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Neurochem Int. 2019 Feb;123:22-33. doi: 10.1016/j.neuint.2018.07.009. Epub 2018 Jul 24.

Selective deletion of glutamine synthetase in the mouse cerebral cortex induces glial dysfunction and vascular impairment that precede epilepsy and neurodegeneration.

Author information

1
Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, N-0317, Oslo, Norway. Electronic address: yun.zhou@medisin.uio.no.
2
Department of Laboratory Medicine, Yale School of Medicine, New Haven, CT, 06520, USA.
3
Magnetic Resonance Research Center, Yale School of Medicine, New Haven, CT, 06520, USA.
4
Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, N-0317, Oslo, Norway.
5
Department of Complex Neurology and Neurohabilitation, Oslo University Hospital, University of Oslo, N-0450, Oslo, Norway.
6
Department of Cell Biology, University of Connecticut Health, Farmington, CT, 06030, USA.
7
Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, N-0317, Oslo, Norway; Department of Laboratory Medicine, Yale School of Medicine, New Haven, CT, 06520, USA. Electronic address: tore.eid@yale.edu.
8
Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, N-0317, Oslo, Norway. Electronic address: n.c.danbolt@medisin.uio.no.

Abstract

Glutamate-ammonia ligase (glutamine synthetase; Glul) is enriched in astrocytes and serves as the primary enzyme for ammonia detoxification and glutamate inactivation in the brain. Loss of astroglial Glul is reported in hippocampi of epileptic patients, but the mechanism by which Glul deficiency might cause disease remains elusive. Here we created a novel mouse model by selectively deleting Glul in the hippocampus and neocortex. The Glul deficient mice were born without any apparent malformations and behaved unremarkably until postnatal week three. There were reductions in tissue levels of aspartate, glutamate, glutamine and GABA and in mRNA encoding glutamate receptor subunits GRIA1 and GRIN2A as well as in the glutamate transporter proteins EAAT1 and EAAT2. Adult Glul-deficient mice developed progressive neurodegeneration and spontaneous seizures which increased in frequency with age. Importantly, progressive astrogliosis occurred before neurodegeneration and was first noted in astrocytes along cerebral blood vessels. The responses to CO2-provocation were attenuated at four weeks of age and dilated microvessels were observed histologically in sclerotic areas of cKO. Thus, the abnormal glutamate metabolism observed in this model appeared to cause epilepsy by first inducing gliopathy and disrupting the neurovascular coupling.

KEYWORDS:

Cerebrovascular dysfunction; Epilepsy; Gliopathy; Glul; Metabolism; Neurodegeneration

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