Abstract
GABAergic interneurons play a critical role in tuning neural networks in the central nervous system, and their defects are associated with neuropsychiatric disorders. Currently, the mDlx enhancer is solely used for adeno-associated virus (AAV) vector-mediated transgene delivery into cortical interneurons. Here, we developed a new inhibitory neuron-specific promoter (designated as the mGAD65 promoter), with a length of 2.5 kb, from a mouse genome upstream of exon 1 of the Gad2 gene encoding glutamic acid decarboxylase (GAD) 65. Intravenous infusion of blood–brain barrier-penetrating AAV-PHP.B expressing an enhanced green fluorescent protein under the control of the mGAD65 promoter transduced the whole brain in an inhibitory neuron-specific manner. The specificity and efficiency of the mGAD65 promoter for GABAergic interneurons, which was assessed at the motor cortex, were almost identical to or slightly higher than those of the mDlx enhancer. Immunohistochemical analysis revealed that the mGAD65 promoter preferentially transduced parvalbumin (PV)-expressing interneurons. Notably, the mGAD65 promoter transduced chandelier cells more efficiently than the mDlx enhancer and robustly labeled their synaptic boutons, called the cartridge, targeting the axon initial segments of excitatory pyramidal neurons. To test the ability of the mGAD65 promoter to express a functional molecule, we virally expressed G-CaMP, a fluorescent Ca2+ indicator, in the motor cortex, and this enabled us to monitor spontaneous and drug-induced Ca2+ activity in GABAergic inhibitory neurons. These results suggest that the mGAD65 promoter is useful for AAV-mediated targeting and manipulation of GABAergic neurons with the dominance of cortical PV-expressing neurons, including chandelier cells.
Highlights
Inhibitory interneurons constitute 10–20% of all neurons in the cerebral cortex [1,2,3]
Identification of a candidate region for inhibitory neuron‐specific promoters Inhibitory neurons release the key inhibitory neurotransmitter, Gamma-aminobutyric acid (GABA), which is synthesized from glutamate by glutamic acid decarboxylase (GAD); GAD is composed of two isoforms, namely GAD67 and GAD65, which are encoded by the Gad1 and Gad2 genes in the mouse, respectively [27]
For the mDlx enhancer, we examined 1161 green fluorescent protein (GFP) ( +) cells in 5 sections from 5 animals, and we found that 1025 cells were co-labeled with tdTomato (88.3 ± 1.3%). ***p = 0.0007 by unpaired t-test. f Graph showing transduction efficiency of cortical interneurons by the mGAD65 promoter, in comparison to the mDlx enhancer
Summary
Inhibitory interneurons constitute 10–20% of all neurons in the cerebral cortex [1,2,3]. They have numerous neurochemical, morphological, and functional classes. The PV-expressing basket cell, the most abundant subtype, which accounts for approximately 30% of nonpyramidal neurons, is responsible for the perisomatic inhibition of excitatory pyramidal neurons [6]. Recent studies have revealed that cortical interneuron activity plays a crucial role in shaping excitatory circuits during learning and memory expression [6, 8], and dysfunction of inhibitory neuron subtypes is thought to underlie various aspects of psychiatric disorders [6, 7, 9, 10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
