Hyaluronan deficiency due to Has3 knock-out causes altered neuronal activity and seizures via reduction in brain extracellular space.
Hyaluronan (HA), a large anionic polysaccharide (glycosaminoglycan), is a major constituent of the extracellular matrix of the adult brain. To address its function, we examined the neurophysiology of knock-out mice deficient in hyaluronan synthase (Has) genes. Here we report that these Has mutant mice are prone to epileptic seizures, and that in Has3(-/-) mice, this phenotype is likely derived from a reduction in the size of the brain extracellular space (ECS). Among the three Has knock-out models, namely Has3(-/-), Has1(-/-), and Has2(CKO), the seizures were most prevalent in Has3(-/-) mice, which also showed the greatest HA reduction in the hippocampus. Electrophysiology in Has3(-/-) brain slices demonstrated spontaneous epileptiform activity in CA1 pyramidal neurons, while histological analysis revealed an increase in cell packing in the CA1 stratum pyramidale. Imaging of the diffusion of a fluorescent marker revealed that the transit of molecules through the ECS of this layer was reduced. Quantitative analysis of ECS by the real-time iontophoretic method demonstrated that ECS volume was selectively reduced in the stratum pyramidale by ∼ 40% in Has3(-/-) mice. Finally, osmotic manipulation experiments in brain slices from Has3(-/-) and wild-type mice provided evidence for a causal link between ECS volume and epileptiform activity. Our results provide the first direct evidence for the physiological role of HA in the regulation of ECS volume, and suggest that HA-based preservation of ECS volume may offer a novel avenue for development of antiepileptogenic treatments.
Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, Department of Physiology and Pharmacology, The Robert F. Furchgott Center for Neural and Behavioral Science, and Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, Center for Advanced Brain Imaging, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, New York 10962, Department of Molecular Biosciences, Kyoto Sangyo University, Kyoto 603-8555, Japan, and Research Complex for Medicine Frontiers, Aichi Medical University, Aichi 480-1195, Japan.
Amaia M
AM
Arranz
Katherine L
KL
Perkins
Fumitoshi
F
Irie
David P
DP
Lewis
Jan
J
Hrabe
Fanrong
F
Xiao
Naoki
N
Itano
Koji
K
Kimata
Sabina
S
Hrabetova
Yu
Y
Yamaguchi
D000200:Action Potentials / Q000235:genetics; D000818:Animals; D001921:Brain / Q000473:pathology*; D004558:Electric Stimulation; D004569:Electroencephalography; D004827:Epilepsy / Q000235:genetics / Q000473:pathology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005110:Extracellular Space / Q000235:genetics / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000172:deficiency* / Q000235:genetics; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000172:deficiency*; D066298:In Vitro Techniques; D051379:Mice; D018345:Mice, Knockout; D008959:Models, Neurological; D009154:Mutation / Q000235:genetics; D009415:Nerve Net / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase; C491356:Has3 protein, mouse; D000076002:Hyaluronan Synthases; D010751:Phosphopyruvate Hydratase