Strategies and Tools for Combinatorial Targeting of GABAergic Neurons in Mouse Cerebral Cortex

Abstract

SummarySystematic genetic access to GABAergic cell types will facilitate studying the function and development of inhibitory circuitry. However, single gene-driven recombinase lines mark relatively broad and heterogeneous cell populations. Although intersectional approaches improve precision, it remains unclear whether they can capture cell types defined by multiple features. Here we demonstrate that combinatorial genetic and viral approaches target restricted GABAergic subpopulations and cell types characterized by distinct laminar location, morphology, axonal projection, and electrophysiological properties. Intersectional embryonic transcription factor drivers allow finer fate mapping of progenitor pools that give rise to distinct GABAergic populations, including laminar cohorts. Conversion of progenitor fate restriction signals to constitutive recombinase expression enables viral targeting of cell types based on their lineage and birth time. Properly designed intersection, subtraction, conversion, and multi-color reporters enhance the precision and versatility of drivers and viral vectors. These strategies and tools will facilitate studying GABAergic neurons throughout the mouse brain. eTOC BlurbHe et al. present strategies and tools for the combinatorial targeting of GABAergic neurons in the mouse brain. Specific cell type targeting can be achieved by combining 2 to 3 driver-reporter alleles with viral vectors that engage multiple cell-defining features.

Vasoactive intestinal peptide-expressing interneurons are impaired in a mouse model of Dravet syndrome

“…This prompted us to explore how our data from Scn1a +/- mice mapped onto previously described VIP-IN firing patterns. VIP-INs in superficial layers of mouse and rat barrel cortex exhibit spike frequency adaptation with or without irregular spiking and/or initial bursting (variably referred to in the literature as continuous adapting, irregular spiking, bursting, or fast adapting) (He et al, 2016; Prönneke et al, 2015). However, there is no existing standardized or widely agreed upon nomenclature to describe VIP-IN firing patterns.…”

Intersectional Strategies for Targeting Amacrine and Ganglion Cell Types in the Mouse Retina

“…This reduction allows us to tease apart the intermingled neuron networks in the IPL making it easier to anatomically identify new cell types. By introducing reporter mouse lines ( Madisen et al, 2015 ) and viral vectors ( Fenno et al, 2014 ; Madisen et al, 2015 ; He et al, 2016 ), genetically encoded calcium indicators and optogenetic effectors can be delivered to these new cells for systematic functional analysis.…”

“…We employed an intersectional strategy in which transgene expression is defined by the combination of two recombinases each driven by a distinct gene promoter ( Dymecki et al, 2010 ; Madisen et al, 2015 ; He et al, 2016 ). To date, the most commonly used intersectional combination is the Cre and Flp dual-recombinase system that simultaneously uses both Cre/loxP and Flp/FRT combination to remove a STOP cassette or to reverse a double-floxed inverse open reading frame (DIO/FLEX) ( Atasoy et al, 2008 ; Sohal et al, 2009 ).…”

“…The intersectional approach has been recently used in the nervous system to anatomically map and functionally study genetically-defined subpopulations of neurons ( Madisen et al, 2015 ; He et al, 2016 ), but its effectiveness in retina has not been demonstrated. Here, we screened and analyzed seven new Flp drivers for expression patterns in the retina, lateral geniculate nucleus (LGN), and superior colliculus (SC).…”

Specificity, Versatility, and Continual Development: The Power of Optogenetics for Epilepsy Research

“…However, the increasing availability of Cre- and Flp-recombinase expressing mouse lines and systems (Taniguchi et al, 2011 ; Madisen et al, 2012 , 2015 ; Tang et al, 2015 ; He et al, 2016 ) and recent advances in intersectional approaches for the restricted expression of opsins (Figure 3iii ; Fenno et al, 2014 ) finally allow for more selective targeting and manipulation of cell populations. Importantly, these intersectional tools can aid in maintaining consistent selective expression in epileptic tissue.…”