dizocilpine-maleate and Chromosome-Deletion

Kleefstra syndrome (KS) is a neurodevelopmental disorder caused by mutations in the histone methyltransferase EHMT1. To study the impact of decreased EHMT1 function in human cells, we generated excitatory cortical neurons from induced pluripotent stem (iPS) cells derived from KS patients. Neuronal networks of patient-derived cells exhibit network bursting with a reduced rate, longer duration, and increased temporal irregularity compared to control networks. We show that these changes are mediated by upregulation of NMDA receptor (NMDAR) subunit 1 correlating with reduced deposition of the repressive H3K9me2 mark, the catalytic product of EHMT1, at the GRIN1 promoter. In mice EHMT1 deficiency leads to similar neuronal network impairments with increased NMDAR function. Finally, we rescue the KS patient-derived neuronal network phenotypes by pharmacological inhibition of NMDARs. Summarized, we demonstrate a direct link between EHMT1 deficiency and NMDAR hyperfunction in human neurons, providing a potential basis for more targeted therapeutic approaches for KS.

Topics: Animals; Cerebral Cortex; Chromosome Deletion; Chromosomes, Human, Pair 9; Craniofacial Abnormalities; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; Heart Defects, Congenital; Histone-Lysine N-Methyltransferase; Humans; Induced Pluripotent Stem Cells; Intellectual Disability; Loss of Function Mutation; Male; Mice; Nerve Tissue Proteins; Neurons; Primary Cell Culture; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Up-Regulation

We here report the existence of 6 additional isoforms of the NMDA receptor generated via alternative splicing by molecular analysis of cDNA clones isolated from a rat forebrain cDNA library. These isoforms possess the structures with an insertion at the extracellular amino-terminal region or deletions at two different extracellular carboxyl-terminal regions, or those formed by combinations of the above insertion and deletions. One of the deletions results in the generation of a new carboxyl-terminal sequence. All these isoforms possess the ability to induce electrophysiological responses to NMDA and respond to various antagonists selective to the NMDA receptor in the Xenopus oocyte expression system. In addition, a truncated form of the NMDA receptor also exists that contains only the extreme amino-terminal sequence of this protein molecule. These data indicate that the NMDA receptor consists of heterogeneous molecules that differ in the extracellular sequence of the amino- and carboxyl-terminal regions.

Topics: 2-Amino-5-phosphonovalerate; Amino Acid Sequence; Animals; Base Sequence; Chromosome Deletion; Cloning, Molecular; Dizocilpine Maleate; DNA; Gene Library; Kynurenic Acid; Molecular Sequence Data; N-Methylaspartate; Oocytes; Piperazines; Prosencephalon; Rats; Receptors, N-Methyl-D-Aspartate; Restriction Mapping; RNA Splicing; RNA, Messenger; Xenopus