glutaminase and Brain-Diseases

The identification and understanding of the monogenic causes of neurodevelopmental disorders are of high importance for personalized treatment and genetic counseling.. To identify and characterize novel genes for a specific neurodevelopmental disorder characterized by refractory seizures, respiratory failure, brain abnormalities, and death in the neonatal period; describe the outcome of glutaminase deficiency in humans; and understand the underlying pathological mechanisms.. We performed exome sequencing of cases of neurodevelopmental disorders without a clear genetic diagnosis, followed by genetic and bioinformatic evaluation of candidate variants and genes. Establishing pathogenicity of the variants was achieved by measuring metabolites in dried blood spots by a hydrophilic interaction liquid chromatography method coupled with tandem mass spectrometry. The participants are 2 families with a total of 4 children who each had lethal, therapy-refractory early neonatal seizures with status epilepticus and suppression bursts, respiratory insufficiency, simplified gyral structures, diffuse volume loss of the brain, and cerebral edema. Data analysis occurred from October 2017 to June 2018.. Early neonatal epileptic encephalopathy with glutaminase deficiency and lethal outcome.. A total of 4 infants from 2 unrelated families, each of whom died less than 40 days after birth, were included. We identified a homozygous frameshift variant p.(Asp232Glufs*2) in GLS in the first family, as well as compound heterozygous variants p.(Gln81*) and p.(Arg272Lys) in GLS in the second family. The GLS gene encodes glutaminase (Enzyme Commission 3.5.1.2), which plays a major role in the conversion of glutamine into glutamate, the main excitatory neurotransmitter of the central nervous system. All 3 variants probably lead to a loss of function and thus glutaminase deficiency. Indeed, glutamine was increased in affected children (available z scores, 3.2 and 11.7). We theorize that the potential reduction of glutamate and the excess of glutamine were a probable cause of the described physiological and structural abnormalities of the central nervous system.. We identified a novel autosomal recessive neurometabolic disorder of loss of function of glutaminase that leads to lethal early neonatal encephalopathy. This inborn error of metabolism underlines the importance of GLS for appropriate glutamine homeostasis and respiratory regulation, signal transduction, and survival.

Topics: Brain; Brain Diseases; Epilepsy; Female; Glutaminase; Glutamine; Humans; Infant; Infant, Newborn; Male; Mutation; Seizures

Topics: Ammonia; Brain Diseases; Deamination; Fatty Liver; Glutaminase; Glutamine; Humans; Methods; Reye Syndrome

Topics: Adult; Alanine; Amino Acid Metabolism, Inborn Errors; Amino Acids; Ammonia; Atrophy; Biological Transport; Blood Cell Count; Blood Glucose; Blood Urea Nitrogen; Bone Diseases; Brain Diseases; Dietary Proteins; Female; Glutaminase; Glutamine; Hemoglobins; Humans; Intellectual Disability; Kidney; Kidney Function Tests; Lysine; Metabolism, Inborn Errors; Nitrogen; Proteins; Specific Gravity; Urea; Urine