Three Distinct Glutamate Decarboxylase Genes in Vertebrates

Grone, Brian P.; Maruska, Karen P.

doi:10.1038/srep30507

Cited by 32 publications

(21 citation statements)

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“…To localize vglut ( vglut1, vglut2.1, vglut3 )‐, gad ( gad1, gad2 )‐, and chat ‐expressing cells in the brain, we used chromogenic‐based in situ hybridization (ISH) with riboprobes on cryosectioned brain tissue similar to our previous work (Grone and Maruska, ). Our recent bioinformatic analyses also identified gad3 in A. burtoni , but in situ hybridization and reverse‐transcription polymerase chain reaction (RT‐PCR) attempts failed to detect transcripts in the brain (Grone and Maruska, ). Primers for each mRNA of interest were designed from A. burtoni sequences available in GenBank, commercially synthesized (Life Technologies, Bethesda, MD), and are shown in Table .…”

Section: Methodsmentioning

confidence: 99%

“…While both Gads synthesize GABA, GAD1 synthesizes cytoplasmic GABA for extrasynaptic and metabolic functions, and GAD2 regulates the vesicular pool for release (Kaufman et al, 1991;Soghomonian and Martin, 1998;Tian et al, 1999). A third novel Gad paralog (GAD3) originally described in the deep-sea armed grenadier fish also exists in most other vertebrates, but little is known about its distribution and function (Bosma et al, 1999;Lariviere et al, 2002Lariviere et al, , 2005Grone and Maruska, 2016). In general, glutamate is an excitatory transmitter, while GABA is typically an inhibitory transmitter.…”

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confidence: 99%

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Localization of glutamatergic, GABAergic, and cholinergic neurons in the brain of the African cichlid fish,Astatotilapia burtoni

Maruska

Butler

Field

et al. 2016

J of Comparative Neurology

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Neural communication depends on release and reception of different neurotransmitters within complex circuits that ultimately mediate basic biological functions. We mapped the distribution of glutamatergic, GABAergic, and cholinergic neurons in the brain of the African cichlid fish Astatotilapia burtoni using in situ hybridization to label vesicular glutamate transporters (vglut1, vglut2.1, vglut3), glutamate decarboxylases (gad1, gad2), and choline acetyltransferase (chat). Cells expressing the glutamatergic markers vgluts 1-3 show primarily nonoverlapping distribution patterns, with the most widespread expression observed for vglut2.1, and more restricted expression of vglut1 and vglut3. vglut1 is prominent in granular layers of the cerebellum, habenula, preglomerular nuclei, and several other diencephalic, mesencephalic, and rhombencephalic regions. vglut2.1 is widely expressed in many nuclei from the olfactory bulbs to the hindbrain, while vglut3 is restricted to the hypothalamus and hindbrain. GABAergic cells show largely overlapping gad1 and gad2 expression in most brain regions. GABAergic expression dominates nuclei of the subpallial ventral telencephalon, while glutamatergic expression dominates nuclei of the pallial dorsal telencephalon. chat-expressing cells are prominent in motor cranial nerve nuclei, and some scattered cells lie in the preoptic area and ventral part of the ventral telencephalon. A localization summary of these markers within regions of the conserved social decision-making network reveals a predominance of either GABAergic or glutamatergic cells within individual nuclei. The neurotransmitter distributions described here in the brain of a single fish species provide an important resource for identification of brain nuclei in other fishes, as well as future comparative studies on circuit organization and function. J. Comp. Neurol. 525:610-638, 2017. © 2016 Wiley Periodicals, Inc.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Localization of glutamatergic, GABAergic, and cholinergic neurons in the brain of the African cichlid fish,Astatotilapia burtoni

Maruska

Butler

Field

et al. 2016

J of Comparative Neurology

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“…We quantified mRNA levels for the inhibitory synaptic genes GAD1 and GAD2, which encode distinct GAD (glutamic acid decarboxylase) proteins GAD67 and GAD65, respectively [30]. Our analysis showed a statistically significant increase of approximately 5-and 20-fold changes, respectively in GAD1 and GAD2 mRNA levels in TSC2 neurons as compared to the controls (Fig.…”

Section: Pharmacological Pro Ling Of Tsc2 Patient-derived Neuronal Nementioning

confidence: 84%

Pharmacological intervention to restore connectivity deficits of neuronal networks derived from ASD patient iPSC with a TSC2 mutation

Alsaqati

Heine

Harwood

2020

Preprint

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BackgroundTuberous sclerosis complex (TSC) is a rare genetic multisystemic disorder resulting from autosomal dominant mutations in the TSC1 or TSC2 genes. It is characterised by hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway and has severe neurodevelopmental and neurological components including autism, intellectual disability and epilepsy. In human and rodent models, loss of the TSC proteins causes neuronal hyperexcitability and synaptic dysfunction, although the consequences of these changes for the developing central nervous system is currently unclear.MethodsHere we apply Multi-electrode array (MEA)-based assays to study the effects of TSC2 loss on neuronal network activity using Autism Spectrum Disorder (ASD) patient-derived iPSCs. We examine both temporal synchronisation of neuronal bursting, and spatial connectivity between electrodes across the network.ResultsWe find that TSC2 patient-derived neurons with a functional loss of TSC2, in addition to possessing neuronal hyperactivity, develop a dysfunctional neuronal network with reduced synchronisation of neuronal bursting and lower spatial connectivity. These deficits of network function are associated with elevated expression of genes for inhibitory GABA signalling and decreased expression of those for glutamate signalling, indicating an imbalance of synaptic inhibitory-excitatory signalling. mTORC1 activity functions within a homeostatic triad of protein kinases, AMP-dependent protein Kinase 1 (AMPK), mTORC1 and Unc-51 like Autophagy Activating Kinase 1 (ULK1) that orchestrate the interplay of anabolic cell growth and catabolic autophagy while balancing energy and nutrient homeostasis. The mTORC1 inhibitor rapamycin suppresses neuronal hyperactivity, but does not increase network activity, whereas activation of AMPK restores network activity without affecting the network burst length or regularity. In contrast, the ULK1 activator, LYN-1604 increases the network behaviour, shortens the network burst lengths, and reduces the number of uncorrelated spikes.LimitationsAlthough a robust and consistent phenotype is observed across multiple independent iPSC clones, the results are based on iPSC from one patient. There may be more subtle differences between patients with different TSC2 mutations or differences of polygenic background within their genomes. This may affect the severity of the network deficit or the pharmacological response between TSC2 patients.ConclusionsOur observations suggest that there is a reduction in the network connectivity of the in vitro neuronal network associated with ASD patients with TSC2 mutation, which may arise via an excitatory/inhibitory imbalance due to increased GABA signalling at inhibitory synapses. This deficit can be effectively suppressed via activation of ULK1.

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“…In contrast, signi cant differences were observed in expression of genes encoding enzymes and receptor proteins associated with glutamate-GABA signalling. GAD1 and GAD2, which encode the glutamic acid decarboxylases GAD67 and GAD65 [32] showed a statistically significant increase of approximately 5and 20-fold changes, respectively in TSC2 neurons as compared to the controls (Table 1 , Fig. 3A,B), (p < 0.05, p < 0.01, unpaired t-test).…”

Section: Tsc2 Patient Ipsc-derived Neurons Show An Excitatory/inhibitmentioning

confidence: 91%

Pharmacological intervention to restore connectivity deficits of neuronal networks derived from ASD patient iPSCs with a TSC2 mutation

Alsaqati

Heine

Harwood

2020

Preprint

View full text Add to dashboard Cite

Background Tuberous sclerosis complex (TSC) is a rare genetic multisystemic disorder resulting from autosomal dominant mutations in the TSC1 or TSC2 genes. It is characterised by hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway and has severe neurodevelopmental and neurological components including autism, intellectual disability and epilepsy. In human and rodent models, loss of the TSC proteins causes neuronal hyperexcitability and synaptic dysfunction, although the consequences of these changes for the developing central nervous system is currently unclear.MethodsHere we apply Multi-electrode array (MEA)-based assays to study the effects of TSC2 loss on neuronal network activity using Autism Spectrum Disorder (ASD) patient-derived iPSCs. We examine both temporal synchronisation of neuronal bursting, and spatial connectivity between electrodes across the network. Results We find that ASD patient-derived neurons with a functional loss of TSC2, in addition to possessing neuronal hyperactivity, develop a dysfunctional neuronal network with reduced synchronisation of neuronal bursting and lower spatial connectivity. These deficits of network function are associated with elevated expression of genes for inhibitory GABA signalling and glutamate signalling, indicating a potential abnormality of synaptic inhibitory-excitatory signalling. mTORC1 activity functions within a homeostatic triad of protein kinases, mTOR, AMP-dependent protein Kinase 1 (AMPK), and Unc-51 like Autophagy Activating Kinase 1 (ULK1) that orchestrate the interplay of anabolic cell growth and catabolic autophagy while balancing energy and nutrient homeostasis. The mTOR inhibitor rapamycin suppresses neuronal hyperactivity, but does not increase synchronised network activity, whereas activation of AMPK restores some aspects of network activity. In contrast, the ULK1 activator, LYN-1604 increases the network behaviour, shortens the network burst lengths, and reduces the number of uncorrelated spikes.LimitationsAlthough a robust and consistent phenotype is observed across multiple independent iPSC cultures, the results are based on one patient. There may be more subtle differences between patients with different TSC2 mutations or differences of polygenic background within their genomes. This may affect the severity of the network deficit or the pharmacological response between TSC2 patients.ConclusionsOur observations suggest that there is a reduction in the network connectivity of the in vitro neuronal network associated with ASD patients with TSC2 mutation, which may arise via an excitatory/inhibitory imbalance due to increased GABA-signalling at inhibitory synapses. This abnormality can be effectively suppressed via activation of ULK1.

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Three Distinct Glutamate Decarboxylase Genes in Vertebrates

Cited by 32 publications

References 62 publications

Localization of glutamatergic, GABAergic, and cholinergic neurons in the brain of the African cichlid fish,Astatotilapia burtoni

Localization of glutamatergic, GABAergic, and cholinergic neurons in the brain of the African cichlid fish,Astatotilapia burtoni

Pharmacological intervention to restore connectivity deficits of neuronal networks derived from ASD patient iPSC with a TSC2 mutation

Pharmacological intervention to restore connectivity deficits of neuronal networks derived from ASD patient iPSCs with a TSC2 mutation

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