Restoration of Sp4 in Forebrain GABAergic Neurons Rescues Hypersensitivity to Ketamine in Sp4 Hypomorphic Mice.

BackgroundKetamine produces schizophrenia-like behavioral phenotypes in healthy people. Prolonged ketamine effects and exacerbation of symptoms after the administration of ketamine have been observed in patients with schizophrenia. More recently, ketamine has been used as a potent antidepressant to treat patients with major depression. The genes and neurons that regulate behavioral responses to ketamine, however, remain poorly understood. Sp4 is a transcription factor for which gene expression is restricted to neuronal cells in the brain. Our previous studies demonstrated that Sp4 hypomorphic mice display several behavioral phenotypes relevant to psychiatric disorders, consistent with human SP4 gene associations with schizophrenia, bipolar disorder, and major depression. Among those behavioral phenotypes, hypersensitivity to ketamine-induced hyperlocomotion has been observed in Sp4 hypomorphic mice.MethodsIn the present study, we used the Cre-LoxP system to restore Sp4 gene expression, specifically in either forebrain excitatory or GABAergic inhibitory neurons in Sp4 hypomorphic mice. Mouse behavioral phenotypes related to psychiatric disorders were examined in these distinct rescue mice.ResultsRestoration of Sp4 in forebrain excitatory neurons did not rescue deficient sensorimotor gating nor ketamine-induced hyperlocomotion. Restoration of Sp4 in forebrain GABAergic neurons, however, rescued ketamine-induced hyperlocomotion, but did not rescue deficient sensorimotor gating.ConclusionsOur studies suggest that the Sp4 gene in forebrain GABAergic neurons regulates ketamine-induced hyperlocomotion

A novel animal model for neuroinflammation and white matter degeneration

Small interference RNA has been widely used to suppress gene expression. Three different short hairpin RNAs (shRNAs) against dopamine D1 receptor (Drd1), driven by mouse U6 promoter in self-complementary AAV8 vector (scAAV8), were used to silence mouse striatal Drd1 expression. Transduction of mouse striatum with all three scAAV8-D1shRNA viruses, but not the control scAAV8 virus, causes extensive neuroinflammation, demyelination, and axon degeneration. RNA interference is known to be coupled to the innate immune system as a host cell defense against virus infection. Activation of the innate immune system may play a causal role in the development of neuroinflammation and white matter degeneration, providing a novel animal model for multiple sclerosis (MS) and other neuroinflammatory diseases

Chromogenic immunohistochemical analysis of GAD67 and parvalbumin in mouse cortex.

<p>Mouse brain paraffin section was first used for anti-GAD67 immunostaining. After the stained slide was scanned with Aperio ScanScope, the anti-GAD67 primary antibody and red stain color were completely stripped. The same section was re-used for anti-parvalbumin immunostaining.</p

Multiple rounds of sequential immunohistochemical analysis.

<p>Mouse hippocampus and cortex were immunostained with 5 different antibodies: (<b>a</b>) anti-GAD67, high expression of GAD67 in hippocampal mossy fiber besides in cortex, (<b>b</b>) anti-parvalbumin, no detectable parvalbumin in hippocampal mossy fiber, but abundant in cortex, (<b>c</b>) anti-calretinin, sporadic calretinin positive cells in cortex with abundant calretinin expression in the inner molecular layer of dentate gyrus, (<b>d</b>) anti-Iba-1, numerous microglial cells and their processes across the section, (<b>e</b>) anti-MBP, abundant myelin in <i>corpus callosum</i> and some myelinated neurons in hippocampus and cortex. Scale bar: 500 µm.</p

Co-localization between GAD67, parvalbumin, and calretinin.

<p>Top panel: the images of GAD67, parvalbumin, and calretinin were pseudocolored into green, red, and purple respectively. Bottom panel: the three images were superimposed together. Arrow 1: calretinin positive neuron. Arrow 2: GAD67 positive neuron. Arrow 3: neuron expressing both GAD67 and parvalbumin. Arrow 4: neuron expressing both GAD67 and calretinin. Scale bar: 500 µm.</p