Publications by authors named "Erik A Eklund"

30 Publications

  • Page 1 of 1

Predominant and novel de novo variants in 29 individuals with ALG13 deficiency: Clinical description, biomarker status, biochemical analysis, and treatment suggestions.

J Inherit Metab Dis 2020 11 5;43(6):1333-1348. Epub 2020 Aug 5.

Inova Translational Medicine Institute Division of Medical Genomics Inova Fairfax Hospital Falls Church, Virginia, USA.

Asparagine-linked glycosylation 13 homolog (ALG13) encodes a nonredundant, highly conserved, X-linked uridine diphosphate (UDP)-N-acetylglucosaminyltransferase required for the synthesis of lipid linked oligosaccharide precursor and proper N-linked glycosylation. De novo variants in ALG13 underlie a form of early infantile epileptic encephalopathy known as EIEE36, but given its essential role in glycosylation, it is also considered a congenital disorder of glycosylation (CDG), ALG13-CDG. Twenty-four previously reported ALG13-CDG cases had de novo variants, but surprisingly, unlike most forms of CDG, ALG13-CDG did not show the anticipated glycosylation defects, typically detected by altered transferrin glycosylation. Structural homology modeling of two recurrent de novo variants, p.A81T and p.N107S, suggests both are likely to impact the function of ALG13. Using a corresponding ALG13-deficient yeast strain, we show that expressing yeast ALG13 with either of the highly conserved hotspot variants rescues the observed growth defect, but not its glycosylation abnormality. We present molecular and clinical data on 29 previously unreported individuals with de novo variants in ALG13. This more than doubles the number of known cases. A key finding is that a vast majority of the individuals presents with West syndrome, a feature shared with other CDG types. Among these, the initial epileptic spasms best responded to adrenocorticotropic hormone or prednisolone, while clobazam and felbamate showed promise for continued epilepsy treatment. A ketogenic diet seems to play an important role in the treatment of these individuals.
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http://dx.doi.org/10.1002/jimd.12290DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7722193PMC
November 2020

Early infantile epileptic encephalopathy due to biallelic pathogenic variants in PIGQ: Report of seven new subjects and review of the literature.

J Inherit Metab Dis 2020 11 3;43(6):1321-1332. Epub 2020 Aug 3.

Research Center, CHU Sainte Justine, University of Montreal, Montreal, Quebec, Canada.

We investigated seven children from six families to expand the phenotypic spectrum associated with an early infantile epileptic encephalopathy caused by biallelic pathogenic variants in the phosphatidylinositol glycan anchor biosynthesis class Q (PIGQ) gene. The affected children were all identified by clinical or research exome sequencing. Clinical data, including EEGs and MRIs, was comprehensively reviewed and flow cytometry and transfection experiments were performed to investigate PIGQ function. Pathogenic biallelic PIGQ variants were associated with increased mortality. Epileptic seizures, axial hypotonia, developmental delay and multiple congenital anomalies were consistently observed. Seizure onset occurred between 2.5 months and 7 months of age and varied from treatable seizures to recurrent episodes of status epilepticus. Gastrointestinal issues were common and severe, two affected individuals had midgut volvulus requiring surgical correction. Cardiac anomalies including arrythmias were observed. Flow cytometry using granulocytes and fibroblasts from affected individuals showed reduced expression of glycosylphosphatidylinositol (GPI)-anchored proteins. Transfection of wildtype PIGQ cDNA into patient fibroblasts rescued this phenotype. We expand the phenotypic spectrum of PIGQ-related disease and provide the first functional evidence in human cells of defective GPI-anchoring due to pathogenic variants in PIGQ.
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http://dx.doi.org/10.1002/jimd.12278DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7689772PMC
November 2020

Fasting reveals largely intact systemic lipid mobilization mechanisms in respiratory chain complex III deficient mice.

Biochim Biophys Acta Mol Basis Dis 2020 01 29;1866(1):165573. Epub 2019 Oct 29.

Lund University, Department of Clinical Sciences, Lund, Pediatrics, Lund, Sweden; Folkhälsan Research Center, Helsinki, Finland; Children's Hospital, University of Helsinki, Helsinki. Finland. Electronic address:

Mice homozygous for the human GRACILE syndrome mutation (Bcs1l) display decreased respiratory chain complex III activity, liver dysfunction, hypoglycemia, rapid loss of white adipose tissue and early death. To assess the underlying mechanism of the lipodystrophy in homozygous mice (Bcs1l), these and wild-type control mice were subjected to a short 4-hour fast. The homozygotes had low baseline blood glucose values, but a similar decrease in response to fasting as in wild-type mice, resulting in hypoglycemia in the majority. Despite the already depleted glycogen and increased triacylglycerol content in the mutant livers, the mice responded to fasting by further depletion and increase, respectively. Increased plasma free fatty acids (FAs) upon fasting suggested normal capacity for mobilization of lipids from white adipose tissue into circulation. Strikingly, however, serum glycerol concentration was not increased concomitantly with free FAs, suggesting its rapid uptake into the liver and utilization for fuel or gluconeogenesis in the mutants. The mutant hepatocyte mitochondria were capable of responding to fasting by appropriate morphological changes, as analyzed by electron microscopy, and by increasing respiration. Mutants showed increased hepatic gene expression of major metabolic controllers typically associated with fasting response (Ppargc1a, Fgf21, Cd36) already in the fed state, suggesting a chronic starvation-like metabolic condition. Despite this, the mutant mice responded largely normally to fasting by increasing hepatic respiration and switching to FA utilization, indicating that the mechanisms driving these adaptations are not compromised by the CIII dysfunction. SUMMARY STATEMENT: Bcs1l mutant mice with severe CIII deficiency, energy deprivation and post-weaning lipolysis respond to fasting similarly to wild-type mice, suggesting largely normal systemic lipid mobilization and utilization mechanisms.
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http://dx.doi.org/10.1016/j.bbadis.2019.165573DOI Listing
January 2020

TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.

J Inherit Metab Dis 2019 09 24;42(5):898-908. Epub 2019 Jul 24.

Department of Paediatrics, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.

Exome sequencing has recently identified mutations in the gene TANGO2 (transport and Golgi organization 2) as a cause of developmental delay associated with recurrent crises involving rhabdomyolysis, cardiac arrhythmias, and metabolic derangements. The disease is not well understood, in part as the cellular function and subcellular localization of the TANGO2 protein remain unknown. Furthermore, the clinical syndrome with its heterogeneity of symptoms, signs, and laboratory findings is still being defined. Here, we describe 11 new cases of TANGO2-related disease, confirming and further expanding the previously described clinical phenotype. Patients were homozygous or compound heterozygous for previously described exonic deletions or new frameshift, splice site, and missense mutations. All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia. Of importance, we identify two subjects (aged 12 and 17 years) who have never experienced any overt episode of the catabolism-induced metabolic crises typical for the disease. Mitochondrial complex II activity was mildly reduced in patients investigated in association with crises but normal in other patients. In one deceased patient, post-mortem autopsy revealed heterotopic neurons in the cerebral white matter, indicating a possible role for TANGO2 in neuronal migration. Furthermore, we have addressed the subcellular localization of several alternative isoforms of TANGO2, none of which were mitochondrial but instead appeared to have a primarily cytoplasmic localization. Previously described aberrations in Golgi morphology were not observed in cultured skin fibroblasts.
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http://dx.doi.org/10.1002/jimd.12149DOI Listing
September 2019

DPAGT1 Deficiency with Encephalopathy (DPAGT1-CDG): Clinical and Genetic Description of 11 New Patients.

JIMD Rep 2019 17;44:85-92. Epub 2018 Aug 17.

Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.

Pathogenic mutations in DPAGT1 cause a rare type of a congenital disorder of glycosylation termed DPAGT1-CDG or, alternatively, a milder version with only myasthenia known as DPAGT1-CMS. Fourteen disease-causing mutations in 28 patients from 10 families have previously been reported to cause the systemic form, DPAGT1-CDG. We here report on another 11 patients from 8 families and add 10 new mutations. Most patients have a very severe disease course, where common findings are pronounced muscular hypotonia, intractable epilepsy, global developmental delay/intellectual disability, and early death. We also present data on three affected females that are young adults and have a somewhat milder, stable disease. Our findings expand both the molecular and clinical knowledge of previously published data but also widen the phenotypic spectrum of DPAGT1-CDG.
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http://dx.doi.org/10.1007/8904_2018_128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6323016PMC
August 2018

Three unreported cases of TMEM199-CDG, a rare genetic liver disease with abnormal glycosylation.

Orphanet J Rare Dis 2018 01 10;13(1). Epub 2018 Jan 10.

Division of Pediatrics, Lund University, Lund, Sweden.

Background: TMEM199 deficiency was recently shown in four patients to cause liver disease with steatosis, elevated serum transaminases, cholesterol and alkaline phosphatase and abnormal protein glycosylation. There is no information on the long-term outcome in this disorder.

Results: We here present three novel patients with TMEM199-CDG. All three patients carried the same set of mutations (c.13-14delTT (p.Ser4Serfs*30) and c.92G > C (p.Arg31Pro), despite only two were related (siblings). One mutation (c.92G > C) was described previously whereas the other was deemed pathogenic due to its early frameshift. Western Blot analysis confirmed a reduced level of TMEM199 protein in patient fibroblasts and all patients showed a similar glycosylation defect. The patients presented with a very similar clinical and biochemical phenotype to the initial publication, confirming that TMEM199-CDG is a non-encephalopathic liver disorder. Two of the patients were clinically assessed over two decades without deterioration.

Conclusion: A rising number of disorders affecting Golgi homeostasis have been published over the last few years. A hallmark finding is deficiency in protein glycosylation, both in N- and O-linked types. Most of these disorders have signs of both liver and brain involvement. However, the present and the four previously reported patients do not show encephalopathy but a chronic, non-progressive (over decades) liver disease with hypertransaminasemia and steatosis. This information is crucial for the patient/families and clinician at diagnosis, as it distinguishes it from other Golgi homeostasis disorders, in having a much more favorable course.
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http://dx.doi.org/10.1186/s13023-017-0757-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5763540PMC
January 2018

Respiratory chain complex III deficiency due to mutated BCS1L: a novel phenotype with encephalomyopathy, partially phenocopied in a Bcs1l mutant mouse model.

Orphanet J Rare Dis 2017 04 20;12(1):73. Epub 2017 Apr 20.

Division of Pediatrics, Department of Clinical Sciences, Lund University, 221 84, Lund, Sweden.

Background: Mitochondrial diseases due to defective respiratory chain complex III (CIII) are relatively uncommon. The assembly of the eleven-subunit CIII is completed by the insertion of the Rieske iron-sulfur protein, a process for which BCS1L protein is indispensable. Mutations in the BCS1L gene constitute the most common diagnosed cause of CIII deficiency, and the phenotypic spectrum arising from mutations in this gene is wide.

Results: A case of CIII deficiency was investigated in depth to assess respiratory chain function and assembly, and brain, skeletal muscle and liver histology. Exome sequencing was performed to search for the causative mutation(s). The patient's platelets and muscle mitochondria showed respiration defects and defective assembly of CIII was detected in fibroblast mitochondria. The patient was compound heterozygous for two novel mutations in BCS1L, c.306A > T and c.399delA. In the cerebral cortex a specific pattern of astrogliosis and widespread loss of microglia was observed. Further analysis showed loss of Kupffer cells in the liver. These changes were not found in infants suffering from GRACILE syndrome, the most severe BCS1L-related disorder causing early postnatal mortality, but were partially corroborated in a knock-in mouse model of BCS1L deficiency.

Conclusions: We describe two novel compound heterozygous mutations in BCS1L causing CIII deficiency. The pathogenicity of one of the mutations was unexpected and points to the importance of combining next generation sequencing with a biochemical approach when investigating these patients. We further show novel manifestations in brain, skeletal muscle and liver, including abnormality in specialized resident macrophages (microglia and Kupffer cells). These novel phenotypes forward our understanding of CIII deficiencies caused by BCS1L mutations.
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http://dx.doi.org/10.1186/s13023-017-0624-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5399415PMC
April 2017

Trauma Survival Margin Analysis: A Dissection of Trauma Center Performance through Initial Lactate.

Am Surg 2016 Jul;82(7):649-53

Department of Surgery, University of Virginia, Charlottesville, Virginia, USA.

Measurement of trauma center performance presently relies on W-score calculation and comparison to national data sets. A limitation to this practice is a skewing of the W score, as it determines overall performance of a trauma population that is often heavily weighted by patients of low acuity. The University of Virginia relative mortality metric (RMM) was formulated to provide higher resolution in identifying areas of performance improvement within subpopulations of a trauma center using traditional Trauma Injury Severity Score methodology. Lactic acidosis has been established as a risk factor for mortality in the setting of trauma. This study aims to compare survival margin, defined as the area between actual and predicted mortality curves, in patients with either normal or elevated initial lactate. W score and RMM were calculated and compared in these cohorts. Whereas the W score suggested increased survival within the high initial lactate group, the RMM demonstrated the expected finding of increased survival margin in the normal lactate cohort. The RMM is a potentially valuable tool for trauma centers to monitor and improve performance. In addition, these findings validate the use of lactate as a triage and risk adjustment tool in the trauma setting.
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July 2016

Pulmonary and pleural lymphatic endothelial cells from pediatric, but not adult, patients with Gorham-Stout disease and generalized lymphatic anomaly, show a high proliferation rate.

Orphanet J Rare Dis 2016 05 18;11(1):67. Epub 2016 May 18.

Department of Clinical Sciences, Section for Pediatrics, Lund University, Lund, Sweden.

Background: Gorham-Stout disease (OMIM 123880) and generalized lymphatic anomaly are two rare disorders of lymphendothelial growth in which thoracic involvement with chylothorax is a feared complication. Currently it is believed that both disorders are prenatal malformations that progress slowly after birth. Several pharmaceuticals with antiproliferative properties, including interferon-α-2b, rapamycin and propranolol, have however been shown to affect the disease course in some patients. Deeper knowledge of the growth characteristics of these malformations are therefore needed to guide the clinical approach.

Methods: Lymphatic vessels in lung and pleural tissue from both children and adult patients with generalized lymphatic anomaly or Gorham-Stout disease were studied using an immunohistochemical approach, targeting lymphendothelial markers (D2-40/Prox-1) and a proliferation marker (Ki-67).

Results: We found significant proliferation and growth in these lesions in pediatric patients but not in adults. Furthermore, the data may suggest that the disease process is at least partly reversible.

Conclusions: These malformations of the lymphatic system proliferate at a significant rate long after birth, which could suggest that the clinical approach for children should be different from adults.
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http://dx.doi.org/10.1186/s13023-016-0449-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4870727PMC
May 2016

ALG1-CDG: Clinical and Molecular Characterization of 39 Unreported Patients.

Hum Mutat 2016 07 21;37(7):653-60. Epub 2016 Mar 21.

Center for Metabolic Diseases, University Hospital of Leuven, Leuven, Belgium.

Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over 100 genes leading to impaired protein or lipid glycosylation. ALG1 encodes a β1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol-lipid linked oligosaccharide intermediate required for proper N-linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1-CDG. To date 13 mutations in 18 patients from 14 families have been described with varying degrees of clinical severity. We identified and characterized 39 previously unreported cases of ALG1-CDG from 32 families and add 26 new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1-deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein-linked xeno-tetrasaccharide biomarker, NeuAc-Gal-GlcNAc2 , was seen in all 27 patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.
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http://dx.doi.org/10.1002/humu.22983DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4907823PMC
July 2016

Serum transferrin carrying the xeno-tetrasaccharide NeuAc-Gal-GlcNAc2 is a biomarker of ALG1-CDG.

J Inherit Metab Dis 2016 Jan 3;39(1):107-14. Epub 2015 Sep 3.

Department of Pediatrics, Clinical Sciences, Lund University, BMC D12, 221 84, Lund, Sweden.

ALG1-CDG (formerly CDG-Ik) is a subtype of congenital disorders of glycosylation (CDG) where the genetic defect disrupts the synthesis of the lipid-linked oligosaccharide precursor required for N-glycosylation. The initial step in the investigation for these disorders involves the demonstration of hypoglycosylated serum transferrin (TF). There are no specific biomarkers of this CDG subtype known to date. An LC/MS approach was used to analyze sera from patients with ALG1-CDG, PMM2-CDG, suspected CDG, and individuals with alcohol abuse. We show mass spectrometric data combined with data from enzymatic digestions that suggest the presence of a tetrasaccharide consisting of two N-acetylglucosamines, one galactose, and one sialic acid, appearing on serum TF, is a biomarker of this particular CDG subtype. This is the first time analysis of serum TF can suggest a specific CDG type I subtype and we suggest this tetrasaccharide be used in the clinic to guide the ALG1-CDG diagnostic process.
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http://dx.doi.org/10.1007/s10545-015-9884-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4822552PMC
January 2016

A novel phenotype in N-glycosylation disorders: Gillessen-Kaesbach-Nishimura skeletal dysplasia due to pathogenic variants in ALG9.

Eur J Hum Genet 2016 Feb 13;24(2):198-207. Epub 2015 May 13.

Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.

A rare lethal autosomal recessive syndrome with skeletal dysplasia, polycystic kidneys and multiple malformations was first described by Gillessen-Kaesbach et al and subsequently by Nishimura et al. The skeletal features uniformly comprise a round pelvis, mesomelic shortening of the upper limbs and defective ossification of the cervical spine. We studied two unrelated families including three affected fetuses with Gillessen-Kaesbach-Nishimura syndrome using whole-exome and Sanger sequencing, comparative genome hybridization and homozygosity mapping. All affected patients were shown to have a novel homozygous splice variant NM_024740.2: c.1173+2T>A in the ALG9 gene, encoding alpha-1,2-mannosyltransferase, involved in the formation of the lipid-linked oligosaccharide precursor of N-glycosylation. RNA analysis demonstrated skipping of exon 10, leading to shorter RNA. Mass spectrometric analysis showed an increase in monoglycosylated transferrin as compared with control tissues, confirming that this is a congenital disorder of glycosylation (CDG). Only three liveborn children with ALG9-CDG have been previously reported, all with missense variants. All three suffered from intellectual disability, muscular hypotonia, microcephaly and renal cysts, but none had skeletal dysplasia. Our study shows that some pathogenic variants in ALG9 can present as a lethal skeletal dysplasia with visceral malformations as the most severe phenotype. The skeletal features overlap with that previously reported for ALG3- and ALG12-CDG, suggesting that this subset of glycosylation disorders constitutes a new diagnostic group of skeletal dysplasias.
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http://dx.doi.org/10.1038/ejhg.2015.91DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717212PMC
February 2016

Neurological aspects of human glycosylation disorders.

Annu Rev Neurosci 2015 Jul 2;38:105-25. Epub 2015 Apr 2.

Sanford-Burnham Medical Research Institute, La Jolla, California 92037; email: ,

This review presents principles of glycosylation, describes the relevant glycosylation pathways and their related disorders, and highlights some of the neurological aspects and issues that continue to challenge researchers. More than 100 rare human genetic disorders that result from deficiencies in the different glycosylation pathways are known today. Most of these disorders impact the central and/or peripheral nervous systems. Patients typically have developmental delays/intellectual disabilities, hypotonia, seizures, neuropathy, and metabolic abnormalities in multiple organ systems. Among these disorders there is great clinical diversity because all cell types differentially glycosylate proteins and lipids. The patients have hundreds of misglycosylated products, which afflict a myriad of processes, including cell signaling, cell-cell interaction, and cell migration. This vast complexity in glycan composition and function, along with the limited availability of analytic tools, has impeded the identification of key glycosylated molecules that cause pathologies. To date, few critical target proteins have been pinpointed.
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http://dx.doi.org/10.1146/annurev-neuro-071714-034019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4809143PMC
July 2015

Haploidentical stem cell transplantation in two children with mucopolysaccharidosis VI: clinical and biochemical outcome.

Orphanet J Rare Dis 2013 Sep 5;8:134. Epub 2013 Sep 5.

Department of Pediatrics, Clinical Sciences, Lund University, Lund, Sweden.

Background: Mucopolysaccharidosis VI (MPS VI) is an autosomal recessive progressive multiorgan disorder due to mutation in the gene encoding the enzyme Arylsulfatase B (ARSB). Dysfunctional ARSB causes lysosomal accumulation of glycosaminoglycans (GAG). Currently, enzyme replacement therapy (ERT) is preferred to hematopoietic stem cell transplantation (SCT) due to the treatment-related risks of the latter. However, ERT constitutes an expensive life-long treatment. Increased experience and safety of SCT-procedures in recent years suggest that SCT should be further explored as a treatment option.This is the first report on haploidentical SCT in patients with MPS VI. The primary objective was to assess the treatment safety and clinical and biochemical outcome.

Patients And Methods: Two siblings diagnosed with MPS VI at 10 months of age and at birth with genotype p.C192R, reported as mild to intermediate phenotype, underwent unrelated umbilical cord blood transplantation pre-symptomatic. Due to graft failure, both patients were urgently re-transplantated with haploidentical SCT with the father as donor. Continuous clinical and biochemical status was monitored and concluded 3.8 and 4.6 years after the haploidentical SCT.

Results: Haploidentical SCT resulted in prompt and sustained engraftment. Complete donor chimerism was achieved in both patients, apart from mixed B cells chimerism in patient 2. ARSB activity in leukocytes post transplant increased from 0.0 to 19.0 μkat/kg protein (patient 1) and from 3.6 to 17.9 μkat/kg protein (patient 2) (ref. 17-40). Total urinary GAG normalized in both patients, although patient 2's values slightly exceed normal range since 6 months. However, dermatan sulfaturia was substantially normalized since 16 months and 12 months post-SCT, respectively. Height was -1.85 SD and -1.27 SD at follow-up. Patient 1 had impaired visual acuity and discrete hepatomegaly. Patient 2 had elevated intraocular pressure and X-ray revealed steep acetabular angles and slightly flattened lumbar vertebrae.

Conclusion: This study demonstrates that young children with MPS VI tolerate haploidentical SCT. Normalization of enzyme production and dermatan sulfaturia indicates correction of the inborn error of metabolism and coincide with no obvious symptoms of progressive MPS VI up to 4.6 years post-SCT.
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http://dx.doi.org/10.1186/1750-1172-8-134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3766644PMC
September 2013

Neurology of inherited glycosylation disorders.

Lancet Neurol 2012 May;11(5):453-66

Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.

Congenital disorders of glycosylation comprise most of the nearly 70 genetic disorders known to be caused by impaired synthesis of glycoconjugates. The effects are expressed in most organ systems, and most involve the nervous system. Typical manifestations include structural abnormalities (eg, rapidly progressive cerebellar atrophy), myopathies (including congenital muscular dystrophies and limb-girdle dystrophies), strokes and stroke-like episodes, epileptic seizures, developmental delay, and demyelinating neuropathy. Patients can also have neurological symptoms associated with coagulopathies, immune dysfunction with or without infections, and cardiac, renal, or hepatic failure, which are common features of glycosylation disorders. The diagnosis of congenital disorder of glycosylation should be considered for any patient with multisystem disease and in those with more specific phenotypic features. Measurement of concentrations of selected glycoconjugates can be used to screen for many of these disorders, and molecular diagnosis is becoming more widely available in clinical practice. Disease-modifying treatments are available for only a few disorders, but all affected individuals benefit from early diagnosis and aggressive management.
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http://dx.doi.org/10.1016/S1474-4422(12)70040-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625645PMC
May 2012

A novel treatment approach for paediatric Gorham-Stout syndrome with chylothorax.

Acta Paediatr 2011 Nov 15;100(11):1448-53. Epub 2011 Jun 15.

Department of Clinical Sciences, Section for Paediatrics, The BUT team, Lund University, Sweden.

Aim: To expand the treatment options in paediatric Gorham-Stout syndrome (GSS) when conventional therapy is ineffective.

Method: Two children with biopsy confirmed GSS, a rare disorder with progressive lymphangiomatosis, were treated with a combination of interferon-α-2b, low anticoagulant, low molecular weight heparin, radiotherapy and surgery.

Results: The combined therapy resolved the symptoms in the acute phase, and both patients have since been free of symptoms for >2 years.

Conclusion: The successful addition of a low anticoagulant, low molecular weight heparin (tafoxiparin) to the treatment protocol in two paediatric cases of the GSS may justify the use of this approach in similar cases.
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http://dx.doi.org/10.1111/j.1651-2227.2011.02361.xDOI Listing
November 2011

Reduced production of sulfated glycosaminoglycans occurs in Zambian children with kwashiorkor but not marasmus.

Am J Clin Nutr 2009 Feb 30;89(2):592-600. Epub 2008 Dec 30.

Department of Paediatrics and Child Health, University Teaching Hospital of Lusaka, Lusaka, Zambia.

Background: Kwashiorkor, a form of severe malnutrition with high mortality, is characterized by edema and systemic abnormalities. Although extremely common, its pathophysiology remains poorly understood, and its characteristic physical signs are unexplained.

Objective: Because kwashiorkor can develop in protein-losing enteropathy, which is caused by a loss of enterocyte heparan sulfate proteoglycan (HSPG), and previous observations suggest abnormal sulfated glycosaminoglycan (GAG) metabolism, we examined whether intestinal GAG and HSPG are abnormal in children with kwashiorkor.

Design: Duodenal biopsy samples collected from Zambian children with marasmus (n = 18), marasmic kwashiorkor (n = 8), and kwashiorkor (n = 15) were examined for expression of HSPG, GAGs, and immunologic markers and compared against reference samples from healthy UK control children. GAG and HSPG expression density and inflammatory cell populations were quantitated by computerized analysis.

Results: The kwashiorkor group was less wasted and had a lower HIV incidence than did the other groups. All duodenal biopsy samples showed inflammation compared with the histologically uninflamed control samples. Biopsy samples from marasmic children had greater inflammation and greater CD3+ and HLA-DR (human leukocyte antigen DR)-positive cell densities than did samples from children with kwashiorkor. Expression of both HSPG and GAGs was similar between marasmic and well-nourished UK children but was markedly lower in children with kwashiorkor in both the epithelium and lamina propria. Although underglycosylated and undersulfated, epithelial syndecan-1 protein was normally expressed in kwashiorkor, which confirmed that abnormalities arise after core protein synthesis.

Conclusions: Intestinal HSPG loss occurs in kwashiorkor, which may precipitate protein-losing enteropathy to cause edema. If occurring systemically, impaired HSPG expression could cause several previously unexplained features of kwashiorkor. We speculate that a genetic predisposition to reduced HSPG biosynthesis may offer a contrasting selective advantage, by both diminishing protein catabolism during transient undernutrition and protecting against specific infectious diseases.
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http://dx.doi.org/10.3945/ajcn.2008.27092DOI Listing
February 2009

CDG-Id in two siblings with partially different phenotypes.

Am J Med Genet A 2007 Jul;143A(13):1414-20

Glycobiology and Carbohydrate Chemistry Program, The Burnham Institute for Medical Research, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA.

We present two sibs with congenital disorder of glycosylation (CDG) type Id. Each shows severe global delay, failure to thrive, seizures, microcephaly, axial hypotonia, and disaccharidase deficiency. One sib has more severe digestive issues, while the other is more neurologically impaired. Each is compound heterozygous for a novel point mutation and an already known mutation in the ALG3 gene that leads to the synthesis of a severely truncated oligosaccharide precursor for N-glycans. The defect is corrected by introduction of a normal ALG3 cDNA. CDG should be ruled out in all patients with severe seizures and failure to thrive. (c) 2007 Wiley-Liss, Inc.
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http://dx.doi.org/10.1002/ajmg.a.31796DOI Listing
July 2007

COG8 deficiency causes new congenital disorder of glycosylation type IIh.

Hum Mol Genet 2007 Apr 1;16(7):731-41. Epub 2007 Mar 1.

Burnham Institute for Medical Research, La Jolla, CA 92037, USA.

We describe a new Type II congenital disorder of glycosylation (CDG-II) caused by mutations in the conserved oligomeric Golgi (COG) complex gene, COG8. The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products. Analysis of serum transferrin and total serum N-glycans showed normal addition of one sialic acid, but severe deficiency in subsequent sialylation of mostly normal N-glycans. Patient fibroblasts were deficient in sialylation of both N- and O-glycans, and also showed slower brefeldin A (BFA)-induced disruption of the Golgi matrix, reminiscent of COG7-deficient cells. Patient fibroblasts completely lacked COG8 protein and had reduced levels and/or mislocalization of several other COG proteins. The patient had two COG8 mutations which severely truncated the protein and destabilized the COG complex. The first, IVS3 + 1G > A, altered the conserved splicing site of intron 3, and the second deleted two nucleotides (1687-1688 del TT) in exon 5, truncating the last 47 amino acids. Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption. We propose to call this new disorder CDG-IIh or CDG-II/COG8.
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http://dx.doi.org/10.1093/hmg/ddm028DOI Listing
April 2007

Essentials of glycosylation.

Semin Pediatr Neurol 2005 Sep;12(3):134-43

The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.

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http://dx.doi.org/10.1016/j.spen.2005.11.001DOI Listing
September 2005

The congenital disorders of glycosylation: a multifaceted group of syndromes.

NeuroRx 2006 Apr;3(2):254-63

Department of Cell and Molecular Biology, Lund University, Lund, Sweden.

The congenital disorders of glycosylation (CDG) are a rapidly expanding group of metabolic syndromes with a wide symptomatology and severity. They all stem from deficient N-glycosylation of proteins. To date the group contains 18 different subtypes: 12 of Type I (disrupted synthesis of the lipid-linked oligosaccharide precursor) and 6 of Type II (malfunctioning trimming/processing of the protein-bound oligosaccharide). Main features of CDG involve psychomotor retardation; ataxia; seizures; retinopathy; liver fibrosis; coagulopathies; failure to thrive; dysmorphic features, including inverted nipples and subcutaneous fat pads; and strabismus. No treatment currently is available for the vast majority of these syndromes (CDG-Ib and CDG-IIc are exceptions), even though attempts to synthesize drugs for the most common subtype, CDG-Ia, have been made. In this review we will discuss the individual syndromes, with focus on their neuronal involvement, available and possible treatments, and future directions.
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http://dx.doi.org/10.1016/j.nurx.2006.01.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3593443PMC
April 2006

Clinical and biochemical characterization of a patient with congenital disorder of glycosylation (CDG) IIx.

J Pediatr 2005 Dec;147(6):851-3

Burnham Institute, Program for Glycobiology and Carbohydrate Chemistry, La Jolla, Calif 92037, USA.

We describe a case of congenital disorder of glycosylation with chronic diarrhea, progressive liver cirrhosis, and recurrent infections. Transferrin analysis showed only hyposialylation, but analysis of total serum N-glycans indicated loss of additional sugars, arguing that the latter generates a more informative picture to search for the primary defect.
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http://dx.doi.org/10.1016/j.jpeds.2005.07.038DOI Listing
December 2005

Congenital disorder of glycosylation (CDG)-Ih patient with a severe hepato-intestinal phenotype and evolving central nervous system pathology.

J Pediatr 2005 Dec;147(6):847-50

Glycobiology and Carbohydrate Chemistry Program, The Burnham Institute, La Jolla, California 92037, USA.

We present the clinical, molecular, and biochemical diagnosis of a patient with congenital disorder of glycosylation (CDG)-Ih. We report significant brain dysfunction in this multisystem disease, further expanding its complex clinical spectrum.
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http://dx.doi.org/10.1016/j.jpeds.2005.07.042DOI Listing
December 2005

Ablation of mouse phosphomannose isomerase (Mpi) causes mannose 6-phosphate accumulation, toxicity, and embryonic lethality.

J Biol Chem 2006 Mar 8;281(9):5916-27. Epub 2005 Dec 8.

Glycobiology and Carbohydrate Chemistry Program, Burnham Institute for Medical Research, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA.

MPI encodes phosphomannose isomerase, which interconverts fructose 6-phosphate and mannose 6-phosphate (Man-6-P), used for glycoconjugate biosynthesis. MPI mutations in humans impair protein glycosylation causing congenital disorder of glycosylation Ib (CDG-Ib), but oral mannose supplements normalize glycosylation. To establish a mannose-responsive mouse model for CDG-Ib, we ablated Mpi and provided dams with mannose to rescue the anticipated defective glycosylation. Surprisingly, although glycosylation was normal, Mpi(-/-) embryos died around E11.5. Mannose supplementation even hastened their death, suggesting that man-nose was toxic. Mpi(-/-) embryos showed growth retardation and placental hyperplasia. More than 90% of Mpi(-/-) embryos failed to form yolk sac vasculature, and 35% failed chorioallantoic fusion. We generated primary embryonic fibroblasts to investigate the mechanisms leading to embryonic lethality and found that mannose caused a concentration- and time-dependent accumulation of Man 6-P in Mpi(-/-) fibroblasts. In parallel, ATP decreased by more than 70% after 24 h compared with Mpi(+/+) controls. In cell lysates, Man-6-P inhibited hexokinase (70%), phosphoglucose isomerase (65%), and glucose-6-phosphate dehydrogenase (85%), but not phosphofructokinase. Incubating intact Mpi(-/-) fibroblasts with 2-[(3)H]deoxyglucose confirmed mannose-dependent hexokinase inhibition. Our results in vitro suggest that mannose toxicity in Mpi(-/-) embryos is caused by Man-6-P accumulation, which inhibits glucose metabolism and depletes intracellular ATP. This was confirmed in E10.5 Mpi(-/-) embryos where Man-6-P increased more than 10 times, and ATP decreased by 50% compared with Mpi(+/+) littermates. Because Mpi ablation is embryonic lethal, a murine CDG-Ib model will require hypomorphic Mpi alleles.
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http://dx.doi.org/10.1074/jbc.M511982200DOI Listing
March 2006

Congenital disorder of glycosylation Ic due to a de novo deletion and an hALG-6 mutation.

Biochem Biophys Res Commun 2006 Jan;339(3):755-60

Glycobiology and Carbohydrate Chemistry Program, The Burnham Institute, 10901 N Torrey Pines Road, La Jolla, CA 92037, USA.

We describe a new cause of congenital disorder of glycosylation-Ic (CDG-Ic) in a young girl with a rather mild CDG phenotype. Her cells accumulated lipid-linked oligosaccharides lacking three glucose residues, and sequencing of the ALG6 gene showed what initially appeared to be a homozygous novel point mutation (338G>A). However, haplotype analysis showed that the patient does not carry any paternal DNA markers extending 33kb in the telomeric direction from the ALG6 region, and microsatellite analysis extended the abnormal region to at least 2.5Mb. We used high-resolution karyotyping to confirm a deletion (10-12Mb) [del(1)(p31.2p32.3)] and found no structural abnormalities in the father, suggesting a de novo event. Our findings extend the causes of CDG to larger DNA deletions and identify the first Japanese CDG-Ic mutation.
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http://dx.doi.org/10.1016/j.bbrc.2005.11.073DOI Listing
January 2006

Hydrophobic Man-1-P derivatives correct abnormal glycosylation in Type I congenital disorder of glycosylation fibroblasts.

Glycobiology 2005 Nov 3;15(11):1084-93. Epub 2005 Aug 3.

The Burnham Institute, La Jolla, CA 92037, USA.

Patients with Type I congenital disorders of glycosylation (CDG-I) make incomplete lipid-linked oligosaccharides (LLO). These glycans are poorly transferred to proteins resulting in unoccupied glycosylation sequons. Mutations in phosphomannomutase (PMM2) cause CDG-Ia by reducing the activity of PMM, which converts mannose (Man)-6-P to Man-1-P before formation of GDP-Man. These patients have reduced Man-1-P and GDP-Man. To replenish intracellular Man-1-P pools in CDG-Ia cells, we synthesized two hydrophobic, membrane permeable acylated versions of Man-1-P and determined their ability to normalize LLO size and N-glycosylation in CDG-Ia fibroblasts. Both compounds, compound I (diacetoxymethyl 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl phosphate) (C-I) and compound II (diacetoxymethyl 2,3,4,6-tetra-O-ethyloxycarbonyl-alpha-D-mannopyranosyl phosphate) (C-II), contain two acetoxymethyl (CH2OAc) groups O-linked to phosphorous. C-I contains acetyl esters and C-II contains ethylcarbonate (CO2Et) esters on the Man residue. Both C-I and C-II normalized truncated LLO, but C-II was about 2-fold more efficient than C-I. C-II replenished the GDP-Man pool in CDG-Ia cells and was more efficiently incorporated into glycoproteins than exogenous Man at low concentrations (25-75 mM). In a glycosylation assay of DNaseI in CDG-Ia cells, C-II restored glycosylation to control cell levels. C-II also corrected impaired LLO biosynthesis in cells from a Dolichol (Dol)-P-Man deficient patient (CDG-Ie) and partially corrected LLO in cells from an ALG12 mannosyltransferase-deficient patient (CDG-Ig), whereas cells from an ALG3-deficient patient (CDG-Id) and from an MPDU1-deficient patient (CDG-If) were not corrected. These results validate the general concept of using pro-Man-1-P substrates as potential therapeutics for CDG-I patients.
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http://dx.doi.org/10.1093/glycob/cwj006DOI Listing
November 2005

Clinical and molecular characterization of the first adult congenital disorder of glycosylation (CDG) type Ic patient.

Am J Med Genet A 2005 Aug;137(1):22-6

The Burnham Institute, La Jolla, CA 92037, USA.

Congenital disorder of glycosylation (CDG) type Ic, the second largest subtype of CDG, is caused by mutations in human ALG6 (hALG6). This gene encodes the alpha1,3-glucosyltransferase that catalyzes transfer of the first glucose residue to the lipid-linked oligosaccharide precursor for N-linked glycosylation. In this report, we describe the first adult patient diagnosed with CDG-Ic, carrying two previously unknown mutations. The first is a three base deletion (897-899delAAT) leading to the loss of I299, the second is an intronic mutation (IVS7 + 2T > G) that causes aberrant splicing. Wildtype hALG6, delivered by a lentiviral vector into patient's fibroblasts, clearly improves the biochemical phenotype, which confirms that the mutations are disease-causing. Striking clinical findings include limb deficiencies in the fingers, resembling brachydactyly type B, a deep vein thrombosis, pseudotumor cerebri, and endocrine disturbances with pronounced hyperandrogenism and virilization. However, even in adulthood, this patient shows normal magnetic resonance imaging of the brain.
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http://dx.doi.org/10.1002/ajmg.a.30831DOI Listing
August 2005

Congenital disorder of glycosylation id presenting with hyperinsulinemic hypoglycemia and islet cell hyperplasia.

J Clin Endocrinol Metab 2005 Jul 19;90(7):4371-5. Epub 2005 Apr 19.

The Burnham Institute, Program for Glycobiology and Carbohydrate Chemistry, 10901 North Torrey Pines Road, La Jolla, California 92037, USA.

Context: Inborn errors in protein glycosylation, such as the congenital disorders of glycosylation (CDGs), generate multifaceted syndromes that impair many organ systems. We here report the diagnosis of the third known patient with CDG-Id.

Results: The patient's phenotype was extremely severe, and she succumbed at 19 d of age. Leading features included hyperinsulinemic hypoglycemia, and autopsy revealed islet cell hyperplasia with increased beta-cell mass. Other features were a Dandy-Walker malformation, facial dysmorphisms, and profound hypotonia. The patient carried a novel homozygous point mutation (512G>A) in the hALG3 gene, which encodes a mannosyltransferase. Lentiviral complementation with wild-type hALG3 corrects the biochemical defect in the patient's fibroblasts.

Conclusions: Our findings underscore the importance of proper glycosylation in several major organ systems and emphasize that CDG should be ruled out in patients with persistent hyperinsulinemic hypoglycemia of unknown etiology.
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http://dx.doi.org/10.1210/jc.2005-0250DOI Listing
July 2005

Molecular and clinical description of the first US patients with congenital disorder of glycosylation Ig.

Mol Genet Metab 2005 Jan 11;84(1):25-31. Epub 2004 Nov 11.

The Burnham Institute, Glycobiology and Carbohydrate Chemistry Program, La Jolla, CA 92037, USA.

In this report we describe the first two US patients with congenital disorder of glycosylation type Ig (CDG-Ig). Both patients presented with symptoms indicating CDG, including developmental delay, hypotonia and failure to thrive, and tested positive for deficient glycosylation of transferrin. Labeling of the patients' lipid-linked oligosaccharides suggested mutations in the hALG12 gene, encoding a mannosyltransferase. Both patients were shown to carry previously unpublished hALG12-mutations. Patient 1 has one allele with a deletion of G29, resulting in a premature stop codon, and another allele with an 824G>A mutation yielding an S275N amino acid change. Patient 2 carries two heterozygous mutations (688T>G and 931C>T), resulting in two amino acid exchanges, Y230D and R311C. An adenoviral vector expressing wild type hALG12 corrects the abnormal lipid-linked oligosaccharide pattern of the patients' cells. In addition to common CDG symptoms, these patients also presented with low IgG and genital hypoplasia, symptoms previously described in CDG-Ig patients. We therefore conclude that a combination of developmental delay, low IgG, and genital hypoplasia should prompt CDG testing.
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http://dx.doi.org/10.1016/j.ymgme.2004.09.014DOI Listing
January 2005

Heparan sulfate depletion amplifies TNF-alpha-induced protein leakage in an in vitro model of protein-losing enteropathy.

Am J Physiol Gastrointest Liver Physiol 2005 May 16;288(5):G1015-23. Epub 2004 Dec 16.

The Burnham Institute, Glycobiology and Carbohydrate Chemistry Program, 10901 N. Torrey Pines Rd., La Jolla, California 92037, USA.

Protein-losing enteropathy (PLE), the excessive loss of plasma proteins through the intestine, often correlates with the episodic loss of heparan sulfate (HS) proteoglycans (HSPG) from the basolateral surface of intestinal epithelial cells. PLE onset is often associated with a proinflammatory state. We investigated whether loss of HS or treatment with the proinflammatory cytokine TNF-alpha directly causes protein leakage and whether a combination of both exacerbates this process. We established the first in vitro model of PLE and measured the flux of albumin/FITC through a monolayer of intestinal HT29 or Caco-2 cells grown on transwells and determined the integrity by transepithelial electrical resistance (TER). Loss of HS from the basolateral surface, either by heparanase digestion or by inhibition of HS synthesis, increased albumin flux 1.58 +/- 0.09-fold and reduced TER by 23.4 +/- 6.5%. TNF-alpha treatment increased albumin flux 4.04 +/- 0.03-fold and reduced TER by 75.7 +/- 4.7% but only slightly decreased HS content. The combined effects of HS loss and TNF-alpha treatment were not only additive, but synergistic, with a 7.00 +/- 0.11-fold increase in albumin flux and a 83.9 +/- 8.1% reduction of TER. Coincubation of TNF-alpha with soluble HS or heparin abolished these synergistic effects. Loss of basolateral HS directly causes protein leakage and amplifies the effects of the proinflammatory cytokine TNF-alpha. Our findings imply that loss of HSPGs renders patients more susceptible to PLE and offer a potential explanation for the favorable response some PLE patients have to heparin therapy.
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http://dx.doi.org/10.1152/ajpgi.00461.2004DOI Listing
May 2005