Creating Avian Forebrain Chimeras to Assess Facial Development

Summary

This article describes a tissue transplantation technique that was designed to test the signaling and patterning properties of basal forebrain during craniofacial development.

Abstract

The avian embryo has been used as a model system for more than a century and has led to fundamental understanding of vertebrate development. One of the strengths of this model system is that the effect of, and interaction among, tissues can be directly assessed in chimeric embryos. We have previously shown that signals from the forebrain contribute to facial morphogenesis by regulating the shape of the expression domain of Sonic hedgehog (SHH) in the Frontonasal Ectodermal Zone (FEZ). In this article, the method of generating the forebrain chimeras and provide illustrations of the outcomes of these experiments is described.

Introduction

Much contemporary research in developmental biology focuses on the role of genes in shaping embryos. There are good tools to examine developmental mechanisms from a genetic perspective. However, embryos are assembled and undergo morphogenesis in response to tissue interactions. The avian system is a classic tool used to assess the variety of tissue interactions that regulate development for the following reasons: the embryology is well-understood, the embryos are easily accessible, tools for analysis of avian systems are well-developed, and the embryos are inexpensive.

The avian transplantation system has been widely employed for lineage tr....

Protocol

White Pekin duck (Anas platyrhynchos), white Leghorn chicken (Gallus gallus) and Japanese quail (Cortunix coturnix japonica) are incubated at 37 °C in a humidified chamber until stage-matched at HH7/8¹⁷.

1. Preparing the donor tissue

NOTE: Preparation of reagents and tools and how to open eggs for experimental manipulation has been described⁶.

1. Prepare DMEM media with neutral red, a glass transfer pipette, and sharpened tungsten needles.
2. Expose embryos (as shown in⁶).
3. Harvest tiss....

Results

Assessment of Chimerism and Transplant Contamination
In order to assess the chimeras, the extent of chimerism and contamination of the graft with other cell types should be addressed. Creating chimeras by transplanting quail tissues into chick embryos allows for this type of analysis. Using the QCPN antibody quail cells can be visualized and distinguished from the host tissues (Figure 1 C,D). In this case, only tissues derived from the ventral forebrai.......

Discussion

The method described allows examination of the tissue interactions between the basal forebrain and the adjacent ectoderm. This approach differs from previous forebrain transplant methods, because the donor tissue was restricted to the ventral forebrain. This eliminates transplantation of the neural crest cells, which have been shown to participate in patterning facial morphology^9,10. Hence, restricting the graft to the basal forebrain was essential to evaluate th.......

Materials

Name	Company	Catalog Number	Comments
1x PBS	TEK	TEKZR114
35x10 mm Petri dish	Falcon	1008
DMEM	Thermofisher	11965084
Needle holder	Fine Science Tools	26016-12
Neutral Red	Sigma	553-24-2
No. 5 Dumont forceps	Fine Science Tools	11252-20
Pasteur Pipets	Thermofisher	13-678-6B
QCPN antibody	Developmental Studies Hybridoma bank, Iowa University, Iowa, USA
Scissors	Fine Science Tools	14058-11
Tungsten Needle	Fine Science Tools	26000