments as part of deep phenotyping. This study, Clinical and Basic Investigations into Known and Suspected Congenital Disorders of Glycosylation (NCT02089789), included 14 participants (8 males and 6 females ages 2-33 years) with a confirmed molecular diagnosis of PMM2-CDG. Clinical features of PMM2-CDG in this cohort were neurodevelopmental disorders, faltering growth, hypotonia, cerebellar atrophy, peripheral neuropathy, movement disorders, ophthalmological abnormalities, and auditory function differences. All PMM2-CDG participants met criteria for intellectual disability (or global developmental delay if younger than age 5). The majority never attained certain gross motor and language milestones. Only two participants were ambulatory, and almost all were considered minimally verbal. Overall, individuals with PMM2-CDG present with a complex neurodevelopmental profile characterized by intellectual disability and multisystemic presentations. This systematic quantification of the neurodevelopmental profile of PMM2-CDG expands our understanding of the range in impairments associated with PMM2-CDG and will help guide management strategies.
| S-EPMC11670447 | biostudies-literature
Project description:Congenital disorders of glycosylation (CDGs) are a rapidly enlarging group of inherited diseases with abnormal N-glycosylation of glycoconjugates. Most patients have CDG-Ia, which is due to a phosphomannomutase (PMM) deficiency. In this article, we report that a significant portion (9 of 54) of patients with CDG-Ia had a rather high residual PMM activity in fibroblasts included in the normal range (means of the controls +/- 2 SD) and amounting to 35%-70% of the mean control value. The clinical diagnosis of CDG-Ia was made difficult by the fact that most (6 of 9) of these patients belong to a subgroup characterized by a phenotype that is milder than classical CDG-Ia. These patients lack some of the symptoms that are suggestive for the diagnosis, such as inverted nipples and abnormal fat deposition, and, as a mean, had higher residual PMM activities in fibroblasts (2.05+/-0.61 mU/mg protein, n=9; vs. controls 5.34+/-1.74 mU/mg protein, n=22), compared with patients with moderate (1.32+/-0.86 mU/mg protein, n=18) or severe (0.63+/-0.56 mU/mg protein, n=27, P<.001) cases. Yet they all showed mild mental retardation, hypotonia, cerebellar hypoplasia, and strabismus. All of them had an abnormal serum transferrin pattern and a significantly reduced PMM activity in leukocytes. Six of the nine patients with mild presentations were compound heterozygotes for the C241S mutation, which is known to reduce PMM activity by only approximately 2-fold. Our results indicate that intermediate PMM values in fibroblasts may mask the diagnosis of CDG-Ia, which is better accomplished by measurement of PMM activity in leukocytes and mutation search in the PMM2 gene. They also indicate that there is some degree of correlation between the residual activity in fibroblasts and the clinical phenotype.
| S-EPMC1235268 | biostudies-literature
Project description:BackgroundPMM2-CDG is the most common N-glycosylation defect and shows an increased risk of recurrent and/or severe, sometimes fatal, infections in early life. We hypothesized that natural killer (NK) cells, as important mediators of the immune response against microbial pathogens and regulators of adaptive immunity, might be affected in this genetic disorder.ObjectiveTo evaluate possible defects on PMM2-CDG NK peripheral blood cell number, killing activity and expression of membrane receptors.MethodsWe studied fresh and activated NK cells from twelve PMM2-CDG cells. The number and expression of lymphoid surface receptors were studied by flow cytometry. The NK responsiveness (frequency of degranulated NK cells) and killing activity against K562 target cells was determined in the NK cytotoxicity assay.ResultsWe found an increase of blood NK cells in three patients with a severe phenotype. Two of them, who had suffered from moderate/severe viral infections during their first year of life, also had reduced T lymphocyte numbers. Patient activated NK cells showed increased expression of CD54 adhesion molecule and NKG2D and NKp46 activating receptors. NKp46 and 2B4 expression was inversely correlated with the expression of NKG2D in activated PMM2-CDG cells. Maximal NK activity against K562 target cells was similar in control and PMM2-CDG cells. Interestingly, the NK cell responsiveness was higher in patient cells. NKG2D and specially CD54 increased surface expression significantly correlated with the increased NK cell cytolytic activity according to the modulation of the killer activity by expression of triggering receptors and adhesion molecules.ConclusionsOur results indicate that hypoglycosylation in PMM2-CDG altered NK cell reactivity against target cells and the expression of CD54 and NKG2D, NKp46 and 2B4 activating receptors during NK cell activation. This suggests a defective control of NK cell killing activity and the overall anti-viral immune response in PMM2-CDG patients. The present work improves our understanding of the immunological functions in PMM2-CDG and possibly in other CDG-I types.
| S-EPMC4944953 | biostudies-literature
Project description: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.
| S-EPMC8754259 | biostudies-literature
Project description:BackgroundWe aim to delineate the progression of cerebellar syndrome in children with phosphomannomutase-deficiency (PMM2-CDG) using the International Cooperative Ataxia Rating Scale (ICARS). We sought correlation between cerebellar volumetry and clinical situation. We prospectively evaluated PMM2-CDG patients aged from 5 to 18 years through ICARS at two different time points set apart by at least 20 months. We reviewed available MRIs and performed volumetric analysis when it was possible.ResultsFrom the eligible 24, four patients were excluded due to severe mental disability (n = 2) and supratentorial lesions (n = 2). Two different ICARS evaluations separated by more than 20 months were available for 14 patients showing an improvement in the cerebellar syndrome: ICARS1: 35.71 versus ICARS2: 30.07 (p < 0.001). When we considered time, we saw an improvement of 2.64 points in the ICARS per year with an SD of 1.97 points (p < 0.001). The ICARS subscales results improved with time, reaching statistical significance in "Posture and gait" (p < 0.001), "Kinetic functions" (p = 0.04) and "Speech abnormalities" (p = 0.045). We found a negative correlation between the ICARS results and total cerebellar volume (r = -0.9, p = 0.037) in a group of five patients with available volumetric study, meaning that the higher the ICARS score, the more severe was the cerebellar atrophy.ConclusionsOur study shows a stabilization or mild improvement in the cerebellar functions of paediatric PMM2-CDG patients despite cerebellar volume loss. ICARS is a valid scale to quantify the evolution of cerebellar syndrome in PMM2-CDG patients. The availability of ICARS and other reliable and sensitive follow-up tools may prove essential for the evaluation of potential therapies.
| S-EPMC5602850 | biostudies-literature
Project description:Stroke-like episodes (SLE) occur in phosphomannomutase deficiency (PMM2-CDG), and may complicate the course of channelopathies related to Familial Hemiplegic Migraine (FHM) caused by mutations in CACNA1A (encoding CaV2.1 channel). The underlying pathomechanisms are unknown. We analyze clinical variables to detect risk factors for SLE in a series of 43 PMM2-CDG patients. We explore the hypothesis of abnormal CaV2.1 function due to aberrant N-glycosylation as a potential novel pathomechanism of SLE and ataxia in PMM2-CDG by using whole-cell patch-clamp, N-glycosylation blockade and mutagenesis. Nine SLE were identified. Neuroimages showed no signs of stroke. Comparison of characteristics between SLE positive versus negative patients' group showed no differences. Acute and chronic phenotypes of patients with PMM2-CDG or CACNA1A channelopathies show similarities. Hypoglycosylation of both CaV2.1 subunits (α1A and α2α) induced gain-of-function effects on channel gating that mirrored those reported for pathogenic CACNA1A mutations linked to FHM and ataxia. Unoccupied N-glycosylation site N283 at α1A contributes to a gain-of-function by lessening CaV2.1 inactivation. Hypoglycosylation of the α₂δ subunit also participates in the gain-of-function effect by promoting voltage-dependent opening of the CaV2.1 channel. CaV2.1 hypoglycosylation may cause ataxia and SLEs in PMM2-CDG patients. Aberrant CaV2.1 N-glycosylation as a novel pathomechanism in PMM2-CDG opens new therapeutic possibilities.
| S-EPMC5855841 | biostudies-literature
Project description:PMM2-CDG, formerly known as congenital disorder of glycosylation-Ia (CDG-Ia), is caused by mutations in the gene encoding phosphomannomutase 2 (PMM2). This disease is the most frequent form of inherited CDG-diseases affecting protein N-glycosylation in human. PMM2-CDG is a multisystemic disease with severe psychomotor and mental retardation. In order to study the pathophysiology of PMM2-CDG in a human cell culture model, we generated induced pluripotent stem cells (iPSCs) from fibroblasts of a PMM2-CDG-patient (PMM2-iPSCs). Expression of pluripotency factors andin vitrodifferentiation into cell types of the three germ layers was unaffected in the analyzed clone PMM2-iPSC-C3 compared with nondiseased human pluripotent stem cells (hPSCs), revealing no broader influence of the PMM2 mutation on pluripotency in cell culture. Analysis of gene expression by deep-sequencing did not show obvious differences in the transcriptome between PMM2-iPSC-C3 and nondiseased hPSCs. By multiplexed capillary gel electrophoresis coupled to laser induced fluorescence detection (xCGE-LIF) we could show that PMM2-iPSC-C3 exhibit the common hPSC N-glycosylation pattern with high-mannose-type N-glycans as the predominant species. However, phosphomannomutase activity of PMM2-iPSC-C3 was 27% compared with control hPSCs and lectin staining revealed an overall reduced protein glycosylation. In addition, quantitative assessment of N-glycosylation by xCGE-LIF showed an up to 40% reduction of high-mannose-type N-glycans in PMM2-iPSC-C3, which was in concordance to the observed reduction of the Glc3Man9GlcNAc2 lipid-linked oligosaccharide compared with control hPSCs. Thus we could model the PMM2-CDG disease phenotype of hypoglycosylation with patient derived iPSCsin vitro Knock-down ofPMM2by shRNA in PMM2-iPSC-C3 led to a residual activity of 5% and to a further reduction of the level of N-glycosylation. Taken together we have developed human stem cell-based cell culture models with stepwise reduced levels of N-glycosylation now enabling to study the role of N-glycosylation during early human development.
| S-EPMC4824866 | biostudies-literature
Project description:BackgroundCongenital disorders of glycosylation (CDG) are a growing group of rare genetic disorders. The most common CDG is phosphomannomutase 2 (PMM2)-CDG which often has a severe clinical presentation and life-limiting consequences. There are no approved therapies for this condition. Also, there are no validated disease-specific quality of life (QoL) scales to assess the heterogeneous clinical burden of PMM2-CDG which presents a challenge for the assessment of the disease severity and the impact of a certain treatment on the course of the disease.Aim and methodsThis study aimed to identify the most impactful clinical signs and symptoms of PMM2-CDG, and specific patient and observer reported outcome measures (PROMs and ObsROMs, respectively) that can adequately measure such impact on patients' QoL. The most burdensome signs and symptoms were identified through input from the CDG community using a survey targeting PMM2-CDG families and experts, followed by family interviews to understand the real burden of these symptoms in daily life. The list of signs and symptoms was then verified and refined by patient representatives and medical experts in the field. Finally, a literature search for PROMs and ObsROMs used in other rare or common diseases with similar signs and symptoms to those of PMM2-CDG was performed.ResultsTwenty-four signs/symptoms were identified as the most impactful throughout PMM2-CDG patients' lifetime. We found 239 articles that included tools to measure those community-selected PMM2-CDG symptoms. Among them, we identified 80 QoL scales that address those signs and symptoms and, subsequently, their psychometric quality was analysed. These scales could be applied directly to the PMM2-CDG population or adapted to create the first PMM2-CDG-specific QoL questionnaire.ConclusionIdentifying the impactful clinical manifestations of PMM2-CDG, along with the collection of PROMs/ObsROMs assessing QoL using a creative and community-centric methodology are the first step towards the development of a new, tailored, and specific PMM2-CDG QoL questionnaire. These findings can be used to fill a gap in PMM2-CDG clinical development. Importantly, this methodology is transferable to other CDG and rare diseases with multiple signs and symptoms.
| S-EPMC9618201 | biostudies-literature