Immunostaining to Visualize Murine Enteric Nervous System Development

Summary

The enteric nervous system is formed by neural crest cells that proliferate, migrate and colonize the gut. Neural crest cells differentiate into neurons with markers specific for their neurotransmitter phenotype. This protocol describes a technique for dissecting, fixing and immunostaining of the murine embryonic gastrointestinal tract to visualize enteric nervous system neurotransmitter expression.

Abstract

The enteric nervous system is formed by neural crest cells that proliferate, migrate and colonize the gut. Following colonization, neural crest cells must then differentiate into neurons with markers specific for their neurotransmitter phenotype. Cholinergic neurons, a major neurotransmitter phenotype in the enteric nervous system, are identified by staining for choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine. Historical efforts to visualize cholinergic neurons have been hampered by antibodies with differing specificities to central nervous system versus peripheral nervous system ChAT. We and others have overcome this limitation by using an antibody against placental ChAT, which recognizes both central and peripheral ChAT, to successfully visualize embryonic enteric cholinergic neurons. Additionally, we have compared this antibody to genetic reporters for ChAT and shown that the antibody is more reliable during embryogenesis. This protocol describes a technique for dissecting, fixing and immunostaining of the murine embryonic gastrointestinal tract to visualize enteric nervous system neurotransmitter expression.

Introduction

A functioning Enteric Nervous System (ENS), which controls motility, nutrient absorption, and local blood flow, is essential to life¹. The ENS is formed by neural crest cells (NCC) that proliferate, migrate and colonize the gut, where they differentiate into ganglia containing neurons and glial cells. Hirschsprung’s Disease (HSCR, Online Mendelian Inheritance in Man), a multigeneic congenital disorder with an incidence of 1 in 4,000 live births, can be considered the prototypic disease for studying disrupted ENS formation. In HSCR, NCC fail to migrate to and colonize variable lengths of the distal hindgut². Additionally, other common gastro....

Protocol

The University of Wisconsin Animal Care and Use Committee approved all procedures.

1. Preparation of Solutions

1. Use 1x phosphate buffered saline (PBS) as dissection buffer and rinsing solution.
2. Prepare 30% sucrose by weighing 30 g of sucrose and place into a bottle. Add 99 ml of 1x PBS and add 1 ml 10% sodium azide. Mix thoroughly until all of the sucrose is dissolved. Store at 4 °C until required.
3. Prepare Blocking solution by mixing 1x PBS, 3% bovine serum albumin (BSA) and 0.1% Triton-X-100. Mix thoroughly and store in the fridge until needed.
4. Prepare 8% paraformaldehyde (PFA) solution....

Results

We have previously described the generation of mice expressing both GFP and tdTomato fluorescent reporters that detect ChAT expression¹⁴. Briefly, ChAT-Cre mice were mated with R26R:floxSTOP:tdTomato animals to produce ChAT-Cre;R26R:floxSTOP:tdTomato mice (called ChAT-Cre tdTomato). These animals were then mated with homozygous ChAT-GFP reporter mice. Embryos were isolated and tissues were dissected prior to being fixed and immunostained as above, with the antibodie.......

Discussion

Our laboratory and others have shown that intestinal defects in HSCR are not restricted to the aganglionic colon but extended proximally, even into the ganglionated small intestine^5,15,16. These alterations include changes in ENS neuronal density and neurotransmitter phenotype and may account for dysmotility that has been observed in patients with HSCR. We have utilized the above techniques in our efforts to understand the determinants of ENS formation. Specifically, these techniques have been employed to visu.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Phosphate buffered saline	Oxoid	BR0014G
Sucrose	Fisher	S2
Sodium azide	Fisher	BP9221
Bovine serum albumin	Fisher	BP1605
Triton X-100	Sigma	X100
Paraformaldehyde	Sigma	158127
60 mm Petri dishes	Fisher	FB0875713A
Fluorescence microscope	Nikon	SMZ-18 stereoscope
Dissection microscope	Nikon	SMZ-18 stereoscope
Fine forceps	Fine science tools	11252-20
1.5 ml Eppendorf tubes	VWR	20170-038
Fluoromount-G	SouthernBiotech, Birmingham, AL	0100-01
Glass slides	Fisher	12-550-15
Cover glass	VWR	16004-330
Confocal microscope	Nikon	Nikon A1
Nikon Elements	Nikon