Publications by authors named "Kimiyo Raymond"

76 Publications

Sorbitol Is a Severity Biomarker for PMM2-CDG with Therapeutic Implications.

Ann Neurol 2021 Oct 15. Epub 2021 Oct 15.

Department of Clinical Genomics, Mayo Clinic, Rochester, MN.

Objective: Epalrestat, an aldose reductase inhibitor increases phosphomannomutase (PMM) enzyme activity in a PMM2-congenital disorders of glycosylation (CDG) worm model. Epalrestat also decreases sorbitol level in diabetic neuropathy. We evaluated the genetic, biochemical, and clinical characteristics, including the Nijmegen Progression CDG Rating Scale (NPCRS), urine polyol levels and fibroblast glycoproteomics in patients with PMM2-CDG.

Methods: We performed PMM enzyme measurements, multiplexed proteomics, and glycoproteomics in PMM2-deficient fibroblasts before and after epalrestat treatment. Safety and efficacy of 0.8 mg/kg/day oral epalrestat were studied in a child with PMM2-CDG for 12 months.

Results: PMM enzyme activity increased post-epalrestat treatment. Compared with controls, 24% of glycopeptides had reduced abundance in PMM2-deficient fibroblasts, 46% of which improved upon treatment. Total protein N-glycosylation improved upon epalrestat treatment bringing overall glycosylation toward the control fibroblasts' glycosylation profile. Sorbitol levels were increased in the urine of 74% of patients with PMM2-CDG and correlated with the presence of peripheral neuropathy, and CDG severity rating scale. In the child with PMM2-CDG on epalrestat treatment, ataxia scores improved together with significant growth improvement. Urinary sorbitol levels nearly normalized in 3 months and blood transferrin glycosylation normalized in 6 months.

Interpretation: Epalrestat improved PMM enzyme activity, N-glycosylation, and glycosylation biomarkers in vitro. Leveraging cellular glycoproteome assessment, we provided a systems-level view of treatment efficacy and discovered potential novel biosignatures of therapy response. Epalrestat was well-tolerated and led to significant clinical improvements in the first pediatric patient with PMM2-CDG treated with epalrestat. We also propose urinary sorbitol as a novel biomarker for disease severity and treatment response in future clinical trials in PMM2-CDG. ANN NEUROL 2021.
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http://dx.doi.org/10.1002/ana.26245DOI Listing
October 2021

ALG1-CDG Caused by Non-functional Alternative Splicing Involving a Novel Pathogenic Complex Allele.

Front Genet 2021 9;12:744884. Epub 2021 Sep 9.

Laboratorio de Glicobiología Humana y Diagnóstico Molecular, Centro de Investigación en Dinámica Celular, Instituto de Investigación en Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico.

This study reports on a Mexican mestizo patient with a multi-systemic syndrome including neurological involvement and a type I serum transferrin profile. Clinical exome sequencing revealed complex alleles in , the encoding gene for the chitobiosyldiphosphodolichol beta-mannosyltransferase that participates in the formation of the dolichol-pyrophosphate-GlcNAc2Man5, a lipid-linked glycan intermediate during -glycan synthesis. The identified complex alleles were NM_019109.5(ALG1): c.[208 + 16_208 + 19dup; 208 + 25G > T] and NM_019109.5(ALG1): c.[208 + 16_208 + 19dup; 1312C > T]. Although both alleles carried the benign variant c.208 + 16_208 + 19dup, one allele carried a known pathogenic variant (c.1312C > T), while the other carried a new uncharacterized variant (c.208 + 25G > T) causing non-functional alternative splicing that, in conjunction with the benign variant, defines the pathogenic protein effect (p.N70S_S71ins9). The presence in the patient's serum of the pathognomonic N-linked mannose-deprived tetrasaccharide marker for ALG1-CDG (Neu5Acα2,6Galβ1,4-GlcNAcβ1,4GlcNAc) further supported this diagnosis. This is the first report of an ALG1-CDG patient from Latin America.
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http://dx.doi.org/10.3389/fgene.2021.744884DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8458739PMC
September 2021

The low excretor phenotype of glutaric acidemia type I is a source of false negative newborn screening results and challenging diagnoses.

JIMD Rep 2021 Jul 5;60(1):67-74. Epub 2021 Apr 5.

Biochemical Genetics Laboratory, Mayo Clinic Rochester Minnesota USA.

Background: Glutaric acidemia type I (GA1) is an organic acidemia that is often unrecognized in the newborn period until patients suffer an acute encephalopathic crisis, which can be mistaken for nonaccidental trauma. Presymptomatic identification of GA1 patients is possible by newborn screening (NBS). However, the biochemical "low-excretor" (LE) phenotype with nearly normal levels of disease metabolites can be overlooked, which may result in untreated disease and irreversible neurological sequelae. The LE phenotype is also a potential source of false negative (FN) NBS results that merits further investigation.

Methods: Samples from six LE GA1 patients were analyzed by biochemical and molecular methods and newborn screen outcomes were retrospectively investigated.

Results: Five LE GA1 patients were identified that had normal NBS results and three of these presented clinically with GA1 symptoms. One additional symptomatic patient was identified who did not undergo screening. Semiquantitative urine organic acid analysis was consistent with a GA1 diagnosis in two (33%) of the six patients, while plasma glutarylcarnitine was elevated in four (67%) of the six and urine glutarylcarnitine was elevated in four (80%) of five patients. Five variants were identified in these patients; three of which have not been previously linked to the biochemical LE phenotype.

Conclusions: The data presented here raise awareness of potential FN NBS results for LE GA1 patients. The LE phenotype is not protective against adverse clinical outcomes, and the possibility of FN NBS results calls for high vigilance amongst clinicians, even in the setting of a normal NBS result.
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http://dx.doi.org/10.1002/jmd2.12217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260482PMC
July 2021

A new D-galactose treatment monitoring index for PGM1-CDG.

J Inherit Metab Dis 2021 09 22;44(5):1263-1271. Epub 2021 Jun 22.

Department of Laboratory Medicine and Pathology, Biochemical Genetics Laboratory, Mayo Clinic, Rochester, Minnesota, USA.

Phosphoglucomutase 1 (PGM1) catalyzes the interconversion of glucose-6-phosphate to glucose-1-phosphate and is a key enzyme of glycolysis, glycogenesis, and glycogenolysis. PGM1 deficiency (OMIM: 614921) was initially defined as a glycogen storage disorder (type XIV), and later re-classified as a PGM1-congenital disorder of glycosylation (PGM1-CDG). Serum transferrin (Tf) glycan isoform analysis by liquid chromatography-mass spectrometry (LC-MS) is used as a primary diagnostic screen tool, and reveals a very unique CDG profile described as a mixture of CDG-type I and CDG-type II patterns. Oral d-galactose supplementation shows significant clinical and metabolic improvements, which are indicated by the Tf glycan isoform normalization over time in patients with PGM1-CDG. Thus, there is a need for biomarkers to guide d-galactose dosage in patients in order to maintain effective and safe drug levels. Here, we present a simplified algorithm called PGM1-CDG Treatment Monitoring Index (PGM1-TMI) for assessing the response of PGM1-CDG patients to d-galactose supplementation. For our single-center cohort of 16 PGM1-CDG patients, the Tf glycan profile analysis provided the biochemical diagnosis in all of them. In addition, the PGM1-TMI was reduced in PGM1-CDG patients under d-galactose supplementation as compared with their corresponding values before treatment, indicating that glycosylation proceeds towards normalization. PGM1-TMI allows tracking Tf glycan isoform normalization over time when the patients are on d-galactose supplementation.
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http://dx.doi.org/10.1002/jimd.12406DOI Listing
September 2021

Familial variability of cerebrotendinous xanthomatosis lacking typical biochemical findings.

JIMD Rep 2021 May 8;59(1):3-9. Epub 2021 Jan 8.

Department of Clinical Genomics and Neurology Mayo Clinic Scottsdale Arizona USA.

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder of bile acid synthesis caused by pathogenic variants in the gene encoding the mitochondrial enzyme sterol 27-hydroxylase. Patients with CTX can present with a wide range of symptoms, but most often have evidence of tendon xanthomas along with possible cataracts, atherosclerosis, or neurological dysfunction. Regardless of clinical phenotype, CTX patients typically exhibit levels of cholestanol and bile acid precursors in the circulation that are many fold increased over normal control concentrations. Here we report two siblings, one with the rare spinal xanthomatosis phenotype and the other with a very mild form of CTX manifesting as minor tendon xanthomatosis and gastrointestinal complaints who both carry compound heterozygous variants in : NM_000784.3: c.410G > A (p.Arg137Gln) and c.1183C > T (p.Arg395Cys). However, biochemical analysis of these patients revealed normal levels of serum cholestanol and relatively mild elevations of the bile acid precursors 7α-hydroxy-4-cholesten-3-one and 7α,12α-dihydroxy-4-cholesten-3-one. The atypical biochemical presentation of these cases represents a diagnostic challenge for a disorder once thought to have a sensitive biomarker in cholestanol and highlight the need for thorough investigation of patients with symptomatology consistent with CTX that includes bile acid precursor biochemical testing and molecular analysis.
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http://dx.doi.org/10.1002/jmd2.12197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8100391PMC
May 2021

A mutation in SLC37A4 causes a dominantly inherited congenital disorder of glycosylation characterized by liver dysfunction.

Am J Hum Genet 2021 06 7;108(6):1040-1052. Epub 2021 May 7.

Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.

SLC37A4 encodes an endoplasmic reticulum (ER)-localized multitransmembrane protein required for transporting glucose-6-phosphate (Glc-6P) into the ER. Once transported into the ER, Glc-6P is subsequently hydrolyzed by tissue-specific phosphatases to glucose and inorganic phosphate during times of glucose depletion. Pathogenic variants in SLC37A4 cause an established recessive disorder known as glycogen storage disorder 1b characterized by liver and kidney dysfunction with neutropenia. We report seven individuals who presented with liver dysfunction multifactorial coagulation deficiency and cardiac issues and were heterozygous for the same variant, c.1267C>T (p.Arg423), in SLC37A4; the affected individuals were from four unrelated families. Serum samples from affected individuals showed profound accumulation of both high mannose and hybrid type N-glycans, while N-glycans in fibroblasts and undifferentiated iPSC were normal. Due to the liver-specific nature of this disorder, we generated a CRISPR base-edited hepatoma cell line harboring the c.1267C>T (p.Arg423) variant. These cells replicated the secreted abnormalities seen in serum N-glycosylation, and a portion of the mutant protein appears to relocate to a distinct, non-Golgi compartment, possibly ER exit sites. These cells also show a gene dosage-dependent alteration in the Golgi morphology and reduced intraluminal pH that may account for the altered glycosylation. In summary, we identify a recurrent mutation in SLC37A4 that causes a dominantly inherited congenital disorder of glycosylation characterized by coagulopathy and liver dysfunction with abnormal serum N-glycans.
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http://dx.doi.org/10.1016/j.ajhg.2021.04.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8206404PMC
June 2021

ALG13 X-linked intellectual disability: New variants, glycosylation analysis, and expanded phenotypes.

J Inherit Metab Dis 2021 07 26;44(4):1001-1012. Epub 2021 Mar 26.

Department of Biochemistry, St. George's University School of Medicine, St. George's, Grenada.

Pathogenic variants in ALG13 (ALG13 UDP-N-acetylglucosaminyltransferase subunit) cause an X-linked congenital disorder of glycosylation (ALG13-CDG) where individuals have variable clinical phenotypes that include developmental delay, intellectual disability, infantile spasms, and epileptic encephalopathy. Girls with a recurrent de novo c.3013C>T; p.(Asn107Ser) variant have normal transferrin glycosylation. Using a highly sensitive, semi-quantitative flow injection-electrospray ionization-quadrupole time-of-flight mass spectrometry (ESI-QTOF/MS) N-glycan assay, we report subtle abnormalities in N-glycans that normally account for <0.3% of the total plasma glycans that may increase up to 0.5% in females with the p.(Asn107Ser) variant. Among our 11 unrelated ALG13-CDG individuals, one male had abnormal serum transferrin glycosylation. We describe seven previously unreported subjects including three novel variants in ALG13 and report a milder neurodevelopmental course. We also summarize the molecular, biochemical, and clinical data for the 53 previously reported ALG13-CDG individuals. We provide evidence that ALG13 pathogenic variants may mildly alter N-linked protein glycosylation in both female and male subjects, but the underlying mechanism remains unclear.
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http://dx.doi.org/10.1002/jimd.12378DOI Listing
July 2021

NGLY1 Deficiency: A Rare Newly Described Condition with a Typical Presentation.

Life (Basel) 2021 Feb 27;11(3). Epub 2021 Feb 27.

Department of Metabolic Biochemistry, Normandie University, UNIROUEN, CHU Rouen, INSERM U1245, 76000 Rouen, France.

NGLY1 deficiency is the first recognized autosomal recessive disorder of N-linked deglycosylation (NGLY1-CDDG). This severe multisystemic disease is still poorly known and, to date, most cases have been diagnosed through whole exome or genome sequencing. The aim of this study is to provide the clinical, biochemical and molecular description of the first NGLY1-CDDG patient from France along with a literature review. The index case presented with developmental delay, acquired microcephaly, hypotonia, alacrimia, feeding difficulty, and dysmorphic features. Given the complex clinical picture and the multisystemic involvement, a trio-based exome sequencing was conducted and urine oligosaccharides were assessed using mass spectrometry. The exome sequencing revealed a novel variant in the gene in a homozygous state. NGLY1 deficiency was confirmed by the identification of the Neu5Ac1Hex1GlcNAc1-Asn oligosaccharide in the urine of the patient. Literature review revealed the association of some key clinical and biological features such as global developmental delay-hypertransaminasemia, movement disorders, feeding difficulties and alacrima/hypolacrima.
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http://dx.doi.org/10.3390/life11030187DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7996810PMC
February 2021

Spontaneous improvement of carbohydrate-deficient transferrin in PMM2-CDG without mannose observed in CDG natural history study.

Orphanet J Rare Dis 2021 02 25;16(1):102. Epub 2021 Feb 25.

Department of Clinical Genomics, Mayo Clinic, 200 First Street, SW, Rochester, MN, 55905, USA.

A recent report on long-term dietary mannose supplementation in phosphomannomutase 2 deficiency (PMM2-CDG) claimed improved glycosylation and called for double-blind randomized study of the dietary supplement in PMM2-CDG patients. A lack of efficacy of short-term mannose supplementation in multiple prior reports challenge this study's conclusions. Additionally, some CDG types have previously been reported to demonstrate spontaneous improvement in glycosylated biomarkers, including transferrin. We have likewise observed improvements in transferrin glycosylation without mannose supplementation. This observation questions the reliability of transferrin as a therapeutic outcome measure in clinical trials for PMM2-CDG. We are concerned that renewed focus on mannose therapy in PMM2-CDG will detract from clinical trials of more promising therapies. Approaches to increase efficiency of clinical trials and ultimately improve patients' lives requires prospective natural history studies and identification of reliable biomarkers linked to clinical outcomes in CDG. Collaborations with patients and families are essential to identifying meaningful study outcomes.
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http://dx.doi.org/10.1186/s13023-021-01751-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7908710PMC
February 2021

Expanding the phenotype, genotype and biochemical knowledge of ALG3-CDG.

J Inherit Metab Dis 2021 07 1;44(4):987-1000. Epub 2021 Mar 1.

Division of Genetic Medicine, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington, USA.

Congenital disorders of glycosylation (CDGs) are a continuously expanding group of monogenic disorders of glycoprotein and glycolipid biosynthesis that cause multisystem diseases. Individuals with ALG3-CDG frequently exhibit severe neurological involvement (epilepsy, microcephaly, and hypotonia), ocular anomalies, dysmorphic features, skeletal anomalies, and feeding difficulties. We present 10 unreported individuals diagnosed with ALG3-CDG based on molecular and biochemical testing with 11 novel variants in ALG3, bringing the total to 40 reported individuals. In addition to the typical multisystem disease seen in ALG3-CDG, we expand the symptomatology of ALG3-CDG to now include endocrine abnormalities, neural tube defects, mild aortic root dilatation, immunodeficiency, and renal anomalies. N-glycan analyses of these individuals showed combined deficiencies of hybrid glycans and glycan extension beyond Man GlcNAc consistent with their truncated lipid-linked precursor oligosaccharides. This spectrum of N-glycan changes is unique to ALG3-CDG. These expanded features of ALG3-CDG facilitate diagnosis and suggest that optimal management should include baseline endocrine, renal, cardiac, and immunological evaluation at the time of diagnosis and with ongoing monitoring.
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http://dx.doi.org/10.1002/jimd.12367DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8282734PMC
July 2021

Liver manifestations in a cohort of 39 patients with congenital disorders of glycosylation: pin-pointing the characteristics of liver injury and proposing recommendations for follow-up.

Orphanet J Rare Dis 2021 01 7;16(1):20. Epub 2021 Jan 7.

Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.

Background: The congenital disorders of glycosylation (CDG) are a heterogeneous group of rare metabolic diseases with multi-system involvement. The liver phenotype of CDG varies not only according to the specific disorder, but also from patient to patient. In this study, we sought to identify common patterns of liver injury among patients with a broad spectrum of CDG, and to provide recommendations for follow-up in clinical practice.

Methods: Patients were enrolled in the Frontiers in Congenital Disorders of Glycosylation natural history study. We analyzed clinical history, molecular genetics, serum markers of liver injury, liver ultrasonography and transient elastography, liver histopathology (when available), and clinical scores of 39 patients with 16 different CDG types (PMM2-CDG, n = 19), with a median age of 7 years (range: 10 months to 65 years). For patients with disorders which are treatable by specific interventions, we have added a description of liver parameters on treatment.

Results: Our principal findings are (1) there is a clear pattern in the evolution of the hepatocellular injury markers alanine aminotransferase and aspartate aminotransferase according to age, especially in PMM2-CDG patients but also in other CDG-I, and that the cholangiocellular injury marker gamma-glutamyltransferase is not elevated in most patients, pointing to an exclusive hepatocellular origin of injury; (2) there is a dissociation between liver ultrasound and transient elastography regarding signs of liver fibrosis; (3) histopathological findings in liver tissue of PMM2-CDG patients include cytoplasmic glycogen deposits; and (4) most CDG types show more than one type of liver injury.

Conclusions: Based on these findings, we recommend that all CDG patients have regular systematic, comprehensive screening for liver disease, including physical examination (for hepatomegaly and signs of liver failure), laboratory tests (serum alanine aminotransferase and aspartate aminotransferase), liver ultrasound (for steatosis and liver tumors), and liver elastography (for fibrosis).
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http://dx.doi.org/10.1186/s13023-020-01630-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7788939PMC
January 2021

The Combined Impact of CLIR Post-Analytical Tools and Second Tier Testing on the Performance of Newborn Screening for Disorders of Propionate, Methionine, and Cobalamin Metabolism.

Int J Neonatal Screen 2020 Jun 10;6(2):33. Epub 2020 Apr 10.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA; (A.L.P.); (G.P.); (C.T.); (D.M.); (D.O.); (K.R.); (S.T.); (P.R.).

The expansion of the recommend uniform screening panel to include more than 50 primary and secondary target conditions has resulted in a substantial increase of false positive results. As an alternative to subjective manipulation of cutoff values and overutilization of molecular testing, here we describe the performance outcome of an algorithm for disorders of methionine, cobalamin, and propionate metabolism that includes: (1) first tier screening inclusive of the broadest available spectrum of markers measured by tandem mass spectrometry; (2) integration of all results into a score of likelihood of disease for each target condition calculated by post-analytical interpretive tools created byCollaborative Laboratory Integrated Reports (CLIR), a multivariate pattern recognition software; and (3) further evaluation of abnormal scores by a second tier test measuring homocysteine, methylmalonic acid, and methylcitric acid. This approach can consistently reduce false positive rates to a <0.01% level, which is the threshold of precision newborn screening. We postulate that broader adoption of this algorithm could lead to substantial savings in health care expenditures. More importantly, it could prevent the stress and anxiety experienced by many families when faced with an abnormal newborn screening result that is later resolved as a false positive outcome.
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http://dx.doi.org/10.3390/ijns6020033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423003PMC
June 2020

Incorporation of Second-Tier Biomarker Testing Improves the Specificity of Newborn Screening for Mucopolysaccharidosis Type I.

Int J Neonatal Screen 2020 03 7;6(1):10. Epub 2020 Feb 7.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA; (J.M.L.); (A.L.W.); (G.P.); (A.L.S.); (D.G.); (D.O.); (K.R.); (D.M.); (P.R.).

Enzyme-based newborn screening for Mucopolysaccharidosis type I (MPS I) has a high false-positive rate due to the prevalence of pseudodeficiency alleles, often resulting in unnecessary and costly follow up. The glycosaminoglycans (GAGs), dermatan sulfate (DS) and heparan sulfate (HS) are both substrates for α-l-iduronidase (IDUA). These GAGs are elevated in patients with MPS I and have been shown to be promising biomarkers for both primary and second-tier testing. Since February 2016, we have measured DS and HS in 1213 specimens submitted on infants at risk for MPS I based on newborn screening. Molecular correlation was available for 157 of the tested cases. Samples from infants with MPS I confirmed by molecular analysis all had significantly elevated levels of DS and HS compared to those with confirmed pseudodeficiency and/or heterozygosity. Analysis of our testing population and correlation with molecular results identified few discrepant outcomes and uncovered no evidence of false-negative cases. We have demonstrated that blood spot GAGs analysis accurately discriminates between patients with confirmed MPS I and false-positive cases due to pseudodeficiency or heterozygosity and increases the specificity of newborn screening for MPS I.
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http://dx.doi.org/10.3390/ijns6010010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7422968PMC
March 2020

Immune dysfunction in MGAT2-CDG: A clinical report and review of the literature.

Am J Med Genet A 2021 01 12;185(1):213-218. Epub 2020 Oct 12.

Department of Pediatrics, School of Medicine, University of Washington, Seattle, Washington, USA.

Glycosylation is a critical post/peri-translational modification required for the appropriate development and function of the immune system. As an example, abnormalities in glycosylation can cause antibody deficiency and reduced lymphocyte signaling, although the phenotype can be complex given the diverse roles of glycosylation. Human MGAT2 encodes N-acetylglucosaminyltransferase II, which is a critical enzyme in the processing of oligomannose to complex N-glycans. Complex N-glycans are essential for immune system functionality, but only one individual with MGAT2-CDG has been described to have an abnormal immunologic evaluation. MGAT2-CDG (CDG-IIa) is a congenital disorder of glycosylation (CDG) associated with profound global developmental disability, hypotonia, early onset epilepsy, and other multisystem manifestations. Here, we report a 4-year old female with MGAT2-CDG due to a novel homozygous pathogenic variant in MGAT2, a 4-base pair deletion, c.1006_1009delGACA. In addition to clinical features previously described in MGAT2-CDG, she experienced episodic asystole, persistent hypogammaglobulinemia, and defective ex vivo mitogen and antigen proliferative responses, but intact specific vaccine antibody titers. Her infection history has been mild despite the testing abnormalities. We compare this patient to the 15 previously reported patients in the literature, thus expanding both the genotypic and phenotypic spectrum for MGAT2-CDG.
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http://dx.doi.org/10.1002/ajmg.a.61914DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8098812PMC
January 2021

A Comparative Effectiveness Study of Newborn Screening Methods for Four Lysosomal Storage Disorders.

Int J Neonatal Screen 2020 Jun 30;6(2). Epub 2020 May 30.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.

Newborn screening for one or more lysosomal disorders has been implemented in several US states, Japan and Taiwan by multiplexed enzyme assays using either tandem mass spectrometry or digital microfluidics. Another multiplex assay making use of immunocapture technology has also been proposed. To investigate the potential variability in performance of these analytical approaches, we implemented three high-throughput screening assays for the simultaneous screening for four lysosomal disorders: Fabry disease, Gaucher disease, mucopolysaccharidosis type I, and Pompe disease. These assays were tested in a prospective comparative effectiveness study using nearly 100,000 residual newborn dried blood spot specimens. In addition, 2nd tier enzyme assays and confirmatory molecular genetic testing were employed. Post-analytical interpretive tools were created using the software Collaborative Laboratory Integrated Reports (CLIR) to determine its ability to improve the performance of each assay vs. the traditional result interpretation based on analyte-specific reference ranges and cutoffs. This study showed that all three platforms have high sensitivity, and the application of CLIR tools markedly improves the performance of each platform while reducing the need for 2nd tier testing by 66% to 95%. Moreover, the addition of disease-specific biochemical 2nd tier tests ensures the lowest false positive rates and the highest positive predictive values for any platform.
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http://dx.doi.org/10.3390/ijns6020044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423013PMC
June 2020

International consensus guidelines for phosphoglucomutase 1 deficiency (PGM1-CDG): Diagnosis, follow-up, and management.

J Inherit Metab Dis 2021 01 15;44(1):148-163. Epub 2020 Sep 15.

Center for Child and Adolescent Medicine, Department, University of Heidelberg, Heidelberg, Germany.

Phosphoglucomutase 1 (PGM1) deficiency is a rare genetic disorder that affects glycogen metabolism, glycolysis, and protein glycosylation. Previously known as GSD XIV, it was recently reclassified as a congenital disorder of glycosylation, PGM1-CDG. PGM1-CDG usually manifests as a multisystem disease. Most patients present as infants with cleft palate, liver function abnormalities and hypoglycemia, but some patients present in adulthood with isolated muscle involvement. Some patients develop life-threatening cardiomyopathy. Unlike most other CDG, PGM1-CDG has an effective treatment option, d-galactose, which has been shown to improve many of the patients' symptoms. Therefore, early diagnosis and initiation of treatment for PGM1-CDG patients are crucial decisions. In this article, our group of international experts suggests diagnostic, follow-up, and management guidelines for PGM1-CDG. These guidelines are based on the best available evidence-based data and experts' opinions aiming to provide a practical resource for health care providers to facilitate successful diagnosis and optimal management of PGM1-CDG patients.
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http://dx.doi.org/10.1002/jimd.12286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7855268PMC
January 2021

Laboratory monitoring of patients with hereditary tyrosinemia type I.

Mol Genet Metab 2020 08 6;130(4):247-254. Epub 2020 Jun 6.

Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, Rochester, MN, USA. Electronic address:

Background: The prognosis of patients with Hereditary Tyrosinemia Type 1 (HT-1) has greatly improved with early detection through newborn screening and the introduction of nitisinone (NTBC) therapy. A recent guideline calls for periodic monitoring of biochemical markers and NTBC levels to tailor treatment; however, this is currently only achieved through a combination of clinical laboratory tests. We developed a multiplexed assay measuring relevant amino acids, succinylacetone (SUAC), and NTBC in dried blood spots (DBS) to facilitate treatment monitoring.

Methods: Tyrosine, phenylalanine, methionine, NTBC and SUAC were eluted from DBS with methanol containing internal standards for each analyte and analyzed by liquid chromatography tandem mass spectrometry over 6.5 min in the multiple reaction monitoring positive mode.

Results: Pre-analytical and analytical factors were studied and demonstrated a reliable assay. Chromatography resolved an unknown substance that falsely elevates SUAC concentrations and was present in all samples. To establish control and disease ranges, the method was applied to DBS collected from controls (n = 284) and affected patients before (n = 2) and after initiation of treatment (n = 29). In the treated patients SUAC concentrations were within the normal range over a wide range of NTBC levels.

Conclusions: This assay enables combined, accurate measurement of revelevant metabolites and NTBC in order to simplify treatment monitoring of patients with HT-1. In addition, the use of DBS allows for specimen collection at home to facilitate more standardization in relation to drug and dietary treatment.
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http://dx.doi.org/10.1016/j.ymgme.2020.06.001DOI Listing
August 2020

Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) initially diagnosed as ALG6-CDG: Functional evidence for benignity of the ALG6 c.391T>C (p.Tyr131His) variant and further expanding the BBSOAS phenotype.

Eur J Med Genet 2020 Jul 11;63(7):103941. Epub 2020 May 11.

Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA; Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.

Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) is a recently described autosomal dominant syndrome of developmental delay, cortical vision loss with optic nerve atrophy, epilepsy, and autism spectrum disorder. Due to its many overlapping features with congenital disorders of glycosylation (CDG), the differential diagnosis between these disorders may be difficult and relies on molecular genetic testing. We report on a 31-year-old female initially diagnosed with ALG6-CDG based on glycosylation abnormalities on transferrin isoelectrofocusing and targeted genetic testing, and later diagnosed with BBSOAS by whole-exome sequencing (WES). Functional studies on cultured fibroblasts including Western blotting and RT-qPCR, as well as mass spectrometry of glycosylated transferrin and MALDI-TOF glycan analysis in serum, demonstrated normal glycosylation in this patient. In this report, we extend the phenotype of BBSOAS with ataxia and protein-losing enteropathy. This case is illustrative of the utility of whole exome sequencing in the diagnostic odyssey, and the potential pitfalls of relying on focused genetic testing results for diagnosis of conditions with complex overlapping phenotypes.
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http://dx.doi.org/10.1016/j.ejmg.2020.103941DOI Listing
July 2020

Novel congenital disorder of O-linked glycosylation caused by GALNT2 loss of function.

Brain 2020 04;143(4):1114-1126

Department of Pediatrics, Division of Human Genetics, Section of Biochemical Genetics, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.

Congenital disorders of glycosylation are a growing group of rare genetic disorders caused by deficient protein and lipid glycosylation. Here, we report the clinical, biochemical, and molecular features of seven patients from four families with GALNT2-congenital disorder of glycosylation (GALNT2-CDG), an O-linked glycosylation disorder. GALNT2 encodes the Golgi-localized polypeptide N-acetyl-d-galactosamine-transferase 2 isoenzyme. GALNT2 is widely expressed in most cell types and directs initiation of mucin-type protein O-glycosylation. All patients showed loss of O-glycosylation of apolipoprotein C-III, a non-redundant substrate for GALNT2. Patients with GALNT2-CDG generally exhibit a syndrome characterized by global developmental delay, intellectual disability with language deficit, autistic features, behavioural abnormalities, epilepsy, chronic insomnia, white matter changes on brain MRI, dysmorphic features, decreased stature, and decreased high density lipoprotein cholesterol levels. Rodent (mouse and rat) models of GALNT2-CDG recapitulated much of the human phenotype, including poor growth and neurodevelopmental abnormalities. In behavioural studies, GALNT2-CDG mice demonstrated cerebellar motor deficits, decreased sociability, and impaired sensory integration and processing. The multisystem nature of phenotypes in patients and rodent models of GALNT2-CDG suggest that there are multiple non-redundant protein substrates of GALNT2 in various tissues, including brain, which are critical to normal growth and development.
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http://dx.doi.org/10.1093/brain/awaa063DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7534148PMC
April 2020

B4GALT1-congenital disorders of glycosylation: Expansion of the phenotypic and molecular spectrum and review of the literature.

Clin Genet 2020 06 16;97(6):920-926. Epub 2020 Mar 16.

Genetics Institute, Soroka University Medical Center, Ben Gurion University, Beer Sheva, Israel.

A congenital disorder of glycosylation due to biallelic mutations in B4GALT1 has been previously reported in only three patients with two different mutations. Through homozygosity mapping followed by segregation analysis in an extended pedigree, we identified three additional patients homozygous for a novel mutation in B4GALT1, expanding the phenotypic spectrum of the disease. The patients showed a uniform clinical presentation with intellectual disability, marked pancytopenia requiring chronic management, and novel features including pulmonary hypertension and nephrotic syndrome. Notably, affected individuals exhibited a moderate elevation of Man3GlcNAc4Fuc1 on serum N-glycan analysis, yet two of the patients had a normal pattern of transferrin glycosylation in repeated analysis. The novel mutation is the third disease-causing variant described in B4GALT1, and the first one within its transmembrane domain.
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http://dx.doi.org/10.1111/cge.13735DOI Listing
June 2020

Mutations in the V-ATPase Assembly Factor VMA21 Cause a Congenital Disorder of Glycosylation With Autophagic Liver Disease.

Hepatology 2020 12;72(6):1968-1986

Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, the Netherlands.

Background And Aims: Vacuolar H+-ATP complex (V-ATPase) is a multisubunit protein complex required for acidification of intracellular compartments. At least five different factors are known to be essential for its assembly in the endoplasmic reticulum (ER). Genetic defects in four of these V-ATPase assembly factors show overlapping clinical features, including steatotic liver disease and mild hypercholesterolemia. An exception is the assembly factor vacuolar ATPase assembly integral membrane protein (VMA21), whose X-linked mutations lead to autophagic myopathy.

Approach And Results: Here, we report pathogenic variants in VMA21 in male patients with abnormal protein glycosylation that result in mild cholestasis, chronic elevation of aminotransferases, elevation of (low-density lipoprotein) cholesterol and steatosis in hepatocytes. We also show that the VMA21 variants lead to V-ATPase misassembly and dysfunction. As a consequence, lysosomal acidification and degradation of phagocytosed materials are impaired, causing lipid droplet (LD) accumulation in autolysosomes. Moreover, VMA21 deficiency triggers ER stress and sequestration of unesterified cholesterol in lysosomes, thereby activating the sterol response element-binding protein-mediated cholesterol synthesis pathways.

Conclusions: Together, our data suggest that impaired lipophagy, ER stress, and increased cholesterol synthesis lead to LD accumulation and hepatic steatosis. V-ATPase assembly defects are thus a form of hereditary liver disease with implications for the pathogenesis of nonalcoholic fatty liver disease.
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http://dx.doi.org/10.1002/hep.31218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7483274PMC
December 2020

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease.

Genet Med 2020 06 24;22(6):1108-1118. Epub 2020 Feb 24.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.

Purpose: Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations.

Methods: PSY was extracted from dried blood spots or erythrocytes with methanol containing d-PSY as internal standard, and measured by liquid chromatography-tandem mass spectrometry.

Results: Analysis of PSY in samples from controls (N = 209), GALC pseudodeficiency carriers (N = 55), GALC pathogenic variant carriers (N = 27), patients with infantile KD (N = 26), and patients with late-onset KD (N = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT).

Conclusion: This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.
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http://dx.doi.org/10.1038/s41436-020-0764-yDOI Listing
June 2020

Expanding the molecular and clinical phenotypes of FUT8-CDG.

J Inherit Metab Dis 2020 07 23;43(4):871-879. Epub 2020 Feb 23.

Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.

Pathogenic variants in the Golgi localised alpha 1,6 fucosyltransferase, FUT8, cause a rare inherited metabolic disorder known as FUT8-CDG. To date, only three affected individuals have been reported presenting with a constellation of symptoms including intrauterine growth restriction, severe delays in growth and development, other neurological impairments, significantly shortened limbs, respiratory complications, and shortened lifespan. Here, we report an additional four unrelated affected individuals homozygous for novel pathogenic variants in FUT8. Analysis of serum N-glycans revealed a complete lack of core fucosylation, an important diagnostic biomarker of FUT8-CDG. Our data expands both the molecular and clinical phenotypes of FUT8-CDG and highlights the importance of identifying a reliable biomarker for confirming potentially pathogenic variants.
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http://dx.doi.org/10.1002/jimd.12221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7359201PMC
July 2020

Multiplex testing for the screening of lysosomal storage disease in urine: Sulfatides and glycosaminoglycan profiles in 40 cases of sulfatiduria.

Mol Genet Metab 2020 02 5;129(2):106-110. Epub 2019 Nov 5.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.

Purpose: To describe an efficient and effective multiplex screening strategy for sulfatide degradation disorders and mucolipidosis type II/III (MLII/III) using 3 mL of urine.

Methods: Glycosaminoglycans were analyzed by liquid chromatography-tandem mass spectrometry. Matrix assisted laser desorption/ionization-time of flight tandem mass spectrometry was used to identify free oligosaccharides and identify 22 ceramide trihexosides and 23 sulfatides, which are integrated by 670 calculated ratios. Collaborative Laboratory Integrated Reports (CLIR; https://clir.mayo.edu) was used for post-analytical interpretation of the complex metabolite profile and to aid in the differential diagnosis of abnormal results.

Results: Multiplex analysis was performed on 25 sulfatiduria case samples and compiled with retrospective data from an additional 15 cases revealing unique patterns of biomarkers for each disorder of sulfatide degradation (MLD, MSD, and Saposin B deficiency) and for MLII/III, thus allowing the formulation of a novel algorithm for the biochemical diagnosis of these disorders.

Conclusions: Comprehensive and integrated urine screening could be very effective in the initial workup of patients suspected of having a lysosomal disorder as it covers disorders of sulfatide degradation and narrows down the differential diagnosis in patients with elevated glycosaminoglycans.
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http://dx.doi.org/10.1016/j.ymgme.2019.10.009DOI Listing
February 2020

Defective glycosylation and multisystem abnormalities characterize the primary immunodeficiency XMEN disease.

J Clin Invest 2020 01;130(1):507-522

National Human Genome Research Institute, and.

X-linked immunodeficiency with magnesium defect, EBV infection, and neoplasia (XMEN) disease are caused by deficiency of the magnesium transporter 1 (MAGT1) gene. We studied 23 patients with XMEN, 8 of whom were EBV naive. We observed lymphadenopathy (LAD), cytopenias, liver disease, cavum septum pellucidum (CSP), and increased CD4-CD8-B220-TCRαβ+ T cells (αβDNTs), in addition to the previously described features of an inverted CD4/CD8 ratio, CD4+ T lymphocytopenia, increased B cells, dysgammaglobulinemia, and decreased expression of the natural killer group 2, member D (NKG2D) receptor. EBV-associated B cell malignancies occurred frequently in EBV-infected patients. We studied patients with XMEN and patients with autoimmune lymphoproliferative syndrome (ALPS) by deep immunophenotyping (32 immune markers) using time-of-flight mass cytometry (CyTOF). Our analysis revealed that the abundance of 2 populations of naive B cells (CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4++CD10+CD38+ and CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4+CD10-CD38-) could differentially classify XMEN, ALPS, and healthy individuals. We also performed glycoproteomics analysis on T lymphocytes and show that XMEN disease is a congenital disorder of glycosylation that affects a restricted subset of glycoproteins. Transfection of MAGT1 mRNA enabled us to rescue proteins with defective glycosylation. Together, these data provide new clinical and pathophysiological foundations with important ramifications for the diagnosis and treatment of XMEN disease.
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http://dx.doi.org/10.1172/JCI131116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6934229PMC
January 2020

A novel phosphoglucomutase-deficient mouse model reveals aberrant glycosylation and early embryonic lethality.

J Inherit Metab Dis 2019 09 21;42(5):998-1007. Epub 2019 Jun 21.

Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah.

Patients with phosphoglucomutase (PGM1) deficiency, a congenital disorder of glycosylation (CDG) suffer from multiple disease phenotypes. Midline cleft defects are present at birth. Overtime, additional clinical phenotypes, which include severe hypoglycemia, hepatopathy, growth retardation, hormonal deficiencies, hemostatic anomalies, frequently lethal, early-onset of dilated cardiomyopathy and myopathy emerge, reflecting the central roles of the enzyme in (glycogen) metabolism and glycosylation. To delineate the pathophysiology of the tissue-specific disease phenotypes, we constructed a constitutive Pgm2 (mouse ortholog of human PGM1)-knockout (KO) mouse model using CRISPR-Cas9 technology. After multiple crosses between heterozygous parents, we were unable to identify homozygous life births in 78 newborn pups (P = 1.59897E-06), suggesting an embryonic lethality phenotype in the homozygotes. Ultrasound studies of the course of pregnancy confirmed Pgm2-deficient pups succumb before E9.5. Oral galactose supplementation (9 mg/mL drinking water) did not rescue the lethality. Biochemical studies of tissues and skin fibroblasts harvested from heterozygous animals confirmed reduced Pgm2 enzyme activity and abundance, but no change in glycogen content. However, glycomics analyses in serum revealed an abnormal glycosylation pattern in the Pgm2 animals, similar to that seen in PGM1-CDG.
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http://dx.doi.org/10.1002/jimd.12110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739163PMC
September 2019

Developmental delay, coarse facial features, and epilepsy in a patient with gene variants.

Clin Case Rep 2019 Apr 19;7(4):632-637. Epub 2019 Feb 19.

Department of Clinical Genomics Mayo Clinic Rochester Minnesota.

We report a patient with developmental delay, autism, epilepsy, macrocephaly, facial dysmorphism, gastrointestinal, and behavioral issues due to compound heterozygous likely pathogenic variants. This case report expands the gene mutation database and the clinical spectrum of patients with deficiencies in the heparan sulfate pathway.
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http://dx.doi.org/10.1002/ccr3.2010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6452521PMC
April 2019

International clinical guidelines for the management of phosphomannomutase 2-congenital disorders of glycosylation: Diagnosis, treatment and follow up.

J Inherit Metab Dis 2019 01;42(1):5-28

Division of Genetic Medicine, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington.

Phosphomannomutase 2 (PMM2-CDG) is the most common congenital disorder of N-glycosylation and is caused by a deficient PMM2 activity. The clinical presentation and the onset of PMM2-CDG vary among affected individuals ranging from a severe antenatal presentation with multisystem involvement to mild adulthood presentation limited to minor neurological involvement. Management of affected patients requires a multidisciplinary approach. In this article, a systematic review of the literature on PMM2-CDG was conducted by a group of international experts in different aspects of CDG. Our managment guidelines were initiated based on the available evidence-based data and experts' opinions. This guideline mainly addresses the clinical evaluation of each system/organ involved in PMM2-CDG, and the recommended management approach. It is the first systematic review of current practices in PMM2-CDG and the first guidelines aiming at establishing a practical approach to the recognition, diagnosis and management of PMM2-CDG patients.
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http://dx.doi.org/10.1002/jimd.12024DOI Listing
January 2019
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