Neurodevelopmental defects in a mouse model of O-GlcNAc transferase intellectual disability.

The addition of O-linked β-N-acetylglucosamine (O-GlcNAc) to proteins (referred to as O-GlcNAcylation) is a modification that is crucial for vertebrate development. O-GlcNAcylation is catalyzed by O-GlcNAc transferase (OGT) and reversed by O-GlcNAcase (OGA). Missense variants of OGT have recently been shown to segregate with an X-linked syndromic form of intellectual disability, OGT-linked congenital disorder of glycosylation (OGT-CDG).

Metabolic adaptation of human skin fibroblasts to ER stress caused by glycosylation defect in PMM2-CDG.

PMM2-CDG is the most prevalent type of congenital disorders of glycosylation (CDG). It is caused by pathogenic variants in the gene encoding phosphomannomutase 2 (PMM2), which converts mannose-6-phosphate to mannose-1-phosphate and thus activates this saccharide for further glycosylation processes. Defective glycosylation can lead to an abnormal accumulation of unfolded proteins in endoplasmic reticulum (ER) and cause its stress.

Elevated oxysterol and N-palmitoyl-O-phosphocholineserine levels in congenital disorders of glycosylation.

Congenital disorders of glycosylation (CDG) and Niemann-Pick type C (NPC) disease are inborn errors of metabolism that can both present with infantile-onset severe liver disease and other multisystemic manifestations. Plasma bile acid and N-palmitoyl-O-phosphocholineserine (PPCS) are screening biomarkers with proposed improved sensitivity and specificity for NPC. We report an infant with ATP6AP1-CDG who presented with cholestatic liver failure and elevated plasma oxysterols and bile acid, mimicking NPC clinically and biochemically.

Congenital disorders of glycosylation: Still "hot" in 2020.

Background: Congenital disorders of glycosylation (CDG) are inherited metabolic diseases caused by defects in the genes important for the process of protein and lipid glycosylation. With the ever growing number of the known subtypes and discoveries regarding the disease mechanisms and therapy development, it remains a very active field of study.

Scope Of Review: This review brings an update on the CDG-related research since 2017, describing the novel gene defects, pathobiomechanisms, biomarkers and the patients' phenotypes.

A new role for dolichol isoform profile in the diagnostics of CDG disorders.

Dolichol is a membrane lipid which carries monosaccharides and glycans for N-linked protein glycosylation occurring in the endoplasmic reticulum. Recently, some types of congenital disorders of glycosylation (CDG) have been described as consequences of defects in dolichol biosynthesis and metabolism, yet these types of CDG are not detectable by standard screening methods. The aim of this project was to evaluate the potential of dolichol as a biomarker of CDG.

Severe phenotype of ATP6AP1-CDG in two siblings with a novel mutation leading to a differential tissue-specific ATP6AP1 protein pattern, cellular oxidative stress and hepatic copper accumulation.

Congenital disorders of glycosylation (CDG) represent a wide range of >140 inherited metabolic diseases, continually expanding not only with regards to the number of newly identified causative genes, but also the heterogeneity of the clinical and molecular presentations within each subtype. The deficiency of ATP6AP1, an accessory subunit of the vacuolar H -ATPase, is a recently characterised N- and O-glycosylation defect manifesting with immunodeficiency, hepatopathy and cognitive impairment. At the cellular level, the latest studies demonstrate a complex disturbance of metabolomics involving peroxisomal function and lipid homeostasis in the patients.

Review of SRD5A3 Disease-Causing Sequence Variants and Ocular Findings in Steroid 5α-Reductase Type 3 Congenital Disorder of Glycosylation, and a Detailed New Case.

Steroid 5α-reductase type 3 congenital disorder of glycosylation (SRD5A3-CDG) is a severe metabolic disease manifesting as muscle hypotonia, developmental delay, cerebellar ataxia and ocular symptoms; typically, nystagmus and optic disc pallor. Recently, early onset retinal dystrophy has been reported as an additional feature. In this study, we summarize ocular phenotypes and SRD5A3 variants reported to be associated with SRD5A3-CDG.

Isoelectric Focusing of Serum Apolipoprotein C-III as a Sensitive Screening Method for the Detection of O-glycosylation Disturbances.

Apolipoprotein C-III (ApoC-III) is a glycoprotein carrying the most common O-linked glycan structure and is abundantly present in serum, what renders it a suitable marker for analysis of O-glycosylation abnormalities. Isoelectric focusing followed by a Western blot of ApoC-III, using PhastSystem™ Electrophoresis System (GE Healthcare), was introduced as a rather simple and rapid method for screening of certain subtypes of inherited glycosylation disorders. The study's aim was to establish this method in our laboratory, what included performing the analysis in a group of 170 healthy individuals to set the reference range of detected relative amounts of sialylated ApoC-III isoforms and to evaluate the gender- and age-dependent differences.

Mutation of Nogo-B receptor, a subunit of cis-prenyltransferase, causes a congenital disorder of glycosylation.

Dolichol is an obligate carrier of glycans for N-linked protein glycosylation, O-mannosylation, and GPI anchor biosynthesis. cis-prenyltransferase (cis-PTase) is the first enzyme committed to the synthesis of dolichol. However, the proteins responsible for mammalian cis-PTase activity have not been delineated.

Glycogen storage disease-like phenotype with central nervous system involvement in a PGM1-CDG patient.

Objectives: A 10-year-old boy presented with cleft palate, hepatopathy, cholecystolithiasis, myopathy, coagulopathy, hyperlipidemia, hypoglycemia, hyperuricemia, short stature, obesity, hypothyroidism, microcephaly and mild intellectual disability. The multi-systemic manifestation involving certain distinct clinical features prompted us to search for a subtype of congenital disorders of glycosylation (CDG).

Methods: The patient was screened for CDG by examining the distribution of transferrin (TRF) and apolipoprotein C-III (ApoC-III) sialylated isoforms using isoelectric focusing of serum.

Diagnostic serum glycosylation profile in patients with intellectual disability as a result of MAN1B1 deficiency.

Congenital disorders of glycosylation comprise a group of genetic defects with a high frequency of intellectual disability, caused by deficient glycosylation of proteins and lipids. The molecular basis of the majority of the congenital disorders of glycosylation type I subtypes, localized in the cytosol and endoplasmic reticulum, has been solved. However, elucidation of causative genes for defective Golgi glycosylation (congenital disorders of glycosylation type II) remains challenging because of a lack of sufficiently specific diagnostic serum methods.

RFT1-CDG in adult siblings with novel mutations.

RFT1-CDG is a rare N-glycosylation disorder. Only 6 children with RFT1-CDG have been described, all with failure to thrive, feeding problems, hypotonia, developmental delay, epilepsy, decreased vision, deafness and thrombotic complications. We report on two young adult siblings with RFT1-CDG, compound heterozygotes for the novel missense mutations c.

Clinical picture of S-adenosylhomocysteine hydrolase deficiency resembles phosphomannomutase 2 deficiency.

We report on the seventh known patient with S-adenosylhomocysteine hydrolase (SAHH) deficiency presenting at birth with features resembling phosphomannomutase 2 (PMM2-CDG Ia) deficiency. Plasma methionine and total homocysteine levels were normal at 2 months and increased only after the 8th month of age. SAHH deficiency was confirmed at 4.

Transferrin mutations at the glycosylation site complicate diagnosis of congenital disorders of glycosylation type I.

Congenital disorders of glycosylation (CDG) form a group of metabolic disorders caused by deficient glycosylation of proteins and/or lipids. Isoelectric focusing (IEF) of serum transferrin is the most common screening method to detect abnormalities of protein N-glycosylation. On the basis of the IEF profile, patients can be grouped into CDG type I or CDG type II.