Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Summary

This video demonstrates a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. Dissociated commissural neurons are useful to study the cellular and molecular mechanisms of axon growth and guidance.

Abstract

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies of these neurons are located in the dorsal spinal cord and their axons follow stereotyped trajectories during embryonic development. Commissural axons initially project ventrally towards the floorplate. After crossing the midline, these axons turn anteriorly and project towards the brain. Each of these steps is regulated by the action of several guidance cues. Cultures highly enriched in commissural neurons are ideally suited for many experiments addressing the mechanisms of axon pathfinding, including turning assays, immunochemistry and biochemistry. Here, we describe a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. First, the spinal cord is isolated and dorsal strips are dissected out. The dorsal tissue is then dissociated into a cell suspension by trypsinization and mechanical disruption. Neurons are plated onto poly-L-lysine-coated glass coverslips or tissue-culture dishes. After 30 hours in vitro, most neurons have extended an axon. The purity of the culture (Yam et al. 2009), typically over 90%, can be assessed by immunolabeling with the commissural neuron markers DCC, LH2 and TAG1 (Helms and Johnson, 1998). This neuronal preparation is a useful tool for in vitro studies of the cellular and molecular mechanisms of commissural axon growth and guidance during spinal cord development.

Protocol

1. Dissection of embryonic rat dorsal spinal cord

General recommendations

Keep L-15 medium on ice and frequently change the medium in the dissection dish to keep the embryos cool. This helps preserve tissue integrity. All steps are performed with two pairs of Dumont #5 forceps unless stated. To avoid contamination, spray all tools and working surfaces with 70% ethanol and keep dissection medium bottle closed. To transfer embryos between dishes, use a cut plastic pipette or a perforated spoon. It is critical not to damage the spinal cord (nicking, stretching) to successfully complete the dissection.

Discussion

We have described a method to dissect and culture commissural neurons from embryonic rat spinal cord. This procedure has been routinely used in our lab to reliably prepare neurons to study the cellular and molecular mechanisms of axon guidance. For cell biology and immunochemistry experiments, dissection of one litter produces sufficient neurons. When more cells are needed, such as in many biochemistry experiments, dissection of two litters may be required. For a trained person, dissection and dissociation of ~20 embryos.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Neurobasal medium, liquid	Invitrogen	21103-049	See Recipes and Comments
B27 supplement 50X	Invitrogen	17504	See Recipes and Comments
Poly-L-lysine 0.01% solution	Sigma-Aldrich	P4707
L-15 medium, powder	Invitrogen	41300-070
Trypsin 2.5% (10X)	Invitrogen	15090-046
DNAse I, 25000 U/mL	Worthington Biochemical
MgSO4	Sigma-Aldrich	M2643
HBSS, Ca2+/Mg2+-free	Invitrogen	14170-112
L-glutamine 200mM, liquid	Invitrogen	25030-081	See Recipes and Comments
Dissection of embryonic rat dorsal spinal cord (see also Table I) E13 pregnancy-staged rat Ethanol 70% Surgical scissors, Fine Science Tools Forceps, Dumont #5, Fine Science Tools Petri dishes L-15 medium Dissection microscope, Leica Plastic transfer pipettes Microscissors, Fine Science Tools Tungsten needles and pin holders (one hook-shaped needle, one L-shapes needle, one straight needle), Fine Science Tools Heat-inactivated Horse Serum (HiHS) 15 ml plastic tubes Commissural neuron culture (see also Table I) Tissue culture incubators (37°C, 5% CO2, humidity controlled) German Desag glass coverslips and/or plastic tissue culture dishes Poly-L-lysine, Sigma Sterile milliQ H2O Neurobasal, Invitrogen Heat-inactivated Fetal Bovine Serum (HiFBS) L-Glutamine B27, Invitrogen Penicillin/Streptomycin antibiotics 37°C waterbath Sterile Pasteur Pipettes Bunsen gas burner HBSS, Ca2+/Mg2+-free, Invitrogen DNAse, Worthington MgSO4 Centrifuge Hemacytometer Trypan Blue Solution