Mutations in the GFPT1 gene are associated with a particular subtype of congenital myasthenia syndrome (CMS) called limb-girdle myasthenia with tubular aggregates. However, not all patients show tubular aggregates in muscle biopsy, suggesting the diversity of myopathology should be further investigated.
In this study, we reported two unrelated patients clinically characterized by easy fatigability, limb-girdle muscle weakness, positive decrements of repetitive stimulation, and response to pyridostigmine. The routine examinations of myopathology were conducted. The causative gene was explored by whole-exome screening. In addition, we summarized all GFPT1-related CMS patients with muscle biopsy in the literature.
Pathogenic biallelic GFPT1 mutations were identified in the two patients. In patient one, muscle biopsy indicated vacuolar myopathic changes and atypical pathological changes of myofibrillar myopathy characterized by desmin deposits, Z-disc disorganization, and electronic dense granulofilamentous aggregation. In patient two, muscle biopsy showed typical myopathy with tubular aggregates. Among the 51 reported GFPT1-related CMS patients with muscle biopsy, most of them showed tubular aggregates myopathy, while rimmed vacuolar myopathy, autophagic vacuolar myopathy, mitochondria-like myopathy, neurogenic myopathy, and unspecific myopathic changes were also observed in some patients. These extra-synaptic pathological changes might be associated with GFPT1-deficiency hypoglycosylation and altered function of muscle-specific glycoproteins, as well as partly responsible for the permanent muscle weakness and resistance to acetylcholinesterase inhibitor therapy.
Most patients with GFPT1-related CMS had tubular aggregates in the muscle biopsy, but some patients could show great diversities of the pathological change. The myopathological findings might be a biomarker to predict the prognosis of the disease.

BACKGROUND: Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the first rate-limiting enzyme of the hexosamine biosynthesis pathway (HBP), which plays a pivotal role in the progression of pancreatic ductal adenocarcinoma (PDAC). Therefore, we investigated the prognostic significance of GFPT1 expression in patients with resectable PDAC.
METHODS: We analyzed public datasets to compare GFPT1 expression in tumor tissues and normal/adjacent pancreatic tissues. We measured the relative GFPT1 expression of 134 resected PDAC specimens in our institution, using real-time polymerase chain reaction (PCR). Survival was compared between high and low GFPT1 expression groups using Kaplan-Meier curves and log-rank tests. Multivariate analyses were estimated using Cox regression and logistic regression models.
RESULTS: GFPT1 is generally upregulated in PDAC tissues, according to the analysis of public datasets. The data from our institution shows that high GFPT1 expression was correlated with a high rate of lymph node (LN) metastasis (p = 0.038) and was an independent risk factor for LN metastasis (odds ratio (OR) = 3.14, 95% confidence interval (CI) = 1.42 to 6.90, P = 0.005). High GFPT1 expression was significantly associated with poor overall survival (OS; P = 0.019) in patients with resected PDAC. The multivariable-adjusted hazard ratio (HR) for mortality when comparing patients with high and low GFPT1 expression was 2.54 (95% CI = 1.35 to 4.79, P = 0.004).
CONCLUSIONS: GFPT1 is generally upregulated in PDAC tissue and is associated with a high risk of LN metastasis and an unfavorable outcome in patients with resectable PDAC, suggesting its crucial role in PDAC progression.

Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the first enzyme of the hexosamine biosynthetic pathway. It transfers an amino group from glutamine to fructose-6-phosphate to yield glucosamine-6-phosphate, thus providing the precursor for uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) synthesis. UDP-GlcNAc is an essential substrate for all mammalian glycosylation biosynthetic pathways and N-glycan branching is especially sensitive to alterations in the concentration of this sugar nucleotide. It has been reported that GFPT1 mutations lead to a distinct sub-class of congenital myasthenic syndromes (CMS) termed \"limb-girdle CMS with tubular aggregates\". CMS are hereditary neuromuscular transmission disorders in which neuromuscular junctions are impaired. To investigate whether alterations in protein glycosylation at the neuromuscular junction might be involved in this impairment, we have employed mass spectrometric strategies to study the N-glycomes of myoblasts and myotubes derived from two healthy controls, three GFPT1 patients, and four patients with other muscular diseases, namely CMS caused by mutations in DOK7, myopathy caused by mutations in MTND5, limb girdle muscular dystrophy type 2A (LGMD2A), and Pompe disease. A comparison of the relative abundances of bi-, tri-, and tetra-antennary N-glycans in each of the cell preparations revealed that all samples exhibited broadly similar levels of branching. Moreover, although some differences were observed in the relative abundances of some of the N-glycan constituents, these variations were modest and were not confined to the GFPT1 samples. Therefore, GFPT1 mutations in CMS patients do not appear to compromise global N-glycosylation in muscle cells.