Citations

AbstractCongenital disorders of glycosylation are genetic disorders that occur due to defects in protein and lipid glycosylation pathways. A deficiency of N‐glycanase 1, encoded by the NGLY1 gene, results in a congenital disorder of deglycosylation. The NGLY1 enzyme is mainly involved in cleaving N‐glycans from misfolded, retro‐translocated glycoproteins in the cytosol from the endoplasmic reticulum before their proteasomal degradation or activation. Despite the essential role of NGLY1 in deglycosylation pathways, the exact consequences of NGLY1 deficiency on global cellular protein glycosylation have not yet been investigated. We undertook a multiplexed tandem mass tags‐labeling‐based quantitative glycoproteomics and proteomics analysis of fibroblasts from NGLY1‐deficient individuals carrying different biallelic pathogenic variants in NGLY1. This quantitative mass spectrometric analysis detected 8041 proteins and defined a proteomic signature of differential expression across affected individuals and controls. Proteins that showed significant differential expression included phospholipid phosphatase 3, stromal cell‐derived factor 1, collagen alpha‐1 (IV) chain, hyaluronan and proteoglycan link protein 1, and thrombospondin‐1. We further detected a total of 3255 N‐glycopeptides derived from 550 glycosylation sites of 407 glycoproteins by multiplexed N‐glycoproteomics. Several extracellular matrix glycoproteins and adhesion molecules showed altered abundance of N‐glycopeptides. Overall, we observed distinct alterations in specific glycoproteins, but our data revealed no global accumulation of glycopeptides in the patient‐derived fibroblasts, despite the genetic defect in NGLY1. Our findings highlight new molecular and system‐level insights for understanding NGLY1‐CDDG.

AbstractTRIT1 defect is a rare, autosomal‐recessive disorder of transcription, initially described as a condition with developmental delay, myoclonic seizures, and abnormal mitochondrial function. Currently, only 13 patients have been reported. We reviewed the genetic, clinical, and metabolic aspects of the disease in all known patients, including two novel, unrelated TRIT1 cases with abnormalities in oxidative phosphorylation complexes I and IV in fibroblasts. Taken together the features of all 15 patients, TRIT1 defect could be identified as a potentially recognizable syndrome including myoclonic epilepsy, speech delay, strabismus, progressive spasticity, and variable microcephaly, with normal lactate levels. Half of the patients had oxidative phosphorylation complex measurements and had multiple complex abnormalities.

AbstractCongenital disorders of glycosylation are a continuously expanding group of monogenic disorders of glycoprotein and glycolipid glycan biosynthesis. These disorders mostly manifest with multisystem involvement. Individuals with ALG8‐CDG commonly present with hypotonia, protein‐losing enteropathy, and hepatic involvement. Here, we describe seven unreported individuals diagnosed with ALG8‐CDG based on biochemical and molecular testing and we identify nine novel variants in ALG8, bringing the total to 26 individuals with ALG8‐CDG in the medical literature. In addition to the typical multisystem involvement documented in ALG8‐CDG, our cohort includes the two oldest patients reported and further expands the phenotype of ALG8‐CDG to include stable intellectual disability, autism spectrum disorder and other neuropsychiatric symptoms. We further expand the clinical features in a variety of organ systems including ocular, musculoskeletal, dermatologic, endocrine, and cardiac abnormalities and suggest a comprehensive evaluation and monitoring strategy to improve clinical management.

AbstractAchalasia is rare in the pediatric population and should prompt clinicians to consider genetic disorders associated with this condition. While AAA syndrome (also known as Allgrove or Triple A syndrome) is commonly considered, GMPPA‐congenital disorder of glycosylation (CDG) should also be in the differential diagnosis. We report a 9‐month‐old female born to nonconsanguineous parents with achalasia and alacrima found to have two novel compound heterozygous variants in the GMPPA gene associated with GMPPA‐CDG. This rare disorder is commonly associated with developmental delay and intellectual disability. We discuss management of this disorder including the importance of confirming a genetic diagnosis and summarize reported cases.

Mannose phosphate isomerase–congenital disorder of glycosylation (MPI-CDG) is a CDG presenting with a clinically recognizable presentation, including early hypoglycemia, coagulation defects, and gastrointestinal and hepatic symptoms. We report on a female patient with biallelic pathogenic mutations in the MPI gene who presented with recurrent respiratory infections and abnormal IgM levels, but none of the classic symptoms associated with MPI-CDG. Oral mannose therapy led to a fast improvement in serum IgM levels and transferrin glycosylation in our patient. The patient did not experience severe infections after the initiation of treatment. We also reviewed the immune phenotype in patients so far reported with MPI-CDG.

AbstractLeukocyte adhesion deficiency type II (LAD II, also known as SLC35C1‐congenital disorder of glycosylation) is an autosomal recessive disorder characterized by growth and cognitive impairment, peripheral neutrophilia, recurrent infections, and the Bombay blood phenotype. A subset of patients with a milder presentation has been described with short stature and developmental delay but minimal immune and hematologic features. Some patients with LAD II benefit from oral fucose therapy, though this has not been previously studied in patients with milder disease. In this study, we describe two new patients from separate families with the milder variant of LAD II and review the published literature on this rare disorder. We demonstrate improvement in speech and cognition, CD15 expression, and core fucosylation of serum glycoproteins after 27 months of oral fucose supplementation in one patient. These patients further support the stratification of this disorder into distinct subtypes, a classical severe and an attenuated variant, and provide preliminary evidence of benefit of fucose therapy in the latter group.