Viral-mediated Labeling and Transplantation of Medial Ganglionic Eminence (MGE) Cells for In Vivo Studies

Summary

GABAergic cortical interneuron progenitors disperse, develop and synaptically integrate into a host cortex after transplantation. These cells can be easily transduced before transplantation for in vivo studies of genetically modified GABAergic precursors. Here, we show viral labeling techniques to target specific interneuron subgroups using existing Cre lines and Cre-dependent reporters.

Abstract

GABAergic cortical interneurons, derived from the embryonic medial and caudal ganglionic eminences (MGE and CGE), are functionally and morphologically diverse. Inroads have been made in understanding the roles of distinct cortical interneuron subgroups, however, there are still many mechanisms to be worked out that may contribute to the development and maturation of different types of GABAergic cells. Moreover, altered GABAergic signaling may contribute to phenotypes of autism, schizophrenia and epilepsy. Specific Cre-driver lines have begun to parcel out the functions of unique interneuron subgroups. Despite the advances in mouse models, it is often difficult to efficiently study GABAergic cortical interneuron progenitors with molecular approaches in vivo. One important technique used to study the cell autonomous programming of these cells is transplantation of MGE cells into host cortices. These transplanted cells migrate extensively, differentiate, and functionally integrate. In addition, MGE cells can be efficiently transduced with lentivirus immediately prior to transplantation, allowing for a multitude of molecular approaches. Here we detail a protocol to efficiently transduce MGE cells before transplantation for in vivo analysis, using available Cre-driver lines and Cre-dependent expression vectors. This approach is advantageous because it combines precise genetic manipulation with the ability of these cells to disperse after transplantation, permitting greater cell-type specific resolution in vivo.

Introduction

GABAergic cortical interneurons comprise ~20-30% of neurons in the mammalian neocortex, while the rest correspond to excitatory, glutamatergic principal neurons. Interneurons are highly diverse in electrophysiological properties, axon and dendrite morphology and synaptic targeting ¹, and imbalances in excitatory/inhibitory tone are hypothesized to underlie some phenotypes of neurological/neuropsychiatric disorders including autism, schizophrenia and epilepsy ². The overall goal of the protocol described herein is to provide a means to efficiently genetically modify GABAergic cortical interneuron progenitors before transplantation for in vivo<....

Protocol

Ethics statement: The following procedures have been approved by our institution and animal protocol. Make sure to get approval for all procedures involving survival surgeries before beginning experiments and verify all protocols are up to date.

1. Lentivirus Preparation (Optional Step)

1. Split three 10 cm plates of HEK293T cells for each lentivirus to be made, in the presence of 10 ml DMEM/10% FBS, and grow to ~60-70% confluence. Grow cells in an incubator at 37 °C with 5% CO₂.
2. Transfect the following DNA plasmids (10 µg total) into each plate using any transfection reagent: 6.4 µg CAG....

Results

Since MGE cells have the unique ability to migrate and integrate when transplanted into a host neocortex ¹⁶, they provide an excellent model system for genetic manipulation before in vivo studies. Herein, we show how one can isolate MGE tissue from E13.5 embryos (Figures 1 and 2), which can then be transduced with lentiviruses either in vitro or in a rapid manner before transplantation for in vivo studies. Labeling MGE via lentiviruses has been performed before using.......

Discussion

The use of GABAergic cortical interneuron precursors from the embryonic ganglionic eminences (GEs) for cell based therapies is showing promise for many conditions ^12–14. Precise molecular techniques are needed to track, and express genes of interest in specific interneuron subgroups. Here we provide a detailed protocol for labeling embryonic MGE cells with lentiviruses before transplantation and show how this technique can be used to express genes of interest in specific cortical in.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Reagents and equipment for MGE cell transplantation
1 ml syringe	REF 309602	BD, Becton Dickinson and company
30 1/2 G needle	305106	BD, Becton Dickinson and company
Precision bore to deliver 5 µl (comes with plunger)	5-000-1005	Drummond scientific company
Parafilm	PM-999	Polysciences, Inc.
Stereo microscope with boomstand **	MZ6	Leica
Digital just for mice stereotaxic instrument **	51725D	Stoelting company
Single-axis oil hydraulic fine micromanipulator **	MO-10	Narishige
Diamond coated rotary beveler		made in house
Needle pipette puller	730	Kopf instruments
Mineral oil		Any drug store or pharmacy
Any pipette and tips that can reliaby measure 1 µl of volume
** These are the particular models we use, but many other setups should work
Optional Reagents (for making Lentiviruses)
25 mm, 0.45 µm filter	09-719B	Fisher Scientific
Ultra-clear centrifuge tubes (25 x 89 mm)	344058	Beckman Coulter®
Lipofectamine 2000 (1.5 ml size)	11668019	Invitrogen
Other commercially available supplies
pMDLg/pRRE plasmid encoding gag/pol	12251	Addgene
pRSV-Rev plasmid encoding Rev	12253	Addgene
pMD2.G plasmid encoding VSVG	12259	Addgene
pAAV-Flex-GFP	28304	Addgene