title: Mice lacking brain/kidney phosphate-activated glutaminase have impaired glutamatergic synaptic transmission, altered breathing, disorganized goal-directed behavior and die shortly after birth.
abstract: Neurotransmitter glutamate has been thought to derive mainly from glutamine via the action of glutaminase type 1 (GLS1). To address the importance of this pathway in glutamatergic transmission, we knocked out GLS1 in mice. The insertion of a STOP cassette by homologous recombination produced a null allele that blocked transcription, encoded no immunoreactive protein, and abolished GLS1 enzymatic activity. Null mutants were slightly smaller, were deficient in goal-directed behavior, hypoventilated, and died in the first postnatal day. No gross or microscopic defects were detected in peripheral organs or in the CNS. In cultured neurons from the null mutants, miniature EPSC amplitude and duration were normal; however, the amplitude of evoked EPSCs decayed more rapidly with sustained 10 Hz stimulation, consistent with an observed reduction in depolarization-evoked glutamate release. Because of this activity-dependent impairment in glutamatergic transmission, we surmised that respiratory networks, which require temporal summation of synaptic input, would be particularly affected. We found that the amplitude of inspirations was decreased in vivo, chemosensitivity to CO2 was severely altered, and the frequency of pacemaker activity recorded in the respiratory generator in the pre-Bötzinger complex, a glutamatergic brainstem network that can be isolated in vitro, was increased. Our results show that although alternate pathways to GLS1 glutamate synthesis support baseline glutamatergic transmission, the GLS1 pathway is essential for maintaining the function of active synapses, and thus the mutation is associated with impaired respiratory function, abnormal goal-directed behavior, and neonatal demise.
authors.affiliation: Unité Mixte de Recherche U677, NeuroPsychoPharmacologie, Faculté de Médecine Pitié-Salpêtrière, 75634 Paris Cedex 13, France. jumasson@ext.jussieu.fr
authors.forename: Justine
authors.initials: J
authors.lastname: Masson
authors.forename: Michèle
authors.initials: M
authors.lastname: Darmon
authors.forename: Agnès
authors.initials: A
authors.lastname: Conjard
authors.forename: Nao
authors.initials: N
authors.lastname: Chuhma
authors.forename: Nicole
authors.initials: N
authors.lastname: Ropert
authors.forename: Muriel
authors.initials: M
authors.lastname: Thoby-Brisson
authors.forename: Arthur S
authors.initials: AS
authors.lastname: Foutz
authors.forename: Sandrine
authors.initials: S
authors.lastname: Parrot
authors.forename: Gretchen M
authors.initials: GM
authors.lastname: Miller
authors.forename: Renée
authors.initials: R
authors.lastname: Jorisch
authors.forename: Jonathan
authors.initials: J
authors.lastname: Polan
authors.forename: Michel
authors.initials: M
authors.lastname: Hamon
authors.forename: René
authors.initials: R
authors.lastname: Hen
authors.forename: Stephen
authors.initials: S
authors.lastname: Rayport
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000201:enzymology*; D018698:Glutamic Acid / Q000378:metabolism*; D005972:Glutaminase / Q000172:deficiency*; D006040:Goals; D007040:Hypoventilation / Q000503:physiopathology*; D007668:Kidney / Q000201:enzymology*; D001523:Mental Disorders / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D009434:Neural Pathways / Q000378:metabolism; D012120:Respiration Disorders; D015656:Respiratory Mechanics; D015996:Survival Rate; D009435:Synaptic Transmission
chemical_list: D018698:Glutamic Acid; D005972:Glutaminase