GABAA and GABAB receptor dysregulation in superior frontal cortex of subjects with schizophrenia and bipolar disorder.

Schizophrenia and bipolar disorder are complex psychiatric disorders that affect millions of people worldwide. Evidence from gene association and postmortem studies has identified abnormalities of the gamma-aminobutyric acid (GABA) signaling system in both disorders. Abnormal GABAergic signaling and transmission could contribute to the symptomatology of these disorders, potentially through impaired gamma oscillations which normally occur during cognitive processing. In the current study, we examined the protein expression of 14 GABAA and two GABAB receptor subunits in the superior frontal cortex of subjects with schizophrenia, bipolar disorder, and healthy controls. Analyses of Variance (ANOVAs) identified significant group effects for protein levels for the α1, α6, ß1, ß3, δ, ɛ, and π GABAA receptor subunits and R1 and R2 GABAB receptor subunits. Follow-up t tests confirmed changes for these subunits in subjects with schizophrenia, subjects with bipolar disorder, or both groups. Alterations in stoichiometry of GABA receptor subunits could result in altered ligand binding, transmission, and pharmacology of GABA receptors in superior frontal cortex. Thus, impaired GABAergic transmission may negatively contribute to symptoms such as anxiety or panic as well as impaired learning and information processing, all of which are disrupted in schizophrenia and bipolar disorder. Taken together, these results provide additional evidence of GABAergic receptor abnormalities in these disorders.

A Study of Gene Expression Changes in Human Spinal and Oculomotor Neurons; Identifying Potential Links to Sporadic ALS.

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease that causes compromised function of motor neurons and neuronal death. However, oculomotor neurons are largely spared from disease symptoms. The underlying causes for sporadic ALS as well as for the resistance of oculomotor neurons to disease symptoms remain poorly understood. In this bioinformatic-analysis, we compared the gene expression profiles of spinal and oculomotor tissue samples from control individuals and sporadic ALS patients. We show that the genes GAD2 and GABRE (involved in GABA signaling), and CALB1 (involved in intracellular Ca2+ ion buffering) are downregulated in the spinal tissues of ALS patients, but their endogenous levels are higher in oculomotor tissues relative to the spinal tissues. Our results suggest that the downregulation of these genes and processes in spinal tissues are related to sporadic ALS disease progression and their upregulation in oculomotor neurons confer upon them resistance to ALS symptoms. These results build upon prevailing models of excitotoxicity that are relevant to sporadic ALS disease progression and point out unique opportunities for better understanding the progression of neurodegenerative properties associated with sporadic ALS.

Rare variants in the GABAA receptor subunit ε identified in patients with a wide spectrum of epileptic phenotypes.

BACKGROUND: Epilepsy belongs to a group of chronic and highly heterogeneous brain disorders. Many types of epilepsy and epileptic syndromes are caused by genetic factors. The neural amino acid y-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the mammalian central nervous system. It regulates activity of channel pores by binding to transmembrane GABA-receptors (GABRs). The GABRs are heteropentamers assembled from different receptor subunits (α1-6, ß1-3, γ1-3, δ, ε, θ, π, and ρ1-3). Several epileptic disorders are caused by mutations in genes encoding single GABRs. METHODS: We applied trio- and single-whole exome sequencing to search for genetic sequence variants associated with a wide range of epileptic phenotypes accompanied by intellectual disability and/or global developmental delay in the investigated patients. RESULTS: We identified four hemizygous sequence variants in the GABAA receptor subunit ε gene (GABRE), including one nonsense (NM_004961.3: c.399C>A, p.Tyr133*), two missense variants (NM_004961.3: c.664G>A, p.Glu222Lys; NM_004961.3: c.1045G>A, p.Val349Ile), and one variant affecting the translation initiation codon (NM_004961.3: c.1A>G, p.Met1?) in four unrelated families. CONCLUSION: Our clinical and molecular genetic findings suggest that GABRE is a likely candidate gene for epilepsy. Nevertheless, functional studies are necessary to better understand pathogenicity of the GABRE-mutations and their associations with epileptic phenotypes.