Erythrocyte Galactose-1-phosphate measurement by GC-MS in the monitoring of classical galactosemia

Neonatal classic galactosemia-diagnosis, clinical profile and molecular characteristics in unscreened Turkish population

BACKGROUND

Classic galactosemia (CG) is a rare hereditary disease that can cause serious morbidity and death if it is not diagnosed and treated in early periods of life. Clinical findings usually occur in the neonatal period after the neonate is fed with milk that contains galactose. Most patients are presented with jaundice, hepatomegaly, hypoglycemia and cataracts.

OBJECTIVE

We aimed to document the clinical, molecular characteristics, regional estimated incidence and time of diagnosis in newborn with CG.

MATERIALS AND METHOD

The data of 63 newborn with CG who were diagnosed and followed up between January 2011 and January 2018 were analyzed retrospectively.

RESULTS

During the study period, 63 (33 boys and 30 girls) newborns were diagnosed with CG. The median gestational age was 39 weeks (33-42). Major presenting symptoms were jaundice 90.5% and cataract 41.2%. The mean age at first symptom was 12 ± 7.4 days while the mean age at diagnosis was 18.9 ± 10.6 days. Nearly half of the patients (55.5%) were diagnosed later than the postnatal 15th day. Genetic analysis was performed on 56 patients and homozygous Q188R mutation was found in 92.8%. There were signs of sepsis in 33.3% of the cases. Six patients died due to sepsis. There was consanguinity in 84.1% of the parents and regional estimated incidence was calculated as 1 in 6103 live births.

CONCLUSION

Q188R mutation was found in 92.8% of our cases. The regional estimated incidence was found as 1 in 6103 live births. Our study strongly supports that galactosemia should be included in the national newborn screening program.

Overelaborated synaptic architecture and reduced synaptomatrix glycosylation in a Drosophila classic galactosemia disease model

Classic galactosemia (CG) is an autosomal recessive disorder resulting from loss of galactose-1-phosphate uridyltransferase (GALT), which catalyzes conversion of galactose-1-phosphate and uridine diphosphate (UDP)-glucose to glucose-1-phosphate and UDP-galactose, immediately upstream of UDP-N-acetylgalactosamine and UDP-N-acetylglucosamine synthesis. These four UDP-sugars are essential donors for driving the synthesis of glycoproteins and glycolipids, which heavily decorate cell surfaces and extracellular spaces. In addition to acute, potentially lethal neonatal symptoms, maturing individuals with CG develop striking neurodevelopmental, motor and cognitive impairments. Previous studies suggest that neurological symptoms are associated with glycosylation defects, with CG recently being described as a congenital disorder of glycosylation (CDG), showing defects in both N- and O-linked glycans. Here, we characterize behavioral traits, synaptic development and glycosylated synaptomatrix formation in a GALT-deficient Drosophila disease model. Loss of Drosophila GALT (dGALT) greatly impairs coordinated movement and results in structural overelaboration and architectural abnormalities at the neuromuscular junction (NMJ). Dietary galactose and mutation of galactokinase (dGALK) or UDP-glucose dehydrogenase (sugarless) genes are identified, respectively, as critical environmental and genetic modifiers of behavioral and cellular defects. Assaying the NMJ extracellular synaptomatrix with a broad panel of lectin probes reveals profound alterations in dGALT mutants, including depletion of galactosyl, N-acetylgalactosamine and fucosylated horseradish peroxidase (HRP) moieties, which are differentially corrected by dGALK co-removal and sugarless overexpression. Synaptogenesis relies on trans-synaptic signals modulated by this synaptomatrix carbohydrate environment, and dGALT-null NMJs display striking changes in heparan sulfate proteoglycan (HSPG) co-receptor and Wnt ligand levels, which are also corrected by dGALK co-removal and sugarless overexpression. These results reveal synaptomatrix glycosylation losses, altered trans-synaptic signaling pathway components, defective synaptogenesis and impaired coordinated movement in a CG neurological disease model.

GALK inhibitors for classic galactosemia

Classic galactosemia is an inherited metabolic disease for which, at present, no therapy is available apart from galactose-restricted diet. However, the efficacy of the diet is questionable, since it is not able to prevent the insurgence of chronic complications later in life. In addition, it is possible that dietary restriction itself could induce negative side effects. Therefore, there is a need for an alternative therapeutic approach that can avert the manifestation of chronic complications in the patients. In this review, the authors describe the development of a novel class of pharmaceutical agents that target the production of a toxic metabolite, galactose-1-phosphate, considered as the main culprit for the cause of the complications, in the patients.